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64db4cff PM |
1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2 of the License, or | |
7 | * (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
87de1cfd PM |
15 | * along with this program; if not, you can access it online at |
16 | * http://www.gnu.org/licenses/gpl-2.0.html. | |
64db4cff PM |
17 | * |
18 | * Copyright IBM Corporation, 2008 | |
19 | * | |
20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> | |
21 | * Manfred Spraul <manfred@colorfullife.com> | |
22 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version | |
23 | * | |
24 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> | |
25 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. | |
26 | * | |
27 | * For detailed explanation of Read-Copy Update mechanism see - | |
a71fca58 | 28 | * Documentation/RCU |
64db4cff PM |
29 | */ |
30 | #include <linux/types.h> | |
31 | #include <linux/kernel.h> | |
32 | #include <linux/init.h> | |
33 | #include <linux/spinlock.h> | |
34 | #include <linux/smp.h> | |
35 | #include <linux/rcupdate.h> | |
36 | #include <linux/interrupt.h> | |
37 | #include <linux/sched.h> | |
c1dc0b9c | 38 | #include <linux/nmi.h> |
8826f3b0 | 39 | #include <linux/atomic.h> |
64db4cff | 40 | #include <linux/bitops.h> |
9984de1a | 41 | #include <linux/export.h> |
64db4cff PM |
42 | #include <linux/completion.h> |
43 | #include <linux/moduleparam.h> | |
4102adab | 44 | #include <linux/module.h> |
64db4cff PM |
45 | #include <linux/percpu.h> |
46 | #include <linux/notifier.h> | |
47 | #include <linux/cpu.h> | |
48 | #include <linux/mutex.h> | |
49 | #include <linux/time.h> | |
bbad9379 | 50 | #include <linux/kernel_stat.h> |
a26ac245 PM |
51 | #include <linux/wait.h> |
52 | #include <linux/kthread.h> | |
268bb0ce | 53 | #include <linux/prefetch.h> |
3d3b7db0 PM |
54 | #include <linux/delay.h> |
55 | #include <linux/stop_machine.h> | |
661a85dc | 56 | #include <linux/random.h> |
af658dca | 57 | #include <linux/trace_events.h> |
d1d74d14 | 58 | #include <linux/suspend.h> |
64db4cff | 59 | |
4102adab | 60 | #include "tree.h" |
29c00b4a | 61 | #include "rcu.h" |
9f77da9f | 62 | |
4102adab PM |
63 | MODULE_ALIAS("rcutree"); |
64 | #ifdef MODULE_PARAM_PREFIX | |
65 | #undef MODULE_PARAM_PREFIX | |
66 | #endif | |
67 | #define MODULE_PARAM_PREFIX "rcutree." | |
68 | ||
64db4cff PM |
69 | /* Data structures. */ |
70 | ||
f885b7f2 | 71 | static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; |
394f2769 | 72 | static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; |
385b73c0 | 73 | static struct lock_class_key rcu_exp_class[RCU_NUM_LVLS]; |
88b91c7c | 74 | |
f7f7bac9 SRRH |
75 | /* |
76 | * In order to export the rcu_state name to the tracing tools, it | |
77 | * needs to be added in the __tracepoint_string section. | |
78 | * This requires defining a separate variable tp_<sname>_varname | |
79 | * that points to the string being used, and this will allow | |
80 | * the tracing userspace tools to be able to decipher the string | |
81 | * address to the matching string. | |
82 | */ | |
a8a29b3b AB |
83 | #ifdef CONFIG_TRACING |
84 | # define DEFINE_RCU_TPS(sname) \ | |
f7f7bac9 | 85 | static char sname##_varname[] = #sname; \ |
a8a29b3b AB |
86 | static const char *tp_##sname##_varname __used __tracepoint_string = sname##_varname; |
87 | # define RCU_STATE_NAME(sname) sname##_varname | |
88 | #else | |
89 | # define DEFINE_RCU_TPS(sname) | |
90 | # define RCU_STATE_NAME(sname) __stringify(sname) | |
91 | #endif | |
92 | ||
93 | #define RCU_STATE_INITIALIZER(sname, sabbr, cr) \ | |
94 | DEFINE_RCU_TPS(sname) \ | |
c92fb057 | 95 | static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, sname##_data); \ |
a41bfeb2 | 96 | struct rcu_state sname##_state = { \ |
6c90cc7b | 97 | .level = { &sname##_state.node[0] }, \ |
2723249a | 98 | .rda = &sname##_data, \ |
037b64ed | 99 | .call = cr, \ |
af446b70 | 100 | .fqs_state = RCU_GP_IDLE, \ |
42c3533e PM |
101 | .gpnum = 0UL - 300UL, \ |
102 | .completed = 0UL - 300UL, \ | |
7b2e6011 | 103 | .orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \ |
6c90cc7b PM |
104 | .orphan_nxttail = &sname##_state.orphan_nxtlist, \ |
105 | .orphan_donetail = &sname##_state.orphan_donelist, \ | |
7be7f0be | 106 | .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \ |
a8a29b3b | 107 | .name = RCU_STATE_NAME(sname), \ |
a4889858 | 108 | .abbr = sabbr, \ |
2723249a | 109 | } |
64db4cff | 110 | |
a41bfeb2 SRRH |
111 | RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched); |
112 | RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh); | |
b1f77b05 | 113 | |
b28a7c01 | 114 | static struct rcu_state *const rcu_state_p; |
2927a689 | 115 | static struct rcu_data __percpu *const rcu_data_p; |
6ce75a23 | 116 | LIST_HEAD(rcu_struct_flavors); |
27f4d280 | 117 | |
a3dc2948 PM |
118 | /* Dump rcu_node combining tree at boot to verify correct setup. */ |
119 | static bool dump_tree; | |
120 | module_param(dump_tree, bool, 0444); | |
7fa27001 PM |
121 | /* Control rcu_node-tree auto-balancing at boot time. */ |
122 | static bool rcu_fanout_exact; | |
123 | module_param(rcu_fanout_exact, bool, 0444); | |
47d631af PM |
124 | /* Increase (but not decrease) the RCU_FANOUT_LEAF at boot time. */ |
125 | static int rcu_fanout_leaf = RCU_FANOUT_LEAF; | |
7e5c2dfb | 126 | module_param(rcu_fanout_leaf, int, 0444); |
f885b7f2 | 127 | int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; |
cb007102 AG |
128 | /* Number of rcu_nodes at specified level. */ |
129 | static int num_rcu_lvl[] = NUM_RCU_LVL_INIT; | |
f885b7f2 PM |
130 | int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ |
131 | ||
b0d30417 PM |
132 | /* |
133 | * The rcu_scheduler_active variable transitions from zero to one just | |
134 | * before the first task is spawned. So when this variable is zero, RCU | |
135 | * can assume that there is but one task, allowing RCU to (for example) | |
b44f6656 | 136 | * optimize synchronize_sched() to a simple barrier(). When this variable |
b0d30417 PM |
137 | * is one, RCU must actually do all the hard work required to detect real |
138 | * grace periods. This variable is also used to suppress boot-time false | |
139 | * positives from lockdep-RCU error checking. | |
140 | */ | |
bbad9379 PM |
141 | int rcu_scheduler_active __read_mostly; |
142 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
143 | ||
b0d30417 PM |
144 | /* |
145 | * The rcu_scheduler_fully_active variable transitions from zero to one | |
146 | * during the early_initcall() processing, which is after the scheduler | |
147 | * is capable of creating new tasks. So RCU processing (for example, | |
148 | * creating tasks for RCU priority boosting) must be delayed until after | |
149 | * rcu_scheduler_fully_active transitions from zero to one. We also | |
150 | * currently delay invocation of any RCU callbacks until after this point. | |
151 | * | |
152 | * It might later prove better for people registering RCU callbacks during | |
153 | * early boot to take responsibility for these callbacks, but one step at | |
154 | * a time. | |
155 | */ | |
156 | static int rcu_scheduler_fully_active __read_mostly; | |
157 | ||
0aa04b05 PM |
158 | static void rcu_init_new_rnp(struct rcu_node *rnp_leaf); |
159 | static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf); | |
5d01bbd1 | 160 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); |
a46e0899 PM |
161 | static void invoke_rcu_core(void); |
162 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); | |
6587a23b PM |
163 | static void rcu_report_exp_rdp(struct rcu_state *rsp, |
164 | struct rcu_data *rdp, bool wake); | |
a26ac245 | 165 | |
a94844b2 | 166 | /* rcuc/rcub kthread realtime priority */ |
26730f55 | 167 | #ifdef CONFIG_RCU_KTHREAD_PRIO |
a94844b2 | 168 | static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO; |
26730f55 PM |
169 | #else /* #ifdef CONFIG_RCU_KTHREAD_PRIO */ |
170 | static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0; | |
171 | #endif /* #else #ifdef CONFIG_RCU_KTHREAD_PRIO */ | |
a94844b2 PM |
172 | module_param(kthread_prio, int, 0644); |
173 | ||
8d7dc928 | 174 | /* Delay in jiffies for grace-period initialization delays, debug only. */ |
0f41c0dd PM |
175 | |
176 | #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT | |
177 | static int gp_preinit_delay = CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT_DELAY; | |
178 | module_param(gp_preinit_delay, int, 0644); | |
179 | #else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT */ | |
180 | static const int gp_preinit_delay; | |
181 | #endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT */ | |
182 | ||
8d7dc928 PM |
183 | #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT |
184 | static int gp_init_delay = CONFIG_RCU_TORTURE_TEST_SLOW_INIT_DELAY; | |
37745d28 | 185 | module_param(gp_init_delay, int, 0644); |
8d7dc928 PM |
186 | #else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT */ |
187 | static const int gp_init_delay; | |
188 | #endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT */ | |
eab128e8 | 189 | |
0f41c0dd PM |
190 | #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP |
191 | static int gp_cleanup_delay = CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY; | |
192 | module_param(gp_cleanup_delay, int, 0644); | |
193 | #else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP */ | |
194 | static const int gp_cleanup_delay; | |
195 | #endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP */ | |
196 | ||
eab128e8 PM |
197 | /* |
198 | * Number of grace periods between delays, normalized by the duration of | |
199 | * the delay. The longer the the delay, the more the grace periods between | |
200 | * each delay. The reason for this normalization is that it means that, | |
201 | * for non-zero delays, the overall slowdown of grace periods is constant | |
202 | * regardless of the duration of the delay. This arrangement balances | |
203 | * the need for long delays to increase some race probabilities with the | |
204 | * need for fast grace periods to increase other race probabilities. | |
205 | */ | |
206 | #define PER_RCU_NODE_PERIOD 3 /* Number of grace periods between delays. */ | |
37745d28 | 207 | |
4a298656 PM |
208 | /* |
209 | * Track the rcutorture test sequence number and the update version | |
210 | * number within a given test. The rcutorture_testseq is incremented | |
211 | * on every rcutorture module load and unload, so has an odd value | |
212 | * when a test is running. The rcutorture_vernum is set to zero | |
213 | * when rcutorture starts and is incremented on each rcutorture update. | |
214 | * These variables enable correlating rcutorture output with the | |
215 | * RCU tracing information. | |
216 | */ | |
217 | unsigned long rcutorture_testseq; | |
218 | unsigned long rcutorture_vernum; | |
219 | ||
0aa04b05 PM |
220 | /* |
221 | * Compute the mask of online CPUs for the specified rcu_node structure. | |
222 | * This will not be stable unless the rcu_node structure's ->lock is | |
223 | * held, but the bit corresponding to the current CPU will be stable | |
224 | * in most contexts. | |
225 | */ | |
226 | unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp) | |
227 | { | |
7d0ae808 | 228 | return READ_ONCE(rnp->qsmaskinitnext); |
0aa04b05 PM |
229 | } |
230 | ||
fc2219d4 | 231 | /* |
7d0ae808 | 232 | * Return true if an RCU grace period is in progress. The READ_ONCE()s |
fc2219d4 PM |
233 | * permit this function to be invoked without holding the root rcu_node |
234 | * structure's ->lock, but of course results can be subject to change. | |
235 | */ | |
236 | static int rcu_gp_in_progress(struct rcu_state *rsp) | |
237 | { | |
7d0ae808 | 238 | return READ_ONCE(rsp->completed) != READ_ONCE(rsp->gpnum); |
fc2219d4 PM |
239 | } |
240 | ||
b1f77b05 | 241 | /* |
d6714c22 | 242 | * Note a quiescent state. Because we do not need to know |
b1f77b05 | 243 | * how many quiescent states passed, just if there was at least |
d6714c22 | 244 | * one since the start of the grace period, this just sets a flag. |
e4cc1f22 | 245 | * The caller must have disabled preemption. |
b1f77b05 | 246 | */ |
284a8c93 | 247 | void rcu_sched_qs(void) |
b1f77b05 | 248 | { |
5b74c458 | 249 | if (__this_cpu_read(rcu_sched_data.cpu_no_qs.s)) { |
284a8c93 PM |
250 | trace_rcu_grace_period(TPS("rcu_sched"), |
251 | __this_cpu_read(rcu_sched_data.gpnum), | |
252 | TPS("cpuqs")); | |
5b74c458 | 253 | __this_cpu_write(rcu_sched_data.cpu_no_qs.b.norm, false); |
6587a23b PM |
254 | if (__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp)) { |
255 | __this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, false); | |
256 | rcu_report_exp_rdp(&rcu_sched_state, | |
257 | this_cpu_ptr(&rcu_sched_data), | |
258 | true); | |
259 | } | |
284a8c93 | 260 | } |
b1f77b05 IM |
261 | } |
262 | ||
284a8c93 | 263 | void rcu_bh_qs(void) |
b1f77b05 | 264 | { |
5b74c458 | 265 | if (__this_cpu_read(rcu_bh_data.cpu_no_qs.s)) { |
284a8c93 PM |
266 | trace_rcu_grace_period(TPS("rcu_bh"), |
267 | __this_cpu_read(rcu_bh_data.gpnum), | |
268 | TPS("cpuqs")); | |
5b74c458 | 269 | __this_cpu_write(rcu_bh_data.cpu_no_qs.b.norm, false); |
284a8c93 | 270 | } |
b1f77b05 | 271 | } |
64db4cff | 272 | |
4a81e832 PM |
273 | static DEFINE_PER_CPU(int, rcu_sched_qs_mask); |
274 | ||
275 | static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { | |
276 | .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, | |
277 | .dynticks = ATOMIC_INIT(1), | |
278 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE | |
279 | .dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE, | |
280 | .dynticks_idle = ATOMIC_INIT(1), | |
281 | #endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ | |
282 | }; | |
283 | ||
5cd37193 PM |
284 | DEFINE_PER_CPU_SHARED_ALIGNED(unsigned long, rcu_qs_ctr); |
285 | EXPORT_PER_CPU_SYMBOL_GPL(rcu_qs_ctr); | |
286 | ||
4a81e832 PM |
287 | /* |
288 | * Let the RCU core know that this CPU has gone through the scheduler, | |
289 | * which is a quiescent state. This is called when the need for a | |
290 | * quiescent state is urgent, so we burn an atomic operation and full | |
291 | * memory barriers to let the RCU core know about it, regardless of what | |
292 | * this CPU might (or might not) do in the near future. | |
293 | * | |
294 | * We inform the RCU core by emulating a zero-duration dyntick-idle | |
295 | * period, which we in turn do by incrementing the ->dynticks counter | |
296 | * by two. | |
297 | */ | |
298 | static void rcu_momentary_dyntick_idle(void) | |
299 | { | |
300 | unsigned long flags; | |
301 | struct rcu_data *rdp; | |
302 | struct rcu_dynticks *rdtp; | |
303 | int resched_mask; | |
304 | struct rcu_state *rsp; | |
305 | ||
306 | local_irq_save(flags); | |
307 | ||
308 | /* | |
309 | * Yes, we can lose flag-setting operations. This is OK, because | |
310 | * the flag will be set again after some delay. | |
311 | */ | |
312 | resched_mask = raw_cpu_read(rcu_sched_qs_mask); | |
313 | raw_cpu_write(rcu_sched_qs_mask, 0); | |
314 | ||
315 | /* Find the flavor that needs a quiescent state. */ | |
316 | for_each_rcu_flavor(rsp) { | |
317 | rdp = raw_cpu_ptr(rsp->rda); | |
318 | if (!(resched_mask & rsp->flavor_mask)) | |
319 | continue; | |
320 | smp_mb(); /* rcu_sched_qs_mask before cond_resched_completed. */ | |
7d0ae808 PM |
321 | if (READ_ONCE(rdp->mynode->completed) != |
322 | READ_ONCE(rdp->cond_resched_completed)) | |
4a81e832 PM |
323 | continue; |
324 | ||
325 | /* | |
326 | * Pretend to be momentarily idle for the quiescent state. | |
327 | * This allows the grace-period kthread to record the | |
328 | * quiescent state, with no need for this CPU to do anything | |
329 | * further. | |
330 | */ | |
331 | rdtp = this_cpu_ptr(&rcu_dynticks); | |
332 | smp_mb__before_atomic(); /* Earlier stuff before QS. */ | |
333 | atomic_add(2, &rdtp->dynticks); /* QS. */ | |
334 | smp_mb__after_atomic(); /* Later stuff after QS. */ | |
335 | break; | |
336 | } | |
337 | local_irq_restore(flags); | |
338 | } | |
339 | ||
25502a6c PM |
340 | /* |
341 | * Note a context switch. This is a quiescent state for RCU-sched, | |
342 | * and requires special handling for preemptible RCU. | |
e4cc1f22 | 343 | * The caller must have disabled preemption. |
25502a6c | 344 | */ |
38200cf2 | 345 | void rcu_note_context_switch(void) |
25502a6c | 346 | { |
f7f7bac9 | 347 | trace_rcu_utilization(TPS("Start context switch")); |
284a8c93 | 348 | rcu_sched_qs(); |
38200cf2 | 349 | rcu_preempt_note_context_switch(); |
4a81e832 PM |
350 | if (unlikely(raw_cpu_read(rcu_sched_qs_mask))) |
351 | rcu_momentary_dyntick_idle(); | |
f7f7bac9 | 352 | trace_rcu_utilization(TPS("End context switch")); |
25502a6c | 353 | } |
29ce8310 | 354 | EXPORT_SYMBOL_GPL(rcu_note_context_switch); |
25502a6c | 355 | |
5cd37193 | 356 | /* |
1925d196 | 357 | * Register a quiescent state for all RCU flavors. If there is an |
5cd37193 PM |
358 | * emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight |
359 | * dyntick-idle quiescent state visible to other CPUs (but only for those | |
1925d196 | 360 | * RCU flavors in desperate need of a quiescent state, which will normally |
5cd37193 PM |
361 | * be none of them). Either way, do a lightweight quiescent state for |
362 | * all RCU flavors. | |
363 | */ | |
364 | void rcu_all_qs(void) | |
365 | { | |
366 | if (unlikely(raw_cpu_read(rcu_sched_qs_mask))) | |
367 | rcu_momentary_dyntick_idle(); | |
368 | this_cpu_inc(rcu_qs_ctr); | |
369 | } | |
370 | EXPORT_SYMBOL_GPL(rcu_all_qs); | |
371 | ||
878d7439 ED |
372 | static long blimit = 10; /* Maximum callbacks per rcu_do_batch. */ |
373 | static long qhimark = 10000; /* If this many pending, ignore blimit. */ | |
374 | static long qlowmark = 100; /* Once only this many pending, use blimit. */ | |
64db4cff | 375 | |
878d7439 ED |
376 | module_param(blimit, long, 0444); |
377 | module_param(qhimark, long, 0444); | |
378 | module_param(qlowmark, long, 0444); | |
3d76c082 | 379 | |
026ad283 PM |
380 | static ulong jiffies_till_first_fqs = ULONG_MAX; |
381 | static ulong jiffies_till_next_fqs = ULONG_MAX; | |
d40011f6 PM |
382 | |
383 | module_param(jiffies_till_first_fqs, ulong, 0644); | |
384 | module_param(jiffies_till_next_fqs, ulong, 0644); | |
385 | ||
4a81e832 PM |
386 | /* |
387 | * How long the grace period must be before we start recruiting | |
388 | * quiescent-state help from rcu_note_context_switch(). | |
389 | */ | |
390 | static ulong jiffies_till_sched_qs = HZ / 20; | |
391 | module_param(jiffies_till_sched_qs, ulong, 0644); | |
392 | ||
48a7639c | 393 | static bool rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, |
910ee45d | 394 | struct rcu_data *rdp); |
217af2a2 PM |
395 | static void force_qs_rnp(struct rcu_state *rsp, |
396 | int (*f)(struct rcu_data *rsp, bool *isidle, | |
397 | unsigned long *maxj), | |
398 | bool *isidle, unsigned long *maxj); | |
4cdfc175 | 399 | static void force_quiescent_state(struct rcu_state *rsp); |
e3950ecd | 400 | static int rcu_pending(void); |
64db4cff PM |
401 | |
402 | /* | |
917963d0 | 403 | * Return the number of RCU batches started thus far for debug & stats. |
64db4cff | 404 | */ |
917963d0 PM |
405 | unsigned long rcu_batches_started(void) |
406 | { | |
407 | return rcu_state_p->gpnum; | |
408 | } | |
409 | EXPORT_SYMBOL_GPL(rcu_batches_started); | |
410 | ||
411 | /* | |
412 | * Return the number of RCU-sched batches started thus far for debug & stats. | |
64db4cff | 413 | */ |
917963d0 PM |
414 | unsigned long rcu_batches_started_sched(void) |
415 | { | |
416 | return rcu_sched_state.gpnum; | |
417 | } | |
418 | EXPORT_SYMBOL_GPL(rcu_batches_started_sched); | |
419 | ||
420 | /* | |
421 | * Return the number of RCU BH batches started thus far for debug & stats. | |
422 | */ | |
423 | unsigned long rcu_batches_started_bh(void) | |
424 | { | |
425 | return rcu_bh_state.gpnum; | |
426 | } | |
427 | EXPORT_SYMBOL_GPL(rcu_batches_started_bh); | |
428 | ||
429 | /* | |
430 | * Return the number of RCU batches completed thus far for debug & stats. | |
431 | */ | |
432 | unsigned long rcu_batches_completed(void) | |
433 | { | |
434 | return rcu_state_p->completed; | |
435 | } | |
436 | EXPORT_SYMBOL_GPL(rcu_batches_completed); | |
437 | ||
438 | /* | |
439 | * Return the number of RCU-sched batches completed thus far for debug & stats. | |
64db4cff | 440 | */ |
9733e4f0 | 441 | unsigned long rcu_batches_completed_sched(void) |
64db4cff | 442 | { |
d6714c22 | 443 | return rcu_sched_state.completed; |
64db4cff | 444 | } |
d6714c22 | 445 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
64db4cff PM |
446 | |
447 | /* | |
917963d0 | 448 | * Return the number of RCU BH batches completed thus far for debug & stats. |
64db4cff | 449 | */ |
9733e4f0 | 450 | unsigned long rcu_batches_completed_bh(void) |
64db4cff PM |
451 | { |
452 | return rcu_bh_state.completed; | |
453 | } | |
454 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
455 | ||
a381d757 ACB |
456 | /* |
457 | * Force a quiescent state. | |
458 | */ | |
459 | void rcu_force_quiescent_state(void) | |
460 | { | |
e534165b | 461 | force_quiescent_state(rcu_state_p); |
a381d757 ACB |
462 | } |
463 | EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); | |
464 | ||
bf66f18e PM |
465 | /* |
466 | * Force a quiescent state for RCU BH. | |
467 | */ | |
468 | void rcu_bh_force_quiescent_state(void) | |
469 | { | |
4cdfc175 | 470 | force_quiescent_state(&rcu_bh_state); |
bf66f18e PM |
471 | } |
472 | EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); | |
473 | ||
e7580f33 PM |
474 | /* |
475 | * Force a quiescent state for RCU-sched. | |
476 | */ | |
477 | void rcu_sched_force_quiescent_state(void) | |
478 | { | |
479 | force_quiescent_state(&rcu_sched_state); | |
480 | } | |
481 | EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); | |
482 | ||
afea227f PM |
483 | /* |
484 | * Show the state of the grace-period kthreads. | |
485 | */ | |
486 | void show_rcu_gp_kthreads(void) | |
487 | { | |
488 | struct rcu_state *rsp; | |
489 | ||
490 | for_each_rcu_flavor(rsp) { | |
491 | pr_info("%s: wait state: %d ->state: %#lx\n", | |
492 | rsp->name, rsp->gp_state, rsp->gp_kthread->state); | |
493 | /* sched_show_task(rsp->gp_kthread); */ | |
494 | } | |
495 | } | |
496 | EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads); | |
497 | ||
4a298656 PM |
498 | /* |
499 | * Record the number of times rcutorture tests have been initiated and | |
500 | * terminated. This information allows the debugfs tracing stats to be | |
501 | * correlated to the rcutorture messages, even when the rcutorture module | |
502 | * is being repeatedly loaded and unloaded. In other words, we cannot | |
503 | * store this state in rcutorture itself. | |
504 | */ | |
505 | void rcutorture_record_test_transition(void) | |
506 | { | |
507 | rcutorture_testseq++; | |
508 | rcutorture_vernum = 0; | |
509 | } | |
510 | EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); | |
511 | ||
ad0dc7f9 PM |
512 | /* |
513 | * Send along grace-period-related data for rcutorture diagnostics. | |
514 | */ | |
515 | void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, | |
516 | unsigned long *gpnum, unsigned long *completed) | |
517 | { | |
518 | struct rcu_state *rsp = NULL; | |
519 | ||
520 | switch (test_type) { | |
521 | case RCU_FLAVOR: | |
e534165b | 522 | rsp = rcu_state_p; |
ad0dc7f9 PM |
523 | break; |
524 | case RCU_BH_FLAVOR: | |
525 | rsp = &rcu_bh_state; | |
526 | break; | |
527 | case RCU_SCHED_FLAVOR: | |
528 | rsp = &rcu_sched_state; | |
529 | break; | |
530 | default: | |
531 | break; | |
532 | } | |
533 | if (rsp != NULL) { | |
7d0ae808 PM |
534 | *flags = READ_ONCE(rsp->gp_flags); |
535 | *gpnum = READ_ONCE(rsp->gpnum); | |
536 | *completed = READ_ONCE(rsp->completed); | |
ad0dc7f9 PM |
537 | return; |
538 | } | |
539 | *flags = 0; | |
540 | *gpnum = 0; | |
541 | *completed = 0; | |
542 | } | |
543 | EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); | |
544 | ||
4a298656 PM |
545 | /* |
546 | * Record the number of writer passes through the current rcutorture test. | |
547 | * This is also used to correlate debugfs tracing stats with the rcutorture | |
548 | * messages. | |
549 | */ | |
550 | void rcutorture_record_progress(unsigned long vernum) | |
551 | { | |
552 | rcutorture_vernum++; | |
553 | } | |
554 | EXPORT_SYMBOL_GPL(rcutorture_record_progress); | |
555 | ||
64db4cff PM |
556 | /* |
557 | * Does the CPU have callbacks ready to be invoked? | |
558 | */ | |
559 | static int | |
560 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) | |
561 | { | |
3fbfbf7a PM |
562 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL] && |
563 | rdp->nxttail[RCU_DONE_TAIL] != NULL; | |
64db4cff PM |
564 | } |
565 | ||
365187fb PM |
566 | /* |
567 | * Return the root node of the specified rcu_state structure. | |
568 | */ | |
569 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) | |
570 | { | |
571 | return &rsp->node[0]; | |
572 | } | |
573 | ||
574 | /* | |
575 | * Is there any need for future grace periods? | |
576 | * Interrupts must be disabled. If the caller does not hold the root | |
577 | * rnp_node structure's ->lock, the results are advisory only. | |
578 | */ | |
579 | static int rcu_future_needs_gp(struct rcu_state *rsp) | |
580 | { | |
581 | struct rcu_node *rnp = rcu_get_root(rsp); | |
7d0ae808 | 582 | int idx = (READ_ONCE(rnp->completed) + 1) & 0x1; |
365187fb PM |
583 | int *fp = &rnp->need_future_gp[idx]; |
584 | ||
7d0ae808 | 585 | return READ_ONCE(*fp); |
365187fb PM |
586 | } |
587 | ||
64db4cff | 588 | /* |
dc35c893 PM |
589 | * Does the current CPU require a not-yet-started grace period? |
590 | * The caller must have disabled interrupts to prevent races with | |
591 | * normal callback registry. | |
64db4cff PM |
592 | */ |
593 | static int | |
594 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) | |
595 | { | |
dc35c893 | 596 | int i; |
3fbfbf7a | 597 | |
dc35c893 PM |
598 | if (rcu_gp_in_progress(rsp)) |
599 | return 0; /* No, a grace period is already in progress. */ | |
365187fb | 600 | if (rcu_future_needs_gp(rsp)) |
34ed6246 | 601 | return 1; /* Yes, a no-CBs CPU needs one. */ |
dc35c893 PM |
602 | if (!rdp->nxttail[RCU_NEXT_TAIL]) |
603 | return 0; /* No, this is a no-CBs (or offline) CPU. */ | |
604 | if (*rdp->nxttail[RCU_NEXT_READY_TAIL]) | |
605 | return 1; /* Yes, this CPU has newly registered callbacks. */ | |
606 | for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) | |
607 | if (rdp->nxttail[i - 1] != rdp->nxttail[i] && | |
7d0ae808 | 608 | ULONG_CMP_LT(READ_ONCE(rsp->completed), |
dc35c893 PM |
609 | rdp->nxtcompleted[i])) |
610 | return 1; /* Yes, CBs for future grace period. */ | |
611 | return 0; /* No grace period needed. */ | |
64db4cff PM |
612 | } |
613 | ||
9b2e4f18 | 614 | /* |
adf5091e | 615 | * rcu_eqs_enter_common - current CPU is moving towards extended quiescent state |
9b2e4f18 PM |
616 | * |
617 | * If the new value of the ->dynticks_nesting counter now is zero, | |
618 | * we really have entered idle, and must do the appropriate accounting. | |
619 | * The caller must have disabled interrupts. | |
620 | */ | |
28ced795 | 621 | static void rcu_eqs_enter_common(long long oldval, bool user) |
9b2e4f18 | 622 | { |
96d3fd0d PM |
623 | struct rcu_state *rsp; |
624 | struct rcu_data *rdp; | |
28ced795 | 625 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
96d3fd0d | 626 | |
f7f7bac9 | 627 | trace_rcu_dyntick(TPS("Start"), oldval, rdtp->dynticks_nesting); |
1ce46ee5 PM |
628 | if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
629 | !user && !is_idle_task(current)) { | |
289828e6 PM |
630 | struct task_struct *idle __maybe_unused = |
631 | idle_task(smp_processor_id()); | |
0989cb46 | 632 | |
f7f7bac9 | 633 | trace_rcu_dyntick(TPS("Error on entry: not idle task"), oldval, 0); |
bf1304e9 | 634 | ftrace_dump(DUMP_ORIG); |
0989cb46 PM |
635 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
636 | current->pid, current->comm, | |
637 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 | 638 | } |
96d3fd0d PM |
639 | for_each_rcu_flavor(rsp) { |
640 | rdp = this_cpu_ptr(rsp->rda); | |
641 | do_nocb_deferred_wakeup(rdp); | |
642 | } | |
198bbf81 | 643 | rcu_prepare_for_idle(); |
9b2e4f18 | 644 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
4e857c58 | 645 | smp_mb__before_atomic(); /* See above. */ |
9b2e4f18 | 646 | atomic_inc(&rdtp->dynticks); |
4e857c58 | 647 | smp_mb__after_atomic(); /* Force ordering with next sojourn. */ |
1ce46ee5 PM |
648 | WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
649 | atomic_read(&rdtp->dynticks) & 0x1); | |
176f8f7a | 650 | rcu_dynticks_task_enter(); |
c44e2cdd PM |
651 | |
652 | /* | |
adf5091e | 653 | * It is illegal to enter an extended quiescent state while |
c44e2cdd PM |
654 | * in an RCU read-side critical section. |
655 | */ | |
f78f5b90 PM |
656 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_lock_map), |
657 | "Illegal idle entry in RCU read-side critical section."); | |
658 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map), | |
659 | "Illegal idle entry in RCU-bh read-side critical section."); | |
660 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_sched_lock_map), | |
661 | "Illegal idle entry in RCU-sched read-side critical section."); | |
9b2e4f18 | 662 | } |
64db4cff | 663 | |
adf5091e FW |
664 | /* |
665 | * Enter an RCU extended quiescent state, which can be either the | |
666 | * idle loop or adaptive-tickless usermode execution. | |
64db4cff | 667 | */ |
adf5091e | 668 | static void rcu_eqs_enter(bool user) |
64db4cff | 669 | { |
4145fa7f | 670 | long long oldval; |
64db4cff PM |
671 | struct rcu_dynticks *rdtp; |
672 | ||
c9d4b0af | 673 | rdtp = this_cpu_ptr(&rcu_dynticks); |
4145fa7f | 674 | oldval = rdtp->dynticks_nesting; |
1ce46ee5 PM |
675 | WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
676 | (oldval & DYNTICK_TASK_NEST_MASK) == 0); | |
3a592405 | 677 | if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) { |
29e37d81 | 678 | rdtp->dynticks_nesting = 0; |
28ced795 | 679 | rcu_eqs_enter_common(oldval, user); |
3a592405 | 680 | } else { |
29e37d81 | 681 | rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE; |
3a592405 | 682 | } |
64db4cff | 683 | } |
adf5091e FW |
684 | |
685 | /** | |
686 | * rcu_idle_enter - inform RCU that current CPU is entering idle | |
687 | * | |
688 | * Enter idle mode, in other words, -leave- the mode in which RCU | |
689 | * read-side critical sections can occur. (Though RCU read-side | |
690 | * critical sections can occur in irq handlers in idle, a possibility | |
691 | * handled by irq_enter() and irq_exit().) | |
692 | * | |
693 | * We crowbar the ->dynticks_nesting field to zero to allow for | |
694 | * the possibility of usermode upcalls having messed up our count | |
695 | * of interrupt nesting level during the prior busy period. | |
696 | */ | |
697 | void rcu_idle_enter(void) | |
698 | { | |
c5d900bf FW |
699 | unsigned long flags; |
700 | ||
701 | local_irq_save(flags); | |
cb349ca9 | 702 | rcu_eqs_enter(false); |
28ced795 | 703 | rcu_sysidle_enter(0); |
c5d900bf | 704 | local_irq_restore(flags); |
adf5091e | 705 | } |
8a2ecf47 | 706 | EXPORT_SYMBOL_GPL(rcu_idle_enter); |
64db4cff | 707 | |
d1ec4c34 | 708 | #ifdef CONFIG_NO_HZ_FULL |
adf5091e FW |
709 | /** |
710 | * rcu_user_enter - inform RCU that we are resuming userspace. | |
711 | * | |
712 | * Enter RCU idle mode right before resuming userspace. No use of RCU | |
713 | * is permitted between this call and rcu_user_exit(). This way the | |
714 | * CPU doesn't need to maintain the tick for RCU maintenance purposes | |
715 | * when the CPU runs in userspace. | |
716 | */ | |
717 | void rcu_user_enter(void) | |
718 | { | |
91d1aa43 | 719 | rcu_eqs_enter(1); |
adf5091e | 720 | } |
d1ec4c34 | 721 | #endif /* CONFIG_NO_HZ_FULL */ |
19dd1591 | 722 | |
9b2e4f18 PM |
723 | /** |
724 | * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle | |
725 | * | |
726 | * Exit from an interrupt handler, which might possibly result in entering | |
727 | * idle mode, in other words, leaving the mode in which read-side critical | |
728 | * sections can occur. | |
64db4cff | 729 | * |
9b2e4f18 PM |
730 | * This code assumes that the idle loop never does anything that might |
731 | * result in unbalanced calls to irq_enter() and irq_exit(). If your | |
732 | * architecture violates this assumption, RCU will give you what you | |
733 | * deserve, good and hard. But very infrequently and irreproducibly. | |
734 | * | |
735 | * Use things like work queues to work around this limitation. | |
736 | * | |
737 | * You have been warned. | |
64db4cff | 738 | */ |
9b2e4f18 | 739 | void rcu_irq_exit(void) |
64db4cff PM |
740 | { |
741 | unsigned long flags; | |
4145fa7f | 742 | long long oldval; |
64db4cff PM |
743 | struct rcu_dynticks *rdtp; |
744 | ||
745 | local_irq_save(flags); | |
c9d4b0af | 746 | rdtp = this_cpu_ptr(&rcu_dynticks); |
4145fa7f | 747 | oldval = rdtp->dynticks_nesting; |
9b2e4f18 | 748 | rdtp->dynticks_nesting--; |
1ce46ee5 PM |
749 | WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
750 | rdtp->dynticks_nesting < 0); | |
b6fc6020 | 751 | if (rdtp->dynticks_nesting) |
f7f7bac9 | 752 | trace_rcu_dyntick(TPS("--="), oldval, rdtp->dynticks_nesting); |
b6fc6020 | 753 | else |
28ced795 CL |
754 | rcu_eqs_enter_common(oldval, true); |
755 | rcu_sysidle_enter(1); | |
9b2e4f18 PM |
756 | local_irq_restore(flags); |
757 | } | |
758 | ||
759 | /* | |
adf5091e | 760 | * rcu_eqs_exit_common - current CPU moving away from extended quiescent state |
9b2e4f18 PM |
761 | * |
762 | * If the new value of the ->dynticks_nesting counter was previously zero, | |
763 | * we really have exited idle, and must do the appropriate accounting. | |
764 | * The caller must have disabled interrupts. | |
765 | */ | |
28ced795 | 766 | static void rcu_eqs_exit_common(long long oldval, int user) |
9b2e4f18 | 767 | { |
28ced795 CL |
768 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
769 | ||
176f8f7a | 770 | rcu_dynticks_task_exit(); |
4e857c58 | 771 | smp_mb__before_atomic(); /* Force ordering w/previous sojourn. */ |
23b5c8fa PM |
772 | atomic_inc(&rdtp->dynticks); |
773 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
4e857c58 | 774 | smp_mb__after_atomic(); /* See above. */ |
1ce46ee5 PM |
775 | WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
776 | !(atomic_read(&rdtp->dynticks) & 0x1)); | |
8fa7845d | 777 | rcu_cleanup_after_idle(); |
f7f7bac9 | 778 | trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting); |
1ce46ee5 PM |
779 | if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
780 | !user && !is_idle_task(current)) { | |
289828e6 PM |
781 | struct task_struct *idle __maybe_unused = |
782 | idle_task(smp_processor_id()); | |
0989cb46 | 783 | |
f7f7bac9 | 784 | trace_rcu_dyntick(TPS("Error on exit: not idle task"), |
4145fa7f | 785 | oldval, rdtp->dynticks_nesting); |
bf1304e9 | 786 | ftrace_dump(DUMP_ORIG); |
0989cb46 PM |
787 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
788 | current->pid, current->comm, | |
789 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 PM |
790 | } |
791 | } | |
792 | ||
adf5091e FW |
793 | /* |
794 | * Exit an RCU extended quiescent state, which can be either the | |
795 | * idle loop or adaptive-tickless usermode execution. | |
9b2e4f18 | 796 | */ |
adf5091e | 797 | static void rcu_eqs_exit(bool user) |
9b2e4f18 | 798 | { |
9b2e4f18 PM |
799 | struct rcu_dynticks *rdtp; |
800 | long long oldval; | |
801 | ||
c9d4b0af | 802 | rdtp = this_cpu_ptr(&rcu_dynticks); |
9b2e4f18 | 803 | oldval = rdtp->dynticks_nesting; |
1ce46ee5 | 804 | WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0); |
3a592405 | 805 | if (oldval & DYNTICK_TASK_NEST_MASK) { |
29e37d81 | 806 | rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE; |
3a592405 | 807 | } else { |
29e37d81 | 808 | rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
28ced795 | 809 | rcu_eqs_exit_common(oldval, user); |
3a592405 | 810 | } |
9b2e4f18 | 811 | } |
adf5091e FW |
812 | |
813 | /** | |
814 | * rcu_idle_exit - inform RCU that current CPU is leaving idle | |
815 | * | |
816 | * Exit idle mode, in other words, -enter- the mode in which RCU | |
817 | * read-side critical sections can occur. | |
818 | * | |
819 | * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to | |
820 | * allow for the possibility of usermode upcalls messing up our count | |
821 | * of interrupt nesting level during the busy period that is just | |
822 | * now starting. | |
823 | */ | |
824 | void rcu_idle_exit(void) | |
825 | { | |
c5d900bf FW |
826 | unsigned long flags; |
827 | ||
828 | local_irq_save(flags); | |
cb349ca9 | 829 | rcu_eqs_exit(false); |
28ced795 | 830 | rcu_sysidle_exit(0); |
c5d900bf | 831 | local_irq_restore(flags); |
adf5091e | 832 | } |
8a2ecf47 | 833 | EXPORT_SYMBOL_GPL(rcu_idle_exit); |
9b2e4f18 | 834 | |
d1ec4c34 | 835 | #ifdef CONFIG_NO_HZ_FULL |
adf5091e FW |
836 | /** |
837 | * rcu_user_exit - inform RCU that we are exiting userspace. | |
838 | * | |
839 | * Exit RCU idle mode while entering the kernel because it can | |
840 | * run a RCU read side critical section anytime. | |
841 | */ | |
842 | void rcu_user_exit(void) | |
843 | { | |
91d1aa43 | 844 | rcu_eqs_exit(1); |
adf5091e | 845 | } |
d1ec4c34 | 846 | #endif /* CONFIG_NO_HZ_FULL */ |
19dd1591 | 847 | |
9b2e4f18 PM |
848 | /** |
849 | * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle | |
850 | * | |
851 | * Enter an interrupt handler, which might possibly result in exiting | |
852 | * idle mode, in other words, entering the mode in which read-side critical | |
853 | * sections can occur. | |
854 | * | |
855 | * Note that the Linux kernel is fully capable of entering an interrupt | |
856 | * handler that it never exits, for example when doing upcalls to | |
857 | * user mode! This code assumes that the idle loop never does upcalls to | |
858 | * user mode. If your architecture does do upcalls from the idle loop (or | |
859 | * does anything else that results in unbalanced calls to the irq_enter() | |
860 | * and irq_exit() functions), RCU will give you what you deserve, good | |
861 | * and hard. But very infrequently and irreproducibly. | |
862 | * | |
863 | * Use things like work queues to work around this limitation. | |
864 | * | |
865 | * You have been warned. | |
866 | */ | |
867 | void rcu_irq_enter(void) | |
868 | { | |
869 | unsigned long flags; | |
870 | struct rcu_dynticks *rdtp; | |
871 | long long oldval; | |
872 | ||
873 | local_irq_save(flags); | |
c9d4b0af | 874 | rdtp = this_cpu_ptr(&rcu_dynticks); |
9b2e4f18 PM |
875 | oldval = rdtp->dynticks_nesting; |
876 | rdtp->dynticks_nesting++; | |
1ce46ee5 PM |
877 | WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
878 | rdtp->dynticks_nesting == 0); | |
b6fc6020 | 879 | if (oldval) |
f7f7bac9 | 880 | trace_rcu_dyntick(TPS("++="), oldval, rdtp->dynticks_nesting); |
b6fc6020 | 881 | else |
28ced795 CL |
882 | rcu_eqs_exit_common(oldval, true); |
883 | rcu_sysidle_exit(1); | |
64db4cff | 884 | local_irq_restore(flags); |
64db4cff PM |
885 | } |
886 | ||
887 | /** | |
888 | * rcu_nmi_enter - inform RCU of entry to NMI context | |
889 | * | |
734d1680 PM |
890 | * If the CPU was idle from RCU's viewpoint, update rdtp->dynticks and |
891 | * rdtp->dynticks_nmi_nesting to let the RCU grace-period handling know | |
892 | * that the CPU is active. This implementation permits nested NMIs, as | |
893 | * long as the nesting level does not overflow an int. (You will probably | |
894 | * run out of stack space first.) | |
64db4cff PM |
895 | */ |
896 | void rcu_nmi_enter(void) | |
897 | { | |
c9d4b0af | 898 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
734d1680 | 899 | int incby = 2; |
64db4cff | 900 | |
734d1680 PM |
901 | /* Complain about underflow. */ |
902 | WARN_ON_ONCE(rdtp->dynticks_nmi_nesting < 0); | |
903 | ||
904 | /* | |
905 | * If idle from RCU viewpoint, atomically increment ->dynticks | |
906 | * to mark non-idle and increment ->dynticks_nmi_nesting by one. | |
907 | * Otherwise, increment ->dynticks_nmi_nesting by two. This means | |
908 | * if ->dynticks_nmi_nesting is equal to one, we are guaranteed | |
909 | * to be in the outermost NMI handler that interrupted an RCU-idle | |
910 | * period (observation due to Andy Lutomirski). | |
911 | */ | |
912 | if (!(atomic_read(&rdtp->dynticks) & 0x1)) { | |
913 | smp_mb__before_atomic(); /* Force delay from prior write. */ | |
914 | atomic_inc(&rdtp->dynticks); | |
915 | /* atomic_inc() before later RCU read-side crit sects */ | |
916 | smp_mb__after_atomic(); /* See above. */ | |
917 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
918 | incby = 1; | |
919 | } | |
920 | rdtp->dynticks_nmi_nesting += incby; | |
921 | barrier(); | |
64db4cff PM |
922 | } |
923 | ||
924 | /** | |
925 | * rcu_nmi_exit - inform RCU of exit from NMI context | |
926 | * | |
734d1680 PM |
927 | * If we are returning from the outermost NMI handler that interrupted an |
928 | * RCU-idle period, update rdtp->dynticks and rdtp->dynticks_nmi_nesting | |
929 | * to let the RCU grace-period handling know that the CPU is back to | |
930 | * being RCU-idle. | |
64db4cff PM |
931 | */ |
932 | void rcu_nmi_exit(void) | |
933 | { | |
c9d4b0af | 934 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
64db4cff | 935 | |
734d1680 PM |
936 | /* |
937 | * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks. | |
938 | * (We are exiting an NMI handler, so RCU better be paying attention | |
939 | * to us!) | |
940 | */ | |
941 | WARN_ON_ONCE(rdtp->dynticks_nmi_nesting <= 0); | |
942 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
943 | ||
944 | /* | |
945 | * If the nesting level is not 1, the CPU wasn't RCU-idle, so | |
946 | * leave it in non-RCU-idle state. | |
947 | */ | |
948 | if (rdtp->dynticks_nmi_nesting != 1) { | |
949 | rdtp->dynticks_nmi_nesting -= 2; | |
64db4cff | 950 | return; |
734d1680 PM |
951 | } |
952 | ||
953 | /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */ | |
954 | rdtp->dynticks_nmi_nesting = 0; | |
23b5c8fa | 955 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
4e857c58 | 956 | smp_mb__before_atomic(); /* See above. */ |
23b5c8fa | 957 | atomic_inc(&rdtp->dynticks); |
4e857c58 | 958 | smp_mb__after_atomic(); /* Force delay to next write. */ |
23b5c8fa | 959 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); |
64db4cff PM |
960 | } |
961 | ||
962 | /** | |
5c173eb8 PM |
963 | * __rcu_is_watching - are RCU read-side critical sections safe? |
964 | * | |
965 | * Return true if RCU is watching the running CPU, which means that | |
966 | * this CPU can safely enter RCU read-side critical sections. Unlike | |
967 | * rcu_is_watching(), the caller of __rcu_is_watching() must have at | |
968 | * least disabled preemption. | |
969 | */ | |
9418fb20 | 970 | bool notrace __rcu_is_watching(void) |
5c173eb8 PM |
971 | { |
972 | return atomic_read(this_cpu_ptr(&rcu_dynticks.dynticks)) & 0x1; | |
973 | } | |
974 | ||
975 | /** | |
976 | * rcu_is_watching - see if RCU thinks that the current CPU is idle | |
64db4cff | 977 | * |
9b2e4f18 | 978 | * If the current CPU is in its idle loop and is neither in an interrupt |
34240697 | 979 | * or NMI handler, return true. |
64db4cff | 980 | */ |
9418fb20 | 981 | bool notrace rcu_is_watching(void) |
64db4cff | 982 | { |
f534ed1f | 983 | bool ret; |
34240697 | 984 | |
46f00d18 | 985 | preempt_disable_notrace(); |
5c173eb8 | 986 | ret = __rcu_is_watching(); |
46f00d18 | 987 | preempt_enable_notrace(); |
34240697 | 988 | return ret; |
64db4cff | 989 | } |
5c173eb8 | 990 | EXPORT_SYMBOL_GPL(rcu_is_watching); |
64db4cff | 991 | |
62fde6ed | 992 | #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) |
c0d6d01b PM |
993 | |
994 | /* | |
995 | * Is the current CPU online? Disable preemption to avoid false positives | |
996 | * that could otherwise happen due to the current CPU number being sampled, | |
997 | * this task being preempted, its old CPU being taken offline, resuming | |
998 | * on some other CPU, then determining that its old CPU is now offline. | |
999 | * It is OK to use RCU on an offline processor during initial boot, hence | |
2036d94a PM |
1000 | * the check for rcu_scheduler_fully_active. Note also that it is OK |
1001 | * for a CPU coming online to use RCU for one jiffy prior to marking itself | |
1002 | * online in the cpu_online_mask. Similarly, it is OK for a CPU going | |
1003 | * offline to continue to use RCU for one jiffy after marking itself | |
1004 | * offline in the cpu_online_mask. This leniency is necessary given the | |
1005 | * non-atomic nature of the online and offline processing, for example, | |
1006 | * the fact that a CPU enters the scheduler after completing the CPU_DYING | |
1007 | * notifiers. | |
1008 | * | |
1009 | * This is also why RCU internally marks CPUs online during the | |
1010 | * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase. | |
c0d6d01b PM |
1011 | * |
1012 | * Disable checking if in an NMI handler because we cannot safely report | |
1013 | * errors from NMI handlers anyway. | |
1014 | */ | |
1015 | bool rcu_lockdep_current_cpu_online(void) | |
1016 | { | |
2036d94a PM |
1017 | struct rcu_data *rdp; |
1018 | struct rcu_node *rnp; | |
c0d6d01b PM |
1019 | bool ret; |
1020 | ||
1021 | if (in_nmi()) | |
f6f7ee9a | 1022 | return true; |
c0d6d01b | 1023 | preempt_disable(); |
c9d4b0af | 1024 | rdp = this_cpu_ptr(&rcu_sched_data); |
2036d94a | 1025 | rnp = rdp->mynode; |
0aa04b05 | 1026 | ret = (rdp->grpmask & rcu_rnp_online_cpus(rnp)) || |
c0d6d01b PM |
1027 | !rcu_scheduler_fully_active; |
1028 | preempt_enable(); | |
1029 | return ret; | |
1030 | } | |
1031 | EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); | |
1032 | ||
62fde6ed | 1033 | #endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */ |
9b2e4f18 | 1034 | |
64db4cff | 1035 | /** |
9b2e4f18 | 1036 | * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle |
64db4cff | 1037 | * |
9b2e4f18 PM |
1038 | * If the current CPU is idle or running at a first-level (not nested) |
1039 | * interrupt from idle, return true. The caller must have at least | |
1040 | * disabled preemption. | |
64db4cff | 1041 | */ |
62e3cb14 | 1042 | static int rcu_is_cpu_rrupt_from_idle(void) |
64db4cff | 1043 | { |
c9d4b0af | 1044 | return __this_cpu_read(rcu_dynticks.dynticks_nesting) <= 1; |
64db4cff PM |
1045 | } |
1046 | ||
64db4cff PM |
1047 | /* |
1048 | * Snapshot the specified CPU's dynticks counter so that we can later | |
1049 | * credit them with an implicit quiescent state. Return 1 if this CPU | |
1eba8f84 | 1050 | * is in dynticks idle mode, which is an extended quiescent state. |
64db4cff | 1051 | */ |
217af2a2 PM |
1052 | static int dyntick_save_progress_counter(struct rcu_data *rdp, |
1053 | bool *isidle, unsigned long *maxj) | |
64db4cff | 1054 | { |
23b5c8fa | 1055 | rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); |
0edd1b17 | 1056 | rcu_sysidle_check_cpu(rdp, isidle, maxj); |
7941dbde ACB |
1057 | if ((rdp->dynticks_snap & 0x1) == 0) { |
1058 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti")); | |
1059 | return 1; | |
1060 | } else { | |
7d0ae808 | 1061 | if (ULONG_CMP_LT(READ_ONCE(rdp->gpnum) + ULONG_MAX / 4, |
e3663b10 | 1062 | rdp->mynode->gpnum)) |
7d0ae808 | 1063 | WRITE_ONCE(rdp->gpwrap, true); |
7941dbde ACB |
1064 | return 0; |
1065 | } | |
64db4cff PM |
1066 | } |
1067 | ||
1068 | /* | |
1069 | * Return true if the specified CPU has passed through a quiescent | |
1070 | * state by virtue of being in or having passed through an dynticks | |
1071 | * idle state since the last call to dyntick_save_progress_counter() | |
a82dcc76 | 1072 | * for this same CPU, or by virtue of having been offline. |
64db4cff | 1073 | */ |
217af2a2 PM |
1074 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, |
1075 | bool *isidle, unsigned long *maxj) | |
64db4cff | 1076 | { |
7eb4f455 | 1077 | unsigned int curr; |
4a81e832 | 1078 | int *rcrmp; |
7eb4f455 | 1079 | unsigned int snap; |
64db4cff | 1080 | |
7eb4f455 PM |
1081 | curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks); |
1082 | snap = (unsigned int)rdp->dynticks_snap; | |
64db4cff PM |
1083 | |
1084 | /* | |
1085 | * If the CPU passed through or entered a dynticks idle phase with | |
1086 | * no active irq/NMI handlers, then we can safely pretend that the CPU | |
1087 | * already acknowledged the request to pass through a quiescent | |
1088 | * state. Either way, that CPU cannot possibly be in an RCU | |
1089 | * read-side critical section that started before the beginning | |
1090 | * of the current RCU grace period. | |
1091 | */ | |
7eb4f455 | 1092 | if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) { |
f7f7bac9 | 1093 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti")); |
64db4cff PM |
1094 | rdp->dynticks_fqs++; |
1095 | return 1; | |
1096 | } | |
1097 | ||
a82dcc76 PM |
1098 | /* |
1099 | * Check for the CPU being offline, but only if the grace period | |
1100 | * is old enough. We don't need to worry about the CPU changing | |
1101 | * state: If we see it offline even once, it has been through a | |
1102 | * quiescent state. | |
1103 | * | |
1104 | * The reason for insisting that the grace period be at least | |
1105 | * one jiffy old is that CPUs that are not quite online and that | |
1106 | * have just gone offline can still execute RCU read-side critical | |
1107 | * sections. | |
1108 | */ | |
1109 | if (ULONG_CMP_GE(rdp->rsp->gp_start + 2, jiffies)) | |
1110 | return 0; /* Grace period is not old enough. */ | |
1111 | barrier(); | |
1112 | if (cpu_is_offline(rdp->cpu)) { | |
f7f7bac9 | 1113 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("ofl")); |
a82dcc76 PM |
1114 | rdp->offline_fqs++; |
1115 | return 1; | |
1116 | } | |
65d798f0 PM |
1117 | |
1118 | /* | |
4a81e832 PM |
1119 | * A CPU running for an extended time within the kernel can |
1120 | * delay RCU grace periods. When the CPU is in NO_HZ_FULL mode, | |
1121 | * even context-switching back and forth between a pair of | |
1122 | * in-kernel CPU-bound tasks cannot advance grace periods. | |
1123 | * So if the grace period is old enough, make the CPU pay attention. | |
1124 | * Note that the unsynchronized assignments to the per-CPU | |
1125 | * rcu_sched_qs_mask variable are safe. Yes, setting of | |
1126 | * bits can be lost, but they will be set again on the next | |
1127 | * force-quiescent-state pass. So lost bit sets do not result | |
1128 | * in incorrect behavior, merely in a grace period lasting | |
1129 | * a few jiffies longer than it might otherwise. Because | |
1130 | * there are at most four threads involved, and because the | |
1131 | * updates are only once every few jiffies, the probability of | |
1132 | * lossage (and thus of slight grace-period extension) is | |
1133 | * quite low. | |
1134 | * | |
1135 | * Note that if the jiffies_till_sched_qs boot/sysfs parameter | |
1136 | * is set too high, we override with half of the RCU CPU stall | |
1137 | * warning delay. | |
6193c76a | 1138 | */ |
4a81e832 PM |
1139 | rcrmp = &per_cpu(rcu_sched_qs_mask, rdp->cpu); |
1140 | if (ULONG_CMP_GE(jiffies, | |
1141 | rdp->rsp->gp_start + jiffies_till_sched_qs) || | |
cb1e78cf | 1142 | ULONG_CMP_GE(jiffies, rdp->rsp->jiffies_resched)) { |
7d0ae808 PM |
1143 | if (!(READ_ONCE(*rcrmp) & rdp->rsp->flavor_mask)) { |
1144 | WRITE_ONCE(rdp->cond_resched_completed, | |
1145 | READ_ONCE(rdp->mynode->completed)); | |
4a81e832 | 1146 | smp_mb(); /* ->cond_resched_completed before *rcrmp. */ |
7d0ae808 PM |
1147 | WRITE_ONCE(*rcrmp, |
1148 | READ_ONCE(*rcrmp) + rdp->rsp->flavor_mask); | |
4a81e832 PM |
1149 | resched_cpu(rdp->cpu); /* Force CPU into scheduler. */ |
1150 | rdp->rsp->jiffies_resched += 5; /* Enable beating. */ | |
1151 | } else if (ULONG_CMP_GE(jiffies, rdp->rsp->jiffies_resched)) { | |
1152 | /* Time to beat on that CPU again! */ | |
1153 | resched_cpu(rdp->cpu); /* Force CPU into scheduler. */ | |
1154 | rdp->rsp->jiffies_resched += 5; /* Re-enable beating. */ | |
1155 | } | |
6193c76a PM |
1156 | } |
1157 | ||
a82dcc76 | 1158 | return 0; |
64db4cff PM |
1159 | } |
1160 | ||
64db4cff PM |
1161 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
1162 | { | |
cb1e78cf | 1163 | unsigned long j = jiffies; |
6193c76a | 1164 | unsigned long j1; |
26cdfedf PM |
1165 | |
1166 | rsp->gp_start = j; | |
1167 | smp_wmb(); /* Record start time before stall time. */ | |
6193c76a | 1168 | j1 = rcu_jiffies_till_stall_check(); |
7d0ae808 | 1169 | WRITE_ONCE(rsp->jiffies_stall, j + j1); |
6193c76a | 1170 | rsp->jiffies_resched = j + j1 / 2; |
7d0ae808 | 1171 | rsp->n_force_qs_gpstart = READ_ONCE(rsp->n_force_qs); |
64db4cff PM |
1172 | } |
1173 | ||
fb81a44b PM |
1174 | /* |
1175 | * Complain about starvation of grace-period kthread. | |
1176 | */ | |
1177 | static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp) | |
1178 | { | |
1179 | unsigned long gpa; | |
1180 | unsigned long j; | |
1181 | ||
1182 | j = jiffies; | |
7d0ae808 | 1183 | gpa = READ_ONCE(rsp->gp_activity); |
fb81a44b | 1184 | if (j - gpa > 2 * HZ) |
319362c9 | 1185 | pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x s%d ->state=%#lx\n", |
81e701e4 | 1186 | rsp->name, j - gpa, |
319362c9 PM |
1187 | rsp->gpnum, rsp->completed, |
1188 | rsp->gp_flags, rsp->gp_state, | |
1189 | rsp->gp_kthread ? rsp->gp_kthread->state : 0); | |
64db4cff PM |
1190 | } |
1191 | ||
b637a328 | 1192 | /* |
bc1dce51 | 1193 | * Dump stacks of all tasks running on stalled CPUs. |
b637a328 PM |
1194 | */ |
1195 | static void rcu_dump_cpu_stacks(struct rcu_state *rsp) | |
1196 | { | |
1197 | int cpu; | |
1198 | unsigned long flags; | |
1199 | struct rcu_node *rnp; | |
1200 | ||
1201 | rcu_for_each_leaf_node(rsp, rnp) { | |
1202 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
1203 | if (rnp->qsmask != 0) { | |
1204 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) | |
1205 | if (rnp->qsmask & (1UL << cpu)) | |
1206 | dump_cpu_task(rnp->grplo + cpu); | |
1207 | } | |
1208 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1209 | } | |
1210 | } | |
1211 | ||
6ccd2ecd | 1212 | static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum) |
64db4cff PM |
1213 | { |
1214 | int cpu; | |
1215 | long delta; | |
1216 | unsigned long flags; | |
6ccd2ecd PM |
1217 | unsigned long gpa; |
1218 | unsigned long j; | |
285fe294 | 1219 | int ndetected = 0; |
64db4cff | 1220 | struct rcu_node *rnp = rcu_get_root(rsp); |
53bb857c | 1221 | long totqlen = 0; |
64db4cff PM |
1222 | |
1223 | /* Only let one CPU complain about others per time interval. */ | |
1224 | ||
1304afb2 | 1225 | raw_spin_lock_irqsave(&rnp->lock, flags); |
7d0ae808 | 1226 | delta = jiffies - READ_ONCE(rsp->jiffies_stall); |
fc2219d4 | 1227 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
1304afb2 | 1228 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1229 | return; |
1230 | } | |
7d0ae808 PM |
1231 | WRITE_ONCE(rsp->jiffies_stall, |
1232 | jiffies + 3 * rcu_jiffies_till_stall_check() + 3); | |
1304afb2 | 1233 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 1234 | |
8cdd32a9 PM |
1235 | /* |
1236 | * OK, time to rat on our buddy... | |
1237 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
1238 | * RCU CPU stall warnings. | |
1239 | */ | |
d7f3e207 | 1240 | pr_err("INFO: %s detected stalls on CPUs/tasks:", |
4300aa64 | 1241 | rsp->name); |
a858af28 | 1242 | print_cpu_stall_info_begin(); |
a0b6c9a7 | 1243 | rcu_for_each_leaf_node(rsp, rnp) { |
3acd9eb3 | 1244 | raw_spin_lock_irqsave(&rnp->lock, flags); |
9bc8b558 | 1245 | ndetected += rcu_print_task_stall(rnp); |
c8020a67 PM |
1246 | if (rnp->qsmask != 0) { |
1247 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) | |
1248 | if (rnp->qsmask & (1UL << cpu)) { | |
1249 | print_cpu_stall_info(rsp, | |
1250 | rnp->grplo + cpu); | |
1251 | ndetected++; | |
1252 | } | |
1253 | } | |
3acd9eb3 | 1254 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 1255 | } |
a858af28 | 1256 | |
a858af28 | 1257 | print_cpu_stall_info_end(); |
53bb857c PM |
1258 | for_each_possible_cpu(cpu) |
1259 | totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen; | |
83ebe63e | 1260 | pr_cont("(detected by %d, t=%ld jiffies, g=%ld, c=%ld, q=%lu)\n", |
eee05882 | 1261 | smp_processor_id(), (long)(jiffies - rsp->gp_start), |
83ebe63e | 1262 | (long)rsp->gpnum, (long)rsp->completed, totqlen); |
6ccd2ecd | 1263 | if (ndetected) { |
b637a328 | 1264 | rcu_dump_cpu_stacks(rsp); |
6ccd2ecd | 1265 | } else { |
7d0ae808 PM |
1266 | if (READ_ONCE(rsp->gpnum) != gpnum || |
1267 | READ_ONCE(rsp->completed) == gpnum) { | |
6ccd2ecd PM |
1268 | pr_err("INFO: Stall ended before state dump start\n"); |
1269 | } else { | |
1270 | j = jiffies; | |
7d0ae808 | 1271 | gpa = READ_ONCE(rsp->gp_activity); |
237a0f21 | 1272 | pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n", |
6ccd2ecd | 1273 | rsp->name, j - gpa, j, gpa, |
237a0f21 PM |
1274 | jiffies_till_next_fqs, |
1275 | rcu_get_root(rsp)->qsmask); | |
6ccd2ecd PM |
1276 | /* In this case, the current CPU might be at fault. */ |
1277 | sched_show_task(current); | |
1278 | } | |
1279 | } | |
c1dc0b9c | 1280 | |
4cdfc175 | 1281 | /* Complain about tasks blocking the grace period. */ |
1ed509a2 PM |
1282 | rcu_print_detail_task_stall(rsp); |
1283 | ||
fb81a44b PM |
1284 | rcu_check_gp_kthread_starvation(rsp); |
1285 | ||
4cdfc175 | 1286 | force_quiescent_state(rsp); /* Kick them all. */ |
64db4cff PM |
1287 | } |
1288 | ||
1289 | static void print_cpu_stall(struct rcu_state *rsp) | |
1290 | { | |
53bb857c | 1291 | int cpu; |
64db4cff PM |
1292 | unsigned long flags; |
1293 | struct rcu_node *rnp = rcu_get_root(rsp); | |
53bb857c | 1294 | long totqlen = 0; |
64db4cff | 1295 | |
8cdd32a9 PM |
1296 | /* |
1297 | * OK, time to rat on ourselves... | |
1298 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
1299 | * RCU CPU stall warnings. | |
1300 | */ | |
d7f3e207 | 1301 | pr_err("INFO: %s self-detected stall on CPU", rsp->name); |
a858af28 PM |
1302 | print_cpu_stall_info_begin(); |
1303 | print_cpu_stall_info(rsp, smp_processor_id()); | |
1304 | print_cpu_stall_info_end(); | |
53bb857c PM |
1305 | for_each_possible_cpu(cpu) |
1306 | totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen; | |
83ebe63e PM |
1307 | pr_cont(" (t=%lu jiffies g=%ld c=%ld q=%lu)\n", |
1308 | jiffies - rsp->gp_start, | |
1309 | (long)rsp->gpnum, (long)rsp->completed, totqlen); | |
fb81a44b PM |
1310 | |
1311 | rcu_check_gp_kthread_starvation(rsp); | |
1312 | ||
bc1dce51 | 1313 | rcu_dump_cpu_stacks(rsp); |
c1dc0b9c | 1314 | |
1304afb2 | 1315 | raw_spin_lock_irqsave(&rnp->lock, flags); |
7d0ae808 PM |
1316 | if (ULONG_CMP_GE(jiffies, READ_ONCE(rsp->jiffies_stall))) |
1317 | WRITE_ONCE(rsp->jiffies_stall, | |
1318 | jiffies + 3 * rcu_jiffies_till_stall_check() + 3); | |
1304afb2 | 1319 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c1dc0b9c | 1320 | |
b021fe3e PZ |
1321 | /* |
1322 | * Attempt to revive the RCU machinery by forcing a context switch. | |
1323 | * | |
1324 | * A context switch would normally allow the RCU state machine to make | |
1325 | * progress and it could be we're stuck in kernel space without context | |
1326 | * switches for an entirely unreasonable amount of time. | |
1327 | */ | |
1328 | resched_cpu(smp_processor_id()); | |
64db4cff PM |
1329 | } |
1330 | ||
1331 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
1332 | { | |
26cdfedf PM |
1333 | unsigned long completed; |
1334 | unsigned long gpnum; | |
1335 | unsigned long gps; | |
bad6e139 PM |
1336 | unsigned long j; |
1337 | unsigned long js; | |
64db4cff PM |
1338 | struct rcu_node *rnp; |
1339 | ||
26cdfedf | 1340 | if (rcu_cpu_stall_suppress || !rcu_gp_in_progress(rsp)) |
c68de209 | 1341 | return; |
cb1e78cf | 1342 | j = jiffies; |
26cdfedf PM |
1343 | |
1344 | /* | |
1345 | * Lots of memory barriers to reject false positives. | |
1346 | * | |
1347 | * The idea is to pick up rsp->gpnum, then rsp->jiffies_stall, | |
1348 | * then rsp->gp_start, and finally rsp->completed. These values | |
1349 | * are updated in the opposite order with memory barriers (or | |
1350 | * equivalent) during grace-period initialization and cleanup. | |
1351 | * Now, a false positive can occur if we get an new value of | |
1352 | * rsp->gp_start and a old value of rsp->jiffies_stall. But given | |
1353 | * the memory barriers, the only way that this can happen is if one | |
1354 | * grace period ends and another starts between these two fetches. | |
1355 | * Detect this by comparing rsp->completed with the previous fetch | |
1356 | * from rsp->gpnum. | |
1357 | * | |
1358 | * Given this check, comparisons of jiffies, rsp->jiffies_stall, | |
1359 | * and rsp->gp_start suffice to forestall false positives. | |
1360 | */ | |
7d0ae808 | 1361 | gpnum = READ_ONCE(rsp->gpnum); |
26cdfedf | 1362 | smp_rmb(); /* Pick up ->gpnum first... */ |
7d0ae808 | 1363 | js = READ_ONCE(rsp->jiffies_stall); |
26cdfedf | 1364 | smp_rmb(); /* ...then ->jiffies_stall before the rest... */ |
7d0ae808 | 1365 | gps = READ_ONCE(rsp->gp_start); |
26cdfedf | 1366 | smp_rmb(); /* ...and finally ->gp_start before ->completed. */ |
7d0ae808 | 1367 | completed = READ_ONCE(rsp->completed); |
26cdfedf PM |
1368 | if (ULONG_CMP_GE(completed, gpnum) || |
1369 | ULONG_CMP_LT(j, js) || | |
1370 | ULONG_CMP_GE(gps, js)) | |
1371 | return; /* No stall or GP completed since entering function. */ | |
64db4cff | 1372 | rnp = rdp->mynode; |
c96ea7cf | 1373 | if (rcu_gp_in_progress(rsp) && |
7d0ae808 | 1374 | (READ_ONCE(rnp->qsmask) & rdp->grpmask)) { |
64db4cff PM |
1375 | |
1376 | /* We haven't checked in, so go dump stack. */ | |
1377 | print_cpu_stall(rsp); | |
1378 | ||
bad6e139 PM |
1379 | } else if (rcu_gp_in_progress(rsp) && |
1380 | ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) { | |
64db4cff | 1381 | |
bad6e139 | 1382 | /* They had a few time units to dump stack, so complain. */ |
6ccd2ecd | 1383 | print_other_cpu_stall(rsp, gpnum); |
64db4cff PM |
1384 | } |
1385 | } | |
1386 | ||
53d84e00 PM |
1387 | /** |
1388 | * rcu_cpu_stall_reset - prevent further stall warnings in current grace period | |
1389 | * | |
1390 | * Set the stall-warning timeout way off into the future, thus preventing | |
1391 | * any RCU CPU stall-warning messages from appearing in the current set of | |
1392 | * RCU grace periods. | |
1393 | * | |
1394 | * The caller must disable hard irqs. | |
1395 | */ | |
1396 | void rcu_cpu_stall_reset(void) | |
1397 | { | |
6ce75a23 PM |
1398 | struct rcu_state *rsp; |
1399 | ||
1400 | for_each_rcu_flavor(rsp) | |
7d0ae808 | 1401 | WRITE_ONCE(rsp->jiffies_stall, jiffies + ULONG_MAX / 2); |
53d84e00 PM |
1402 | } |
1403 | ||
3f5d3ea6 | 1404 | /* |
d3f3f3f2 PM |
1405 | * Initialize the specified rcu_data structure's default callback list |
1406 | * to empty. The default callback list is the one that is not used by | |
1407 | * no-callbacks CPUs. | |
3f5d3ea6 | 1408 | */ |
d3f3f3f2 | 1409 | static void init_default_callback_list(struct rcu_data *rdp) |
3f5d3ea6 PM |
1410 | { |
1411 | int i; | |
1412 | ||
1413 | rdp->nxtlist = NULL; | |
1414 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
1415 | rdp->nxttail[i] = &rdp->nxtlist; | |
1416 | } | |
1417 | ||
d3f3f3f2 PM |
1418 | /* |
1419 | * Initialize the specified rcu_data structure's callback list to empty. | |
1420 | */ | |
1421 | static void init_callback_list(struct rcu_data *rdp) | |
1422 | { | |
1423 | if (init_nocb_callback_list(rdp)) | |
1424 | return; | |
1425 | init_default_callback_list(rdp); | |
1426 | } | |
1427 | ||
dc35c893 PM |
1428 | /* |
1429 | * Determine the value that ->completed will have at the end of the | |
1430 | * next subsequent grace period. This is used to tag callbacks so that | |
1431 | * a CPU can invoke callbacks in a timely fashion even if that CPU has | |
1432 | * been dyntick-idle for an extended period with callbacks under the | |
1433 | * influence of RCU_FAST_NO_HZ. | |
1434 | * | |
1435 | * The caller must hold rnp->lock with interrupts disabled. | |
1436 | */ | |
1437 | static unsigned long rcu_cbs_completed(struct rcu_state *rsp, | |
1438 | struct rcu_node *rnp) | |
1439 | { | |
1440 | /* | |
1441 | * If RCU is idle, we just wait for the next grace period. | |
1442 | * But we can only be sure that RCU is idle if we are looking | |
1443 | * at the root rcu_node structure -- otherwise, a new grace | |
1444 | * period might have started, but just not yet gotten around | |
1445 | * to initializing the current non-root rcu_node structure. | |
1446 | */ | |
1447 | if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed) | |
1448 | return rnp->completed + 1; | |
1449 | ||
1450 | /* | |
1451 | * Otherwise, wait for a possible partial grace period and | |
1452 | * then the subsequent full grace period. | |
1453 | */ | |
1454 | return rnp->completed + 2; | |
1455 | } | |
1456 | ||
0446be48 PM |
1457 | /* |
1458 | * Trace-event helper function for rcu_start_future_gp() and | |
1459 | * rcu_nocb_wait_gp(). | |
1460 | */ | |
1461 | static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, | |
e66c33d5 | 1462 | unsigned long c, const char *s) |
0446be48 PM |
1463 | { |
1464 | trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum, | |
1465 | rnp->completed, c, rnp->level, | |
1466 | rnp->grplo, rnp->grphi, s); | |
1467 | } | |
1468 | ||
1469 | /* | |
1470 | * Start some future grace period, as needed to handle newly arrived | |
1471 | * callbacks. The required future grace periods are recorded in each | |
48a7639c PM |
1472 | * rcu_node structure's ->need_future_gp field. Returns true if there |
1473 | * is reason to awaken the grace-period kthread. | |
0446be48 PM |
1474 | * |
1475 | * The caller must hold the specified rcu_node structure's ->lock. | |
1476 | */ | |
48a7639c PM |
1477 | static bool __maybe_unused |
1478 | rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, | |
1479 | unsigned long *c_out) | |
0446be48 PM |
1480 | { |
1481 | unsigned long c; | |
1482 | int i; | |
48a7639c | 1483 | bool ret = false; |
0446be48 PM |
1484 | struct rcu_node *rnp_root = rcu_get_root(rdp->rsp); |
1485 | ||
1486 | /* | |
1487 | * Pick up grace-period number for new callbacks. If this | |
1488 | * grace period is already marked as needed, return to the caller. | |
1489 | */ | |
1490 | c = rcu_cbs_completed(rdp->rsp, rnp); | |
f7f7bac9 | 1491 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf")); |
0446be48 | 1492 | if (rnp->need_future_gp[c & 0x1]) { |
f7f7bac9 | 1493 | trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf")); |
48a7639c | 1494 | goto out; |
0446be48 PM |
1495 | } |
1496 | ||
1497 | /* | |
1498 | * If either this rcu_node structure or the root rcu_node structure | |
1499 | * believe that a grace period is in progress, then we must wait | |
1500 | * for the one following, which is in "c". Because our request | |
1501 | * will be noticed at the end of the current grace period, we don't | |
48bd8e9b PK |
1502 | * need to explicitly start one. We only do the lockless check |
1503 | * of rnp_root's fields if the current rcu_node structure thinks | |
1504 | * there is no grace period in flight, and because we hold rnp->lock, | |
1505 | * the only possible change is when rnp_root's two fields are | |
1506 | * equal, in which case rnp_root->gpnum might be concurrently | |
1507 | * incremented. But that is OK, as it will just result in our | |
1508 | * doing some extra useless work. | |
0446be48 PM |
1509 | */ |
1510 | if (rnp->gpnum != rnp->completed || | |
7d0ae808 | 1511 | READ_ONCE(rnp_root->gpnum) != READ_ONCE(rnp_root->completed)) { |
0446be48 | 1512 | rnp->need_future_gp[c & 0x1]++; |
f7f7bac9 | 1513 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf")); |
48a7639c | 1514 | goto out; |
0446be48 PM |
1515 | } |
1516 | ||
1517 | /* | |
1518 | * There might be no grace period in progress. If we don't already | |
1519 | * hold it, acquire the root rcu_node structure's lock in order to | |
1520 | * start one (if needed). | |
1521 | */ | |
6303b9c8 | 1522 | if (rnp != rnp_root) { |
0446be48 | 1523 | raw_spin_lock(&rnp_root->lock); |
6303b9c8 PM |
1524 | smp_mb__after_unlock_lock(); |
1525 | } | |
0446be48 PM |
1526 | |
1527 | /* | |
1528 | * Get a new grace-period number. If there really is no grace | |
1529 | * period in progress, it will be smaller than the one we obtained | |
1530 | * earlier. Adjust callbacks as needed. Note that even no-CBs | |
1531 | * CPUs have a ->nxtcompleted[] array, so no no-CBs checks needed. | |
1532 | */ | |
1533 | c = rcu_cbs_completed(rdp->rsp, rnp_root); | |
1534 | for (i = RCU_DONE_TAIL; i < RCU_NEXT_TAIL; i++) | |
1535 | if (ULONG_CMP_LT(c, rdp->nxtcompleted[i])) | |
1536 | rdp->nxtcompleted[i] = c; | |
1537 | ||
1538 | /* | |
1539 | * If the needed for the required grace period is already | |
1540 | * recorded, trace and leave. | |
1541 | */ | |
1542 | if (rnp_root->need_future_gp[c & 0x1]) { | |
f7f7bac9 | 1543 | trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot")); |
0446be48 PM |
1544 | goto unlock_out; |
1545 | } | |
1546 | ||
1547 | /* Record the need for the future grace period. */ | |
1548 | rnp_root->need_future_gp[c & 0x1]++; | |
1549 | ||
1550 | /* If a grace period is not already in progress, start one. */ | |
1551 | if (rnp_root->gpnum != rnp_root->completed) { | |
f7f7bac9 | 1552 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot")); |
0446be48 | 1553 | } else { |
f7f7bac9 | 1554 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot")); |
48a7639c | 1555 | ret = rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp); |
0446be48 PM |
1556 | } |
1557 | unlock_out: | |
1558 | if (rnp != rnp_root) | |
1559 | raw_spin_unlock(&rnp_root->lock); | |
48a7639c PM |
1560 | out: |
1561 | if (c_out != NULL) | |
1562 | *c_out = c; | |
1563 | return ret; | |
0446be48 PM |
1564 | } |
1565 | ||
1566 | /* | |
1567 | * Clean up any old requests for the just-ended grace period. Also return | |
1568 | * whether any additional grace periods have been requested. Also invoke | |
1569 | * rcu_nocb_gp_cleanup() in order to wake up any no-callbacks kthreads | |
1570 | * waiting for this grace period to complete. | |
1571 | */ | |
1572 | static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) | |
1573 | { | |
1574 | int c = rnp->completed; | |
1575 | int needmore; | |
1576 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); | |
1577 | ||
1578 | rcu_nocb_gp_cleanup(rsp, rnp); | |
1579 | rnp->need_future_gp[c & 0x1] = 0; | |
1580 | needmore = rnp->need_future_gp[(c + 1) & 0x1]; | |
f7f7bac9 SRRH |
1581 | trace_rcu_future_gp(rnp, rdp, c, |
1582 | needmore ? TPS("CleanupMore") : TPS("Cleanup")); | |
0446be48 PM |
1583 | return needmore; |
1584 | } | |
1585 | ||
48a7639c PM |
1586 | /* |
1587 | * Awaken the grace-period kthread for the specified flavor of RCU. | |
1588 | * Don't do a self-awaken, and don't bother awakening when there is | |
1589 | * nothing for the grace-period kthread to do (as in several CPUs | |
1590 | * raced to awaken, and we lost), and finally don't try to awaken | |
1591 | * a kthread that has not yet been created. | |
1592 | */ | |
1593 | static void rcu_gp_kthread_wake(struct rcu_state *rsp) | |
1594 | { | |
1595 | if (current == rsp->gp_kthread || | |
7d0ae808 | 1596 | !READ_ONCE(rsp->gp_flags) || |
48a7639c PM |
1597 | !rsp->gp_kthread) |
1598 | return; | |
1599 | wake_up(&rsp->gp_wq); | |
1600 | } | |
1601 | ||
dc35c893 PM |
1602 | /* |
1603 | * If there is room, assign a ->completed number to any callbacks on | |
1604 | * this CPU that have not already been assigned. Also accelerate any | |
1605 | * callbacks that were previously assigned a ->completed number that has | |
1606 | * since proven to be too conservative, which can happen if callbacks get | |
1607 | * assigned a ->completed number while RCU is idle, but with reference to | |
1608 | * a non-root rcu_node structure. This function is idempotent, so it does | |
48a7639c PM |
1609 | * not hurt to call it repeatedly. Returns an flag saying that we should |
1610 | * awaken the RCU grace-period kthread. | |
dc35c893 PM |
1611 | * |
1612 | * The caller must hold rnp->lock with interrupts disabled. | |
1613 | */ | |
48a7639c | 1614 | static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, |
dc35c893 PM |
1615 | struct rcu_data *rdp) |
1616 | { | |
1617 | unsigned long c; | |
1618 | int i; | |
48a7639c | 1619 | bool ret; |
dc35c893 PM |
1620 | |
1621 | /* If the CPU has no callbacks, nothing to do. */ | |
1622 | if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL]) | |
48a7639c | 1623 | return false; |
dc35c893 PM |
1624 | |
1625 | /* | |
1626 | * Starting from the sublist containing the callbacks most | |
1627 | * recently assigned a ->completed number and working down, find the | |
1628 | * first sublist that is not assignable to an upcoming grace period. | |
1629 | * Such a sublist has something in it (first two tests) and has | |
1630 | * a ->completed number assigned that will complete sooner than | |
1631 | * the ->completed number for newly arrived callbacks (last test). | |
1632 | * | |
1633 | * The key point is that any later sublist can be assigned the | |
1634 | * same ->completed number as the newly arrived callbacks, which | |
1635 | * means that the callbacks in any of these later sublist can be | |
1636 | * grouped into a single sublist, whether or not they have already | |
1637 | * been assigned a ->completed number. | |
1638 | */ | |
1639 | c = rcu_cbs_completed(rsp, rnp); | |
1640 | for (i = RCU_NEXT_TAIL - 1; i > RCU_DONE_TAIL; i--) | |
1641 | if (rdp->nxttail[i] != rdp->nxttail[i - 1] && | |
1642 | !ULONG_CMP_GE(rdp->nxtcompleted[i], c)) | |
1643 | break; | |
1644 | ||
1645 | /* | |
1646 | * If there are no sublist for unassigned callbacks, leave. | |
1647 | * At the same time, advance "i" one sublist, so that "i" will | |
1648 | * index into the sublist where all the remaining callbacks should | |
1649 | * be grouped into. | |
1650 | */ | |
1651 | if (++i >= RCU_NEXT_TAIL) | |
48a7639c | 1652 | return false; |
dc35c893 PM |
1653 | |
1654 | /* | |
1655 | * Assign all subsequent callbacks' ->completed number to the next | |
1656 | * full grace period and group them all in the sublist initially | |
1657 | * indexed by "i". | |
1658 | */ | |
1659 | for (; i <= RCU_NEXT_TAIL; i++) { | |
1660 | rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL]; | |
1661 | rdp->nxtcompleted[i] = c; | |
1662 | } | |
910ee45d | 1663 | /* Record any needed additional grace periods. */ |
48a7639c | 1664 | ret = rcu_start_future_gp(rnp, rdp, NULL); |
6d4b418c PM |
1665 | |
1666 | /* Trace depending on how much we were able to accelerate. */ | |
1667 | if (!*rdp->nxttail[RCU_WAIT_TAIL]) | |
f7f7bac9 | 1668 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccWaitCB")); |
6d4b418c | 1669 | else |
f7f7bac9 | 1670 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccReadyCB")); |
48a7639c | 1671 | return ret; |
dc35c893 PM |
1672 | } |
1673 | ||
1674 | /* | |
1675 | * Move any callbacks whose grace period has completed to the | |
1676 | * RCU_DONE_TAIL sublist, then compact the remaining sublists and | |
1677 | * assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL | |
1678 | * sublist. This function is idempotent, so it does not hurt to | |
1679 | * invoke it repeatedly. As long as it is not invoked -too- often... | |
48a7639c | 1680 | * Returns true if the RCU grace-period kthread needs to be awakened. |
dc35c893 PM |
1681 | * |
1682 | * The caller must hold rnp->lock with interrupts disabled. | |
1683 | */ | |
48a7639c | 1684 | static bool rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp, |
dc35c893 PM |
1685 | struct rcu_data *rdp) |
1686 | { | |
1687 | int i, j; | |
1688 | ||
1689 | /* If the CPU has no callbacks, nothing to do. */ | |
1690 | if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL]) | |
48a7639c | 1691 | return false; |
dc35c893 PM |
1692 | |
1693 | /* | |
1694 | * Find all callbacks whose ->completed numbers indicate that they | |
1695 | * are ready to invoke, and put them into the RCU_DONE_TAIL sublist. | |
1696 | */ | |
1697 | for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) { | |
1698 | if (ULONG_CMP_LT(rnp->completed, rdp->nxtcompleted[i])) | |
1699 | break; | |
1700 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[i]; | |
1701 | } | |
1702 | /* Clean up any sublist tail pointers that were misordered above. */ | |
1703 | for (j = RCU_WAIT_TAIL; j < i; j++) | |
1704 | rdp->nxttail[j] = rdp->nxttail[RCU_DONE_TAIL]; | |
1705 | ||
1706 | /* Copy down callbacks to fill in empty sublists. */ | |
1707 | for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) { | |
1708 | if (rdp->nxttail[j] == rdp->nxttail[RCU_NEXT_TAIL]) | |
1709 | break; | |
1710 | rdp->nxttail[j] = rdp->nxttail[i]; | |
1711 | rdp->nxtcompleted[j] = rdp->nxtcompleted[i]; | |
1712 | } | |
1713 | ||
1714 | /* Classify any remaining callbacks. */ | |
48a7639c | 1715 | return rcu_accelerate_cbs(rsp, rnp, rdp); |
dc35c893 PM |
1716 | } |
1717 | ||
d09b62df | 1718 | /* |
ba9fbe95 PM |
1719 | * Update CPU-local rcu_data state to record the beginnings and ends of |
1720 | * grace periods. The caller must hold the ->lock of the leaf rcu_node | |
1721 | * structure corresponding to the current CPU, and must have irqs disabled. | |
48a7639c | 1722 | * Returns true if the grace-period kthread needs to be awakened. |
d09b62df | 1723 | */ |
48a7639c PM |
1724 | static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, |
1725 | struct rcu_data *rdp) | |
d09b62df | 1726 | { |
48a7639c PM |
1727 | bool ret; |
1728 | ||
ba9fbe95 | 1729 | /* Handle the ends of any preceding grace periods first. */ |
e3663b10 | 1730 | if (rdp->completed == rnp->completed && |
7d0ae808 | 1731 | !unlikely(READ_ONCE(rdp->gpwrap))) { |
d09b62df | 1732 | |
ba9fbe95 | 1733 | /* No grace period end, so just accelerate recent callbacks. */ |
48a7639c | 1734 | ret = rcu_accelerate_cbs(rsp, rnp, rdp); |
d09b62df | 1735 | |
dc35c893 PM |
1736 | } else { |
1737 | ||
1738 | /* Advance callbacks. */ | |
48a7639c | 1739 | ret = rcu_advance_cbs(rsp, rnp, rdp); |
d09b62df PM |
1740 | |
1741 | /* Remember that we saw this grace-period completion. */ | |
1742 | rdp->completed = rnp->completed; | |
f7f7bac9 | 1743 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuend")); |
d09b62df | 1744 | } |
398ebe60 | 1745 | |
7d0ae808 | 1746 | if (rdp->gpnum != rnp->gpnum || unlikely(READ_ONCE(rdp->gpwrap))) { |
6eaef633 PM |
1747 | /* |
1748 | * If the current grace period is waiting for this CPU, | |
1749 | * set up to detect a quiescent state, otherwise don't | |
1750 | * go looking for one. | |
1751 | */ | |
1752 | rdp->gpnum = rnp->gpnum; | |
f7f7bac9 | 1753 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart")); |
5b74c458 | 1754 | rdp->cpu_no_qs.b.norm = true; |
5cd37193 | 1755 | rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr); |
97c668b8 | 1756 | rdp->core_needs_qs = !!(rnp->qsmask & rdp->grpmask); |
6eaef633 | 1757 | zero_cpu_stall_ticks(rdp); |
7d0ae808 | 1758 | WRITE_ONCE(rdp->gpwrap, false); |
6eaef633 | 1759 | } |
48a7639c | 1760 | return ret; |
6eaef633 PM |
1761 | } |
1762 | ||
d34ea322 | 1763 | static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp) |
6eaef633 PM |
1764 | { |
1765 | unsigned long flags; | |
48a7639c | 1766 | bool needwake; |
6eaef633 PM |
1767 | struct rcu_node *rnp; |
1768 | ||
1769 | local_irq_save(flags); | |
1770 | rnp = rdp->mynode; | |
7d0ae808 PM |
1771 | if ((rdp->gpnum == READ_ONCE(rnp->gpnum) && |
1772 | rdp->completed == READ_ONCE(rnp->completed) && | |
1773 | !unlikely(READ_ONCE(rdp->gpwrap))) || /* w/out lock. */ | |
6eaef633 PM |
1774 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
1775 | local_irq_restore(flags); | |
1776 | return; | |
1777 | } | |
6303b9c8 | 1778 | smp_mb__after_unlock_lock(); |
48a7639c | 1779 | needwake = __note_gp_changes(rsp, rnp, rdp); |
6eaef633 | 1780 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
48a7639c PM |
1781 | if (needwake) |
1782 | rcu_gp_kthread_wake(rsp); | |
6eaef633 PM |
1783 | } |
1784 | ||
0f41c0dd PM |
1785 | static void rcu_gp_slow(struct rcu_state *rsp, int delay) |
1786 | { | |
1787 | if (delay > 0 && | |
1788 | !(rsp->gpnum % (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay))) | |
1789 | schedule_timeout_uninterruptible(delay); | |
1790 | } | |
1791 | ||
b3dbec76 | 1792 | /* |
f7be8209 | 1793 | * Initialize a new grace period. Return 0 if no grace period required. |
b3dbec76 | 1794 | */ |
7fdefc10 | 1795 | static int rcu_gp_init(struct rcu_state *rsp) |
b3dbec76 | 1796 | { |
0aa04b05 | 1797 | unsigned long oldmask; |
b3dbec76 | 1798 | struct rcu_data *rdp; |
7fdefc10 | 1799 | struct rcu_node *rnp = rcu_get_root(rsp); |
b3dbec76 | 1800 | |
7d0ae808 | 1801 | WRITE_ONCE(rsp->gp_activity, jiffies); |
7fdefc10 | 1802 | raw_spin_lock_irq(&rnp->lock); |
6303b9c8 | 1803 | smp_mb__after_unlock_lock(); |
7d0ae808 | 1804 | if (!READ_ONCE(rsp->gp_flags)) { |
f7be8209 PM |
1805 | /* Spurious wakeup, tell caller to go back to sleep. */ |
1806 | raw_spin_unlock_irq(&rnp->lock); | |
1807 | return 0; | |
1808 | } | |
7d0ae808 | 1809 | WRITE_ONCE(rsp->gp_flags, 0); /* Clear all flags: New grace period. */ |
b3dbec76 | 1810 | |
f7be8209 PM |
1811 | if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) { |
1812 | /* | |
1813 | * Grace period already in progress, don't start another. | |
1814 | * Not supposed to be able to happen. | |
1815 | */ | |
7fdefc10 PM |
1816 | raw_spin_unlock_irq(&rnp->lock); |
1817 | return 0; | |
1818 | } | |
1819 | ||
7fdefc10 | 1820 | /* Advance to a new grace period and initialize state. */ |
26cdfedf | 1821 | record_gp_stall_check_time(rsp); |
765a3f4f PM |
1822 | /* Record GP times before starting GP, hence smp_store_release(). */ |
1823 | smp_store_release(&rsp->gpnum, rsp->gpnum + 1); | |
f7f7bac9 | 1824 | trace_rcu_grace_period(rsp->name, rsp->gpnum, TPS("start")); |
7fdefc10 PM |
1825 | raw_spin_unlock_irq(&rnp->lock); |
1826 | ||
0aa04b05 PM |
1827 | /* |
1828 | * Apply per-leaf buffered online and offline operations to the | |
1829 | * rcu_node tree. Note that this new grace period need not wait | |
1830 | * for subsequent online CPUs, and that quiescent-state forcing | |
1831 | * will handle subsequent offline CPUs. | |
1832 | */ | |
1833 | rcu_for_each_leaf_node(rsp, rnp) { | |
0f41c0dd | 1834 | rcu_gp_slow(rsp, gp_preinit_delay); |
0aa04b05 PM |
1835 | raw_spin_lock_irq(&rnp->lock); |
1836 | smp_mb__after_unlock_lock(); | |
1837 | if (rnp->qsmaskinit == rnp->qsmaskinitnext && | |
1838 | !rnp->wait_blkd_tasks) { | |
1839 | /* Nothing to do on this leaf rcu_node structure. */ | |
1840 | raw_spin_unlock_irq(&rnp->lock); | |
1841 | continue; | |
1842 | } | |
1843 | ||
1844 | /* Record old state, apply changes to ->qsmaskinit field. */ | |
1845 | oldmask = rnp->qsmaskinit; | |
1846 | rnp->qsmaskinit = rnp->qsmaskinitnext; | |
1847 | ||
1848 | /* If zero-ness of ->qsmaskinit changed, propagate up tree. */ | |
1849 | if (!oldmask != !rnp->qsmaskinit) { | |
1850 | if (!oldmask) /* First online CPU for this rcu_node. */ | |
1851 | rcu_init_new_rnp(rnp); | |
1852 | else if (rcu_preempt_has_tasks(rnp)) /* blocked tasks */ | |
1853 | rnp->wait_blkd_tasks = true; | |
1854 | else /* Last offline CPU and can propagate. */ | |
1855 | rcu_cleanup_dead_rnp(rnp); | |
1856 | } | |
1857 | ||
1858 | /* | |
1859 | * If all waited-on tasks from prior grace period are | |
1860 | * done, and if all this rcu_node structure's CPUs are | |
1861 | * still offline, propagate up the rcu_node tree and | |
1862 | * clear ->wait_blkd_tasks. Otherwise, if one of this | |
1863 | * rcu_node structure's CPUs has since come back online, | |
1864 | * simply clear ->wait_blkd_tasks (but rcu_cleanup_dead_rnp() | |
1865 | * checks for this, so just call it unconditionally). | |
1866 | */ | |
1867 | if (rnp->wait_blkd_tasks && | |
1868 | (!rcu_preempt_has_tasks(rnp) || | |
1869 | rnp->qsmaskinit)) { | |
1870 | rnp->wait_blkd_tasks = false; | |
1871 | rcu_cleanup_dead_rnp(rnp); | |
1872 | } | |
1873 | ||
1874 | raw_spin_unlock_irq(&rnp->lock); | |
1875 | } | |
7fdefc10 PM |
1876 | |
1877 | /* | |
1878 | * Set the quiescent-state-needed bits in all the rcu_node | |
1879 | * structures for all currently online CPUs in breadth-first order, | |
1880 | * starting from the root rcu_node structure, relying on the layout | |
1881 | * of the tree within the rsp->node[] array. Note that other CPUs | |
1882 | * will access only the leaves of the hierarchy, thus seeing that no | |
1883 | * grace period is in progress, at least until the corresponding | |
1884 | * leaf node has been initialized. In addition, we have excluded | |
1885 | * CPU-hotplug operations. | |
1886 | * | |
1887 | * The grace period cannot complete until the initialization | |
1888 | * process finishes, because this kthread handles both. | |
1889 | */ | |
1890 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
0f41c0dd | 1891 | rcu_gp_slow(rsp, gp_init_delay); |
b3dbec76 | 1892 | raw_spin_lock_irq(&rnp->lock); |
6303b9c8 | 1893 | smp_mb__after_unlock_lock(); |
b3dbec76 | 1894 | rdp = this_cpu_ptr(rsp->rda); |
7fdefc10 PM |
1895 | rcu_preempt_check_blocked_tasks(rnp); |
1896 | rnp->qsmask = rnp->qsmaskinit; | |
7d0ae808 | 1897 | WRITE_ONCE(rnp->gpnum, rsp->gpnum); |
3f47da0f | 1898 | if (WARN_ON_ONCE(rnp->completed != rsp->completed)) |
7d0ae808 | 1899 | WRITE_ONCE(rnp->completed, rsp->completed); |
7fdefc10 | 1900 | if (rnp == rdp->mynode) |
48a7639c | 1901 | (void)__note_gp_changes(rsp, rnp, rdp); |
7fdefc10 PM |
1902 | rcu_preempt_boost_start_gp(rnp); |
1903 | trace_rcu_grace_period_init(rsp->name, rnp->gpnum, | |
1904 | rnp->level, rnp->grplo, | |
1905 | rnp->grphi, rnp->qsmask); | |
1906 | raw_spin_unlock_irq(&rnp->lock); | |
bde6c3aa | 1907 | cond_resched_rcu_qs(); |
7d0ae808 | 1908 | WRITE_ONCE(rsp->gp_activity, jiffies); |
7fdefc10 | 1909 | } |
b3dbec76 | 1910 | |
7fdefc10 PM |
1911 | return 1; |
1912 | } | |
b3dbec76 | 1913 | |
b9a425cf PM |
1914 | /* |
1915 | * Helper function for wait_event_interruptible_timeout() wakeup | |
1916 | * at force-quiescent-state time. | |
1917 | */ | |
1918 | static bool rcu_gp_fqs_check_wake(struct rcu_state *rsp, int *gfp) | |
1919 | { | |
1920 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1921 | ||
1922 | /* Someone like call_rcu() requested a force-quiescent-state scan. */ | |
1923 | *gfp = READ_ONCE(rsp->gp_flags); | |
1924 | if (*gfp & RCU_GP_FLAG_FQS) | |
1925 | return true; | |
1926 | ||
1927 | /* The current grace period has completed. */ | |
1928 | if (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp)) | |
1929 | return true; | |
1930 | ||
1931 | return false; | |
1932 | } | |
1933 | ||
4cdfc175 PM |
1934 | /* |
1935 | * Do one round of quiescent-state forcing. | |
1936 | */ | |
01896f7e | 1937 | static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in) |
4cdfc175 PM |
1938 | { |
1939 | int fqs_state = fqs_state_in; | |
217af2a2 PM |
1940 | bool isidle = false; |
1941 | unsigned long maxj; | |
4cdfc175 PM |
1942 | struct rcu_node *rnp = rcu_get_root(rsp); |
1943 | ||
7d0ae808 | 1944 | WRITE_ONCE(rsp->gp_activity, jiffies); |
4cdfc175 PM |
1945 | rsp->n_force_qs++; |
1946 | if (fqs_state == RCU_SAVE_DYNTICK) { | |
1947 | /* Collect dyntick-idle snapshots. */ | |
0edd1b17 | 1948 | if (is_sysidle_rcu_state(rsp)) { |
e02b2edf | 1949 | isidle = true; |
0edd1b17 PM |
1950 | maxj = jiffies - ULONG_MAX / 4; |
1951 | } | |
217af2a2 PM |
1952 | force_qs_rnp(rsp, dyntick_save_progress_counter, |
1953 | &isidle, &maxj); | |
0edd1b17 | 1954 | rcu_sysidle_report_gp(rsp, isidle, maxj); |
4cdfc175 PM |
1955 | fqs_state = RCU_FORCE_QS; |
1956 | } else { | |
1957 | /* Handle dyntick-idle and offline CPUs. */ | |
675da67f | 1958 | isidle = true; |
217af2a2 | 1959 | force_qs_rnp(rsp, rcu_implicit_dynticks_qs, &isidle, &maxj); |
4cdfc175 PM |
1960 | } |
1961 | /* Clear flag to prevent immediate re-entry. */ | |
7d0ae808 | 1962 | if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { |
4cdfc175 | 1963 | raw_spin_lock_irq(&rnp->lock); |
6303b9c8 | 1964 | smp_mb__after_unlock_lock(); |
7d0ae808 PM |
1965 | WRITE_ONCE(rsp->gp_flags, |
1966 | READ_ONCE(rsp->gp_flags) & ~RCU_GP_FLAG_FQS); | |
4cdfc175 PM |
1967 | raw_spin_unlock_irq(&rnp->lock); |
1968 | } | |
1969 | return fqs_state; | |
1970 | } | |
1971 | ||
7fdefc10 PM |
1972 | /* |
1973 | * Clean up after the old grace period. | |
1974 | */ | |
4cdfc175 | 1975 | static void rcu_gp_cleanup(struct rcu_state *rsp) |
7fdefc10 PM |
1976 | { |
1977 | unsigned long gp_duration; | |
48a7639c | 1978 | bool needgp = false; |
dae6e64d | 1979 | int nocb = 0; |
7fdefc10 PM |
1980 | struct rcu_data *rdp; |
1981 | struct rcu_node *rnp = rcu_get_root(rsp); | |
b3dbec76 | 1982 | |
7d0ae808 | 1983 | WRITE_ONCE(rsp->gp_activity, jiffies); |
7fdefc10 | 1984 | raw_spin_lock_irq(&rnp->lock); |
6303b9c8 | 1985 | smp_mb__after_unlock_lock(); |
7fdefc10 PM |
1986 | gp_duration = jiffies - rsp->gp_start; |
1987 | if (gp_duration > rsp->gp_max) | |
1988 | rsp->gp_max = gp_duration; | |
b3dbec76 | 1989 | |
7fdefc10 PM |
1990 | /* |
1991 | * We know the grace period is complete, but to everyone else | |
1992 | * it appears to still be ongoing. But it is also the case | |
1993 | * that to everyone else it looks like there is nothing that | |
1994 | * they can do to advance the grace period. It is therefore | |
1995 | * safe for us to drop the lock in order to mark the grace | |
1996 | * period as completed in all of the rcu_node structures. | |
7fdefc10 | 1997 | */ |
5d4b8659 | 1998 | raw_spin_unlock_irq(&rnp->lock); |
b3dbec76 | 1999 | |
5d4b8659 PM |
2000 | /* |
2001 | * Propagate new ->completed value to rcu_node structures so | |
2002 | * that other CPUs don't have to wait until the start of the next | |
2003 | * grace period to process their callbacks. This also avoids | |
2004 | * some nasty RCU grace-period initialization races by forcing | |
2005 | * the end of the current grace period to be completely recorded in | |
2006 | * all of the rcu_node structures before the beginning of the next | |
2007 | * grace period is recorded in any of the rcu_node structures. | |
2008 | */ | |
2009 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
755609a9 | 2010 | raw_spin_lock_irq(&rnp->lock); |
6303b9c8 | 2011 | smp_mb__after_unlock_lock(); |
5c60d25f PM |
2012 | WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); |
2013 | WARN_ON_ONCE(rnp->qsmask); | |
7d0ae808 | 2014 | WRITE_ONCE(rnp->completed, rsp->gpnum); |
b11cc576 PM |
2015 | rdp = this_cpu_ptr(rsp->rda); |
2016 | if (rnp == rdp->mynode) | |
48a7639c | 2017 | needgp = __note_gp_changes(rsp, rnp, rdp) || needgp; |
78e4bc34 | 2018 | /* smp_mb() provided by prior unlock-lock pair. */ |
0446be48 | 2019 | nocb += rcu_future_gp_cleanup(rsp, rnp); |
5d4b8659 | 2020 | raw_spin_unlock_irq(&rnp->lock); |
bde6c3aa | 2021 | cond_resched_rcu_qs(); |
7d0ae808 | 2022 | WRITE_ONCE(rsp->gp_activity, jiffies); |
0f41c0dd | 2023 | rcu_gp_slow(rsp, gp_cleanup_delay); |
7fdefc10 | 2024 | } |
5d4b8659 PM |
2025 | rnp = rcu_get_root(rsp); |
2026 | raw_spin_lock_irq(&rnp->lock); | |
765a3f4f | 2027 | smp_mb__after_unlock_lock(); /* Order GP before ->completed update. */ |
dae6e64d | 2028 | rcu_nocb_gp_set(rnp, nocb); |
7fdefc10 | 2029 | |
765a3f4f | 2030 | /* Declare grace period done. */ |
7d0ae808 | 2031 | WRITE_ONCE(rsp->completed, rsp->gpnum); |
f7f7bac9 | 2032 | trace_rcu_grace_period(rsp->name, rsp->completed, TPS("end")); |
7fdefc10 | 2033 | rsp->fqs_state = RCU_GP_IDLE; |
5d4b8659 | 2034 | rdp = this_cpu_ptr(rsp->rda); |
48a7639c PM |
2035 | /* Advance CBs to reduce false positives below. */ |
2036 | needgp = rcu_advance_cbs(rsp, rnp, rdp) || needgp; | |
2037 | if (needgp || cpu_needs_another_gp(rsp, rdp)) { | |
7d0ae808 | 2038 | WRITE_ONCE(rsp->gp_flags, RCU_GP_FLAG_INIT); |
bb311ecc | 2039 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2040 | READ_ONCE(rsp->gpnum), |
bb311ecc PM |
2041 | TPS("newreq")); |
2042 | } | |
7fdefc10 | 2043 | raw_spin_unlock_irq(&rnp->lock); |
7fdefc10 PM |
2044 | } |
2045 | ||
2046 | /* | |
2047 | * Body of kthread that handles grace periods. | |
2048 | */ | |
2049 | static int __noreturn rcu_gp_kthread(void *arg) | |
2050 | { | |
4cdfc175 | 2051 | int fqs_state; |
88d6df61 | 2052 | int gf; |
d40011f6 | 2053 | unsigned long j; |
4cdfc175 | 2054 | int ret; |
7fdefc10 PM |
2055 | struct rcu_state *rsp = arg; |
2056 | struct rcu_node *rnp = rcu_get_root(rsp); | |
2057 | ||
5871968d | 2058 | rcu_bind_gp_kthread(); |
7fdefc10 PM |
2059 | for (;;) { |
2060 | ||
2061 | /* Handle grace-period start. */ | |
2062 | for (;;) { | |
63c4db78 | 2063 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2064 | READ_ONCE(rsp->gpnum), |
63c4db78 | 2065 | TPS("reqwait")); |
afea227f | 2066 | rsp->gp_state = RCU_GP_WAIT_GPS; |
4cdfc175 | 2067 | wait_event_interruptible(rsp->gp_wq, |
7d0ae808 | 2068 | READ_ONCE(rsp->gp_flags) & |
4cdfc175 | 2069 | RCU_GP_FLAG_INIT); |
319362c9 | 2070 | rsp->gp_state = RCU_GP_DONE_GPS; |
78e4bc34 | 2071 | /* Locking provides needed memory barrier. */ |
f7be8209 | 2072 | if (rcu_gp_init(rsp)) |
7fdefc10 | 2073 | break; |
bde6c3aa | 2074 | cond_resched_rcu_qs(); |
7d0ae808 | 2075 | WRITE_ONCE(rsp->gp_activity, jiffies); |
73a860cd | 2076 | WARN_ON(signal_pending(current)); |
63c4db78 | 2077 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2078 | READ_ONCE(rsp->gpnum), |
63c4db78 | 2079 | TPS("reqwaitsig")); |
7fdefc10 | 2080 | } |
cabc49c1 | 2081 | |
4cdfc175 PM |
2082 | /* Handle quiescent-state forcing. */ |
2083 | fqs_state = RCU_SAVE_DYNTICK; | |
d40011f6 PM |
2084 | j = jiffies_till_first_fqs; |
2085 | if (j > HZ) { | |
2086 | j = HZ; | |
2087 | jiffies_till_first_fqs = HZ; | |
2088 | } | |
88d6df61 | 2089 | ret = 0; |
cabc49c1 | 2090 | for (;;) { |
88d6df61 PM |
2091 | if (!ret) |
2092 | rsp->jiffies_force_qs = jiffies + j; | |
63c4db78 | 2093 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2094 | READ_ONCE(rsp->gpnum), |
63c4db78 | 2095 | TPS("fqswait")); |
afea227f | 2096 | rsp->gp_state = RCU_GP_WAIT_FQS; |
4cdfc175 | 2097 | ret = wait_event_interruptible_timeout(rsp->gp_wq, |
b9a425cf | 2098 | rcu_gp_fqs_check_wake(rsp, &gf), j); |
32bb1c79 | 2099 | rsp->gp_state = RCU_GP_DOING_FQS; |
78e4bc34 | 2100 | /* Locking provides needed memory barriers. */ |
4cdfc175 | 2101 | /* If grace period done, leave loop. */ |
7d0ae808 | 2102 | if (!READ_ONCE(rnp->qsmask) && |
4cdfc175 | 2103 | !rcu_preempt_blocked_readers_cgp(rnp)) |
cabc49c1 | 2104 | break; |
4cdfc175 | 2105 | /* If time for quiescent-state forcing, do it. */ |
88d6df61 PM |
2106 | if (ULONG_CMP_GE(jiffies, rsp->jiffies_force_qs) || |
2107 | (gf & RCU_GP_FLAG_FQS)) { | |
63c4db78 | 2108 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2109 | READ_ONCE(rsp->gpnum), |
63c4db78 | 2110 | TPS("fqsstart")); |
4cdfc175 | 2111 | fqs_state = rcu_gp_fqs(rsp, fqs_state); |
63c4db78 | 2112 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2113 | READ_ONCE(rsp->gpnum), |
63c4db78 | 2114 | TPS("fqsend")); |
bde6c3aa | 2115 | cond_resched_rcu_qs(); |
7d0ae808 | 2116 | WRITE_ONCE(rsp->gp_activity, jiffies); |
4cdfc175 PM |
2117 | } else { |
2118 | /* Deal with stray signal. */ | |
bde6c3aa | 2119 | cond_resched_rcu_qs(); |
7d0ae808 | 2120 | WRITE_ONCE(rsp->gp_activity, jiffies); |
73a860cd | 2121 | WARN_ON(signal_pending(current)); |
63c4db78 | 2122 | trace_rcu_grace_period(rsp->name, |
7d0ae808 | 2123 | READ_ONCE(rsp->gpnum), |
63c4db78 | 2124 | TPS("fqswaitsig")); |
4cdfc175 | 2125 | } |
d40011f6 PM |
2126 | j = jiffies_till_next_fqs; |
2127 | if (j > HZ) { | |
2128 | j = HZ; | |
2129 | jiffies_till_next_fqs = HZ; | |
2130 | } else if (j < 1) { | |
2131 | j = 1; | |
2132 | jiffies_till_next_fqs = 1; | |
2133 | } | |
cabc49c1 | 2134 | } |
4cdfc175 PM |
2135 | |
2136 | /* Handle grace-period end. */ | |
319362c9 | 2137 | rsp->gp_state = RCU_GP_CLEANUP; |
4cdfc175 | 2138 | rcu_gp_cleanup(rsp); |
319362c9 | 2139 | rsp->gp_state = RCU_GP_CLEANED; |
b3dbec76 | 2140 | } |
b3dbec76 PM |
2141 | } |
2142 | ||
64db4cff PM |
2143 | /* |
2144 | * Start a new RCU grace period if warranted, re-initializing the hierarchy | |
2145 | * in preparation for detecting the next grace period. The caller must hold | |
b8462084 | 2146 | * the root node's ->lock and hard irqs must be disabled. |
e5601400 PM |
2147 | * |
2148 | * Note that it is legal for a dying CPU (which is marked as offline) to | |
2149 | * invoke this function. This can happen when the dying CPU reports its | |
2150 | * quiescent state. | |
48a7639c PM |
2151 | * |
2152 | * Returns true if the grace-period kthread must be awakened. | |
64db4cff | 2153 | */ |
48a7639c | 2154 | static bool |
910ee45d PM |
2155 | rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, |
2156 | struct rcu_data *rdp) | |
64db4cff | 2157 | { |
b8462084 | 2158 | if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) { |
afe24b12 | 2159 | /* |
b3dbec76 | 2160 | * Either we have not yet spawned the grace-period |
62da1921 PM |
2161 | * task, this CPU does not need another grace period, |
2162 | * or a grace period is already in progress. | |
b3dbec76 | 2163 | * Either way, don't start a new grace period. |
afe24b12 | 2164 | */ |
48a7639c | 2165 | return false; |
afe24b12 | 2166 | } |
7d0ae808 PM |
2167 | WRITE_ONCE(rsp->gp_flags, RCU_GP_FLAG_INIT); |
2168 | trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gpnum), | |
bb311ecc | 2169 | TPS("newreq")); |
62da1921 | 2170 | |
016a8d5b SR |
2171 | /* |
2172 | * We can't do wakeups while holding the rnp->lock, as that | |
1eafd31c | 2173 | * could cause possible deadlocks with the rq->lock. Defer |
48a7639c | 2174 | * the wakeup to our caller. |
016a8d5b | 2175 | */ |
48a7639c | 2176 | return true; |
64db4cff PM |
2177 | } |
2178 | ||
910ee45d PM |
2179 | /* |
2180 | * Similar to rcu_start_gp_advanced(), but also advance the calling CPU's | |
2181 | * callbacks. Note that rcu_start_gp_advanced() cannot do this because it | |
2182 | * is invoked indirectly from rcu_advance_cbs(), which would result in | |
2183 | * endless recursion -- or would do so if it wasn't for the self-deadlock | |
2184 | * that is encountered beforehand. | |
48a7639c PM |
2185 | * |
2186 | * Returns true if the grace-period kthread needs to be awakened. | |
910ee45d | 2187 | */ |
48a7639c | 2188 | static bool rcu_start_gp(struct rcu_state *rsp) |
910ee45d PM |
2189 | { |
2190 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); | |
2191 | struct rcu_node *rnp = rcu_get_root(rsp); | |
48a7639c | 2192 | bool ret = false; |
910ee45d PM |
2193 | |
2194 | /* | |
2195 | * If there is no grace period in progress right now, any | |
2196 | * callbacks we have up to this point will be satisfied by the | |
2197 | * next grace period. Also, advancing the callbacks reduces the | |
2198 | * probability of false positives from cpu_needs_another_gp() | |
2199 | * resulting in pointless grace periods. So, advance callbacks | |
2200 | * then start the grace period! | |
2201 | */ | |
48a7639c PM |
2202 | ret = rcu_advance_cbs(rsp, rnp, rdp) || ret; |
2203 | ret = rcu_start_gp_advanced(rsp, rnp, rdp) || ret; | |
2204 | return ret; | |
910ee45d PM |
2205 | } |
2206 | ||
f41d911f | 2207 | /* |
d3f6bad3 PM |
2208 | * Report a full set of quiescent states to the specified rcu_state |
2209 | * data structure. This involves cleaning up after the prior grace | |
2210 | * period and letting rcu_start_gp() start up the next grace period | |
b8462084 PM |
2211 | * if one is needed. Note that the caller must hold rnp->lock, which |
2212 | * is released before return. | |
f41d911f | 2213 | */ |
d3f6bad3 | 2214 | static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
fc2219d4 | 2215 | __releases(rcu_get_root(rsp)->lock) |
f41d911f | 2216 | { |
fc2219d4 | 2217 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
cd73ca21 | 2218 | WRITE_ONCE(rsp->gp_flags, READ_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS); |
cabc49c1 | 2219 | raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); |
2aa792e6 | 2220 | rcu_gp_kthread_wake(rsp); |
f41d911f PM |
2221 | } |
2222 | ||
64db4cff | 2223 | /* |
d3f6bad3 PM |
2224 | * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
2225 | * Allows quiescent states for a group of CPUs to be reported at one go | |
2226 | * to the specified rcu_node structure, though all the CPUs in the group | |
654e9533 PM |
2227 | * must be represented by the same rcu_node structure (which need not be a |
2228 | * leaf rcu_node structure, though it often will be). The gps parameter | |
2229 | * is the grace-period snapshot, which means that the quiescent states | |
2230 | * are valid only if rnp->gpnum is equal to gps. That structure's lock | |
2231 | * must be held upon entry, and it is released before return. | |
64db4cff PM |
2232 | */ |
2233 | static void | |
d3f6bad3 | 2234 | rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
654e9533 | 2235 | struct rcu_node *rnp, unsigned long gps, unsigned long flags) |
64db4cff PM |
2236 | __releases(rnp->lock) |
2237 | { | |
654e9533 | 2238 | unsigned long oldmask = 0; |
28ecd580 PM |
2239 | struct rcu_node *rnp_c; |
2240 | ||
64db4cff PM |
2241 | /* Walk up the rcu_node hierarchy. */ |
2242 | for (;;) { | |
654e9533 | 2243 | if (!(rnp->qsmask & mask) || rnp->gpnum != gps) { |
64db4cff | 2244 | |
654e9533 PM |
2245 | /* |
2246 | * Our bit has already been cleared, or the | |
2247 | * relevant grace period is already over, so done. | |
2248 | */ | |
1304afb2 | 2249 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
2250 | return; |
2251 | } | |
654e9533 | 2252 | WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */ |
64db4cff | 2253 | rnp->qsmask &= ~mask; |
d4c08f2a PM |
2254 | trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum, |
2255 | mask, rnp->qsmask, rnp->level, | |
2256 | rnp->grplo, rnp->grphi, | |
2257 | !!rnp->gp_tasks); | |
27f4d280 | 2258 | if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
64db4cff PM |
2259 | |
2260 | /* Other bits still set at this level, so done. */ | |
1304afb2 | 2261 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
2262 | return; |
2263 | } | |
2264 | mask = rnp->grpmask; | |
2265 | if (rnp->parent == NULL) { | |
2266 | ||
2267 | /* No more levels. Exit loop holding root lock. */ | |
2268 | ||
2269 | break; | |
2270 | } | |
1304afb2 | 2271 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
28ecd580 | 2272 | rnp_c = rnp; |
64db4cff | 2273 | rnp = rnp->parent; |
1304afb2 | 2274 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 2275 | smp_mb__after_unlock_lock(); |
654e9533 | 2276 | oldmask = rnp_c->qsmask; |
64db4cff PM |
2277 | } |
2278 | ||
2279 | /* | |
2280 | * Get here if we are the last CPU to pass through a quiescent | |
d3f6bad3 | 2281 | * state for this grace period. Invoke rcu_report_qs_rsp() |
f41d911f | 2282 | * to clean up and start the next grace period if one is needed. |
64db4cff | 2283 | */ |
d3f6bad3 | 2284 | rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
64db4cff PM |
2285 | } |
2286 | ||
cc99a310 PM |
2287 | /* |
2288 | * Record a quiescent state for all tasks that were previously queued | |
2289 | * on the specified rcu_node structure and that were blocking the current | |
2290 | * RCU grace period. The caller must hold the specified rnp->lock with | |
2291 | * irqs disabled, and this lock is released upon return, but irqs remain | |
2292 | * disabled. | |
2293 | */ | |
0aa04b05 | 2294 | static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp, |
cc99a310 PM |
2295 | struct rcu_node *rnp, unsigned long flags) |
2296 | __releases(rnp->lock) | |
2297 | { | |
654e9533 | 2298 | unsigned long gps; |
cc99a310 PM |
2299 | unsigned long mask; |
2300 | struct rcu_node *rnp_p; | |
2301 | ||
a77da14c PM |
2302 | if (rcu_state_p == &rcu_sched_state || rsp != rcu_state_p || |
2303 | rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { | |
cc99a310 PM |
2304 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
2305 | return; /* Still need more quiescent states! */ | |
2306 | } | |
2307 | ||
2308 | rnp_p = rnp->parent; | |
2309 | if (rnp_p == NULL) { | |
2310 | /* | |
a77da14c PM |
2311 | * Only one rcu_node structure in the tree, so don't |
2312 | * try to report up to its nonexistent parent! | |
cc99a310 PM |
2313 | */ |
2314 | rcu_report_qs_rsp(rsp, flags); | |
2315 | return; | |
2316 | } | |
2317 | ||
654e9533 PM |
2318 | /* Report up the rest of the hierarchy, tracking current ->gpnum. */ |
2319 | gps = rnp->gpnum; | |
cc99a310 PM |
2320 | mask = rnp->grpmask; |
2321 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
2322 | raw_spin_lock(&rnp_p->lock); /* irqs already disabled. */ | |
2323 | smp_mb__after_unlock_lock(); | |
654e9533 | 2324 | rcu_report_qs_rnp(mask, rsp, rnp_p, gps, flags); |
cc99a310 PM |
2325 | } |
2326 | ||
64db4cff | 2327 | /* |
d3f6bad3 PM |
2328 | * Record a quiescent state for the specified CPU to that CPU's rcu_data |
2329 | * structure. This must be either called from the specified CPU, or | |
2330 | * called when the specified CPU is known to be offline (and when it is | |
2331 | * also known that no other CPU is concurrently trying to help the offline | |
2332 | * CPU). The lastcomp argument is used to make sure we are still in the | |
2333 | * grace period of interest. We don't want to end the current grace period | |
2334 | * based on quiescent states detected in an earlier grace period! | |
64db4cff PM |
2335 | */ |
2336 | static void | |
d7d6a11e | 2337 | rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
2338 | { |
2339 | unsigned long flags; | |
2340 | unsigned long mask; | |
48a7639c | 2341 | bool needwake; |
64db4cff PM |
2342 | struct rcu_node *rnp; |
2343 | ||
2344 | rnp = rdp->mynode; | |
1304afb2 | 2345 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 2346 | smp_mb__after_unlock_lock(); |
5b74c458 | 2347 | if ((rdp->cpu_no_qs.b.norm && |
5cd37193 PM |
2348 | rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) || |
2349 | rdp->gpnum != rnp->gpnum || rnp->completed == rnp->gpnum || | |
2350 | rdp->gpwrap) { | |
64db4cff PM |
2351 | |
2352 | /* | |
e4cc1f22 PM |
2353 | * The grace period in which this quiescent state was |
2354 | * recorded has ended, so don't report it upwards. | |
2355 | * We will instead need a new quiescent state that lies | |
2356 | * within the current grace period. | |
64db4cff | 2357 | */ |
5b74c458 | 2358 | rdp->cpu_no_qs.b.norm = true; /* need qs for new gp. */ |
5cd37193 | 2359 | rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr); |
1304afb2 | 2360 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
2361 | return; |
2362 | } | |
2363 | mask = rdp->grpmask; | |
2364 | if ((rnp->qsmask & mask) == 0) { | |
1304afb2 | 2365 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 2366 | } else { |
97c668b8 | 2367 | rdp->core_needs_qs = 0; |
64db4cff PM |
2368 | |
2369 | /* | |
2370 | * This GP can't end until cpu checks in, so all of our | |
2371 | * callbacks can be processed during the next GP. | |
2372 | */ | |
48a7639c | 2373 | needwake = rcu_accelerate_cbs(rsp, rnp, rdp); |
64db4cff | 2374 | |
654e9533 PM |
2375 | rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags); |
2376 | /* ^^^ Released rnp->lock */ | |
48a7639c PM |
2377 | if (needwake) |
2378 | rcu_gp_kthread_wake(rsp); | |
64db4cff PM |
2379 | } |
2380 | } | |
2381 | ||
2382 | /* | |
2383 | * Check to see if there is a new grace period of which this CPU | |
2384 | * is not yet aware, and if so, set up local rcu_data state for it. | |
2385 | * Otherwise, see if this CPU has just passed through its first | |
2386 | * quiescent state for this grace period, and record that fact if so. | |
2387 | */ | |
2388 | static void | |
2389 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) | |
2390 | { | |
05eb552b PM |
2391 | /* Check for grace-period ends and beginnings. */ |
2392 | note_gp_changes(rsp, rdp); | |
64db4cff PM |
2393 | |
2394 | /* | |
2395 | * Does this CPU still need to do its part for current grace period? | |
2396 | * If no, return and let the other CPUs do their part as well. | |
2397 | */ | |
97c668b8 | 2398 | if (!rdp->core_needs_qs) |
64db4cff PM |
2399 | return; |
2400 | ||
2401 | /* | |
2402 | * Was there a quiescent state since the beginning of the grace | |
2403 | * period? If no, then exit and wait for the next call. | |
2404 | */ | |
5b74c458 | 2405 | if (rdp->cpu_no_qs.b.norm && |
5cd37193 | 2406 | rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) |
64db4cff PM |
2407 | return; |
2408 | ||
d3f6bad3 PM |
2409 | /* |
2410 | * Tell RCU we are done (but rcu_report_qs_rdp() will be the | |
2411 | * judge of that). | |
2412 | */ | |
d7d6a11e | 2413 | rcu_report_qs_rdp(rdp->cpu, rsp, rdp); |
64db4cff PM |
2414 | } |
2415 | ||
e74f4c45 | 2416 | /* |
b1420f1c PM |
2417 | * Send the specified CPU's RCU callbacks to the orphanage. The |
2418 | * specified CPU must be offline, and the caller must hold the | |
7b2e6011 | 2419 | * ->orphan_lock. |
e74f4c45 | 2420 | */ |
b1420f1c PM |
2421 | static void |
2422 | rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp, | |
2423 | struct rcu_node *rnp, struct rcu_data *rdp) | |
e74f4c45 | 2424 | { |
3fbfbf7a | 2425 | /* No-CBs CPUs do not have orphanable callbacks. */ |
ea46351c | 2426 | if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || rcu_is_nocb_cpu(rdp->cpu)) |
3fbfbf7a PM |
2427 | return; |
2428 | ||
b1420f1c PM |
2429 | /* |
2430 | * Orphan the callbacks. First adjust the counts. This is safe | |
abfd6e58 PM |
2431 | * because _rcu_barrier() excludes CPU-hotplug operations, so it |
2432 | * cannot be running now. Thus no memory barrier is required. | |
b1420f1c | 2433 | */ |
a50c3af9 | 2434 | if (rdp->nxtlist != NULL) { |
b1420f1c PM |
2435 | rsp->qlen_lazy += rdp->qlen_lazy; |
2436 | rsp->qlen += rdp->qlen; | |
2437 | rdp->n_cbs_orphaned += rdp->qlen; | |
a50c3af9 | 2438 | rdp->qlen_lazy = 0; |
7d0ae808 | 2439 | WRITE_ONCE(rdp->qlen, 0); |
a50c3af9 PM |
2440 | } |
2441 | ||
2442 | /* | |
b1420f1c PM |
2443 | * Next, move those callbacks still needing a grace period to |
2444 | * the orphanage, where some other CPU will pick them up. | |
2445 | * Some of the callbacks might have gone partway through a grace | |
2446 | * period, but that is too bad. They get to start over because we | |
2447 | * cannot assume that grace periods are synchronized across CPUs. | |
2448 | * We don't bother updating the ->nxttail[] array yet, instead | |
2449 | * we just reset the whole thing later on. | |
a50c3af9 | 2450 | */ |
b1420f1c PM |
2451 | if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) { |
2452 | *rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL]; | |
2453 | rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL]; | |
2454 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
a50c3af9 PM |
2455 | } |
2456 | ||
2457 | /* | |
b1420f1c PM |
2458 | * Then move the ready-to-invoke callbacks to the orphanage, |
2459 | * where some other CPU will pick them up. These will not be | |
2460 | * required to pass though another grace period: They are done. | |
a50c3af9 | 2461 | */ |
e5601400 | 2462 | if (rdp->nxtlist != NULL) { |
b1420f1c PM |
2463 | *rsp->orphan_donetail = rdp->nxtlist; |
2464 | rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL]; | |
e5601400 | 2465 | } |
e74f4c45 | 2466 | |
b33078b6 PM |
2467 | /* |
2468 | * Finally, initialize the rcu_data structure's list to empty and | |
2469 | * disallow further callbacks on this CPU. | |
2470 | */ | |
3f5d3ea6 | 2471 | init_callback_list(rdp); |
b33078b6 | 2472 | rdp->nxttail[RCU_NEXT_TAIL] = NULL; |
b1420f1c PM |
2473 | } |
2474 | ||
2475 | /* | |
2476 | * Adopt the RCU callbacks from the specified rcu_state structure's | |
7b2e6011 | 2477 | * orphanage. The caller must hold the ->orphan_lock. |
b1420f1c | 2478 | */ |
96d3fd0d | 2479 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags) |
b1420f1c PM |
2480 | { |
2481 | int i; | |
fa07a58f | 2482 | struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); |
b1420f1c | 2483 | |
3fbfbf7a | 2484 | /* No-CBs CPUs are handled specially. */ |
ea46351c PM |
2485 | if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || |
2486 | rcu_nocb_adopt_orphan_cbs(rsp, rdp, flags)) | |
3fbfbf7a PM |
2487 | return; |
2488 | ||
b1420f1c PM |
2489 | /* Do the accounting first. */ |
2490 | rdp->qlen_lazy += rsp->qlen_lazy; | |
2491 | rdp->qlen += rsp->qlen; | |
2492 | rdp->n_cbs_adopted += rsp->qlen; | |
8f5af6f1 PM |
2493 | if (rsp->qlen_lazy != rsp->qlen) |
2494 | rcu_idle_count_callbacks_posted(); | |
b1420f1c PM |
2495 | rsp->qlen_lazy = 0; |
2496 | rsp->qlen = 0; | |
2497 | ||
2498 | /* | |
2499 | * We do not need a memory barrier here because the only way we | |
2500 | * can get here if there is an rcu_barrier() in flight is if | |
2501 | * we are the task doing the rcu_barrier(). | |
2502 | */ | |
2503 | ||
2504 | /* First adopt the ready-to-invoke callbacks. */ | |
2505 | if (rsp->orphan_donelist != NULL) { | |
2506 | *rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL]; | |
2507 | *rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist; | |
2508 | for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--) | |
2509 | if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) | |
2510 | rdp->nxttail[i] = rsp->orphan_donetail; | |
2511 | rsp->orphan_donelist = NULL; | |
2512 | rsp->orphan_donetail = &rsp->orphan_donelist; | |
2513 | } | |
2514 | ||
2515 | /* And then adopt the callbacks that still need a grace period. */ | |
2516 | if (rsp->orphan_nxtlist != NULL) { | |
2517 | *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist; | |
2518 | rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail; | |
2519 | rsp->orphan_nxtlist = NULL; | |
2520 | rsp->orphan_nxttail = &rsp->orphan_nxtlist; | |
2521 | } | |
2522 | } | |
2523 | ||
2524 | /* | |
2525 | * Trace the fact that this CPU is going offline. | |
2526 | */ | |
2527 | static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) | |
2528 | { | |
2529 | RCU_TRACE(unsigned long mask); | |
2530 | RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda)); | |
2531 | RCU_TRACE(struct rcu_node *rnp = rdp->mynode); | |
2532 | ||
ea46351c PM |
2533 | if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) |
2534 | return; | |
2535 | ||
b1420f1c | 2536 | RCU_TRACE(mask = rdp->grpmask); |
e5601400 PM |
2537 | trace_rcu_grace_period(rsp->name, |
2538 | rnp->gpnum + 1 - !!(rnp->qsmask & mask), | |
f7f7bac9 | 2539 | TPS("cpuofl")); |
64db4cff PM |
2540 | } |
2541 | ||
8af3a5e7 PM |
2542 | /* |
2543 | * All CPUs for the specified rcu_node structure have gone offline, | |
2544 | * and all tasks that were preempted within an RCU read-side critical | |
2545 | * section while running on one of those CPUs have since exited their RCU | |
2546 | * read-side critical section. Some other CPU is reporting this fact with | |
2547 | * the specified rcu_node structure's ->lock held and interrupts disabled. | |
2548 | * This function therefore goes up the tree of rcu_node structures, | |
2549 | * clearing the corresponding bits in the ->qsmaskinit fields. Note that | |
2550 | * the leaf rcu_node structure's ->qsmaskinit field has already been | |
2551 | * updated | |
2552 | * | |
2553 | * This function does check that the specified rcu_node structure has | |
2554 | * all CPUs offline and no blocked tasks, so it is OK to invoke it | |
2555 | * prematurely. That said, invoking it after the fact will cost you | |
2556 | * a needless lock acquisition. So once it has done its work, don't | |
2557 | * invoke it again. | |
2558 | */ | |
2559 | static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf) | |
2560 | { | |
2561 | long mask; | |
2562 | struct rcu_node *rnp = rnp_leaf; | |
2563 | ||
ea46351c PM |
2564 | if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || |
2565 | rnp->qsmaskinit || rcu_preempt_has_tasks(rnp)) | |
8af3a5e7 PM |
2566 | return; |
2567 | for (;;) { | |
2568 | mask = rnp->grpmask; | |
2569 | rnp = rnp->parent; | |
2570 | if (!rnp) | |
2571 | break; | |
2572 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ | |
2573 | smp_mb__after_unlock_lock(); /* GP memory ordering. */ | |
2574 | rnp->qsmaskinit &= ~mask; | |
0aa04b05 | 2575 | rnp->qsmask &= ~mask; |
8af3a5e7 PM |
2576 | if (rnp->qsmaskinit) { |
2577 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
2578 | return; | |
2579 | } | |
2580 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
2581 | } | |
2582 | } | |
2583 | ||
88428cc5 PM |
2584 | /* |
2585 | * The CPU is exiting the idle loop into the arch_cpu_idle_dead() | |
2586 | * function. We now remove it from the rcu_node tree's ->qsmaskinit | |
2587 | * bit masks. | |
2588 | */ | |
2589 | static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp) | |
2590 | { | |
2591 | unsigned long flags; | |
2592 | unsigned long mask; | |
2593 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); | |
2594 | struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ | |
2595 | ||
ea46351c PM |
2596 | if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) |
2597 | return; | |
2598 | ||
88428cc5 PM |
2599 | /* Remove outgoing CPU from mask in the leaf rcu_node structure. */ |
2600 | mask = rdp->grpmask; | |
2601 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
2602 | smp_mb__after_unlock_lock(); /* Enforce GP memory-order guarantee. */ | |
2603 | rnp->qsmaskinitnext &= ~mask; | |
2604 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
2605 | } | |
2606 | ||
64db4cff | 2607 | /* |
e5601400 | 2608 | * The CPU has been completely removed, and some other CPU is reporting |
b1420f1c PM |
2609 | * this fact from process context. Do the remainder of the cleanup, |
2610 | * including orphaning the outgoing CPU's RCU callbacks, and also | |
1331e7a1 PM |
2611 | * adopting them. There can only be one CPU hotplug operation at a time, |
2612 | * so no other CPU can be attempting to update rcu_cpu_kthread_task. | |
64db4cff | 2613 | */ |
e5601400 | 2614 | static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
64db4cff | 2615 | { |
2036d94a | 2616 | unsigned long flags; |
e5601400 | 2617 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
b1420f1c | 2618 | struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ |
e5601400 | 2619 | |
ea46351c PM |
2620 | if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) |
2621 | return; | |
2622 | ||
2036d94a | 2623 | /* Adjust any no-longer-needed kthreads. */ |
5d01bbd1 | 2624 | rcu_boost_kthread_setaffinity(rnp, -1); |
2036d94a | 2625 | |
b1420f1c | 2626 | /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */ |
78043c46 | 2627 | raw_spin_lock_irqsave(&rsp->orphan_lock, flags); |
b1420f1c | 2628 | rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp); |
96d3fd0d | 2629 | rcu_adopt_orphan_cbs(rsp, flags); |
a8f4cbad | 2630 | raw_spin_unlock_irqrestore(&rsp->orphan_lock, flags); |
b1420f1c | 2631 | |
cf01537e PM |
2632 | WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL, |
2633 | "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n", | |
2634 | cpu, rdp->qlen, rdp->nxtlist); | |
64db4cff PM |
2635 | } |
2636 | ||
64db4cff PM |
2637 | /* |
2638 | * Invoke any RCU callbacks that have made it to the end of their grace | |
2639 | * period. Thottle as specified by rdp->blimit. | |
2640 | */ | |
37c72e56 | 2641 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
2642 | { |
2643 | unsigned long flags; | |
2644 | struct rcu_head *next, *list, **tail; | |
878d7439 ED |
2645 | long bl, count, count_lazy; |
2646 | int i; | |
64db4cff | 2647 | |
dc35c893 | 2648 | /* If no callbacks are ready, just return. */ |
29c00b4a | 2649 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) { |
486e2593 | 2650 | trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0); |
7d0ae808 | 2651 | trace_rcu_batch_end(rsp->name, 0, !!READ_ONCE(rdp->nxtlist), |
4968c300 PM |
2652 | need_resched(), is_idle_task(current), |
2653 | rcu_is_callbacks_kthread()); | |
64db4cff | 2654 | return; |
29c00b4a | 2655 | } |
64db4cff PM |
2656 | |
2657 | /* | |
2658 | * Extract the list of ready callbacks, disabling to prevent | |
2659 | * races with call_rcu() from interrupt handlers. | |
2660 | */ | |
2661 | local_irq_save(flags); | |
8146c4e2 | 2662 | WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); |
29c00b4a | 2663 | bl = rdp->blimit; |
486e2593 | 2664 | trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl); |
64db4cff PM |
2665 | list = rdp->nxtlist; |
2666 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; | |
2667 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
2668 | tail = rdp->nxttail[RCU_DONE_TAIL]; | |
b41772ab PM |
2669 | for (i = RCU_NEXT_SIZE - 1; i >= 0; i--) |
2670 | if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) | |
2671 | rdp->nxttail[i] = &rdp->nxtlist; | |
64db4cff PM |
2672 | local_irq_restore(flags); |
2673 | ||
2674 | /* Invoke callbacks. */ | |
486e2593 | 2675 | count = count_lazy = 0; |
64db4cff PM |
2676 | while (list) { |
2677 | next = list->next; | |
2678 | prefetch(next); | |
551d55a9 | 2679 | debug_rcu_head_unqueue(list); |
486e2593 PM |
2680 | if (__rcu_reclaim(rsp->name, list)) |
2681 | count_lazy++; | |
64db4cff | 2682 | list = next; |
dff1672d PM |
2683 | /* Stop only if limit reached and CPU has something to do. */ |
2684 | if (++count >= bl && | |
2685 | (need_resched() || | |
2686 | (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) | |
64db4cff PM |
2687 | break; |
2688 | } | |
2689 | ||
2690 | local_irq_save(flags); | |
4968c300 PM |
2691 | trace_rcu_batch_end(rsp->name, count, !!list, need_resched(), |
2692 | is_idle_task(current), | |
2693 | rcu_is_callbacks_kthread()); | |
64db4cff PM |
2694 | |
2695 | /* Update count, and requeue any remaining callbacks. */ | |
64db4cff PM |
2696 | if (list != NULL) { |
2697 | *tail = rdp->nxtlist; | |
2698 | rdp->nxtlist = list; | |
b41772ab PM |
2699 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
2700 | if (&rdp->nxtlist == rdp->nxttail[i]) | |
2701 | rdp->nxttail[i] = tail; | |
64db4cff PM |
2702 | else |
2703 | break; | |
2704 | } | |
b1420f1c PM |
2705 | smp_mb(); /* List handling before counting for rcu_barrier(). */ |
2706 | rdp->qlen_lazy -= count_lazy; | |
7d0ae808 | 2707 | WRITE_ONCE(rdp->qlen, rdp->qlen - count); |
b1420f1c | 2708 | rdp->n_cbs_invoked += count; |
64db4cff PM |
2709 | |
2710 | /* Reinstate batch limit if we have worked down the excess. */ | |
2711 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) | |
2712 | rdp->blimit = blimit; | |
2713 | ||
37c72e56 PM |
2714 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
2715 | if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { | |
2716 | rdp->qlen_last_fqs_check = 0; | |
2717 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
2718 | } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) | |
2719 | rdp->qlen_last_fqs_check = rdp->qlen; | |
cfca9279 | 2720 | WARN_ON_ONCE((rdp->nxtlist == NULL) != (rdp->qlen == 0)); |
37c72e56 | 2721 | |
64db4cff PM |
2722 | local_irq_restore(flags); |
2723 | ||
e0f23060 | 2724 | /* Re-invoke RCU core processing if there are callbacks remaining. */ |
64db4cff | 2725 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
a46e0899 | 2726 | invoke_rcu_core(); |
64db4cff PM |
2727 | } |
2728 | ||
2729 | /* | |
2730 | * Check to see if this CPU is in a non-context-switch quiescent state | |
2731 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). | |
e0f23060 | 2732 | * Also schedule RCU core processing. |
64db4cff | 2733 | * |
9b2e4f18 | 2734 | * This function must be called from hardirq context. It is normally |
64db4cff PM |
2735 | * invoked from the scheduling-clock interrupt. If rcu_pending returns |
2736 | * false, there is no point in invoking rcu_check_callbacks(). | |
2737 | */ | |
c3377c2d | 2738 | void rcu_check_callbacks(int user) |
64db4cff | 2739 | { |
f7f7bac9 | 2740 | trace_rcu_utilization(TPS("Start scheduler-tick")); |
a858af28 | 2741 | increment_cpu_stall_ticks(); |
9b2e4f18 | 2742 | if (user || rcu_is_cpu_rrupt_from_idle()) { |
64db4cff PM |
2743 | |
2744 | /* | |
2745 | * Get here if this CPU took its interrupt from user | |
2746 | * mode or from the idle loop, and if this is not a | |
2747 | * nested interrupt. In this case, the CPU is in | |
d6714c22 | 2748 | * a quiescent state, so note it. |
64db4cff PM |
2749 | * |
2750 | * No memory barrier is required here because both | |
d6714c22 PM |
2751 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
2752 | * variables that other CPUs neither access nor modify, | |
2753 | * at least not while the corresponding CPU is online. | |
64db4cff PM |
2754 | */ |
2755 | ||
284a8c93 PM |
2756 | rcu_sched_qs(); |
2757 | rcu_bh_qs(); | |
64db4cff PM |
2758 | |
2759 | } else if (!in_softirq()) { | |
2760 | ||
2761 | /* | |
2762 | * Get here if this CPU did not take its interrupt from | |
2763 | * softirq, in other words, if it is not interrupting | |
2764 | * a rcu_bh read-side critical section. This is an _bh | |
d6714c22 | 2765 | * critical section, so note it. |
64db4cff PM |
2766 | */ |
2767 | ||
284a8c93 | 2768 | rcu_bh_qs(); |
64db4cff | 2769 | } |
86aea0e6 | 2770 | rcu_preempt_check_callbacks(); |
e3950ecd | 2771 | if (rcu_pending()) |
a46e0899 | 2772 | invoke_rcu_core(); |
8315f422 PM |
2773 | if (user) |
2774 | rcu_note_voluntary_context_switch(current); | |
f7f7bac9 | 2775 | trace_rcu_utilization(TPS("End scheduler-tick")); |
64db4cff PM |
2776 | } |
2777 | ||
64db4cff PM |
2778 | /* |
2779 | * Scan the leaf rcu_node structures, processing dyntick state for any that | |
2780 | * have not yet encountered a quiescent state, using the function specified. | |
27f4d280 PM |
2781 | * Also initiate boosting for any threads blocked on the root rcu_node. |
2782 | * | |
ee47eb9f | 2783 | * The caller must have suppressed start of new grace periods. |
64db4cff | 2784 | */ |
217af2a2 PM |
2785 | static void force_qs_rnp(struct rcu_state *rsp, |
2786 | int (*f)(struct rcu_data *rsp, bool *isidle, | |
2787 | unsigned long *maxj), | |
2788 | bool *isidle, unsigned long *maxj) | |
64db4cff PM |
2789 | { |
2790 | unsigned long bit; | |
2791 | int cpu; | |
2792 | unsigned long flags; | |
2793 | unsigned long mask; | |
a0b6c9a7 | 2794 | struct rcu_node *rnp; |
64db4cff | 2795 | |
a0b6c9a7 | 2796 | rcu_for_each_leaf_node(rsp, rnp) { |
bde6c3aa | 2797 | cond_resched_rcu_qs(); |
64db4cff | 2798 | mask = 0; |
1304afb2 | 2799 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 2800 | smp_mb__after_unlock_lock(); |
a0b6c9a7 | 2801 | if (rnp->qsmask == 0) { |
a77da14c PM |
2802 | if (rcu_state_p == &rcu_sched_state || |
2803 | rsp != rcu_state_p || | |
2804 | rcu_preempt_blocked_readers_cgp(rnp)) { | |
2805 | /* | |
2806 | * No point in scanning bits because they | |
2807 | * are all zero. But we might need to | |
2808 | * priority-boost blocked readers. | |
2809 | */ | |
2810 | rcu_initiate_boost(rnp, flags); | |
2811 | /* rcu_initiate_boost() releases rnp->lock */ | |
2812 | continue; | |
2813 | } | |
2814 | if (rnp->parent && | |
2815 | (rnp->parent->qsmask & rnp->grpmask)) { | |
2816 | /* | |
2817 | * Race between grace-period | |
2818 | * initialization and task exiting RCU | |
2819 | * read-side critical section: Report. | |
2820 | */ | |
2821 | rcu_report_unblock_qs_rnp(rsp, rnp, flags); | |
2822 | /* rcu_report_unblock_qs_rnp() rlses ->lock */ | |
2823 | continue; | |
2824 | } | |
64db4cff | 2825 | } |
a0b6c9a7 | 2826 | cpu = rnp->grplo; |
64db4cff | 2827 | bit = 1; |
a0b6c9a7 | 2828 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
0edd1b17 | 2829 | if ((rnp->qsmask & bit) != 0) { |
0edd1b17 PM |
2830 | if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj)) |
2831 | mask |= bit; | |
2832 | } | |
64db4cff | 2833 | } |
45f014c5 | 2834 | if (mask != 0) { |
654e9533 PM |
2835 | /* Idle/offline CPUs, report (releases rnp->lock. */ |
2836 | rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags); | |
0aa04b05 PM |
2837 | } else { |
2838 | /* Nothing to do here, so just drop the lock. */ | |
2839 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
64db4cff | 2840 | } |
64db4cff | 2841 | } |
64db4cff PM |
2842 | } |
2843 | ||
2844 | /* | |
2845 | * Force quiescent states on reluctant CPUs, and also detect which | |
2846 | * CPUs are in dyntick-idle mode. | |
2847 | */ | |
4cdfc175 | 2848 | static void force_quiescent_state(struct rcu_state *rsp) |
64db4cff PM |
2849 | { |
2850 | unsigned long flags; | |
394f2769 PM |
2851 | bool ret; |
2852 | struct rcu_node *rnp; | |
2853 | struct rcu_node *rnp_old = NULL; | |
2854 | ||
2855 | /* Funnel through hierarchy to reduce memory contention. */ | |
d860d403 | 2856 | rnp = __this_cpu_read(rsp->rda->mynode); |
394f2769 | 2857 | for (; rnp != NULL; rnp = rnp->parent) { |
7d0ae808 | 2858 | ret = (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) || |
394f2769 PM |
2859 | !raw_spin_trylock(&rnp->fqslock); |
2860 | if (rnp_old != NULL) | |
2861 | raw_spin_unlock(&rnp_old->fqslock); | |
2862 | if (ret) { | |
a792563b | 2863 | rsp->n_force_qs_lh++; |
394f2769 PM |
2864 | return; |
2865 | } | |
2866 | rnp_old = rnp; | |
2867 | } | |
2868 | /* rnp_old == rcu_get_root(rsp), rnp == NULL. */ | |
64db4cff | 2869 | |
394f2769 PM |
2870 | /* Reached the root of the rcu_node tree, acquire lock. */ |
2871 | raw_spin_lock_irqsave(&rnp_old->lock, flags); | |
6303b9c8 | 2872 | smp_mb__after_unlock_lock(); |
394f2769 | 2873 | raw_spin_unlock(&rnp_old->fqslock); |
7d0ae808 | 2874 | if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { |
a792563b | 2875 | rsp->n_force_qs_lh++; |
394f2769 | 2876 | raw_spin_unlock_irqrestore(&rnp_old->lock, flags); |
4cdfc175 | 2877 | return; /* Someone beat us to it. */ |
46a1e34e | 2878 | } |
7d0ae808 | 2879 | WRITE_ONCE(rsp->gp_flags, READ_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS); |
394f2769 | 2880 | raw_spin_unlock_irqrestore(&rnp_old->lock, flags); |
2aa792e6 | 2881 | rcu_gp_kthread_wake(rsp); |
64db4cff PM |
2882 | } |
2883 | ||
64db4cff | 2884 | /* |
e0f23060 PM |
2885 | * This does the RCU core processing work for the specified rcu_state |
2886 | * and rcu_data structures. This may be called only from the CPU to | |
2887 | * whom the rdp belongs. | |
64db4cff PM |
2888 | */ |
2889 | static void | |
1bca8cf1 | 2890 | __rcu_process_callbacks(struct rcu_state *rsp) |
64db4cff PM |
2891 | { |
2892 | unsigned long flags; | |
48a7639c | 2893 | bool needwake; |
fa07a58f | 2894 | struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); |
64db4cff | 2895 | |
2e597558 PM |
2896 | WARN_ON_ONCE(rdp->beenonline == 0); |
2897 | ||
64db4cff PM |
2898 | /* Update RCU state based on any recent quiescent states. */ |
2899 | rcu_check_quiescent_state(rsp, rdp); | |
2900 | ||
2901 | /* Does this CPU require a not-yet-started grace period? */ | |
dc35c893 | 2902 | local_irq_save(flags); |
64db4cff | 2903 | if (cpu_needs_another_gp(rsp, rdp)) { |
dc35c893 | 2904 | raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */ |
48a7639c | 2905 | needwake = rcu_start_gp(rsp); |
b8462084 | 2906 | raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); |
48a7639c PM |
2907 | if (needwake) |
2908 | rcu_gp_kthread_wake(rsp); | |
dc35c893 PM |
2909 | } else { |
2910 | local_irq_restore(flags); | |
64db4cff PM |
2911 | } |
2912 | ||
2913 | /* If there are callbacks ready, invoke them. */ | |
09223371 | 2914 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
a46e0899 | 2915 | invoke_rcu_callbacks(rsp, rdp); |
96d3fd0d PM |
2916 | |
2917 | /* Do any needed deferred wakeups of rcuo kthreads. */ | |
2918 | do_nocb_deferred_wakeup(rdp); | |
09223371 SL |
2919 | } |
2920 | ||
64db4cff | 2921 | /* |
e0f23060 | 2922 | * Do RCU core processing for the current CPU. |
64db4cff | 2923 | */ |
09223371 | 2924 | static void rcu_process_callbacks(struct softirq_action *unused) |
64db4cff | 2925 | { |
6ce75a23 PM |
2926 | struct rcu_state *rsp; |
2927 | ||
bfa00b4c PM |
2928 | if (cpu_is_offline(smp_processor_id())) |
2929 | return; | |
f7f7bac9 | 2930 | trace_rcu_utilization(TPS("Start RCU core")); |
6ce75a23 PM |
2931 | for_each_rcu_flavor(rsp) |
2932 | __rcu_process_callbacks(rsp); | |
f7f7bac9 | 2933 | trace_rcu_utilization(TPS("End RCU core")); |
64db4cff PM |
2934 | } |
2935 | ||
a26ac245 | 2936 | /* |
e0f23060 PM |
2937 | * Schedule RCU callback invocation. If the specified type of RCU |
2938 | * does not support RCU priority boosting, just do a direct call, | |
2939 | * otherwise wake up the per-CPU kernel kthread. Note that because we | |
924df8a0 | 2940 | * are running on the current CPU with softirqs disabled, the |
e0f23060 | 2941 | * rcu_cpu_kthread_task cannot disappear out from under us. |
a26ac245 | 2942 | */ |
a46e0899 | 2943 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
a26ac245 | 2944 | { |
7d0ae808 | 2945 | if (unlikely(!READ_ONCE(rcu_scheduler_fully_active))) |
b0d30417 | 2946 | return; |
a46e0899 PM |
2947 | if (likely(!rsp->boost)) { |
2948 | rcu_do_batch(rsp, rdp); | |
a26ac245 PM |
2949 | return; |
2950 | } | |
a46e0899 | 2951 | invoke_rcu_callbacks_kthread(); |
a26ac245 PM |
2952 | } |
2953 | ||
a46e0899 | 2954 | static void invoke_rcu_core(void) |
09223371 | 2955 | { |
b0f74036 PM |
2956 | if (cpu_online(smp_processor_id())) |
2957 | raise_softirq(RCU_SOFTIRQ); | |
09223371 SL |
2958 | } |
2959 | ||
29154c57 PM |
2960 | /* |
2961 | * Handle any core-RCU processing required by a call_rcu() invocation. | |
2962 | */ | |
2963 | static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, | |
2964 | struct rcu_head *head, unsigned long flags) | |
64db4cff | 2965 | { |
48a7639c PM |
2966 | bool needwake; |
2967 | ||
62fde6ed PM |
2968 | /* |
2969 | * If called from an extended quiescent state, invoke the RCU | |
2970 | * core in order to force a re-evaluation of RCU's idleness. | |
2971 | */ | |
9910affa | 2972 | if (!rcu_is_watching()) |
62fde6ed PM |
2973 | invoke_rcu_core(); |
2974 | ||
a16b7a69 | 2975 | /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ |
29154c57 | 2976 | if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) |
2655d57e | 2977 | return; |
64db4cff | 2978 | |
37c72e56 PM |
2979 | /* |
2980 | * Force the grace period if too many callbacks or too long waiting. | |
2981 | * Enforce hysteresis, and don't invoke force_quiescent_state() | |
2982 | * if some other CPU has recently done so. Also, don't bother | |
2983 | * invoking force_quiescent_state() if the newly enqueued callback | |
2984 | * is the only one waiting for a grace period to complete. | |
2985 | */ | |
2655d57e | 2986 | if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { |
b52573d2 PM |
2987 | |
2988 | /* Are we ignoring a completed grace period? */ | |
470716fc | 2989 | note_gp_changes(rsp, rdp); |
b52573d2 PM |
2990 | |
2991 | /* Start a new grace period if one not already started. */ | |
2992 | if (!rcu_gp_in_progress(rsp)) { | |
b52573d2 PM |
2993 | struct rcu_node *rnp_root = rcu_get_root(rsp); |
2994 | ||
b8462084 | 2995 | raw_spin_lock(&rnp_root->lock); |
6303b9c8 | 2996 | smp_mb__after_unlock_lock(); |
48a7639c | 2997 | needwake = rcu_start_gp(rsp); |
b8462084 | 2998 | raw_spin_unlock(&rnp_root->lock); |
48a7639c PM |
2999 | if (needwake) |
3000 | rcu_gp_kthread_wake(rsp); | |
b52573d2 PM |
3001 | } else { |
3002 | /* Give the grace period a kick. */ | |
3003 | rdp->blimit = LONG_MAX; | |
3004 | if (rsp->n_force_qs == rdp->n_force_qs_snap && | |
3005 | *rdp->nxttail[RCU_DONE_TAIL] != head) | |
4cdfc175 | 3006 | force_quiescent_state(rsp); |
b52573d2 PM |
3007 | rdp->n_force_qs_snap = rsp->n_force_qs; |
3008 | rdp->qlen_last_fqs_check = rdp->qlen; | |
3009 | } | |
4cdfc175 | 3010 | } |
29154c57 PM |
3011 | } |
3012 | ||
ae150184 PM |
3013 | /* |
3014 | * RCU callback function to leak a callback. | |
3015 | */ | |
3016 | static void rcu_leak_callback(struct rcu_head *rhp) | |
3017 | { | |
3018 | } | |
3019 | ||
3fbfbf7a PM |
3020 | /* |
3021 | * Helper function for call_rcu() and friends. The cpu argument will | |
3022 | * normally be -1, indicating "currently running CPU". It may specify | |
3023 | * a CPU only if that CPU is a no-CBs CPU. Currently, only _rcu_barrier() | |
3024 | * is expected to specify a CPU. | |
3025 | */ | |
64db4cff PM |
3026 | static void |
3027 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), | |
3fbfbf7a | 3028 | struct rcu_state *rsp, int cpu, bool lazy) |
64db4cff PM |
3029 | { |
3030 | unsigned long flags; | |
3031 | struct rcu_data *rdp; | |
3032 | ||
1146edcb | 3033 | WARN_ON_ONCE((unsigned long)head & 0x1); /* Misaligned rcu_head! */ |
ae150184 PM |
3034 | if (debug_rcu_head_queue(head)) { |
3035 | /* Probable double call_rcu(), so leak the callback. */ | |
7d0ae808 | 3036 | WRITE_ONCE(head->func, rcu_leak_callback); |
ae150184 PM |
3037 | WARN_ONCE(1, "__call_rcu(): Leaked duplicate callback\n"); |
3038 | return; | |
3039 | } | |
64db4cff PM |
3040 | head->func = func; |
3041 | head->next = NULL; | |
3042 | ||
64db4cff PM |
3043 | /* |
3044 | * Opportunistically note grace-period endings and beginnings. | |
3045 | * Note that we might see a beginning right after we see an | |
3046 | * end, but never vice versa, since this CPU has to pass through | |
3047 | * a quiescent state betweentimes. | |
3048 | */ | |
3049 | local_irq_save(flags); | |
394f99a9 | 3050 | rdp = this_cpu_ptr(rsp->rda); |
64db4cff PM |
3051 | |
3052 | /* Add the callback to our list. */ | |
3fbfbf7a PM |
3053 | if (unlikely(rdp->nxttail[RCU_NEXT_TAIL] == NULL) || cpu != -1) { |
3054 | int offline; | |
3055 | ||
3056 | if (cpu != -1) | |
3057 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
143da9c2 PM |
3058 | if (likely(rdp->mynode)) { |
3059 | /* Post-boot, so this should be for a no-CBs CPU. */ | |
3060 | offline = !__call_rcu_nocb(rdp, head, lazy, flags); | |
3061 | WARN_ON_ONCE(offline); | |
3062 | /* Offline CPU, _call_rcu() illegal, leak callback. */ | |
3063 | local_irq_restore(flags); | |
3064 | return; | |
3065 | } | |
3066 | /* | |
3067 | * Very early boot, before rcu_init(). Initialize if needed | |
3068 | * and then drop through to queue the callback. | |
3069 | */ | |
3070 | BUG_ON(cpu != -1); | |
34404ca8 | 3071 | WARN_ON_ONCE(!rcu_is_watching()); |
143da9c2 PM |
3072 | if (!likely(rdp->nxtlist)) |
3073 | init_default_callback_list(rdp); | |
0d8ee37e | 3074 | } |
7d0ae808 | 3075 | WRITE_ONCE(rdp->qlen, rdp->qlen + 1); |
486e2593 PM |
3076 | if (lazy) |
3077 | rdp->qlen_lazy++; | |
c57afe80 PM |
3078 | else |
3079 | rcu_idle_count_callbacks_posted(); | |
b1420f1c PM |
3080 | smp_mb(); /* Count before adding callback for rcu_barrier(). */ |
3081 | *rdp->nxttail[RCU_NEXT_TAIL] = head; | |
3082 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; | |
2655d57e | 3083 | |
d4c08f2a PM |
3084 | if (__is_kfree_rcu_offset((unsigned long)func)) |
3085 | trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func, | |
486e2593 | 3086 | rdp->qlen_lazy, rdp->qlen); |
d4c08f2a | 3087 | else |
486e2593 | 3088 | trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen); |
d4c08f2a | 3089 | |
29154c57 PM |
3090 | /* Go handle any RCU core processing required. */ |
3091 | __call_rcu_core(rsp, rdp, head, flags); | |
64db4cff PM |
3092 | local_irq_restore(flags); |
3093 | } | |
3094 | ||
3095 | /* | |
d6714c22 | 3096 | * Queue an RCU-sched callback for invocation after a grace period. |
64db4cff | 3097 | */ |
d6714c22 | 3098 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
64db4cff | 3099 | { |
3fbfbf7a | 3100 | __call_rcu(head, func, &rcu_sched_state, -1, 0); |
64db4cff | 3101 | } |
d6714c22 | 3102 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
64db4cff PM |
3103 | |
3104 | /* | |
486e2593 | 3105 | * Queue an RCU callback for invocation after a quicker grace period. |
64db4cff PM |
3106 | */ |
3107 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
3108 | { | |
3fbfbf7a | 3109 | __call_rcu(head, func, &rcu_bh_state, -1, 0); |
64db4cff PM |
3110 | } |
3111 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
3112 | ||
495aa969 ACB |
3113 | /* |
3114 | * Queue an RCU callback for lazy invocation after a grace period. | |
3115 | * This will likely be later named something like "call_rcu_lazy()", | |
3116 | * but this change will require some way of tagging the lazy RCU | |
3117 | * callbacks in the list of pending callbacks. Until then, this | |
3118 | * function may only be called from __kfree_rcu(). | |
3119 | */ | |
3120 | void kfree_call_rcu(struct rcu_head *head, | |
3121 | void (*func)(struct rcu_head *rcu)) | |
3122 | { | |
e534165b | 3123 | __call_rcu(head, func, rcu_state_p, -1, 1); |
495aa969 ACB |
3124 | } |
3125 | EXPORT_SYMBOL_GPL(kfree_call_rcu); | |
3126 | ||
6d813391 PM |
3127 | /* |
3128 | * Because a context switch is a grace period for RCU-sched and RCU-bh, | |
3129 | * any blocking grace-period wait automatically implies a grace period | |
3130 | * if there is only one CPU online at any point time during execution | |
3131 | * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to | |
3132 | * occasionally incorrectly indicate that there are multiple CPUs online | |
3133 | * when there was in fact only one the whole time, as this just adds | |
3134 | * some overhead: RCU still operates correctly. | |
6d813391 PM |
3135 | */ |
3136 | static inline int rcu_blocking_is_gp(void) | |
3137 | { | |
95f0c1de PM |
3138 | int ret; |
3139 | ||
6d813391 | 3140 | might_sleep(); /* Check for RCU read-side critical section. */ |
95f0c1de PM |
3141 | preempt_disable(); |
3142 | ret = num_online_cpus() <= 1; | |
3143 | preempt_enable(); | |
3144 | return ret; | |
6d813391 PM |
3145 | } |
3146 | ||
6ebb237b PM |
3147 | /** |
3148 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. | |
3149 | * | |
3150 | * Control will return to the caller some time after a full rcu-sched | |
3151 | * grace period has elapsed, in other words after all currently executing | |
3152 | * rcu-sched read-side critical sections have completed. These read-side | |
3153 | * critical sections are delimited by rcu_read_lock_sched() and | |
3154 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), | |
3155 | * local_irq_disable(), and so on may be used in place of | |
3156 | * rcu_read_lock_sched(). | |
3157 | * | |
3158 | * This means that all preempt_disable code sequences, including NMI and | |
f0a0e6f2 PM |
3159 | * non-threaded hardware-interrupt handlers, in progress on entry will |
3160 | * have completed before this primitive returns. However, this does not | |
3161 | * guarantee that softirq handlers will have completed, since in some | |
3162 | * kernels, these handlers can run in process context, and can block. | |
3163 | * | |
3164 | * Note that this guarantee implies further memory-ordering guarantees. | |
3165 | * On systems with more than one CPU, when synchronize_sched() returns, | |
3166 | * each CPU is guaranteed to have executed a full memory barrier since the | |
3167 | * end of its last RCU-sched read-side critical section whose beginning | |
3168 | * preceded the call to synchronize_sched(). In addition, each CPU having | |
3169 | * an RCU read-side critical section that extends beyond the return from | |
3170 | * synchronize_sched() is guaranteed to have executed a full memory barrier | |
3171 | * after the beginning of synchronize_sched() and before the beginning of | |
3172 | * that RCU read-side critical section. Note that these guarantees include | |
3173 | * CPUs that are offline, idle, or executing in user mode, as well as CPUs | |
3174 | * that are executing in the kernel. | |
3175 | * | |
3176 | * Furthermore, if CPU A invoked synchronize_sched(), which returned | |
3177 | * to its caller on CPU B, then both CPU A and CPU B are guaranteed | |
3178 | * to have executed a full memory barrier during the execution of | |
3179 | * synchronize_sched() -- even if CPU A and CPU B are the same CPU (but | |
3180 | * again only if the system has more than one CPU). | |
6ebb237b PM |
3181 | * |
3182 | * This primitive provides the guarantees made by the (now removed) | |
3183 | * synchronize_kernel() API. In contrast, synchronize_rcu() only | |
3184 | * guarantees that rcu_read_lock() sections will have completed. | |
3185 | * In "classic RCU", these two guarantees happen to be one and | |
3186 | * the same, but can differ in realtime RCU implementations. | |
3187 | */ | |
3188 | void synchronize_sched(void) | |
3189 | { | |
f78f5b90 PM |
3190 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || |
3191 | lock_is_held(&rcu_lock_map) || | |
3192 | lock_is_held(&rcu_sched_lock_map), | |
3193 | "Illegal synchronize_sched() in RCU-sched read-side critical section"); | |
6ebb237b PM |
3194 | if (rcu_blocking_is_gp()) |
3195 | return; | |
5afff48b | 3196 | if (rcu_gp_is_expedited()) |
3705b88d AM |
3197 | synchronize_sched_expedited(); |
3198 | else | |
3199 | wait_rcu_gp(call_rcu_sched); | |
6ebb237b PM |
3200 | } |
3201 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
3202 | ||
3203 | /** | |
3204 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. | |
3205 | * | |
3206 | * Control will return to the caller some time after a full rcu_bh grace | |
3207 | * period has elapsed, in other words after all currently executing rcu_bh | |
3208 | * read-side critical sections have completed. RCU read-side critical | |
3209 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), | |
3210 | * and may be nested. | |
f0a0e6f2 PM |
3211 | * |
3212 | * See the description of synchronize_sched() for more detailed information | |
3213 | * on memory ordering guarantees. | |
6ebb237b PM |
3214 | */ |
3215 | void synchronize_rcu_bh(void) | |
3216 | { | |
f78f5b90 PM |
3217 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || |
3218 | lock_is_held(&rcu_lock_map) || | |
3219 | lock_is_held(&rcu_sched_lock_map), | |
3220 | "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section"); | |
6ebb237b PM |
3221 | if (rcu_blocking_is_gp()) |
3222 | return; | |
5afff48b | 3223 | if (rcu_gp_is_expedited()) |
3705b88d AM |
3224 | synchronize_rcu_bh_expedited(); |
3225 | else | |
3226 | wait_rcu_gp(call_rcu_bh); | |
6ebb237b PM |
3227 | } |
3228 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); | |
3229 | ||
765a3f4f PM |
3230 | /** |
3231 | * get_state_synchronize_rcu - Snapshot current RCU state | |
3232 | * | |
3233 | * Returns a cookie that is used by a later call to cond_synchronize_rcu() | |
3234 | * to determine whether or not a full grace period has elapsed in the | |
3235 | * meantime. | |
3236 | */ | |
3237 | unsigned long get_state_synchronize_rcu(void) | |
3238 | { | |
3239 | /* | |
3240 | * Any prior manipulation of RCU-protected data must happen | |
3241 | * before the load from ->gpnum. | |
3242 | */ | |
3243 | smp_mb(); /* ^^^ */ | |
3244 | ||
3245 | /* | |
3246 | * Make sure this load happens before the purportedly | |
3247 | * time-consuming work between get_state_synchronize_rcu() | |
3248 | * and cond_synchronize_rcu(). | |
3249 | */ | |
e534165b | 3250 | return smp_load_acquire(&rcu_state_p->gpnum); |
765a3f4f PM |
3251 | } |
3252 | EXPORT_SYMBOL_GPL(get_state_synchronize_rcu); | |
3253 | ||
3254 | /** | |
3255 | * cond_synchronize_rcu - Conditionally wait for an RCU grace period | |
3256 | * | |
3257 | * @oldstate: return value from earlier call to get_state_synchronize_rcu() | |
3258 | * | |
3259 | * If a full RCU grace period has elapsed since the earlier call to | |
3260 | * get_state_synchronize_rcu(), just return. Otherwise, invoke | |
3261 | * synchronize_rcu() to wait for a full grace period. | |
3262 | * | |
3263 | * Yes, this function does not take counter wrap into account. But | |
3264 | * counter wrap is harmless. If the counter wraps, we have waited for | |
3265 | * more than 2 billion grace periods (and way more on a 64-bit system!), | |
3266 | * so waiting for one additional grace period should be just fine. | |
3267 | */ | |
3268 | void cond_synchronize_rcu(unsigned long oldstate) | |
3269 | { | |
3270 | unsigned long newstate; | |
3271 | ||
3272 | /* | |
3273 | * Ensure that this load happens before any RCU-destructive | |
3274 | * actions the caller might carry out after we return. | |
3275 | */ | |
e534165b | 3276 | newstate = smp_load_acquire(&rcu_state_p->completed); |
765a3f4f PM |
3277 | if (ULONG_CMP_GE(oldstate, newstate)) |
3278 | synchronize_rcu(); | |
3279 | } | |
3280 | EXPORT_SYMBOL_GPL(cond_synchronize_rcu); | |
3281 | ||
24560056 PM |
3282 | /** |
3283 | * get_state_synchronize_sched - Snapshot current RCU-sched state | |
3284 | * | |
3285 | * Returns a cookie that is used by a later call to cond_synchronize_sched() | |
3286 | * to determine whether or not a full grace period has elapsed in the | |
3287 | * meantime. | |
3288 | */ | |
3289 | unsigned long get_state_synchronize_sched(void) | |
3290 | { | |
3291 | /* | |
3292 | * Any prior manipulation of RCU-protected data must happen | |
3293 | * before the load from ->gpnum. | |
3294 | */ | |
3295 | smp_mb(); /* ^^^ */ | |
3296 | ||
3297 | /* | |
3298 | * Make sure this load happens before the purportedly | |
3299 | * time-consuming work between get_state_synchronize_sched() | |
3300 | * and cond_synchronize_sched(). | |
3301 | */ | |
3302 | return smp_load_acquire(&rcu_sched_state.gpnum); | |
3303 | } | |
3304 | EXPORT_SYMBOL_GPL(get_state_synchronize_sched); | |
3305 | ||
3306 | /** | |
3307 | * cond_synchronize_sched - Conditionally wait for an RCU-sched grace period | |
3308 | * | |
3309 | * @oldstate: return value from earlier call to get_state_synchronize_sched() | |
3310 | * | |
3311 | * If a full RCU-sched grace period has elapsed since the earlier call to | |
3312 | * get_state_synchronize_sched(), just return. Otherwise, invoke | |
3313 | * synchronize_sched() to wait for a full grace period. | |
3314 | * | |
3315 | * Yes, this function does not take counter wrap into account. But | |
3316 | * counter wrap is harmless. If the counter wraps, we have waited for | |
3317 | * more than 2 billion grace periods (and way more on a 64-bit system!), | |
3318 | * so waiting for one additional grace period should be just fine. | |
3319 | */ | |
3320 | void cond_synchronize_sched(unsigned long oldstate) | |
3321 | { | |
3322 | unsigned long newstate; | |
3323 | ||
3324 | /* | |
3325 | * Ensure that this load happens before any RCU-destructive | |
3326 | * actions the caller might carry out after we return. | |
3327 | */ | |
3328 | newstate = smp_load_acquire(&rcu_sched_state.completed); | |
3329 | if (ULONG_CMP_GE(oldstate, newstate)) | |
3330 | synchronize_sched(); | |
3331 | } | |
3332 | EXPORT_SYMBOL_GPL(cond_synchronize_sched); | |
3333 | ||
28f00767 PM |
3334 | /* Adjust sequence number for start of update-side operation. */ |
3335 | static void rcu_seq_start(unsigned long *sp) | |
3336 | { | |
3337 | WRITE_ONCE(*sp, *sp + 1); | |
3338 | smp_mb(); /* Ensure update-side operation after counter increment. */ | |
3339 | WARN_ON_ONCE(!(*sp & 0x1)); | |
3340 | } | |
3341 | ||
3342 | /* Adjust sequence number for end of update-side operation. */ | |
3343 | static void rcu_seq_end(unsigned long *sp) | |
3344 | { | |
3345 | smp_mb(); /* Ensure update-side operation before counter increment. */ | |
3346 | WRITE_ONCE(*sp, *sp + 1); | |
3347 | WARN_ON_ONCE(*sp & 0x1); | |
3348 | } | |
3349 | ||
3350 | /* Take a snapshot of the update side's sequence number. */ | |
3351 | static unsigned long rcu_seq_snap(unsigned long *sp) | |
3352 | { | |
3353 | unsigned long s; | |
3354 | ||
3355 | smp_mb(); /* Caller's modifications seen first by other CPUs. */ | |
3356 | s = (READ_ONCE(*sp) + 3) & ~0x1; | |
3357 | smp_mb(); /* Above access must not bleed into critical section. */ | |
3358 | return s; | |
3359 | } | |
3360 | ||
3361 | /* | |
3362 | * Given a snapshot from rcu_seq_snap(), determine whether or not a | |
3363 | * full update-side operation has occurred. | |
3364 | */ | |
3365 | static bool rcu_seq_done(unsigned long *sp, unsigned long s) | |
3366 | { | |
3367 | return ULONG_CMP_GE(READ_ONCE(*sp), s); | |
3368 | } | |
3369 | ||
3370 | /* Wrapper functions for expedited grace periods. */ | |
3371 | static void rcu_exp_gp_seq_start(struct rcu_state *rsp) | |
3372 | { | |
3373 | rcu_seq_start(&rsp->expedited_sequence); | |
3374 | } | |
3375 | static void rcu_exp_gp_seq_end(struct rcu_state *rsp) | |
3376 | { | |
3377 | rcu_seq_end(&rsp->expedited_sequence); | |
704dd435 | 3378 | smp_mb(); /* Ensure that consecutive grace periods serialize. */ |
28f00767 PM |
3379 | } |
3380 | static unsigned long rcu_exp_gp_seq_snap(struct rcu_state *rsp) | |
3381 | { | |
3382 | return rcu_seq_snap(&rsp->expedited_sequence); | |
3383 | } | |
3384 | static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s) | |
3385 | { | |
3386 | return rcu_seq_done(&rsp->expedited_sequence, s); | |
3387 | } | |
3388 | ||
b9585e94 PM |
3389 | /* |
3390 | * Reset the ->expmaskinit values in the rcu_node tree to reflect any | |
3391 | * recent CPU-online activity. Note that these masks are not cleared | |
3392 | * when CPUs go offline, so they reflect the union of all CPUs that have | |
3393 | * ever been online. This means that this function normally takes its | |
3394 | * no-work-to-do fastpath. | |
3395 | */ | |
3396 | static void sync_exp_reset_tree_hotplug(struct rcu_state *rsp) | |
3397 | { | |
3398 | bool done; | |
3399 | unsigned long flags; | |
3400 | unsigned long mask; | |
3401 | unsigned long oldmask; | |
3402 | int ncpus = READ_ONCE(rsp->ncpus); | |
3403 | struct rcu_node *rnp; | |
3404 | struct rcu_node *rnp_up; | |
3405 | ||
3406 | /* If no new CPUs onlined since last time, nothing to do. */ | |
3407 | if (likely(ncpus == rsp->ncpus_snap)) | |
3408 | return; | |
3409 | rsp->ncpus_snap = ncpus; | |
3410 | ||
3411 | /* | |
3412 | * Each pass through the following loop propagates newly onlined | |
3413 | * CPUs for the current rcu_node structure up the rcu_node tree. | |
3414 | */ | |
3415 | rcu_for_each_leaf_node(rsp, rnp) { | |
3416 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
3417 | smp_mb__after_unlock_lock(); | |
3418 | if (rnp->expmaskinit == rnp->expmaskinitnext) { | |
3419 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
3420 | continue; /* No new CPUs, nothing to do. */ | |
3421 | } | |
3422 | ||
3423 | /* Update this node's mask, track old value for propagation. */ | |
3424 | oldmask = rnp->expmaskinit; | |
3425 | rnp->expmaskinit = rnp->expmaskinitnext; | |
3426 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
3427 | ||
3428 | /* If was already nonzero, nothing to propagate. */ | |
3429 | if (oldmask) | |
3430 | continue; | |
3431 | ||
3432 | /* Propagate the new CPU up the tree. */ | |
3433 | mask = rnp->grpmask; | |
3434 | rnp_up = rnp->parent; | |
3435 | done = false; | |
3436 | while (rnp_up) { | |
3437 | raw_spin_lock_irqsave(&rnp_up->lock, flags); | |
3438 | smp_mb__after_unlock_lock(); | |
3439 | if (rnp_up->expmaskinit) | |
3440 | done = true; | |
3441 | rnp_up->expmaskinit |= mask; | |
3442 | raw_spin_unlock_irqrestore(&rnp_up->lock, flags); | |
3443 | if (done) | |
3444 | break; | |
3445 | mask = rnp_up->grpmask; | |
3446 | rnp_up = rnp_up->parent; | |
3447 | } | |
3448 | } | |
3449 | } | |
3450 | ||
3451 | /* | |
3452 | * Reset the ->expmask values in the rcu_node tree in preparation for | |
3453 | * a new expedited grace period. | |
3454 | */ | |
3455 | static void __maybe_unused sync_exp_reset_tree(struct rcu_state *rsp) | |
3456 | { | |
3457 | unsigned long flags; | |
3458 | struct rcu_node *rnp; | |
3459 | ||
3460 | sync_exp_reset_tree_hotplug(rsp); | |
3461 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
3462 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
3463 | smp_mb__after_unlock_lock(); | |
3464 | WARN_ON_ONCE(rnp->expmask); | |
3465 | rnp->expmask = rnp->expmaskinit; | |
3466 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
3467 | } | |
3468 | } | |
3469 | ||
7922cd0e | 3470 | /* |
8203d6d0 | 3471 | * Return non-zero if there is no RCU expedited grace period in progress |
7922cd0e PM |
3472 | * for the specified rcu_node structure, in other words, if all CPUs and |
3473 | * tasks covered by the specified rcu_node structure have done their bit | |
3474 | * for the current expedited grace period. Works only for preemptible | |
3475 | * RCU -- other RCU implementation use other means. | |
3476 | * | |
3477 | * Caller must hold the root rcu_node's exp_funnel_mutex. | |
3478 | */ | |
3479 | static int sync_rcu_preempt_exp_done(struct rcu_node *rnp) | |
3480 | { | |
8203d6d0 | 3481 | return rnp->exp_tasks == NULL && |
7922cd0e PM |
3482 | READ_ONCE(rnp->expmask) == 0; |
3483 | } | |
3484 | ||
3485 | /* | |
3486 | * Report the exit from RCU read-side critical section for the last task | |
3487 | * that queued itself during or before the current expedited preemptible-RCU | |
3488 | * grace period. This event is reported either to the rcu_node structure on | |
3489 | * which the task was queued or to one of that rcu_node structure's ancestors, | |
3490 | * recursively up the tree. (Calm down, calm down, we do the recursion | |
3491 | * iteratively!) | |
3492 | * | |
8203d6d0 PM |
3493 | * Caller must hold the root rcu_node's exp_funnel_mutex and the |
3494 | * specified rcu_node structure's ->lock. | |
7922cd0e | 3495 | */ |
8203d6d0 PM |
3496 | static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, |
3497 | bool wake, unsigned long flags) | |
3498 | __releases(rnp->lock) | |
7922cd0e | 3499 | { |
7922cd0e PM |
3500 | unsigned long mask; |
3501 | ||
7922cd0e PM |
3502 | for (;;) { |
3503 | if (!sync_rcu_preempt_exp_done(rnp)) { | |
8203d6d0 PM |
3504 | if (!rnp->expmask) |
3505 | rcu_initiate_boost(rnp, flags); | |
3506 | else | |
3507 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
7922cd0e PM |
3508 | break; |
3509 | } | |
3510 | if (rnp->parent == NULL) { | |
3511 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
3512 | if (wake) { | |
3513 | smp_mb(); /* EGP done before wake_up(). */ | |
3514 | wake_up(&rsp->expedited_wq); | |
3515 | } | |
3516 | break; | |
3517 | } | |
3518 | mask = rnp->grpmask; | |
3519 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ | |
3520 | rnp = rnp->parent; | |
3521 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ | |
3522 | smp_mb__after_unlock_lock(); | |
8203d6d0 | 3523 | WARN_ON_ONCE(!(rnp->expmask & mask)); |
7922cd0e PM |
3524 | rnp->expmask &= ~mask; |
3525 | } | |
3526 | } | |
3527 | ||
8203d6d0 PM |
3528 | /* |
3529 | * Report expedited quiescent state for specified node. This is a | |
3530 | * lock-acquisition wrapper function for __rcu_report_exp_rnp(). | |
3531 | * | |
3532 | * Caller must hold the root rcu_node's exp_funnel_mutex. | |
3533 | */ | |
3534 | static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp, | |
3535 | struct rcu_node *rnp, bool wake) | |
3536 | { | |
3537 | unsigned long flags; | |
3538 | ||
3539 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
3540 | smp_mb__after_unlock_lock(); | |
3541 | __rcu_report_exp_rnp(rsp, rnp, wake, flags); | |
3542 | } | |
3543 | ||
3544 | /* | |
3545 | * Report expedited quiescent state for multiple CPUs, all covered by the | |
3546 | * specified leaf rcu_node structure. Caller must hold the root | |
3547 | * rcu_node's exp_funnel_mutex. | |
3548 | */ | |
3549 | static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp, | |
3550 | unsigned long mask, bool wake) | |
3551 | { | |
3552 | unsigned long flags; | |
3553 | ||
3554 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
3555 | smp_mb__after_unlock_lock(); | |
3556 | WARN_ON_ONCE((rnp->expmask & mask) != mask); | |
3557 | rnp->expmask &= ~mask; | |
3558 | __rcu_report_exp_rnp(rsp, rnp, wake, flags); /* Releases rnp->lock. */ | |
3559 | } | |
3560 | ||
3561 | /* | |
3562 | * Report expedited quiescent state for specified rcu_data (CPU). | |
3563 | * Caller must hold the root rcu_node's exp_funnel_mutex. | |
3564 | */ | |
6587a23b PM |
3565 | static void rcu_report_exp_rdp(struct rcu_state *rsp, struct rcu_data *rdp, |
3566 | bool wake) | |
8203d6d0 PM |
3567 | { |
3568 | rcu_report_exp_cpu_mult(rsp, rdp->mynode, rdp->grpmask, wake); | |
3569 | } | |
3570 | ||
29fd9309 PM |
3571 | /* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */ |
3572 | static bool sync_exp_work_done(struct rcu_state *rsp, struct rcu_node *rnp, | |
2cd6ffaf | 3573 | struct rcu_data *rdp, |
29fd9309 | 3574 | atomic_long_t *stat, unsigned long s) |
3d3b7db0 | 3575 | { |
28f00767 | 3576 | if (rcu_exp_gp_seq_done(rsp, s)) { |
385b73c0 PM |
3577 | if (rnp) |
3578 | mutex_unlock(&rnp->exp_funnel_mutex); | |
2cd6ffaf PM |
3579 | else if (rdp) |
3580 | mutex_unlock(&rdp->exp_funnel_mutex); | |
385b73c0 PM |
3581 | /* Ensure test happens before caller kfree(). */ |
3582 | smp_mb__before_atomic(); /* ^^^ */ | |
3583 | atomic_long_inc(stat); | |
385b73c0 PM |
3584 | return true; |
3585 | } | |
3586 | return false; | |
3587 | } | |
3588 | ||
b09e5f86 PM |
3589 | /* |
3590 | * Funnel-lock acquisition for expedited grace periods. Returns a | |
3591 | * pointer to the root rcu_node structure, or NULL if some other | |
3592 | * task did the expedited grace period for us. | |
3593 | */ | |
3594 | static struct rcu_node *exp_funnel_lock(struct rcu_state *rsp, unsigned long s) | |
3595 | { | |
2cd6ffaf | 3596 | struct rcu_data *rdp; |
b09e5f86 PM |
3597 | struct rcu_node *rnp0; |
3598 | struct rcu_node *rnp1 = NULL; | |
3599 | ||
3d3b7db0 | 3600 | /* |
cdacbe1f PM |
3601 | * First try directly acquiring the root lock in order to reduce |
3602 | * latency in the common case where expedited grace periods are | |
3603 | * rare. We check mutex_is_locked() to avoid pathological levels of | |
3604 | * memory contention on ->exp_funnel_mutex in the heavy-load case. | |
3d3b7db0 | 3605 | */ |
cdacbe1f PM |
3606 | rnp0 = rcu_get_root(rsp); |
3607 | if (!mutex_is_locked(&rnp0->exp_funnel_mutex)) { | |
3608 | if (mutex_trylock(&rnp0->exp_funnel_mutex)) { | |
3609 | if (sync_exp_work_done(rsp, rnp0, NULL, | |
3610 | &rsp->expedited_workdone0, s)) | |
3611 | return NULL; | |
3612 | return rnp0; | |
3613 | } | |
3614 | } | |
3615 | ||
b09e5f86 PM |
3616 | /* |
3617 | * Each pass through the following loop works its way | |
3618 | * up the rcu_node tree, returning if others have done the | |
3619 | * work or otherwise falls through holding the root rnp's | |
3620 | * ->exp_funnel_mutex. The mapping from CPU to rcu_node structure | |
3621 | * can be inexact, as it is just promoting locality and is not | |
3622 | * strictly needed for correctness. | |
3623 | */ | |
2cd6ffaf PM |
3624 | rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id()); |
3625 | if (sync_exp_work_done(rsp, NULL, NULL, &rsp->expedited_workdone1, s)) | |
3626 | return NULL; | |
3627 | mutex_lock(&rdp->exp_funnel_mutex); | |
3628 | rnp0 = rdp->mynode; | |
b09e5f86 | 3629 | for (; rnp0 != NULL; rnp0 = rnp0->parent) { |
2cd6ffaf PM |
3630 | if (sync_exp_work_done(rsp, rnp1, rdp, |
3631 | &rsp->expedited_workdone2, s)) | |
b09e5f86 PM |
3632 | return NULL; |
3633 | mutex_lock(&rnp0->exp_funnel_mutex); | |
3634 | if (rnp1) | |
3635 | mutex_unlock(&rnp1->exp_funnel_mutex); | |
2cd6ffaf PM |
3636 | else |
3637 | mutex_unlock(&rdp->exp_funnel_mutex); | |
b09e5f86 PM |
3638 | rnp1 = rnp0; |
3639 | } | |
2cd6ffaf PM |
3640 | if (sync_exp_work_done(rsp, rnp1, rdp, |
3641 | &rsp->expedited_workdone3, s)) | |
b09e5f86 PM |
3642 | return NULL; |
3643 | return rnp1; | |
3644 | } | |
3645 | ||
cf3620a6 | 3646 | /* Invoked on each online non-idle CPU for expedited quiescent state. */ |
6587a23b | 3647 | static void synchronize_sched_expedited_cpu_stop(void *data) |
b09e5f86 | 3648 | { |
6587a23b PM |
3649 | __this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, true); |
3650 | resched_cpu(smp_processor_id()); | |
3d3b7db0 PM |
3651 | } |
3652 | ||
bce5fa12 PM |
3653 | /* |
3654 | * Select the nodes that the upcoming expedited grace period needs | |
3655 | * to wait for. | |
3656 | */ | |
dcdb8807 PM |
3657 | static void sync_rcu_exp_select_cpus(struct rcu_state *rsp, |
3658 | smp_call_func_t func) | |
bce5fa12 PM |
3659 | { |
3660 | int cpu; | |
3661 | unsigned long flags; | |
3662 | unsigned long mask; | |
3663 | unsigned long mask_ofl_test; | |
3664 | unsigned long mask_ofl_ipi; | |
6587a23b | 3665 | int ret; |
bce5fa12 PM |
3666 | struct rcu_node *rnp; |
3667 | ||
3668 | sync_exp_reset_tree(rsp); | |
3669 | rcu_for_each_leaf_node(rsp, rnp) { | |
3670 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
3671 | smp_mb__after_unlock_lock(); | |
3672 | ||
3673 | /* Each pass checks a CPU for identity, offline, and idle. */ | |
3674 | mask_ofl_test = 0; | |
3675 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) { | |
3676 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); | |
3677 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); | |
3678 | ||
3679 | if (raw_smp_processor_id() == cpu || | |
3680 | cpu_is_offline(cpu) || | |
3681 | !(atomic_add_return(0, &rdtp->dynticks) & 0x1)) | |
3682 | mask_ofl_test |= rdp->grpmask; | |
3683 | } | |
3684 | mask_ofl_ipi = rnp->expmask & ~mask_ofl_test; | |
3685 | ||
3686 | /* | |
3687 | * Need to wait for any blocked tasks as well. Note that | |
3688 | * additional blocking tasks will also block the expedited | |
3689 | * GP until such time as the ->expmask bits are cleared. | |
3690 | */ | |
3691 | if (rcu_preempt_has_tasks(rnp)) | |
3692 | rnp->exp_tasks = rnp->blkd_tasks.next; | |
3693 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
3694 | ||
3695 | /* IPI the remaining CPUs for expedited quiescent state. */ | |
3696 | mask = 1; | |
3697 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) { | |
3698 | if (!(mask_ofl_ipi & mask)) | |
3699 | continue; | |
dcdb8807 | 3700 | ret = smp_call_function_single(cpu, func, rsp, 0); |
6587a23b PM |
3701 | if (!ret) |
3702 | mask_ofl_ipi &= ~mask; | |
bce5fa12 PM |
3703 | } |
3704 | /* Report quiescent states for those that went offline. */ | |
3705 | mask_ofl_test |= mask_ofl_ipi; | |
3706 | if (mask_ofl_test) | |
3707 | rcu_report_exp_cpu_mult(rsp, rnp, mask_ofl_test, false); | |
3708 | } | |
3709 | } | |
3710 | ||
cf3620a6 PM |
3711 | static void synchronize_sched_expedited_wait(struct rcu_state *rsp) |
3712 | { | |
3713 | int cpu; | |
3714 | unsigned long jiffies_stall; | |
3715 | unsigned long jiffies_start; | |
bce5fa12 PM |
3716 | unsigned long mask; |
3717 | struct rcu_node *rnp; | |
3718 | struct rcu_node *rnp_root = rcu_get_root(rsp); | |
cf3620a6 PM |
3719 | int ret; |
3720 | ||
3721 | jiffies_stall = rcu_jiffies_till_stall_check(); | |
3722 | jiffies_start = jiffies; | |
3723 | ||
3724 | for (;;) { | |
3725 | ret = wait_event_interruptible_timeout( | |
3726 | rsp->expedited_wq, | |
bce5fa12 | 3727 | sync_rcu_preempt_exp_done(rnp_root), |
cf3620a6 PM |
3728 | jiffies_stall); |
3729 | if (ret > 0) | |
3730 | return; | |
3731 | if (ret < 0) { | |
3732 | /* Hit a signal, disable CPU stall warnings. */ | |
3733 | wait_event(rsp->expedited_wq, | |
bce5fa12 | 3734 | sync_rcu_preempt_exp_done(rnp_root)); |
cf3620a6 PM |
3735 | return; |
3736 | } | |
c5865638 | 3737 | pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {", |
cf3620a6 | 3738 | rsp->name); |
bce5fa12 | 3739 | rcu_for_each_leaf_node(rsp, rnp) { |
74611ecb | 3740 | (void)rcu_print_task_exp_stall(rnp); |
bce5fa12 PM |
3741 | mask = 1; |
3742 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) { | |
74611ecb PM |
3743 | struct rcu_data *rdp; |
3744 | ||
bce5fa12 PM |
3745 | if (!(rnp->expmask & mask)) |
3746 | continue; | |
74611ecb PM |
3747 | rdp = per_cpu_ptr(rsp->rda, cpu); |
3748 | pr_cont(" %d-%c%c%c", cpu, | |
3749 | "O."[cpu_online(cpu)], | |
3750 | "o."[!!(rdp->grpmask & rnp->expmaskinit)], | |
3751 | "N."[!!(rdp->grpmask & rnp->expmaskinitnext)]); | |
bce5fa12 PM |
3752 | } |
3753 | mask <<= 1; | |
cf3620a6 PM |
3754 | } |
3755 | pr_cont(" } %lu jiffies s: %lu\n", | |
3756 | jiffies - jiffies_start, rsp->expedited_sequence); | |
bce5fa12 PM |
3757 | rcu_for_each_leaf_node(rsp, rnp) { |
3758 | mask = 1; | |
3759 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) { | |
3760 | if (!(rnp->expmask & mask)) | |
3761 | continue; | |
3762 | dump_cpu_task(cpu); | |
3763 | } | |
cf3620a6 PM |
3764 | } |
3765 | jiffies_stall = 3 * rcu_jiffies_till_stall_check() + 3; | |
3766 | } | |
3767 | } | |
3768 | ||
236fefaf PM |
3769 | /** |
3770 | * synchronize_sched_expedited - Brute-force RCU-sched grace period | |
3771 | * | |
3772 | * Wait for an RCU-sched grace period to elapse, but use a "big hammer" | |
3773 | * approach to force the grace period to end quickly. This consumes | |
3774 | * significant time on all CPUs and is unfriendly to real-time workloads, | |
3775 | * so is thus not recommended for any sort of common-case code. In fact, | |
3776 | * if you are using synchronize_sched_expedited() in a loop, please | |
3777 | * restructure your code to batch your updates, and then use a single | |
3778 | * synchronize_sched() instead. | |
3d3b7db0 | 3779 | * |
d6ada2cf PM |
3780 | * This implementation can be thought of as an application of sequence |
3781 | * locking to expedited grace periods, but using the sequence counter to | |
3782 | * determine when someone else has already done the work instead of for | |
385b73c0 | 3783 | * retrying readers. |
3d3b7db0 PM |
3784 | */ |
3785 | void synchronize_sched_expedited(void) | |
3786 | { | |
7fd0ddc5 | 3787 | unsigned long s; |
b09e5f86 | 3788 | struct rcu_node *rnp; |
40694d66 | 3789 | struct rcu_state *rsp = &rcu_sched_state; |
3d3b7db0 | 3790 | |
d6ada2cf | 3791 | /* Take a snapshot of the sequence number. */ |
28f00767 | 3792 | s = rcu_exp_gp_seq_snap(rsp); |
3d3b7db0 | 3793 | |
b09e5f86 | 3794 | rnp = exp_funnel_lock(rsp, s); |
807226e2 | 3795 | if (rnp == NULL) |
b09e5f86 | 3796 | return; /* Someone else did our work for us. */ |
e0775cef | 3797 | |
28f00767 | 3798 | rcu_exp_gp_seq_start(rsp); |
dcdb8807 | 3799 | sync_rcu_exp_select_cpus(rsp, synchronize_sched_expedited_cpu_stop); |
bce5fa12 | 3800 | synchronize_sched_expedited_wait(rsp); |
e0775cef | 3801 | |
28f00767 | 3802 | rcu_exp_gp_seq_end(rsp); |
b09e5f86 | 3803 | mutex_unlock(&rnp->exp_funnel_mutex); |
3d3b7db0 PM |
3804 | } |
3805 | EXPORT_SYMBOL_GPL(synchronize_sched_expedited); | |
3806 | ||
64db4cff PM |
3807 | /* |
3808 | * Check to see if there is any immediate RCU-related work to be done | |
3809 | * by the current CPU, for the specified type of RCU, returning 1 if so. | |
3810 | * The checks are in order of increasing expense: checks that can be | |
3811 | * carried out against CPU-local state are performed first. However, | |
3812 | * we must check for CPU stalls first, else we might not get a chance. | |
3813 | */ | |
3814 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) | |
3815 | { | |
2f51f988 PM |
3816 | struct rcu_node *rnp = rdp->mynode; |
3817 | ||
64db4cff PM |
3818 | rdp->n_rcu_pending++; |
3819 | ||
3820 | /* Check for CPU stalls, if enabled. */ | |
3821 | check_cpu_stall(rsp, rdp); | |
3822 | ||
a096932f PM |
3823 | /* Is this CPU a NO_HZ_FULL CPU that should ignore RCU? */ |
3824 | if (rcu_nohz_full_cpu(rsp)) | |
3825 | return 0; | |
3826 | ||
64db4cff | 3827 | /* Is the RCU core waiting for a quiescent state from this CPU? */ |
5c51dd73 | 3828 | if (rcu_scheduler_fully_active && |
5b74c458 | 3829 | rdp->core_needs_qs && rdp->cpu_no_qs.b.norm && |
5cd37193 | 3830 | rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) { |
97c668b8 PM |
3831 | rdp->n_rp_core_needs_qs++; |
3832 | } else if (rdp->core_needs_qs && | |
5b74c458 | 3833 | (!rdp->cpu_no_qs.b.norm || |
5cd37193 | 3834 | rdp->rcu_qs_ctr_snap != __this_cpu_read(rcu_qs_ctr))) { |
d21670ac | 3835 | rdp->n_rp_report_qs++; |
64db4cff | 3836 | return 1; |
7ba5c840 | 3837 | } |
64db4cff PM |
3838 | |
3839 | /* Does this CPU have callbacks ready to invoke? */ | |
7ba5c840 PM |
3840 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
3841 | rdp->n_rp_cb_ready++; | |
64db4cff | 3842 | return 1; |
7ba5c840 | 3843 | } |
64db4cff PM |
3844 | |
3845 | /* Has RCU gone idle with this CPU needing another grace period? */ | |
7ba5c840 PM |
3846 | if (cpu_needs_another_gp(rsp, rdp)) { |
3847 | rdp->n_rp_cpu_needs_gp++; | |
64db4cff | 3848 | return 1; |
7ba5c840 | 3849 | } |
64db4cff PM |
3850 | |
3851 | /* Has another RCU grace period completed? */ | |
7d0ae808 | 3852 | if (READ_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
7ba5c840 | 3853 | rdp->n_rp_gp_completed++; |
64db4cff | 3854 | return 1; |
7ba5c840 | 3855 | } |
64db4cff PM |
3856 | |
3857 | /* Has a new RCU grace period started? */ | |
7d0ae808 PM |
3858 | if (READ_ONCE(rnp->gpnum) != rdp->gpnum || |
3859 | unlikely(READ_ONCE(rdp->gpwrap))) { /* outside lock */ | |
7ba5c840 | 3860 | rdp->n_rp_gp_started++; |
64db4cff | 3861 | return 1; |
7ba5c840 | 3862 | } |
64db4cff | 3863 | |
96d3fd0d PM |
3864 | /* Does this CPU need a deferred NOCB wakeup? */ |
3865 | if (rcu_nocb_need_deferred_wakeup(rdp)) { | |
3866 | rdp->n_rp_nocb_defer_wakeup++; | |
3867 | return 1; | |
3868 | } | |
3869 | ||
64db4cff | 3870 | /* nothing to do */ |
7ba5c840 | 3871 | rdp->n_rp_need_nothing++; |
64db4cff PM |
3872 | return 0; |
3873 | } | |
3874 | ||
3875 | /* | |
3876 | * Check to see if there is any immediate RCU-related work to be done | |
3877 | * by the current CPU, returning 1 if so. This function is part of the | |
3878 | * RCU implementation; it is -not- an exported member of the RCU API. | |
3879 | */ | |
e3950ecd | 3880 | static int rcu_pending(void) |
64db4cff | 3881 | { |
6ce75a23 PM |
3882 | struct rcu_state *rsp; |
3883 | ||
3884 | for_each_rcu_flavor(rsp) | |
e3950ecd | 3885 | if (__rcu_pending(rsp, this_cpu_ptr(rsp->rda))) |
6ce75a23 PM |
3886 | return 1; |
3887 | return 0; | |
64db4cff PM |
3888 | } |
3889 | ||
3890 | /* | |
c0f4dfd4 PM |
3891 | * Return true if the specified CPU has any callback. If all_lazy is |
3892 | * non-NULL, store an indication of whether all callbacks are lazy. | |
3893 | * (If there are no callbacks, all of them are deemed to be lazy.) | |
64db4cff | 3894 | */ |
82072c4f | 3895 | static bool __maybe_unused rcu_cpu_has_callbacks(bool *all_lazy) |
64db4cff | 3896 | { |
c0f4dfd4 PM |
3897 | bool al = true; |
3898 | bool hc = false; | |
3899 | struct rcu_data *rdp; | |
6ce75a23 PM |
3900 | struct rcu_state *rsp; |
3901 | ||
c0f4dfd4 | 3902 | for_each_rcu_flavor(rsp) { |
aa6da514 | 3903 | rdp = this_cpu_ptr(rsp->rda); |
69c8d28c PM |
3904 | if (!rdp->nxtlist) |
3905 | continue; | |
3906 | hc = true; | |
3907 | if (rdp->qlen != rdp->qlen_lazy || !all_lazy) { | |
c0f4dfd4 | 3908 | al = false; |
69c8d28c PM |
3909 | break; |
3910 | } | |
c0f4dfd4 PM |
3911 | } |
3912 | if (all_lazy) | |
3913 | *all_lazy = al; | |
3914 | return hc; | |
64db4cff PM |
3915 | } |
3916 | ||
a83eff0a PM |
3917 | /* |
3918 | * Helper function for _rcu_barrier() tracing. If tracing is disabled, | |
3919 | * the compiler is expected to optimize this away. | |
3920 | */ | |
e66c33d5 | 3921 | static void _rcu_barrier_trace(struct rcu_state *rsp, const char *s, |
a83eff0a PM |
3922 | int cpu, unsigned long done) |
3923 | { | |
3924 | trace_rcu_barrier(rsp->name, s, cpu, | |
3925 | atomic_read(&rsp->barrier_cpu_count), done); | |
3926 | } | |
3927 | ||
b1420f1c PM |
3928 | /* |
3929 | * RCU callback function for _rcu_barrier(). If we are last, wake | |
3930 | * up the task executing _rcu_barrier(). | |
3931 | */ | |
24ebbca8 | 3932 | static void rcu_barrier_callback(struct rcu_head *rhp) |
d0ec774c | 3933 | { |
24ebbca8 PM |
3934 | struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head); |
3935 | struct rcu_state *rsp = rdp->rsp; | |
3936 | ||
a83eff0a | 3937 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) { |
4f525a52 | 3938 | _rcu_barrier_trace(rsp, "LastCB", -1, rsp->barrier_sequence); |
7db74df8 | 3939 | complete(&rsp->barrier_completion); |
a83eff0a | 3940 | } else { |
4f525a52 | 3941 | _rcu_barrier_trace(rsp, "CB", -1, rsp->barrier_sequence); |
a83eff0a | 3942 | } |
d0ec774c PM |
3943 | } |
3944 | ||
3945 | /* | |
3946 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
3947 | */ | |
3948 | static void rcu_barrier_func(void *type) | |
3949 | { | |
037b64ed | 3950 | struct rcu_state *rsp = type; |
fa07a58f | 3951 | struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); |
d0ec774c | 3952 | |
4f525a52 | 3953 | _rcu_barrier_trace(rsp, "IRQ", -1, rsp->barrier_sequence); |
24ebbca8 | 3954 | atomic_inc(&rsp->barrier_cpu_count); |
06668efa | 3955 | rsp->call(&rdp->barrier_head, rcu_barrier_callback); |
d0ec774c PM |
3956 | } |
3957 | ||
d0ec774c PM |
3958 | /* |
3959 | * Orchestrate the specified type of RCU barrier, waiting for all | |
3960 | * RCU callbacks of the specified type to complete. | |
3961 | */ | |
037b64ed | 3962 | static void _rcu_barrier(struct rcu_state *rsp) |
d0ec774c | 3963 | { |
b1420f1c | 3964 | int cpu; |
b1420f1c | 3965 | struct rcu_data *rdp; |
4f525a52 | 3966 | unsigned long s = rcu_seq_snap(&rsp->barrier_sequence); |
b1420f1c | 3967 | |
4f525a52 | 3968 | _rcu_barrier_trace(rsp, "Begin", -1, s); |
b1420f1c | 3969 | |
e74f4c45 | 3970 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
7be7f0be | 3971 | mutex_lock(&rsp->barrier_mutex); |
b1420f1c | 3972 | |
4f525a52 PM |
3973 | /* Did someone else do our work for us? */ |
3974 | if (rcu_seq_done(&rsp->barrier_sequence, s)) { | |
3975 | _rcu_barrier_trace(rsp, "EarlyExit", -1, rsp->barrier_sequence); | |
cf3a9c48 PM |
3976 | smp_mb(); /* caller's subsequent code after above check. */ |
3977 | mutex_unlock(&rsp->barrier_mutex); | |
3978 | return; | |
3979 | } | |
3980 | ||
4f525a52 PM |
3981 | /* Mark the start of the barrier operation. */ |
3982 | rcu_seq_start(&rsp->barrier_sequence); | |
3983 | _rcu_barrier_trace(rsp, "Inc1", -1, rsp->barrier_sequence); | |
b1420f1c | 3984 | |
d0ec774c | 3985 | /* |
b1420f1c PM |
3986 | * Initialize the count to one rather than to zero in order to |
3987 | * avoid a too-soon return to zero in case of a short grace period | |
1331e7a1 PM |
3988 | * (or preemption of this task). Exclude CPU-hotplug operations |
3989 | * to ensure that no offline CPU has callbacks queued. | |
d0ec774c | 3990 | */ |
7db74df8 | 3991 | init_completion(&rsp->barrier_completion); |
24ebbca8 | 3992 | atomic_set(&rsp->barrier_cpu_count, 1); |
1331e7a1 | 3993 | get_online_cpus(); |
b1420f1c PM |
3994 | |
3995 | /* | |
1331e7a1 PM |
3996 | * Force each CPU with callbacks to register a new callback. |
3997 | * When that callback is invoked, we will know that all of the | |
3998 | * corresponding CPU's preceding callbacks have been invoked. | |
b1420f1c | 3999 | */ |
3fbfbf7a | 4000 | for_each_possible_cpu(cpu) { |
d1e43fa5 | 4001 | if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu)) |
3fbfbf7a | 4002 | continue; |
b1420f1c | 4003 | rdp = per_cpu_ptr(rsp->rda, cpu); |
d1e43fa5 | 4004 | if (rcu_is_nocb_cpu(cpu)) { |
d7e29933 PM |
4005 | if (!rcu_nocb_cpu_needs_barrier(rsp, cpu)) { |
4006 | _rcu_barrier_trace(rsp, "OfflineNoCB", cpu, | |
4f525a52 | 4007 | rsp->barrier_sequence); |
d7e29933 PM |
4008 | } else { |
4009 | _rcu_barrier_trace(rsp, "OnlineNoCB", cpu, | |
4f525a52 | 4010 | rsp->barrier_sequence); |
41050a00 | 4011 | smp_mb__before_atomic(); |
d7e29933 PM |
4012 | atomic_inc(&rsp->barrier_cpu_count); |
4013 | __call_rcu(&rdp->barrier_head, | |
4014 | rcu_barrier_callback, rsp, cpu, 0); | |
4015 | } | |
7d0ae808 | 4016 | } else if (READ_ONCE(rdp->qlen)) { |
a83eff0a | 4017 | _rcu_barrier_trace(rsp, "OnlineQ", cpu, |
4f525a52 | 4018 | rsp->barrier_sequence); |
037b64ed | 4019 | smp_call_function_single(cpu, rcu_barrier_func, rsp, 1); |
b1420f1c | 4020 | } else { |
a83eff0a | 4021 | _rcu_barrier_trace(rsp, "OnlineNQ", cpu, |
4f525a52 | 4022 | rsp->barrier_sequence); |
b1420f1c PM |
4023 | } |
4024 | } | |
1331e7a1 | 4025 | put_online_cpus(); |
b1420f1c PM |
4026 | |
4027 | /* | |
4028 | * Now that we have an rcu_barrier_callback() callback on each | |
4029 | * CPU, and thus each counted, remove the initial count. | |
4030 | */ | |
24ebbca8 | 4031 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) |
7db74df8 | 4032 | complete(&rsp->barrier_completion); |
b1420f1c PM |
4033 | |
4034 | /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ | |
7db74df8 | 4035 | wait_for_completion(&rsp->barrier_completion); |
b1420f1c | 4036 | |
4f525a52 PM |
4037 | /* Mark the end of the barrier operation. */ |
4038 | _rcu_barrier_trace(rsp, "Inc2", -1, rsp->barrier_sequence); | |
4039 | rcu_seq_end(&rsp->barrier_sequence); | |
4040 | ||
b1420f1c | 4041 | /* Other rcu_barrier() invocations can now safely proceed. */ |
7be7f0be | 4042 | mutex_unlock(&rsp->barrier_mutex); |
d0ec774c | 4043 | } |
d0ec774c PM |
4044 | |
4045 | /** | |
4046 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. | |
4047 | */ | |
4048 | void rcu_barrier_bh(void) | |
4049 | { | |
037b64ed | 4050 | _rcu_barrier(&rcu_bh_state); |
d0ec774c PM |
4051 | } |
4052 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); | |
4053 | ||
4054 | /** | |
4055 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. | |
4056 | */ | |
4057 | void rcu_barrier_sched(void) | |
4058 | { | |
037b64ed | 4059 | _rcu_barrier(&rcu_sched_state); |
d0ec774c PM |
4060 | } |
4061 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); | |
4062 | ||
0aa04b05 PM |
4063 | /* |
4064 | * Propagate ->qsinitmask bits up the rcu_node tree to account for the | |
4065 | * first CPU in a given leaf rcu_node structure coming online. The caller | |
4066 | * must hold the corresponding leaf rcu_node ->lock with interrrupts | |
4067 | * disabled. | |
4068 | */ | |
4069 | static void rcu_init_new_rnp(struct rcu_node *rnp_leaf) | |
4070 | { | |
4071 | long mask; | |
4072 | struct rcu_node *rnp = rnp_leaf; | |
4073 | ||
4074 | for (;;) { | |
4075 | mask = rnp->grpmask; | |
4076 | rnp = rnp->parent; | |
4077 | if (rnp == NULL) | |
4078 | return; | |
4079 | raw_spin_lock(&rnp->lock); /* Interrupts already disabled. */ | |
4080 | rnp->qsmaskinit |= mask; | |
4081 | raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */ | |
4082 | } | |
4083 | } | |
4084 | ||
64db4cff | 4085 | /* |
27569620 | 4086 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
64db4cff | 4087 | */ |
27569620 PM |
4088 | static void __init |
4089 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) | |
64db4cff PM |
4090 | { |
4091 | unsigned long flags; | |
394f99a9 | 4092 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
27569620 PM |
4093 | struct rcu_node *rnp = rcu_get_root(rsp); |
4094 | ||
4095 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 4096 | raw_spin_lock_irqsave(&rnp->lock, flags); |
27569620 | 4097 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
27569620 | 4098 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
29e37d81 | 4099 | WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); |
9b2e4f18 | 4100 | WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1); |
27569620 | 4101 | rdp->cpu = cpu; |
d4c08f2a | 4102 | rdp->rsp = rsp; |
2cd6ffaf | 4103 | mutex_init(&rdp->exp_funnel_mutex); |
3fbfbf7a | 4104 | rcu_boot_init_nocb_percpu_data(rdp); |
1304afb2 | 4105 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27569620 PM |
4106 | } |
4107 | ||
4108 | /* | |
4109 | * Initialize a CPU's per-CPU RCU data. Note that only one online or | |
4110 | * offline event can be happening at a given time. Note also that we | |
4111 | * can accept some slop in the rsp->completed access due to the fact | |
4112 | * that this CPU cannot possibly have any RCU callbacks in flight yet. | |
64db4cff | 4113 | */ |
49fb4c62 | 4114 | static void |
9b67122a | 4115 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp) |
64db4cff PM |
4116 | { |
4117 | unsigned long flags; | |
64db4cff | 4118 | unsigned long mask; |
394f99a9 | 4119 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
64db4cff PM |
4120 | struct rcu_node *rnp = rcu_get_root(rsp); |
4121 | ||
4122 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 4123 | raw_spin_lock_irqsave(&rnp->lock, flags); |
37c72e56 PM |
4124 | rdp->qlen_last_fqs_check = 0; |
4125 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
64db4cff | 4126 | rdp->blimit = blimit; |
39c8d313 PM |
4127 | if (!rdp->nxtlist) |
4128 | init_callback_list(rdp); /* Re-enable callbacks on this CPU. */ | |
29e37d81 | 4129 | rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
2333210b | 4130 | rcu_sysidle_init_percpu_data(rdp->dynticks); |
c92b131b PM |
4131 | atomic_set(&rdp->dynticks->dynticks, |
4132 | (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1); | |
1304afb2 | 4133 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff | 4134 | |
0aa04b05 PM |
4135 | /* |
4136 | * Add CPU to leaf rcu_node pending-online bitmask. Any needed | |
4137 | * propagation up the rcu_node tree will happen at the beginning | |
4138 | * of the next grace period. | |
4139 | */ | |
64db4cff PM |
4140 | rnp = rdp->mynode; |
4141 | mask = rdp->grpmask; | |
0aa04b05 PM |
4142 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
4143 | smp_mb__after_unlock_lock(); | |
4144 | rnp->qsmaskinitnext |= mask; | |
b9585e94 PM |
4145 | rnp->expmaskinitnext |= mask; |
4146 | if (!rdp->beenonline) | |
4147 | WRITE_ONCE(rsp->ncpus, READ_ONCE(rsp->ncpus) + 1); | |
4148 | rdp->beenonline = true; /* We have now been online. */ | |
0aa04b05 PM |
4149 | rdp->gpnum = rnp->completed; /* Make CPU later note any new GP. */ |
4150 | rdp->completed = rnp->completed; | |
5b74c458 | 4151 | rdp->cpu_no_qs.b.norm = true; |
a738eec6 | 4152 | rdp->rcu_qs_ctr_snap = per_cpu(rcu_qs_ctr, cpu); |
97c668b8 | 4153 | rdp->core_needs_qs = false; |
0aa04b05 PM |
4154 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl")); |
4155 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
64db4cff PM |
4156 | } |
4157 | ||
49fb4c62 | 4158 | static void rcu_prepare_cpu(int cpu) |
64db4cff | 4159 | { |
6ce75a23 PM |
4160 | struct rcu_state *rsp; |
4161 | ||
4162 | for_each_rcu_flavor(rsp) | |
9b67122a | 4163 | rcu_init_percpu_data(cpu, rsp); |
64db4cff PM |
4164 | } |
4165 | ||
4166 | /* | |
f41d911f | 4167 | * Handle CPU online/offline notification events. |
64db4cff | 4168 | */ |
88428cc5 PM |
4169 | int rcu_cpu_notify(struct notifier_block *self, |
4170 | unsigned long action, void *hcpu) | |
64db4cff PM |
4171 | { |
4172 | long cpu = (long)hcpu; | |
e534165b | 4173 | struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); |
a26ac245 | 4174 | struct rcu_node *rnp = rdp->mynode; |
6ce75a23 | 4175 | struct rcu_state *rsp; |
64db4cff PM |
4176 | |
4177 | switch (action) { | |
4178 | case CPU_UP_PREPARE: | |
4179 | case CPU_UP_PREPARE_FROZEN: | |
d72bce0e PZ |
4180 | rcu_prepare_cpu(cpu); |
4181 | rcu_prepare_kthreads(cpu); | |
35ce7f29 | 4182 | rcu_spawn_all_nocb_kthreads(cpu); |
a26ac245 PM |
4183 | break; |
4184 | case CPU_ONLINE: | |
0f962a5e | 4185 | case CPU_DOWN_FAILED: |
5d01bbd1 | 4186 | rcu_boost_kthread_setaffinity(rnp, -1); |
0f962a5e PM |
4187 | break; |
4188 | case CPU_DOWN_PREPARE: | |
34ed6246 | 4189 | rcu_boost_kthread_setaffinity(rnp, cpu); |
64db4cff | 4190 | break; |
d0ec774c PM |
4191 | case CPU_DYING: |
4192 | case CPU_DYING_FROZEN: | |
6ce75a23 PM |
4193 | for_each_rcu_flavor(rsp) |
4194 | rcu_cleanup_dying_cpu(rsp); | |
d0ec774c | 4195 | break; |
88428cc5 | 4196 | case CPU_DYING_IDLE: |
6587a23b PM |
4197 | /* QS for any half-done expedited RCU-sched GP. */ |
4198 | rcu_sched_qs(); | |
4199 | ||
88428cc5 PM |
4200 | for_each_rcu_flavor(rsp) { |
4201 | rcu_cleanup_dying_idle_cpu(cpu, rsp); | |
4202 | } | |
4203 | break; | |
64db4cff PM |
4204 | case CPU_DEAD: |
4205 | case CPU_DEAD_FROZEN: | |
4206 | case CPU_UP_CANCELED: | |
4207 | case CPU_UP_CANCELED_FROZEN: | |
776d6807 | 4208 | for_each_rcu_flavor(rsp) { |
6ce75a23 | 4209 | rcu_cleanup_dead_cpu(cpu, rsp); |
776d6807 PM |
4210 | do_nocb_deferred_wakeup(per_cpu_ptr(rsp->rda, cpu)); |
4211 | } | |
64db4cff PM |
4212 | break; |
4213 | default: | |
4214 | break; | |
4215 | } | |
34ed6246 | 4216 | return NOTIFY_OK; |
64db4cff PM |
4217 | } |
4218 | ||
d1d74d14 BP |
4219 | static int rcu_pm_notify(struct notifier_block *self, |
4220 | unsigned long action, void *hcpu) | |
4221 | { | |
4222 | switch (action) { | |
4223 | case PM_HIBERNATION_PREPARE: | |
4224 | case PM_SUSPEND_PREPARE: | |
4225 | if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ | |
5afff48b | 4226 | rcu_expedite_gp(); |
d1d74d14 BP |
4227 | break; |
4228 | case PM_POST_HIBERNATION: | |
4229 | case PM_POST_SUSPEND: | |
5afff48b PM |
4230 | if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ |
4231 | rcu_unexpedite_gp(); | |
d1d74d14 BP |
4232 | break; |
4233 | default: | |
4234 | break; | |
4235 | } | |
4236 | return NOTIFY_OK; | |
4237 | } | |
4238 | ||
b3dbec76 | 4239 | /* |
9386c0b7 | 4240 | * Spawn the kthreads that handle each RCU flavor's grace periods. |
b3dbec76 PM |
4241 | */ |
4242 | static int __init rcu_spawn_gp_kthread(void) | |
4243 | { | |
4244 | unsigned long flags; | |
a94844b2 | 4245 | int kthread_prio_in = kthread_prio; |
b3dbec76 PM |
4246 | struct rcu_node *rnp; |
4247 | struct rcu_state *rsp; | |
a94844b2 | 4248 | struct sched_param sp; |
b3dbec76 PM |
4249 | struct task_struct *t; |
4250 | ||
a94844b2 PM |
4251 | /* Force priority into range. */ |
4252 | if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1) | |
4253 | kthread_prio = 1; | |
4254 | else if (kthread_prio < 0) | |
4255 | kthread_prio = 0; | |
4256 | else if (kthread_prio > 99) | |
4257 | kthread_prio = 99; | |
4258 | if (kthread_prio != kthread_prio_in) | |
4259 | pr_alert("rcu_spawn_gp_kthread(): Limited prio to %d from %d\n", | |
4260 | kthread_prio, kthread_prio_in); | |
4261 | ||
9386c0b7 | 4262 | rcu_scheduler_fully_active = 1; |
b3dbec76 | 4263 | for_each_rcu_flavor(rsp) { |
a94844b2 | 4264 | t = kthread_create(rcu_gp_kthread, rsp, "%s", rsp->name); |
b3dbec76 PM |
4265 | BUG_ON(IS_ERR(t)); |
4266 | rnp = rcu_get_root(rsp); | |
4267 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
4268 | rsp->gp_kthread = t; | |
a94844b2 PM |
4269 | if (kthread_prio) { |
4270 | sp.sched_priority = kthread_prio; | |
4271 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); | |
4272 | } | |
4273 | wake_up_process(t); | |
b3dbec76 PM |
4274 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
4275 | } | |
35ce7f29 | 4276 | rcu_spawn_nocb_kthreads(); |
9386c0b7 | 4277 | rcu_spawn_boost_kthreads(); |
b3dbec76 PM |
4278 | return 0; |
4279 | } | |
4280 | early_initcall(rcu_spawn_gp_kthread); | |
4281 | ||
bbad9379 PM |
4282 | /* |
4283 | * This function is invoked towards the end of the scheduler's initialization | |
4284 | * process. Before this is called, the idle task might contain | |
4285 | * RCU read-side critical sections (during which time, this idle | |
4286 | * task is booting the system). After this function is called, the | |
4287 | * idle tasks are prohibited from containing RCU read-side critical | |
4288 | * sections. This function also enables RCU lockdep checking. | |
4289 | */ | |
4290 | void rcu_scheduler_starting(void) | |
4291 | { | |
4292 | WARN_ON(num_online_cpus() != 1); | |
4293 | WARN_ON(nr_context_switches() > 0); | |
4294 | rcu_scheduler_active = 1; | |
4295 | } | |
4296 | ||
64db4cff PM |
4297 | /* |
4298 | * Compute the per-level fanout, either using the exact fanout specified | |
7fa27001 | 4299 | * or balancing the tree, depending on the rcu_fanout_exact boot parameter. |
64db4cff | 4300 | */ |
199977bf | 4301 | static void __init rcu_init_levelspread(int *levelspread, const int *levelcnt) |
64db4cff | 4302 | { |
64db4cff PM |
4303 | int i; |
4304 | ||
7fa27001 | 4305 | if (rcu_fanout_exact) { |
199977bf | 4306 | levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf; |
66292405 | 4307 | for (i = rcu_num_lvls - 2; i >= 0; i--) |
199977bf | 4308 | levelspread[i] = RCU_FANOUT; |
66292405 PM |
4309 | } else { |
4310 | int ccur; | |
4311 | int cprv; | |
4312 | ||
4313 | cprv = nr_cpu_ids; | |
4314 | for (i = rcu_num_lvls - 1; i >= 0; i--) { | |
199977bf AG |
4315 | ccur = levelcnt[i]; |
4316 | levelspread[i] = (cprv + ccur - 1) / ccur; | |
66292405 PM |
4317 | cprv = ccur; |
4318 | } | |
64db4cff PM |
4319 | } |
4320 | } | |
64db4cff PM |
4321 | |
4322 | /* | |
4323 | * Helper function for rcu_init() that initializes one rcu_state structure. | |
4324 | */ | |
394f99a9 LJ |
4325 | static void __init rcu_init_one(struct rcu_state *rsp, |
4326 | struct rcu_data __percpu *rda) | |
64db4cff | 4327 | { |
cb007102 AG |
4328 | static const char * const buf[] = RCU_NODE_NAME_INIT; |
4329 | static const char * const fqs[] = RCU_FQS_NAME_INIT; | |
385b73c0 | 4330 | static const char * const exp[] = RCU_EXP_NAME_INIT; |
4a81e832 | 4331 | static u8 fl_mask = 0x1; |
199977bf AG |
4332 | |
4333 | int levelcnt[RCU_NUM_LVLS]; /* # nodes in each level. */ | |
4334 | int levelspread[RCU_NUM_LVLS]; /* kids/node in each level. */ | |
64db4cff PM |
4335 | int cpustride = 1; |
4336 | int i; | |
4337 | int j; | |
4338 | struct rcu_node *rnp; | |
4339 | ||
05b84aec | 4340 | BUILD_BUG_ON(RCU_NUM_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
b6407e86 | 4341 | |
3eaaaf6c PM |
4342 | /* Silence gcc 4.8 false positive about array index out of range. */ |
4343 | if (rcu_num_lvls <= 0 || rcu_num_lvls > RCU_NUM_LVLS) | |
4344 | panic("rcu_init_one: rcu_num_lvls out of range"); | |
4930521a | 4345 | |
64db4cff PM |
4346 | /* Initialize the level-tracking arrays. */ |
4347 | ||
f885b7f2 | 4348 | for (i = 0; i < rcu_num_lvls; i++) |
199977bf | 4349 | levelcnt[i] = num_rcu_lvl[i]; |
f885b7f2 | 4350 | for (i = 1; i < rcu_num_lvls; i++) |
199977bf AG |
4351 | rsp->level[i] = rsp->level[i - 1] + levelcnt[i - 1]; |
4352 | rcu_init_levelspread(levelspread, levelcnt); | |
4a81e832 PM |
4353 | rsp->flavor_mask = fl_mask; |
4354 | fl_mask <<= 1; | |
64db4cff PM |
4355 | |
4356 | /* Initialize the elements themselves, starting from the leaves. */ | |
4357 | ||
f885b7f2 | 4358 | for (i = rcu_num_lvls - 1; i >= 0; i--) { |
199977bf | 4359 | cpustride *= levelspread[i]; |
64db4cff | 4360 | rnp = rsp->level[i]; |
199977bf | 4361 | for (j = 0; j < levelcnt[i]; j++, rnp++) { |
1304afb2 | 4362 | raw_spin_lock_init(&rnp->lock); |
b6407e86 PM |
4363 | lockdep_set_class_and_name(&rnp->lock, |
4364 | &rcu_node_class[i], buf[i]); | |
394f2769 PM |
4365 | raw_spin_lock_init(&rnp->fqslock); |
4366 | lockdep_set_class_and_name(&rnp->fqslock, | |
4367 | &rcu_fqs_class[i], fqs[i]); | |
25d30cf4 PM |
4368 | rnp->gpnum = rsp->gpnum; |
4369 | rnp->completed = rsp->completed; | |
64db4cff PM |
4370 | rnp->qsmask = 0; |
4371 | rnp->qsmaskinit = 0; | |
4372 | rnp->grplo = j * cpustride; | |
4373 | rnp->grphi = (j + 1) * cpustride - 1; | |
595f3900 HS |
4374 | if (rnp->grphi >= nr_cpu_ids) |
4375 | rnp->grphi = nr_cpu_ids - 1; | |
64db4cff PM |
4376 | if (i == 0) { |
4377 | rnp->grpnum = 0; | |
4378 | rnp->grpmask = 0; | |
4379 | rnp->parent = NULL; | |
4380 | } else { | |
199977bf | 4381 | rnp->grpnum = j % levelspread[i - 1]; |
64db4cff PM |
4382 | rnp->grpmask = 1UL << rnp->grpnum; |
4383 | rnp->parent = rsp->level[i - 1] + | |
199977bf | 4384 | j / levelspread[i - 1]; |
64db4cff PM |
4385 | } |
4386 | rnp->level = i; | |
12f5f524 | 4387 | INIT_LIST_HEAD(&rnp->blkd_tasks); |
dae6e64d | 4388 | rcu_init_one_nocb(rnp); |
385b73c0 | 4389 | mutex_init(&rnp->exp_funnel_mutex); |
83c2c735 PM |
4390 | lockdep_set_class_and_name(&rnp->exp_funnel_mutex, |
4391 | &rcu_exp_class[i], exp[i]); | |
64db4cff PM |
4392 | } |
4393 | } | |
0c34029a | 4394 | |
b3dbec76 | 4395 | init_waitqueue_head(&rsp->gp_wq); |
f4ecea30 | 4396 | init_waitqueue_head(&rsp->expedited_wq); |
f885b7f2 | 4397 | rnp = rsp->level[rcu_num_lvls - 1]; |
0c34029a | 4398 | for_each_possible_cpu(i) { |
4a90a068 | 4399 | while (i > rnp->grphi) |
0c34029a | 4400 | rnp++; |
394f99a9 | 4401 | per_cpu_ptr(rsp->rda, i)->mynode = rnp; |
0c34029a LJ |
4402 | rcu_boot_init_percpu_data(i, rsp); |
4403 | } | |
6ce75a23 | 4404 | list_add(&rsp->flavors, &rcu_struct_flavors); |
64db4cff PM |
4405 | } |
4406 | ||
f885b7f2 PM |
4407 | /* |
4408 | * Compute the rcu_node tree geometry from kernel parameters. This cannot | |
4102adab | 4409 | * replace the definitions in tree.h because those are needed to size |
f885b7f2 PM |
4410 | * the ->node array in the rcu_state structure. |
4411 | */ | |
4412 | static void __init rcu_init_geometry(void) | |
4413 | { | |
026ad283 | 4414 | ulong d; |
f885b7f2 | 4415 | int i; |
05b84aec | 4416 | int rcu_capacity[RCU_NUM_LVLS]; |
f885b7f2 | 4417 | |
026ad283 PM |
4418 | /* |
4419 | * Initialize any unspecified boot parameters. | |
4420 | * The default values of jiffies_till_first_fqs and | |
4421 | * jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS | |
4422 | * value, which is a function of HZ, then adding one for each | |
4423 | * RCU_JIFFIES_FQS_DIV CPUs that might be on the system. | |
4424 | */ | |
4425 | d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV; | |
4426 | if (jiffies_till_first_fqs == ULONG_MAX) | |
4427 | jiffies_till_first_fqs = d; | |
4428 | if (jiffies_till_next_fqs == ULONG_MAX) | |
4429 | jiffies_till_next_fqs = d; | |
4430 | ||
f885b7f2 | 4431 | /* If the compile-time values are accurate, just leave. */ |
47d631af | 4432 | if (rcu_fanout_leaf == RCU_FANOUT_LEAF && |
b17c7035 | 4433 | nr_cpu_ids == NR_CPUS) |
f885b7f2 | 4434 | return; |
39479098 PM |
4435 | pr_info("RCU: Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%d\n", |
4436 | rcu_fanout_leaf, nr_cpu_ids); | |
f885b7f2 | 4437 | |
f885b7f2 PM |
4438 | /* |
4439 | * The boot-time rcu_fanout_leaf parameter is only permitted | |
4440 | * to increase the leaf-level fanout, not decrease it. Of course, | |
4441 | * the leaf-level fanout cannot exceed the number of bits in | |
75cf15a4 AG |
4442 | * the rcu_node masks. Complain and fall back to the compile- |
4443 | * time values if these limits are exceeded. | |
f885b7f2 | 4444 | */ |
47d631af | 4445 | if (rcu_fanout_leaf < RCU_FANOUT_LEAF || |
75cf15a4 | 4446 | rcu_fanout_leaf > sizeof(unsigned long) * 8) { |
13bd6494 | 4447 | rcu_fanout_leaf = RCU_FANOUT_LEAF; |
f885b7f2 PM |
4448 | WARN_ON(1); |
4449 | return; | |
4450 | } | |
4451 | ||
f885b7f2 PM |
4452 | /* |
4453 | * Compute number of nodes that can be handled an rcu_node tree | |
9618138b | 4454 | * with the given number of levels. |
f885b7f2 | 4455 | */ |
9618138b | 4456 | rcu_capacity[0] = rcu_fanout_leaf; |
05b84aec | 4457 | for (i = 1; i < RCU_NUM_LVLS; i++) |
05c5df31 | 4458 | rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT; |
f885b7f2 PM |
4459 | |
4460 | /* | |
75cf15a4 AG |
4461 | * The tree must be able to accommodate the configured number of CPUs. |
4462 | * If this limit is exceeded than we have a serious problem elsewhere. | |
f885b7f2 | 4463 | */ |
05b84aec | 4464 | if (nr_cpu_ids > rcu_capacity[RCU_NUM_LVLS - 1]) |
75cf15a4 | 4465 | panic("rcu_init_geometry: rcu_capacity[] is too small"); |
f885b7f2 | 4466 | |
679f9858 | 4467 | /* Calculate the number of levels in the tree. */ |
9618138b | 4468 | for (i = 0; nr_cpu_ids > rcu_capacity[i]; i++) { |
679f9858 | 4469 | } |
9618138b | 4470 | rcu_num_lvls = i + 1; |
679f9858 | 4471 | |
f885b7f2 | 4472 | /* Calculate the number of rcu_nodes at each level of the tree. */ |
679f9858 | 4473 | for (i = 0; i < rcu_num_lvls; i++) { |
9618138b | 4474 | int cap = rcu_capacity[(rcu_num_lvls - 1) - i]; |
679f9858 AG |
4475 | num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap); |
4476 | } | |
f885b7f2 PM |
4477 | |
4478 | /* Calculate the total number of rcu_node structures. */ | |
4479 | rcu_num_nodes = 0; | |
679f9858 | 4480 | for (i = 0; i < rcu_num_lvls; i++) |
f885b7f2 | 4481 | rcu_num_nodes += num_rcu_lvl[i]; |
f885b7f2 PM |
4482 | } |
4483 | ||
a3dc2948 PM |
4484 | /* |
4485 | * Dump out the structure of the rcu_node combining tree associated | |
4486 | * with the rcu_state structure referenced by rsp. | |
4487 | */ | |
4488 | static void __init rcu_dump_rcu_node_tree(struct rcu_state *rsp) | |
4489 | { | |
4490 | int level = 0; | |
4491 | struct rcu_node *rnp; | |
4492 | ||
4493 | pr_info("rcu_node tree layout dump\n"); | |
4494 | pr_info(" "); | |
4495 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
4496 | if (rnp->level != level) { | |
4497 | pr_cont("\n"); | |
4498 | pr_info(" "); | |
4499 | level = rnp->level; | |
4500 | } | |
4501 | pr_cont("%d:%d ^%d ", rnp->grplo, rnp->grphi, rnp->grpnum); | |
4502 | } | |
4503 | pr_cont("\n"); | |
4504 | } | |
4505 | ||
9f680ab4 | 4506 | void __init rcu_init(void) |
64db4cff | 4507 | { |
017c4261 | 4508 | int cpu; |
9f680ab4 | 4509 | |
47627678 PM |
4510 | rcu_early_boot_tests(); |
4511 | ||
f41d911f | 4512 | rcu_bootup_announce(); |
f885b7f2 | 4513 | rcu_init_geometry(); |
394f99a9 | 4514 | rcu_init_one(&rcu_bh_state, &rcu_bh_data); |
69c8d28c | 4515 | rcu_init_one(&rcu_sched_state, &rcu_sched_data); |
a3dc2948 PM |
4516 | if (dump_tree) |
4517 | rcu_dump_rcu_node_tree(&rcu_sched_state); | |
f41d911f | 4518 | __rcu_init_preempt(); |
b5b39360 | 4519 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
9f680ab4 PM |
4520 | |
4521 | /* | |
4522 | * We don't need protection against CPU-hotplug here because | |
4523 | * this is called early in boot, before either interrupts | |
4524 | * or the scheduler are operational. | |
4525 | */ | |
4526 | cpu_notifier(rcu_cpu_notify, 0); | |
d1d74d14 | 4527 | pm_notifier(rcu_pm_notify, 0); |
017c4261 PM |
4528 | for_each_online_cpu(cpu) |
4529 | rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); | |
64db4cff PM |
4530 | } |
4531 | ||
4102adab | 4532 | #include "tree_plugin.h" |