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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> |
f7f7bac9 | 57 | #include <linux/ftrace_event.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]; |
88b91c7c | 73 | |
f7f7bac9 SRRH |
74 | /* |
75 | * In order to export the rcu_state name to the tracing tools, it | |
76 | * needs to be added in the __tracepoint_string section. | |
77 | * This requires defining a separate variable tp_<sname>_varname | |
78 | * that points to the string being used, and this will allow | |
79 | * the tracing userspace tools to be able to decipher the string | |
80 | * address to the matching string. | |
81 | */ | |
a41bfeb2 | 82 | #define RCU_STATE_INITIALIZER(sname, sabbr, cr) \ |
f7f7bac9 SRRH |
83 | static char sname##_varname[] = #sname; \ |
84 | static const char *tp_##sname##_varname __used __tracepoint_string = sname##_varname; \ | |
a41bfeb2 | 85 | struct rcu_state sname##_state = { \ |
6c90cc7b | 86 | .level = { &sname##_state.node[0] }, \ |
037b64ed | 87 | .call = cr, \ |
af446b70 | 88 | .fqs_state = RCU_GP_IDLE, \ |
42c3533e PM |
89 | .gpnum = 0UL - 300UL, \ |
90 | .completed = 0UL - 300UL, \ | |
7b2e6011 | 91 | .orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \ |
6c90cc7b PM |
92 | .orphan_nxttail = &sname##_state.orphan_nxtlist, \ |
93 | .orphan_donetail = &sname##_state.orphan_donelist, \ | |
7be7f0be | 94 | .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \ |
a4fbe35a | 95 | .onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \ |
f7f7bac9 | 96 | .name = sname##_varname, \ |
a4889858 | 97 | .abbr = sabbr, \ |
a41bfeb2 SRRH |
98 | }; \ |
99 | DEFINE_PER_CPU(struct rcu_data, sname##_data) | |
64db4cff | 100 | |
a41bfeb2 SRRH |
101 | RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched); |
102 | RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh); | |
b1f77b05 | 103 | |
e534165b | 104 | static struct rcu_state *rcu_state_p; |
6ce75a23 | 105 | LIST_HEAD(rcu_struct_flavors); |
27f4d280 | 106 | |
f885b7f2 PM |
107 | /* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */ |
108 | static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF; | |
7e5c2dfb | 109 | module_param(rcu_fanout_leaf, int, 0444); |
f885b7f2 PM |
110 | int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; |
111 | static int num_rcu_lvl[] = { /* Number of rcu_nodes at specified level. */ | |
112 | NUM_RCU_LVL_0, | |
113 | NUM_RCU_LVL_1, | |
114 | NUM_RCU_LVL_2, | |
115 | NUM_RCU_LVL_3, | |
116 | NUM_RCU_LVL_4, | |
117 | }; | |
118 | int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ | |
119 | ||
b0d30417 PM |
120 | /* |
121 | * The rcu_scheduler_active variable transitions from zero to one just | |
122 | * before the first task is spawned. So when this variable is zero, RCU | |
123 | * can assume that there is but one task, allowing RCU to (for example) | |
b44f6656 | 124 | * optimize synchronize_sched() to a simple barrier(). When this variable |
b0d30417 PM |
125 | * is one, RCU must actually do all the hard work required to detect real |
126 | * grace periods. This variable is also used to suppress boot-time false | |
127 | * positives from lockdep-RCU error checking. | |
128 | */ | |
bbad9379 PM |
129 | int rcu_scheduler_active __read_mostly; |
130 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
131 | ||
b0d30417 PM |
132 | /* |
133 | * The rcu_scheduler_fully_active variable transitions from zero to one | |
134 | * during the early_initcall() processing, which is after the scheduler | |
135 | * is capable of creating new tasks. So RCU processing (for example, | |
136 | * creating tasks for RCU priority boosting) must be delayed until after | |
137 | * rcu_scheduler_fully_active transitions from zero to one. We also | |
138 | * currently delay invocation of any RCU callbacks until after this point. | |
139 | * | |
140 | * It might later prove better for people registering RCU callbacks during | |
141 | * early boot to take responsibility for these callbacks, but one step at | |
142 | * a time. | |
143 | */ | |
144 | static int rcu_scheduler_fully_active __read_mostly; | |
145 | ||
a46e0899 PM |
146 | #ifdef CONFIG_RCU_BOOST |
147 | ||
a26ac245 PM |
148 | /* |
149 | * Control variables for per-CPU and per-rcu_node kthreads. These | |
150 | * handle all flavors of RCU. | |
151 | */ | |
152 | static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); | |
d71df90e | 153 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); |
5ece5bab | 154 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); |
d71df90e | 155 | DEFINE_PER_CPU(char, rcu_cpu_has_work); |
a26ac245 | 156 | |
a46e0899 PM |
157 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
158 | ||
5d01bbd1 | 159 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); |
a46e0899 PM |
160 | static void invoke_rcu_core(void); |
161 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); | |
a26ac245 | 162 | |
4a298656 PM |
163 | /* |
164 | * Track the rcutorture test sequence number and the update version | |
165 | * number within a given test. The rcutorture_testseq is incremented | |
166 | * on every rcutorture module load and unload, so has an odd value | |
167 | * when a test is running. The rcutorture_vernum is set to zero | |
168 | * when rcutorture starts and is incremented on each rcutorture update. | |
169 | * These variables enable correlating rcutorture output with the | |
170 | * RCU tracing information. | |
171 | */ | |
172 | unsigned long rcutorture_testseq; | |
173 | unsigned long rcutorture_vernum; | |
174 | ||
fc2219d4 PM |
175 | /* |
176 | * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s | |
177 | * permit this function to be invoked without holding the root rcu_node | |
178 | * structure's ->lock, but of course results can be subject to change. | |
179 | */ | |
180 | static int rcu_gp_in_progress(struct rcu_state *rsp) | |
181 | { | |
182 | return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); | |
183 | } | |
184 | ||
b1f77b05 | 185 | /* |
d6714c22 | 186 | * Note a quiescent state. Because we do not need to know |
b1f77b05 | 187 | * how many quiescent states passed, just if there was at least |
d6714c22 | 188 | * one since the start of the grace period, this just sets a flag. |
e4cc1f22 | 189 | * The caller must have disabled preemption. |
b1f77b05 | 190 | */ |
d6714c22 | 191 | void rcu_sched_qs(int cpu) |
b1f77b05 | 192 | { |
25502a6c | 193 | struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); |
f41d911f | 194 | |
e4cc1f22 | 195 | if (rdp->passed_quiesce == 0) |
f7f7bac9 | 196 | trace_rcu_grace_period(TPS("rcu_sched"), rdp->gpnum, TPS("cpuqs")); |
e4cc1f22 | 197 | rdp->passed_quiesce = 1; |
b1f77b05 IM |
198 | } |
199 | ||
d6714c22 | 200 | void rcu_bh_qs(int cpu) |
b1f77b05 | 201 | { |
25502a6c | 202 | struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
f41d911f | 203 | |
e4cc1f22 | 204 | if (rdp->passed_quiesce == 0) |
f7f7bac9 | 205 | trace_rcu_grace_period(TPS("rcu_bh"), rdp->gpnum, TPS("cpuqs")); |
e4cc1f22 | 206 | rdp->passed_quiesce = 1; |
b1f77b05 | 207 | } |
64db4cff | 208 | |
25502a6c PM |
209 | /* |
210 | * Note a context switch. This is a quiescent state for RCU-sched, | |
211 | * and requires special handling for preemptible RCU. | |
e4cc1f22 | 212 | * The caller must have disabled preemption. |
25502a6c PM |
213 | */ |
214 | void rcu_note_context_switch(int cpu) | |
215 | { | |
f7f7bac9 | 216 | trace_rcu_utilization(TPS("Start context switch")); |
25502a6c | 217 | rcu_sched_qs(cpu); |
cba6d0d6 | 218 | rcu_preempt_note_context_switch(cpu); |
f7f7bac9 | 219 | trace_rcu_utilization(TPS("End context switch")); |
25502a6c | 220 | } |
29ce8310 | 221 | EXPORT_SYMBOL_GPL(rcu_note_context_switch); |
25502a6c | 222 | |
01896f7e | 223 | static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
29e37d81 | 224 | .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, |
23b5c8fa | 225 | .dynticks = ATOMIC_INIT(1), |
2333210b PM |
226 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE |
227 | .dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE, | |
228 | .dynticks_idle = ATOMIC_INIT(1), | |
229 | #endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ | |
90a4d2c0 | 230 | }; |
64db4cff | 231 | |
878d7439 ED |
232 | static long blimit = 10; /* Maximum callbacks per rcu_do_batch. */ |
233 | static long qhimark = 10000; /* If this many pending, ignore blimit. */ | |
234 | static long qlowmark = 100; /* Once only this many pending, use blimit. */ | |
64db4cff | 235 | |
878d7439 ED |
236 | module_param(blimit, long, 0444); |
237 | module_param(qhimark, long, 0444); | |
238 | module_param(qlowmark, long, 0444); | |
3d76c082 | 239 | |
026ad283 PM |
240 | static ulong jiffies_till_first_fqs = ULONG_MAX; |
241 | static ulong jiffies_till_next_fqs = ULONG_MAX; | |
d40011f6 PM |
242 | |
243 | module_param(jiffies_till_first_fqs, ulong, 0644); | |
244 | module_param(jiffies_till_next_fqs, ulong, 0644); | |
245 | ||
48a7639c | 246 | static bool rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, |
910ee45d | 247 | struct rcu_data *rdp); |
217af2a2 PM |
248 | static void force_qs_rnp(struct rcu_state *rsp, |
249 | int (*f)(struct rcu_data *rsp, bool *isidle, | |
250 | unsigned long *maxj), | |
251 | bool *isidle, unsigned long *maxj); | |
4cdfc175 | 252 | static void force_quiescent_state(struct rcu_state *rsp); |
a157229c | 253 | static int rcu_pending(int cpu); |
64db4cff PM |
254 | |
255 | /* | |
d6714c22 | 256 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
64db4cff | 257 | */ |
d6714c22 | 258 | long rcu_batches_completed_sched(void) |
64db4cff | 259 | { |
d6714c22 | 260 | return rcu_sched_state.completed; |
64db4cff | 261 | } |
d6714c22 | 262 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
64db4cff PM |
263 | |
264 | /* | |
265 | * Return the number of RCU BH batches processed thus far for debug & stats. | |
266 | */ | |
267 | long rcu_batches_completed_bh(void) | |
268 | { | |
269 | return rcu_bh_state.completed; | |
270 | } | |
271 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
272 | ||
a381d757 ACB |
273 | /* |
274 | * Force a quiescent state. | |
275 | */ | |
276 | void rcu_force_quiescent_state(void) | |
277 | { | |
e534165b | 278 | force_quiescent_state(rcu_state_p); |
a381d757 ACB |
279 | } |
280 | EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); | |
281 | ||
bf66f18e PM |
282 | /* |
283 | * Force a quiescent state for RCU BH. | |
284 | */ | |
285 | void rcu_bh_force_quiescent_state(void) | |
286 | { | |
4cdfc175 | 287 | force_quiescent_state(&rcu_bh_state); |
bf66f18e PM |
288 | } |
289 | EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); | |
290 | ||
afea227f PM |
291 | /* |
292 | * Show the state of the grace-period kthreads. | |
293 | */ | |
294 | void show_rcu_gp_kthreads(void) | |
295 | { | |
296 | struct rcu_state *rsp; | |
297 | ||
298 | for_each_rcu_flavor(rsp) { | |
299 | pr_info("%s: wait state: %d ->state: %#lx\n", | |
300 | rsp->name, rsp->gp_state, rsp->gp_kthread->state); | |
301 | /* sched_show_task(rsp->gp_kthread); */ | |
302 | } | |
303 | } | |
304 | EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads); | |
305 | ||
4a298656 PM |
306 | /* |
307 | * Record the number of times rcutorture tests have been initiated and | |
308 | * terminated. This information allows the debugfs tracing stats to be | |
309 | * correlated to the rcutorture messages, even when the rcutorture module | |
310 | * is being repeatedly loaded and unloaded. In other words, we cannot | |
311 | * store this state in rcutorture itself. | |
312 | */ | |
313 | void rcutorture_record_test_transition(void) | |
314 | { | |
315 | rcutorture_testseq++; | |
316 | rcutorture_vernum = 0; | |
317 | } | |
318 | EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); | |
319 | ||
ad0dc7f9 PM |
320 | /* |
321 | * Send along grace-period-related data for rcutorture diagnostics. | |
322 | */ | |
323 | void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, | |
324 | unsigned long *gpnum, unsigned long *completed) | |
325 | { | |
326 | struct rcu_state *rsp = NULL; | |
327 | ||
328 | switch (test_type) { | |
329 | case RCU_FLAVOR: | |
e534165b | 330 | rsp = rcu_state_p; |
ad0dc7f9 PM |
331 | break; |
332 | case RCU_BH_FLAVOR: | |
333 | rsp = &rcu_bh_state; | |
334 | break; | |
335 | case RCU_SCHED_FLAVOR: | |
336 | rsp = &rcu_sched_state; | |
337 | break; | |
338 | default: | |
339 | break; | |
340 | } | |
341 | if (rsp != NULL) { | |
342 | *flags = ACCESS_ONCE(rsp->gp_flags); | |
343 | *gpnum = ACCESS_ONCE(rsp->gpnum); | |
344 | *completed = ACCESS_ONCE(rsp->completed); | |
345 | return; | |
346 | } | |
347 | *flags = 0; | |
348 | *gpnum = 0; | |
349 | *completed = 0; | |
350 | } | |
351 | EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); | |
352 | ||
4a298656 PM |
353 | /* |
354 | * Record the number of writer passes through the current rcutorture test. | |
355 | * This is also used to correlate debugfs tracing stats with the rcutorture | |
356 | * messages. | |
357 | */ | |
358 | void rcutorture_record_progress(unsigned long vernum) | |
359 | { | |
360 | rcutorture_vernum++; | |
361 | } | |
362 | EXPORT_SYMBOL_GPL(rcutorture_record_progress); | |
363 | ||
bf66f18e PM |
364 | /* |
365 | * Force a quiescent state for RCU-sched. | |
366 | */ | |
367 | void rcu_sched_force_quiescent_state(void) | |
368 | { | |
4cdfc175 | 369 | force_quiescent_state(&rcu_sched_state); |
bf66f18e PM |
370 | } |
371 | EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); | |
372 | ||
64db4cff PM |
373 | /* |
374 | * Does the CPU have callbacks ready to be invoked? | |
375 | */ | |
376 | static int | |
377 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) | |
378 | { | |
3fbfbf7a PM |
379 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL] && |
380 | rdp->nxttail[RCU_DONE_TAIL] != NULL; | |
64db4cff PM |
381 | } |
382 | ||
365187fb PM |
383 | /* |
384 | * Return the root node of the specified rcu_state structure. | |
385 | */ | |
386 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) | |
387 | { | |
388 | return &rsp->node[0]; | |
389 | } | |
390 | ||
391 | /* | |
392 | * Is there any need for future grace periods? | |
393 | * Interrupts must be disabled. If the caller does not hold the root | |
394 | * rnp_node structure's ->lock, the results are advisory only. | |
395 | */ | |
396 | static int rcu_future_needs_gp(struct rcu_state *rsp) | |
397 | { | |
398 | struct rcu_node *rnp = rcu_get_root(rsp); | |
399 | int idx = (ACCESS_ONCE(rnp->completed) + 1) & 0x1; | |
400 | int *fp = &rnp->need_future_gp[idx]; | |
401 | ||
402 | return ACCESS_ONCE(*fp); | |
403 | } | |
404 | ||
64db4cff | 405 | /* |
dc35c893 PM |
406 | * Does the current CPU require a not-yet-started grace period? |
407 | * The caller must have disabled interrupts to prevent races with | |
408 | * normal callback registry. | |
64db4cff PM |
409 | */ |
410 | static int | |
411 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) | |
412 | { | |
dc35c893 | 413 | int i; |
3fbfbf7a | 414 | |
dc35c893 PM |
415 | if (rcu_gp_in_progress(rsp)) |
416 | return 0; /* No, a grace period is already in progress. */ | |
365187fb | 417 | if (rcu_future_needs_gp(rsp)) |
34ed6246 | 418 | return 1; /* Yes, a no-CBs CPU needs one. */ |
dc35c893 PM |
419 | if (!rdp->nxttail[RCU_NEXT_TAIL]) |
420 | return 0; /* No, this is a no-CBs (or offline) CPU. */ | |
421 | if (*rdp->nxttail[RCU_NEXT_READY_TAIL]) | |
422 | return 1; /* Yes, this CPU has newly registered callbacks. */ | |
423 | for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) | |
424 | if (rdp->nxttail[i - 1] != rdp->nxttail[i] && | |
425 | ULONG_CMP_LT(ACCESS_ONCE(rsp->completed), | |
426 | rdp->nxtcompleted[i])) | |
427 | return 1; /* Yes, CBs for future grace period. */ | |
428 | return 0; /* No grace period needed. */ | |
64db4cff PM |
429 | } |
430 | ||
9b2e4f18 | 431 | /* |
adf5091e | 432 | * rcu_eqs_enter_common - current CPU is moving towards extended quiescent state |
9b2e4f18 PM |
433 | * |
434 | * If the new value of the ->dynticks_nesting counter now is zero, | |
435 | * we really have entered idle, and must do the appropriate accounting. | |
436 | * The caller must have disabled interrupts. | |
437 | */ | |
adf5091e FW |
438 | static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval, |
439 | bool user) | |
9b2e4f18 | 440 | { |
96d3fd0d PM |
441 | struct rcu_state *rsp; |
442 | struct rcu_data *rdp; | |
443 | ||
f7f7bac9 | 444 | trace_rcu_dyntick(TPS("Start"), oldval, rdtp->dynticks_nesting); |
cb349ca9 | 445 | if (!user && !is_idle_task(current)) { |
289828e6 PM |
446 | struct task_struct *idle __maybe_unused = |
447 | idle_task(smp_processor_id()); | |
0989cb46 | 448 | |
f7f7bac9 | 449 | trace_rcu_dyntick(TPS("Error on entry: not idle task"), oldval, 0); |
bf1304e9 | 450 | ftrace_dump(DUMP_ORIG); |
0989cb46 PM |
451 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
452 | current->pid, current->comm, | |
453 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 | 454 | } |
96d3fd0d PM |
455 | for_each_rcu_flavor(rsp) { |
456 | rdp = this_cpu_ptr(rsp->rda); | |
457 | do_nocb_deferred_wakeup(rdp); | |
458 | } | |
aea1b35e | 459 | rcu_prepare_for_idle(smp_processor_id()); |
9b2e4f18 | 460 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
4e857c58 | 461 | smp_mb__before_atomic(); /* See above. */ |
9b2e4f18 | 462 | atomic_inc(&rdtp->dynticks); |
4e857c58 | 463 | smp_mb__after_atomic(); /* Force ordering with next sojourn. */ |
9b2e4f18 | 464 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); |
c44e2cdd PM |
465 | |
466 | /* | |
adf5091e | 467 | * It is illegal to enter an extended quiescent state while |
c44e2cdd PM |
468 | * in an RCU read-side critical section. |
469 | */ | |
470 | rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), | |
471 | "Illegal idle entry in RCU read-side critical section."); | |
472 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), | |
473 | "Illegal idle entry in RCU-bh read-side critical section."); | |
474 | rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), | |
475 | "Illegal idle entry in RCU-sched read-side critical section."); | |
9b2e4f18 | 476 | } |
64db4cff | 477 | |
adf5091e FW |
478 | /* |
479 | * Enter an RCU extended quiescent state, which can be either the | |
480 | * idle loop or adaptive-tickless usermode execution. | |
64db4cff | 481 | */ |
adf5091e | 482 | static void rcu_eqs_enter(bool user) |
64db4cff | 483 | { |
4145fa7f | 484 | long long oldval; |
64db4cff PM |
485 | struct rcu_dynticks *rdtp; |
486 | ||
c9d4b0af | 487 | rdtp = this_cpu_ptr(&rcu_dynticks); |
4145fa7f | 488 | oldval = rdtp->dynticks_nesting; |
29e37d81 | 489 | WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0); |
3a592405 | 490 | if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) { |
29e37d81 | 491 | rdtp->dynticks_nesting = 0; |
3a592405 PM |
492 | rcu_eqs_enter_common(rdtp, oldval, user); |
493 | } else { | |
29e37d81 | 494 | rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE; |
3a592405 | 495 | } |
64db4cff | 496 | } |
adf5091e FW |
497 | |
498 | /** | |
499 | * rcu_idle_enter - inform RCU that current CPU is entering idle | |
500 | * | |
501 | * Enter idle mode, in other words, -leave- the mode in which RCU | |
502 | * read-side critical sections can occur. (Though RCU read-side | |
503 | * critical sections can occur in irq handlers in idle, a possibility | |
504 | * handled by irq_enter() and irq_exit().) | |
505 | * | |
506 | * We crowbar the ->dynticks_nesting field to zero to allow for | |
507 | * the possibility of usermode upcalls having messed up our count | |
508 | * of interrupt nesting level during the prior busy period. | |
509 | */ | |
510 | void rcu_idle_enter(void) | |
511 | { | |
c5d900bf FW |
512 | unsigned long flags; |
513 | ||
514 | local_irq_save(flags); | |
cb349ca9 | 515 | rcu_eqs_enter(false); |
c9d4b0af | 516 | rcu_sysidle_enter(this_cpu_ptr(&rcu_dynticks), 0); |
c5d900bf | 517 | local_irq_restore(flags); |
adf5091e | 518 | } |
8a2ecf47 | 519 | EXPORT_SYMBOL_GPL(rcu_idle_enter); |
64db4cff | 520 | |
2b1d5024 | 521 | #ifdef CONFIG_RCU_USER_QS |
adf5091e FW |
522 | /** |
523 | * rcu_user_enter - inform RCU that we are resuming userspace. | |
524 | * | |
525 | * Enter RCU idle mode right before resuming userspace. No use of RCU | |
526 | * is permitted between this call and rcu_user_exit(). This way the | |
527 | * CPU doesn't need to maintain the tick for RCU maintenance purposes | |
528 | * when the CPU runs in userspace. | |
529 | */ | |
530 | void rcu_user_enter(void) | |
531 | { | |
91d1aa43 | 532 | rcu_eqs_enter(1); |
adf5091e | 533 | } |
2b1d5024 | 534 | #endif /* CONFIG_RCU_USER_QS */ |
19dd1591 | 535 | |
9b2e4f18 PM |
536 | /** |
537 | * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle | |
538 | * | |
539 | * Exit from an interrupt handler, which might possibly result in entering | |
540 | * idle mode, in other words, leaving the mode in which read-side critical | |
541 | * sections can occur. | |
64db4cff | 542 | * |
9b2e4f18 PM |
543 | * This code assumes that the idle loop never does anything that might |
544 | * result in unbalanced calls to irq_enter() and irq_exit(). If your | |
545 | * architecture violates this assumption, RCU will give you what you | |
546 | * deserve, good and hard. But very infrequently and irreproducibly. | |
547 | * | |
548 | * Use things like work queues to work around this limitation. | |
549 | * | |
550 | * You have been warned. | |
64db4cff | 551 | */ |
9b2e4f18 | 552 | void rcu_irq_exit(void) |
64db4cff PM |
553 | { |
554 | unsigned long flags; | |
4145fa7f | 555 | long long oldval; |
64db4cff PM |
556 | struct rcu_dynticks *rdtp; |
557 | ||
558 | local_irq_save(flags); | |
c9d4b0af | 559 | rdtp = this_cpu_ptr(&rcu_dynticks); |
4145fa7f | 560 | oldval = rdtp->dynticks_nesting; |
9b2e4f18 PM |
561 | rdtp->dynticks_nesting--; |
562 | WARN_ON_ONCE(rdtp->dynticks_nesting < 0); | |
b6fc6020 | 563 | if (rdtp->dynticks_nesting) |
f7f7bac9 | 564 | trace_rcu_dyntick(TPS("--="), oldval, rdtp->dynticks_nesting); |
b6fc6020 | 565 | else |
cb349ca9 | 566 | rcu_eqs_enter_common(rdtp, oldval, true); |
eb348b89 | 567 | rcu_sysidle_enter(rdtp, 1); |
9b2e4f18 PM |
568 | local_irq_restore(flags); |
569 | } | |
570 | ||
571 | /* | |
adf5091e | 572 | * rcu_eqs_exit_common - current CPU moving away from extended quiescent state |
9b2e4f18 PM |
573 | * |
574 | * If the new value of the ->dynticks_nesting counter was previously zero, | |
575 | * we really have exited idle, and must do the appropriate accounting. | |
576 | * The caller must have disabled interrupts. | |
577 | */ | |
adf5091e FW |
578 | static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval, |
579 | int user) | |
9b2e4f18 | 580 | { |
4e857c58 | 581 | smp_mb__before_atomic(); /* Force ordering w/previous sojourn. */ |
23b5c8fa PM |
582 | atomic_inc(&rdtp->dynticks); |
583 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
4e857c58 | 584 | smp_mb__after_atomic(); /* See above. */ |
23b5c8fa | 585 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); |
7cb92499 | 586 | rcu_cleanup_after_idle(smp_processor_id()); |
f7f7bac9 | 587 | trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting); |
cb349ca9 | 588 | if (!user && !is_idle_task(current)) { |
289828e6 PM |
589 | struct task_struct *idle __maybe_unused = |
590 | idle_task(smp_processor_id()); | |
0989cb46 | 591 | |
f7f7bac9 | 592 | trace_rcu_dyntick(TPS("Error on exit: not idle task"), |
4145fa7f | 593 | oldval, rdtp->dynticks_nesting); |
bf1304e9 | 594 | ftrace_dump(DUMP_ORIG); |
0989cb46 PM |
595 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
596 | current->pid, current->comm, | |
597 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 PM |
598 | } |
599 | } | |
600 | ||
adf5091e FW |
601 | /* |
602 | * Exit an RCU extended quiescent state, which can be either the | |
603 | * idle loop or adaptive-tickless usermode execution. | |
9b2e4f18 | 604 | */ |
adf5091e | 605 | static void rcu_eqs_exit(bool user) |
9b2e4f18 | 606 | { |
9b2e4f18 PM |
607 | struct rcu_dynticks *rdtp; |
608 | long long oldval; | |
609 | ||
c9d4b0af | 610 | rdtp = this_cpu_ptr(&rcu_dynticks); |
9b2e4f18 | 611 | oldval = rdtp->dynticks_nesting; |
29e37d81 | 612 | WARN_ON_ONCE(oldval < 0); |
3a592405 | 613 | if (oldval & DYNTICK_TASK_NEST_MASK) { |
29e37d81 | 614 | rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE; |
3a592405 | 615 | } else { |
29e37d81 | 616 | rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
3a592405 PM |
617 | rcu_eqs_exit_common(rdtp, oldval, user); |
618 | } | |
9b2e4f18 | 619 | } |
adf5091e FW |
620 | |
621 | /** | |
622 | * rcu_idle_exit - inform RCU that current CPU is leaving idle | |
623 | * | |
624 | * Exit idle mode, in other words, -enter- the mode in which RCU | |
625 | * read-side critical sections can occur. | |
626 | * | |
627 | * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to | |
628 | * allow for the possibility of usermode upcalls messing up our count | |
629 | * of interrupt nesting level during the busy period that is just | |
630 | * now starting. | |
631 | */ | |
632 | void rcu_idle_exit(void) | |
633 | { | |
c5d900bf FW |
634 | unsigned long flags; |
635 | ||
636 | local_irq_save(flags); | |
cb349ca9 | 637 | rcu_eqs_exit(false); |
c9d4b0af | 638 | rcu_sysidle_exit(this_cpu_ptr(&rcu_dynticks), 0); |
c5d900bf | 639 | local_irq_restore(flags); |
adf5091e | 640 | } |
8a2ecf47 | 641 | EXPORT_SYMBOL_GPL(rcu_idle_exit); |
9b2e4f18 | 642 | |
2b1d5024 | 643 | #ifdef CONFIG_RCU_USER_QS |
adf5091e FW |
644 | /** |
645 | * rcu_user_exit - inform RCU that we are exiting userspace. | |
646 | * | |
647 | * Exit RCU idle mode while entering the kernel because it can | |
648 | * run a RCU read side critical section anytime. | |
649 | */ | |
650 | void rcu_user_exit(void) | |
651 | { | |
91d1aa43 | 652 | rcu_eqs_exit(1); |
adf5091e | 653 | } |
2b1d5024 | 654 | #endif /* CONFIG_RCU_USER_QS */ |
19dd1591 | 655 | |
9b2e4f18 PM |
656 | /** |
657 | * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle | |
658 | * | |
659 | * Enter an interrupt handler, which might possibly result in exiting | |
660 | * idle mode, in other words, entering the mode in which read-side critical | |
661 | * sections can occur. | |
662 | * | |
663 | * Note that the Linux kernel is fully capable of entering an interrupt | |
664 | * handler that it never exits, for example when doing upcalls to | |
665 | * user mode! This code assumes that the idle loop never does upcalls to | |
666 | * user mode. If your architecture does do upcalls from the idle loop (or | |
667 | * does anything else that results in unbalanced calls to the irq_enter() | |
668 | * and irq_exit() functions), RCU will give you what you deserve, good | |
669 | * and hard. But very infrequently and irreproducibly. | |
670 | * | |
671 | * Use things like work queues to work around this limitation. | |
672 | * | |
673 | * You have been warned. | |
674 | */ | |
675 | void rcu_irq_enter(void) | |
676 | { | |
677 | unsigned long flags; | |
678 | struct rcu_dynticks *rdtp; | |
679 | long long oldval; | |
680 | ||
681 | local_irq_save(flags); | |
c9d4b0af | 682 | rdtp = this_cpu_ptr(&rcu_dynticks); |
9b2e4f18 PM |
683 | oldval = rdtp->dynticks_nesting; |
684 | rdtp->dynticks_nesting++; | |
685 | WARN_ON_ONCE(rdtp->dynticks_nesting == 0); | |
b6fc6020 | 686 | if (oldval) |
f7f7bac9 | 687 | trace_rcu_dyntick(TPS("++="), oldval, rdtp->dynticks_nesting); |
b6fc6020 | 688 | else |
cb349ca9 | 689 | rcu_eqs_exit_common(rdtp, oldval, true); |
eb348b89 | 690 | rcu_sysidle_exit(rdtp, 1); |
64db4cff | 691 | local_irq_restore(flags); |
64db4cff PM |
692 | } |
693 | ||
694 | /** | |
695 | * rcu_nmi_enter - inform RCU of entry to NMI context | |
696 | * | |
697 | * If the CPU was idle with dynamic ticks active, and there is no | |
698 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
699 | * RCU grace-period handling know that the CPU is active. | |
700 | */ | |
701 | void rcu_nmi_enter(void) | |
702 | { | |
c9d4b0af | 703 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
64db4cff | 704 | |
23b5c8fa PM |
705 | if (rdtp->dynticks_nmi_nesting == 0 && |
706 | (atomic_read(&rdtp->dynticks) & 0x1)) | |
64db4cff | 707 | return; |
23b5c8fa | 708 | rdtp->dynticks_nmi_nesting++; |
4e857c58 | 709 | smp_mb__before_atomic(); /* Force delay from prior write. */ |
23b5c8fa PM |
710 | atomic_inc(&rdtp->dynticks); |
711 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
4e857c58 | 712 | smp_mb__after_atomic(); /* See above. */ |
23b5c8fa | 713 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); |
64db4cff PM |
714 | } |
715 | ||
716 | /** | |
717 | * rcu_nmi_exit - inform RCU of exit from NMI context | |
718 | * | |
719 | * If the CPU was idle with dynamic ticks active, and there is no | |
720 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
721 | * RCU grace-period handling know that the CPU is no longer active. | |
722 | */ | |
723 | void rcu_nmi_exit(void) | |
724 | { | |
c9d4b0af | 725 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
64db4cff | 726 | |
23b5c8fa PM |
727 | if (rdtp->dynticks_nmi_nesting == 0 || |
728 | --rdtp->dynticks_nmi_nesting != 0) | |
64db4cff | 729 | return; |
23b5c8fa | 730 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
4e857c58 | 731 | smp_mb__before_atomic(); /* See above. */ |
23b5c8fa | 732 | atomic_inc(&rdtp->dynticks); |
4e857c58 | 733 | smp_mb__after_atomic(); /* Force delay to next write. */ |
23b5c8fa | 734 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); |
64db4cff PM |
735 | } |
736 | ||
737 | /** | |
5c173eb8 PM |
738 | * __rcu_is_watching - are RCU read-side critical sections safe? |
739 | * | |
740 | * Return true if RCU is watching the running CPU, which means that | |
741 | * this CPU can safely enter RCU read-side critical sections. Unlike | |
742 | * rcu_is_watching(), the caller of __rcu_is_watching() must have at | |
743 | * least disabled preemption. | |
744 | */ | |
9418fb20 | 745 | bool notrace __rcu_is_watching(void) |
5c173eb8 PM |
746 | { |
747 | return atomic_read(this_cpu_ptr(&rcu_dynticks.dynticks)) & 0x1; | |
748 | } | |
749 | ||
750 | /** | |
751 | * rcu_is_watching - see if RCU thinks that the current CPU is idle | |
64db4cff | 752 | * |
9b2e4f18 | 753 | * If the current CPU is in its idle loop and is neither in an interrupt |
34240697 | 754 | * or NMI handler, return true. |
64db4cff | 755 | */ |
9418fb20 | 756 | bool notrace rcu_is_watching(void) |
64db4cff | 757 | { |
34240697 PM |
758 | int ret; |
759 | ||
760 | preempt_disable(); | |
5c173eb8 | 761 | ret = __rcu_is_watching(); |
34240697 PM |
762 | preempt_enable(); |
763 | return ret; | |
64db4cff | 764 | } |
5c173eb8 | 765 | EXPORT_SYMBOL_GPL(rcu_is_watching); |
64db4cff | 766 | |
62fde6ed | 767 | #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) |
c0d6d01b PM |
768 | |
769 | /* | |
770 | * Is the current CPU online? Disable preemption to avoid false positives | |
771 | * that could otherwise happen due to the current CPU number being sampled, | |
772 | * this task being preempted, its old CPU being taken offline, resuming | |
773 | * on some other CPU, then determining that its old CPU is now offline. | |
774 | * It is OK to use RCU on an offline processor during initial boot, hence | |
2036d94a PM |
775 | * the check for rcu_scheduler_fully_active. Note also that it is OK |
776 | * for a CPU coming online to use RCU for one jiffy prior to marking itself | |
777 | * online in the cpu_online_mask. Similarly, it is OK for a CPU going | |
778 | * offline to continue to use RCU for one jiffy after marking itself | |
779 | * offline in the cpu_online_mask. This leniency is necessary given the | |
780 | * non-atomic nature of the online and offline processing, for example, | |
781 | * the fact that a CPU enters the scheduler after completing the CPU_DYING | |
782 | * notifiers. | |
783 | * | |
784 | * This is also why RCU internally marks CPUs online during the | |
785 | * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase. | |
c0d6d01b PM |
786 | * |
787 | * Disable checking if in an NMI handler because we cannot safely report | |
788 | * errors from NMI handlers anyway. | |
789 | */ | |
790 | bool rcu_lockdep_current_cpu_online(void) | |
791 | { | |
2036d94a PM |
792 | struct rcu_data *rdp; |
793 | struct rcu_node *rnp; | |
c0d6d01b PM |
794 | bool ret; |
795 | ||
796 | if (in_nmi()) | |
f6f7ee9a | 797 | return true; |
c0d6d01b | 798 | preempt_disable(); |
c9d4b0af | 799 | rdp = this_cpu_ptr(&rcu_sched_data); |
2036d94a PM |
800 | rnp = rdp->mynode; |
801 | ret = (rdp->grpmask & rnp->qsmaskinit) || | |
c0d6d01b PM |
802 | !rcu_scheduler_fully_active; |
803 | preempt_enable(); | |
804 | return ret; | |
805 | } | |
806 | EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); | |
807 | ||
62fde6ed | 808 | #endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */ |
9b2e4f18 | 809 | |
64db4cff | 810 | /** |
9b2e4f18 | 811 | * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle |
64db4cff | 812 | * |
9b2e4f18 PM |
813 | * If the current CPU is idle or running at a first-level (not nested) |
814 | * interrupt from idle, return true. The caller must have at least | |
815 | * disabled preemption. | |
64db4cff | 816 | */ |
62e3cb14 | 817 | static int rcu_is_cpu_rrupt_from_idle(void) |
64db4cff | 818 | { |
c9d4b0af | 819 | return __this_cpu_read(rcu_dynticks.dynticks_nesting) <= 1; |
64db4cff PM |
820 | } |
821 | ||
64db4cff PM |
822 | /* |
823 | * Snapshot the specified CPU's dynticks counter so that we can later | |
824 | * credit them with an implicit quiescent state. Return 1 if this CPU | |
1eba8f84 | 825 | * is in dynticks idle mode, which is an extended quiescent state. |
64db4cff | 826 | */ |
217af2a2 PM |
827 | static int dyntick_save_progress_counter(struct rcu_data *rdp, |
828 | bool *isidle, unsigned long *maxj) | |
64db4cff | 829 | { |
23b5c8fa | 830 | rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); |
0edd1b17 | 831 | rcu_sysidle_check_cpu(rdp, isidle, maxj); |
7941dbde ACB |
832 | if ((rdp->dynticks_snap & 0x1) == 0) { |
833 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti")); | |
834 | return 1; | |
835 | } else { | |
836 | return 0; | |
837 | } | |
64db4cff PM |
838 | } |
839 | ||
6193c76a PM |
840 | /* |
841 | * This function really isn't for public consumption, but RCU is special in | |
842 | * that context switches can allow the state machine to make progress. | |
843 | */ | |
844 | extern void resched_cpu(int cpu); | |
845 | ||
64db4cff PM |
846 | /* |
847 | * Return true if the specified CPU has passed through a quiescent | |
848 | * state by virtue of being in or having passed through an dynticks | |
849 | * idle state since the last call to dyntick_save_progress_counter() | |
a82dcc76 | 850 | * for this same CPU, or by virtue of having been offline. |
64db4cff | 851 | */ |
217af2a2 PM |
852 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, |
853 | bool *isidle, unsigned long *maxj) | |
64db4cff | 854 | { |
7eb4f455 PM |
855 | unsigned int curr; |
856 | unsigned int snap; | |
64db4cff | 857 | |
7eb4f455 PM |
858 | curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks); |
859 | snap = (unsigned int)rdp->dynticks_snap; | |
64db4cff PM |
860 | |
861 | /* | |
862 | * If the CPU passed through or entered a dynticks idle phase with | |
863 | * no active irq/NMI handlers, then we can safely pretend that the CPU | |
864 | * already acknowledged the request to pass through a quiescent | |
865 | * state. Either way, that CPU cannot possibly be in an RCU | |
866 | * read-side critical section that started before the beginning | |
867 | * of the current RCU grace period. | |
868 | */ | |
7eb4f455 | 869 | if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) { |
f7f7bac9 | 870 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti")); |
64db4cff PM |
871 | rdp->dynticks_fqs++; |
872 | return 1; | |
873 | } | |
874 | ||
a82dcc76 PM |
875 | /* |
876 | * Check for the CPU being offline, but only if the grace period | |
877 | * is old enough. We don't need to worry about the CPU changing | |
878 | * state: If we see it offline even once, it has been through a | |
879 | * quiescent state. | |
880 | * | |
881 | * The reason for insisting that the grace period be at least | |
882 | * one jiffy old is that CPUs that are not quite online and that | |
883 | * have just gone offline can still execute RCU read-side critical | |
884 | * sections. | |
885 | */ | |
886 | if (ULONG_CMP_GE(rdp->rsp->gp_start + 2, jiffies)) | |
887 | return 0; /* Grace period is not old enough. */ | |
888 | barrier(); | |
889 | if (cpu_is_offline(rdp->cpu)) { | |
f7f7bac9 | 890 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("ofl")); |
a82dcc76 PM |
891 | rdp->offline_fqs++; |
892 | return 1; | |
893 | } | |
65d798f0 PM |
894 | |
895 | /* | |
896 | * There is a possibility that a CPU in adaptive-ticks state | |
897 | * might run in the kernel with the scheduling-clock tick disabled | |
898 | * for an extended time period. Invoke rcu_kick_nohz_cpu() to | |
899 | * force the CPU to restart the scheduling-clock tick in this | |
900 | * CPU is in this state. | |
901 | */ | |
902 | rcu_kick_nohz_cpu(rdp->cpu); | |
903 | ||
6193c76a PM |
904 | /* |
905 | * Alternatively, the CPU might be running in the kernel | |
906 | * for an extended period of time without a quiescent state. | |
907 | * Attempt to force the CPU through the scheduler to gain the | |
908 | * needed quiescent state, but only if the grace period has gone | |
909 | * on for an uncommonly long time. If there are many stuck CPUs, | |
910 | * we will beat on the first one until it gets unstuck, then move | |
911 | * to the next. Only do this for the primary flavor of RCU. | |
912 | */ | |
e534165b | 913 | if (rdp->rsp == rcu_state_p && |
cb1e78cf | 914 | ULONG_CMP_GE(jiffies, rdp->rsp->jiffies_resched)) { |
6193c76a PM |
915 | rdp->rsp->jiffies_resched += 5; |
916 | resched_cpu(rdp->cpu); | |
917 | } | |
918 | ||
a82dcc76 | 919 | return 0; |
64db4cff PM |
920 | } |
921 | ||
64db4cff PM |
922 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
923 | { | |
cb1e78cf | 924 | unsigned long j = jiffies; |
6193c76a | 925 | unsigned long j1; |
26cdfedf PM |
926 | |
927 | rsp->gp_start = j; | |
928 | smp_wmb(); /* Record start time before stall time. */ | |
6193c76a | 929 | j1 = rcu_jiffies_till_stall_check(); |
4fc5b755 | 930 | ACCESS_ONCE(rsp->jiffies_stall) = j + j1; |
6193c76a | 931 | rsp->jiffies_resched = j + j1 / 2; |
64db4cff PM |
932 | } |
933 | ||
b637a328 PM |
934 | /* |
935 | * Dump stacks of all tasks running on stalled CPUs. This is a fallback | |
936 | * for architectures that do not implement trigger_all_cpu_backtrace(). | |
937 | * The NMI-triggered stack traces are more accurate because they are | |
938 | * printed by the target CPU. | |
939 | */ | |
940 | static void rcu_dump_cpu_stacks(struct rcu_state *rsp) | |
941 | { | |
942 | int cpu; | |
943 | unsigned long flags; | |
944 | struct rcu_node *rnp; | |
945 | ||
946 | rcu_for_each_leaf_node(rsp, rnp) { | |
947 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
948 | if (rnp->qsmask != 0) { | |
949 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) | |
950 | if (rnp->qsmask & (1UL << cpu)) | |
951 | dump_cpu_task(rnp->grplo + cpu); | |
952 | } | |
953 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
954 | } | |
955 | } | |
956 | ||
64db4cff PM |
957 | static void print_other_cpu_stall(struct rcu_state *rsp) |
958 | { | |
959 | int cpu; | |
960 | long delta; | |
961 | unsigned long flags; | |
285fe294 | 962 | int ndetected = 0; |
64db4cff | 963 | struct rcu_node *rnp = rcu_get_root(rsp); |
53bb857c | 964 | long totqlen = 0; |
64db4cff PM |
965 | |
966 | /* Only let one CPU complain about others per time interval. */ | |
967 | ||
1304afb2 | 968 | raw_spin_lock_irqsave(&rnp->lock, flags); |
4fc5b755 | 969 | delta = jiffies - ACCESS_ONCE(rsp->jiffies_stall); |
fc2219d4 | 970 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
1304afb2 | 971 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
972 | return; |
973 | } | |
4fc5b755 | 974 | ACCESS_ONCE(rsp->jiffies_stall) = jiffies + 3 * rcu_jiffies_till_stall_check() + 3; |
1304afb2 | 975 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 976 | |
8cdd32a9 PM |
977 | /* |
978 | * OK, time to rat on our buddy... | |
979 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
980 | * RCU CPU stall warnings. | |
981 | */ | |
d7f3e207 | 982 | pr_err("INFO: %s detected stalls on CPUs/tasks:", |
4300aa64 | 983 | rsp->name); |
a858af28 | 984 | print_cpu_stall_info_begin(); |
a0b6c9a7 | 985 | rcu_for_each_leaf_node(rsp, rnp) { |
3acd9eb3 | 986 | raw_spin_lock_irqsave(&rnp->lock, flags); |
9bc8b558 | 987 | ndetected += rcu_print_task_stall(rnp); |
c8020a67 PM |
988 | if (rnp->qsmask != 0) { |
989 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) | |
990 | if (rnp->qsmask & (1UL << cpu)) { | |
991 | print_cpu_stall_info(rsp, | |
992 | rnp->grplo + cpu); | |
993 | ndetected++; | |
994 | } | |
995 | } | |
3acd9eb3 | 996 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 997 | } |
a858af28 PM |
998 | |
999 | /* | |
1000 | * Now rat on any tasks that got kicked up to the root rcu_node | |
1001 | * due to CPU offlining. | |
1002 | */ | |
1003 | rnp = rcu_get_root(rsp); | |
1004 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
285fe294 | 1005 | ndetected += rcu_print_task_stall(rnp); |
a858af28 PM |
1006 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1007 | ||
1008 | print_cpu_stall_info_end(); | |
53bb857c PM |
1009 | for_each_possible_cpu(cpu) |
1010 | totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen; | |
83ebe63e | 1011 | pr_cont("(detected by %d, t=%ld jiffies, g=%ld, c=%ld, q=%lu)\n", |
eee05882 | 1012 | smp_processor_id(), (long)(jiffies - rsp->gp_start), |
83ebe63e | 1013 | (long)rsp->gpnum, (long)rsp->completed, totqlen); |
9bc8b558 | 1014 | if (ndetected == 0) |
d7f3e207 | 1015 | pr_err("INFO: Stall ended before state dump start\n"); |
9bc8b558 | 1016 | else if (!trigger_all_cpu_backtrace()) |
b637a328 | 1017 | rcu_dump_cpu_stacks(rsp); |
c1dc0b9c | 1018 | |
4cdfc175 | 1019 | /* Complain about tasks blocking the grace period. */ |
1ed509a2 PM |
1020 | |
1021 | rcu_print_detail_task_stall(rsp); | |
1022 | ||
4cdfc175 | 1023 | force_quiescent_state(rsp); /* Kick them all. */ |
64db4cff PM |
1024 | } |
1025 | ||
1026 | static void print_cpu_stall(struct rcu_state *rsp) | |
1027 | { | |
53bb857c | 1028 | int cpu; |
64db4cff PM |
1029 | unsigned long flags; |
1030 | struct rcu_node *rnp = rcu_get_root(rsp); | |
53bb857c | 1031 | long totqlen = 0; |
64db4cff | 1032 | |
8cdd32a9 PM |
1033 | /* |
1034 | * OK, time to rat on ourselves... | |
1035 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
1036 | * RCU CPU stall warnings. | |
1037 | */ | |
d7f3e207 | 1038 | pr_err("INFO: %s self-detected stall on CPU", rsp->name); |
a858af28 PM |
1039 | print_cpu_stall_info_begin(); |
1040 | print_cpu_stall_info(rsp, smp_processor_id()); | |
1041 | print_cpu_stall_info_end(); | |
53bb857c PM |
1042 | for_each_possible_cpu(cpu) |
1043 | totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen; | |
83ebe63e PM |
1044 | pr_cont(" (t=%lu jiffies g=%ld c=%ld q=%lu)\n", |
1045 | jiffies - rsp->gp_start, | |
1046 | (long)rsp->gpnum, (long)rsp->completed, totqlen); | |
4627e240 PM |
1047 | if (!trigger_all_cpu_backtrace()) |
1048 | dump_stack(); | |
c1dc0b9c | 1049 | |
1304afb2 | 1050 | raw_spin_lock_irqsave(&rnp->lock, flags); |
4fc5b755 IM |
1051 | if (ULONG_CMP_GE(jiffies, ACCESS_ONCE(rsp->jiffies_stall))) |
1052 | ACCESS_ONCE(rsp->jiffies_stall) = jiffies + | |
6bfc09e2 | 1053 | 3 * rcu_jiffies_till_stall_check() + 3; |
1304afb2 | 1054 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c1dc0b9c | 1055 | |
b021fe3e PZ |
1056 | /* |
1057 | * Attempt to revive the RCU machinery by forcing a context switch. | |
1058 | * | |
1059 | * A context switch would normally allow the RCU state machine to make | |
1060 | * progress and it could be we're stuck in kernel space without context | |
1061 | * switches for an entirely unreasonable amount of time. | |
1062 | */ | |
1063 | resched_cpu(smp_processor_id()); | |
64db4cff PM |
1064 | } |
1065 | ||
1066 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
1067 | { | |
26cdfedf PM |
1068 | unsigned long completed; |
1069 | unsigned long gpnum; | |
1070 | unsigned long gps; | |
bad6e139 PM |
1071 | unsigned long j; |
1072 | unsigned long js; | |
64db4cff PM |
1073 | struct rcu_node *rnp; |
1074 | ||
26cdfedf | 1075 | if (rcu_cpu_stall_suppress || !rcu_gp_in_progress(rsp)) |
c68de209 | 1076 | return; |
cb1e78cf | 1077 | j = jiffies; |
26cdfedf PM |
1078 | |
1079 | /* | |
1080 | * Lots of memory barriers to reject false positives. | |
1081 | * | |
1082 | * The idea is to pick up rsp->gpnum, then rsp->jiffies_stall, | |
1083 | * then rsp->gp_start, and finally rsp->completed. These values | |
1084 | * are updated in the opposite order with memory barriers (or | |
1085 | * equivalent) during grace-period initialization and cleanup. | |
1086 | * Now, a false positive can occur if we get an new value of | |
1087 | * rsp->gp_start and a old value of rsp->jiffies_stall. But given | |
1088 | * the memory barriers, the only way that this can happen is if one | |
1089 | * grace period ends and another starts between these two fetches. | |
1090 | * Detect this by comparing rsp->completed with the previous fetch | |
1091 | * from rsp->gpnum. | |
1092 | * | |
1093 | * Given this check, comparisons of jiffies, rsp->jiffies_stall, | |
1094 | * and rsp->gp_start suffice to forestall false positives. | |
1095 | */ | |
1096 | gpnum = ACCESS_ONCE(rsp->gpnum); | |
1097 | smp_rmb(); /* Pick up ->gpnum first... */ | |
bad6e139 | 1098 | js = ACCESS_ONCE(rsp->jiffies_stall); |
26cdfedf PM |
1099 | smp_rmb(); /* ...then ->jiffies_stall before the rest... */ |
1100 | gps = ACCESS_ONCE(rsp->gp_start); | |
1101 | smp_rmb(); /* ...and finally ->gp_start before ->completed. */ | |
1102 | completed = ACCESS_ONCE(rsp->completed); | |
1103 | if (ULONG_CMP_GE(completed, gpnum) || | |
1104 | ULONG_CMP_LT(j, js) || | |
1105 | ULONG_CMP_GE(gps, js)) | |
1106 | return; /* No stall or GP completed since entering function. */ | |
64db4cff | 1107 | rnp = rdp->mynode; |
c96ea7cf | 1108 | if (rcu_gp_in_progress(rsp) && |
26cdfedf | 1109 | (ACCESS_ONCE(rnp->qsmask) & rdp->grpmask)) { |
64db4cff PM |
1110 | |
1111 | /* We haven't checked in, so go dump stack. */ | |
1112 | print_cpu_stall(rsp); | |
1113 | ||
bad6e139 PM |
1114 | } else if (rcu_gp_in_progress(rsp) && |
1115 | ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) { | |
64db4cff | 1116 | |
bad6e139 | 1117 | /* They had a few time units to dump stack, so complain. */ |
64db4cff PM |
1118 | print_other_cpu_stall(rsp); |
1119 | } | |
1120 | } | |
1121 | ||
53d84e00 PM |
1122 | /** |
1123 | * rcu_cpu_stall_reset - prevent further stall warnings in current grace period | |
1124 | * | |
1125 | * Set the stall-warning timeout way off into the future, thus preventing | |
1126 | * any RCU CPU stall-warning messages from appearing in the current set of | |
1127 | * RCU grace periods. | |
1128 | * | |
1129 | * The caller must disable hard irqs. | |
1130 | */ | |
1131 | void rcu_cpu_stall_reset(void) | |
1132 | { | |
6ce75a23 PM |
1133 | struct rcu_state *rsp; |
1134 | ||
1135 | for_each_rcu_flavor(rsp) | |
4fc5b755 | 1136 | ACCESS_ONCE(rsp->jiffies_stall) = jiffies + ULONG_MAX / 2; |
53d84e00 PM |
1137 | } |
1138 | ||
3f5d3ea6 PM |
1139 | /* |
1140 | * Initialize the specified rcu_data structure's callback list to empty. | |
1141 | */ | |
1142 | static void init_callback_list(struct rcu_data *rdp) | |
1143 | { | |
1144 | int i; | |
1145 | ||
34ed6246 PM |
1146 | if (init_nocb_callback_list(rdp)) |
1147 | return; | |
3f5d3ea6 PM |
1148 | rdp->nxtlist = NULL; |
1149 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
1150 | rdp->nxttail[i] = &rdp->nxtlist; | |
1151 | } | |
1152 | ||
dc35c893 PM |
1153 | /* |
1154 | * Determine the value that ->completed will have at the end of the | |
1155 | * next subsequent grace period. This is used to tag callbacks so that | |
1156 | * a CPU can invoke callbacks in a timely fashion even if that CPU has | |
1157 | * been dyntick-idle for an extended period with callbacks under the | |
1158 | * influence of RCU_FAST_NO_HZ. | |
1159 | * | |
1160 | * The caller must hold rnp->lock with interrupts disabled. | |
1161 | */ | |
1162 | static unsigned long rcu_cbs_completed(struct rcu_state *rsp, | |
1163 | struct rcu_node *rnp) | |
1164 | { | |
1165 | /* | |
1166 | * If RCU is idle, we just wait for the next grace period. | |
1167 | * But we can only be sure that RCU is idle if we are looking | |
1168 | * at the root rcu_node structure -- otherwise, a new grace | |
1169 | * period might have started, but just not yet gotten around | |
1170 | * to initializing the current non-root rcu_node structure. | |
1171 | */ | |
1172 | if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed) | |
1173 | return rnp->completed + 1; | |
1174 | ||
1175 | /* | |
1176 | * Otherwise, wait for a possible partial grace period and | |
1177 | * then the subsequent full grace period. | |
1178 | */ | |
1179 | return rnp->completed + 2; | |
1180 | } | |
1181 | ||
0446be48 PM |
1182 | /* |
1183 | * Trace-event helper function for rcu_start_future_gp() and | |
1184 | * rcu_nocb_wait_gp(). | |
1185 | */ | |
1186 | static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, | |
e66c33d5 | 1187 | unsigned long c, const char *s) |
0446be48 PM |
1188 | { |
1189 | trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum, | |
1190 | rnp->completed, c, rnp->level, | |
1191 | rnp->grplo, rnp->grphi, s); | |
1192 | } | |
1193 | ||
1194 | /* | |
1195 | * Start some future grace period, as needed to handle newly arrived | |
1196 | * callbacks. The required future grace periods are recorded in each | |
48a7639c PM |
1197 | * rcu_node structure's ->need_future_gp field. Returns true if there |
1198 | * is reason to awaken the grace-period kthread. | |
0446be48 PM |
1199 | * |
1200 | * The caller must hold the specified rcu_node structure's ->lock. | |
1201 | */ | |
48a7639c PM |
1202 | static bool __maybe_unused |
1203 | rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, | |
1204 | unsigned long *c_out) | |
0446be48 PM |
1205 | { |
1206 | unsigned long c; | |
1207 | int i; | |
48a7639c | 1208 | bool ret = false; |
0446be48 PM |
1209 | struct rcu_node *rnp_root = rcu_get_root(rdp->rsp); |
1210 | ||
1211 | /* | |
1212 | * Pick up grace-period number for new callbacks. If this | |
1213 | * grace period is already marked as needed, return to the caller. | |
1214 | */ | |
1215 | c = rcu_cbs_completed(rdp->rsp, rnp); | |
f7f7bac9 | 1216 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf")); |
0446be48 | 1217 | if (rnp->need_future_gp[c & 0x1]) { |
f7f7bac9 | 1218 | trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf")); |
48a7639c | 1219 | goto out; |
0446be48 PM |
1220 | } |
1221 | ||
1222 | /* | |
1223 | * If either this rcu_node structure or the root rcu_node structure | |
1224 | * believe that a grace period is in progress, then we must wait | |
1225 | * for the one following, which is in "c". Because our request | |
1226 | * will be noticed at the end of the current grace period, we don't | |
1227 | * need to explicitly start one. | |
1228 | */ | |
1229 | if (rnp->gpnum != rnp->completed || | |
1230 | ACCESS_ONCE(rnp->gpnum) != ACCESS_ONCE(rnp->completed)) { | |
1231 | rnp->need_future_gp[c & 0x1]++; | |
f7f7bac9 | 1232 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf")); |
48a7639c | 1233 | goto out; |
0446be48 PM |
1234 | } |
1235 | ||
1236 | /* | |
1237 | * There might be no grace period in progress. If we don't already | |
1238 | * hold it, acquire the root rcu_node structure's lock in order to | |
1239 | * start one (if needed). | |
1240 | */ | |
6303b9c8 | 1241 | if (rnp != rnp_root) { |
0446be48 | 1242 | raw_spin_lock(&rnp_root->lock); |
6303b9c8 PM |
1243 | smp_mb__after_unlock_lock(); |
1244 | } | |
0446be48 PM |
1245 | |
1246 | /* | |
1247 | * Get a new grace-period number. If there really is no grace | |
1248 | * period in progress, it will be smaller than the one we obtained | |
1249 | * earlier. Adjust callbacks as needed. Note that even no-CBs | |
1250 | * CPUs have a ->nxtcompleted[] array, so no no-CBs checks needed. | |
1251 | */ | |
1252 | c = rcu_cbs_completed(rdp->rsp, rnp_root); | |
1253 | for (i = RCU_DONE_TAIL; i < RCU_NEXT_TAIL; i++) | |
1254 | if (ULONG_CMP_LT(c, rdp->nxtcompleted[i])) | |
1255 | rdp->nxtcompleted[i] = c; | |
1256 | ||
1257 | /* | |
1258 | * If the needed for the required grace period is already | |
1259 | * recorded, trace and leave. | |
1260 | */ | |
1261 | if (rnp_root->need_future_gp[c & 0x1]) { | |
f7f7bac9 | 1262 | trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot")); |
0446be48 PM |
1263 | goto unlock_out; |
1264 | } | |
1265 | ||
1266 | /* Record the need for the future grace period. */ | |
1267 | rnp_root->need_future_gp[c & 0x1]++; | |
1268 | ||
1269 | /* If a grace period is not already in progress, start one. */ | |
1270 | if (rnp_root->gpnum != rnp_root->completed) { | |
f7f7bac9 | 1271 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot")); |
0446be48 | 1272 | } else { |
f7f7bac9 | 1273 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot")); |
48a7639c | 1274 | ret = rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp); |
0446be48 PM |
1275 | } |
1276 | unlock_out: | |
1277 | if (rnp != rnp_root) | |
1278 | raw_spin_unlock(&rnp_root->lock); | |
48a7639c PM |
1279 | out: |
1280 | if (c_out != NULL) | |
1281 | *c_out = c; | |
1282 | return ret; | |
0446be48 PM |
1283 | } |
1284 | ||
1285 | /* | |
1286 | * Clean up any old requests for the just-ended grace period. Also return | |
1287 | * whether any additional grace periods have been requested. Also invoke | |
1288 | * rcu_nocb_gp_cleanup() in order to wake up any no-callbacks kthreads | |
1289 | * waiting for this grace period to complete. | |
1290 | */ | |
1291 | static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) | |
1292 | { | |
1293 | int c = rnp->completed; | |
1294 | int needmore; | |
1295 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); | |
1296 | ||
1297 | rcu_nocb_gp_cleanup(rsp, rnp); | |
1298 | rnp->need_future_gp[c & 0x1] = 0; | |
1299 | needmore = rnp->need_future_gp[(c + 1) & 0x1]; | |
f7f7bac9 SRRH |
1300 | trace_rcu_future_gp(rnp, rdp, c, |
1301 | needmore ? TPS("CleanupMore") : TPS("Cleanup")); | |
0446be48 PM |
1302 | return needmore; |
1303 | } | |
1304 | ||
48a7639c PM |
1305 | /* |
1306 | * Awaken the grace-period kthread for the specified flavor of RCU. | |
1307 | * Don't do a self-awaken, and don't bother awakening when there is | |
1308 | * nothing for the grace-period kthread to do (as in several CPUs | |
1309 | * raced to awaken, and we lost), and finally don't try to awaken | |
1310 | * a kthread that has not yet been created. | |
1311 | */ | |
1312 | static void rcu_gp_kthread_wake(struct rcu_state *rsp) | |
1313 | { | |
1314 | if (current == rsp->gp_kthread || | |
1315 | !ACCESS_ONCE(rsp->gp_flags) || | |
1316 | !rsp->gp_kthread) | |
1317 | return; | |
1318 | wake_up(&rsp->gp_wq); | |
1319 | } | |
1320 | ||
dc35c893 PM |
1321 | /* |
1322 | * If there is room, assign a ->completed number to any callbacks on | |
1323 | * this CPU that have not already been assigned. Also accelerate any | |
1324 | * callbacks that were previously assigned a ->completed number that has | |
1325 | * since proven to be too conservative, which can happen if callbacks get | |
1326 | * assigned a ->completed number while RCU is idle, but with reference to | |
1327 | * a non-root rcu_node structure. This function is idempotent, so it does | |
48a7639c PM |
1328 | * not hurt to call it repeatedly. Returns an flag saying that we should |
1329 | * awaken the RCU grace-period kthread. | |
dc35c893 PM |
1330 | * |
1331 | * The caller must hold rnp->lock with interrupts disabled. | |
1332 | */ | |
48a7639c | 1333 | static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, |
dc35c893 PM |
1334 | struct rcu_data *rdp) |
1335 | { | |
1336 | unsigned long c; | |
1337 | int i; | |
48a7639c | 1338 | bool ret; |
dc35c893 PM |
1339 | |
1340 | /* If the CPU has no callbacks, nothing to do. */ | |
1341 | if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL]) | |
48a7639c | 1342 | return false; |
dc35c893 PM |
1343 | |
1344 | /* | |
1345 | * Starting from the sublist containing the callbacks most | |
1346 | * recently assigned a ->completed number and working down, find the | |
1347 | * first sublist that is not assignable to an upcoming grace period. | |
1348 | * Such a sublist has something in it (first two tests) and has | |
1349 | * a ->completed number assigned that will complete sooner than | |
1350 | * the ->completed number for newly arrived callbacks (last test). | |
1351 | * | |
1352 | * The key point is that any later sublist can be assigned the | |
1353 | * same ->completed number as the newly arrived callbacks, which | |
1354 | * means that the callbacks in any of these later sublist can be | |
1355 | * grouped into a single sublist, whether or not they have already | |
1356 | * been assigned a ->completed number. | |
1357 | */ | |
1358 | c = rcu_cbs_completed(rsp, rnp); | |
1359 | for (i = RCU_NEXT_TAIL - 1; i > RCU_DONE_TAIL; i--) | |
1360 | if (rdp->nxttail[i] != rdp->nxttail[i - 1] && | |
1361 | !ULONG_CMP_GE(rdp->nxtcompleted[i], c)) | |
1362 | break; | |
1363 | ||
1364 | /* | |
1365 | * If there are no sublist for unassigned callbacks, leave. | |
1366 | * At the same time, advance "i" one sublist, so that "i" will | |
1367 | * index into the sublist where all the remaining callbacks should | |
1368 | * be grouped into. | |
1369 | */ | |
1370 | if (++i >= RCU_NEXT_TAIL) | |
48a7639c | 1371 | return false; |
dc35c893 PM |
1372 | |
1373 | /* | |
1374 | * Assign all subsequent callbacks' ->completed number to the next | |
1375 | * full grace period and group them all in the sublist initially | |
1376 | * indexed by "i". | |
1377 | */ | |
1378 | for (; i <= RCU_NEXT_TAIL; i++) { | |
1379 | rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL]; | |
1380 | rdp->nxtcompleted[i] = c; | |
1381 | } | |
910ee45d | 1382 | /* Record any needed additional grace periods. */ |
48a7639c | 1383 | ret = rcu_start_future_gp(rnp, rdp, NULL); |
6d4b418c PM |
1384 | |
1385 | /* Trace depending on how much we were able to accelerate. */ | |
1386 | if (!*rdp->nxttail[RCU_WAIT_TAIL]) | |
f7f7bac9 | 1387 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccWaitCB")); |
6d4b418c | 1388 | else |
f7f7bac9 | 1389 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccReadyCB")); |
48a7639c | 1390 | return ret; |
dc35c893 PM |
1391 | } |
1392 | ||
1393 | /* | |
1394 | * Move any callbacks whose grace period has completed to the | |
1395 | * RCU_DONE_TAIL sublist, then compact the remaining sublists and | |
1396 | * assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL | |
1397 | * sublist. This function is idempotent, so it does not hurt to | |
1398 | * invoke it repeatedly. As long as it is not invoked -too- often... | |
48a7639c | 1399 | * Returns true if the RCU grace-period kthread needs to be awakened. |
dc35c893 PM |
1400 | * |
1401 | * The caller must hold rnp->lock with interrupts disabled. | |
1402 | */ | |
48a7639c | 1403 | static bool rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp, |
dc35c893 PM |
1404 | struct rcu_data *rdp) |
1405 | { | |
1406 | int i, j; | |
1407 | ||
1408 | /* If the CPU has no callbacks, nothing to do. */ | |
1409 | if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL]) | |
48a7639c | 1410 | return false; |
dc35c893 PM |
1411 | |
1412 | /* | |
1413 | * Find all callbacks whose ->completed numbers indicate that they | |
1414 | * are ready to invoke, and put them into the RCU_DONE_TAIL sublist. | |
1415 | */ | |
1416 | for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) { | |
1417 | if (ULONG_CMP_LT(rnp->completed, rdp->nxtcompleted[i])) | |
1418 | break; | |
1419 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[i]; | |
1420 | } | |
1421 | /* Clean up any sublist tail pointers that were misordered above. */ | |
1422 | for (j = RCU_WAIT_TAIL; j < i; j++) | |
1423 | rdp->nxttail[j] = rdp->nxttail[RCU_DONE_TAIL]; | |
1424 | ||
1425 | /* Copy down callbacks to fill in empty sublists. */ | |
1426 | for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) { | |
1427 | if (rdp->nxttail[j] == rdp->nxttail[RCU_NEXT_TAIL]) | |
1428 | break; | |
1429 | rdp->nxttail[j] = rdp->nxttail[i]; | |
1430 | rdp->nxtcompleted[j] = rdp->nxtcompleted[i]; | |
1431 | } | |
1432 | ||
1433 | /* Classify any remaining callbacks. */ | |
48a7639c | 1434 | return rcu_accelerate_cbs(rsp, rnp, rdp); |
dc35c893 PM |
1435 | } |
1436 | ||
d09b62df | 1437 | /* |
ba9fbe95 PM |
1438 | * Update CPU-local rcu_data state to record the beginnings and ends of |
1439 | * grace periods. The caller must hold the ->lock of the leaf rcu_node | |
1440 | * structure corresponding to the current CPU, and must have irqs disabled. | |
48a7639c | 1441 | * Returns true if the grace-period kthread needs to be awakened. |
d09b62df | 1442 | */ |
48a7639c PM |
1443 | static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, |
1444 | struct rcu_data *rdp) | |
d09b62df | 1445 | { |
48a7639c PM |
1446 | bool ret; |
1447 | ||
ba9fbe95 | 1448 | /* Handle the ends of any preceding grace periods first. */ |
dc35c893 | 1449 | if (rdp->completed == rnp->completed) { |
d09b62df | 1450 | |
ba9fbe95 | 1451 | /* No grace period end, so just accelerate recent callbacks. */ |
48a7639c | 1452 | ret = rcu_accelerate_cbs(rsp, rnp, rdp); |
d09b62df | 1453 | |
dc35c893 PM |
1454 | } else { |
1455 | ||
1456 | /* Advance callbacks. */ | |
48a7639c | 1457 | ret = rcu_advance_cbs(rsp, rnp, rdp); |
d09b62df PM |
1458 | |
1459 | /* Remember that we saw this grace-period completion. */ | |
1460 | rdp->completed = rnp->completed; | |
f7f7bac9 | 1461 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuend")); |
d09b62df | 1462 | } |
398ebe60 | 1463 | |
6eaef633 PM |
1464 | if (rdp->gpnum != rnp->gpnum) { |
1465 | /* | |
1466 | * If the current grace period is waiting for this CPU, | |
1467 | * set up to detect a quiescent state, otherwise don't | |
1468 | * go looking for one. | |
1469 | */ | |
1470 | rdp->gpnum = rnp->gpnum; | |
f7f7bac9 | 1471 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart")); |
6eaef633 PM |
1472 | rdp->passed_quiesce = 0; |
1473 | rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask); | |
1474 | zero_cpu_stall_ticks(rdp); | |
1475 | } | |
48a7639c | 1476 | return ret; |
6eaef633 PM |
1477 | } |
1478 | ||
d34ea322 | 1479 | static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp) |
6eaef633 PM |
1480 | { |
1481 | unsigned long flags; | |
48a7639c | 1482 | bool needwake; |
6eaef633 PM |
1483 | struct rcu_node *rnp; |
1484 | ||
1485 | local_irq_save(flags); | |
1486 | rnp = rdp->mynode; | |
d34ea322 PM |
1487 | if ((rdp->gpnum == ACCESS_ONCE(rnp->gpnum) && |
1488 | rdp->completed == ACCESS_ONCE(rnp->completed)) || /* w/out lock. */ | |
6eaef633 PM |
1489 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
1490 | local_irq_restore(flags); | |
1491 | return; | |
1492 | } | |
6303b9c8 | 1493 | smp_mb__after_unlock_lock(); |
48a7639c | 1494 | needwake = __note_gp_changes(rsp, rnp, rdp); |
6eaef633 | 1495 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
48a7639c PM |
1496 | if (needwake) |
1497 | rcu_gp_kthread_wake(rsp); | |
6eaef633 PM |
1498 | } |
1499 | ||
b3dbec76 | 1500 | /* |
f7be8209 | 1501 | * Initialize a new grace period. Return 0 if no grace period required. |
b3dbec76 | 1502 | */ |
7fdefc10 | 1503 | static int rcu_gp_init(struct rcu_state *rsp) |
b3dbec76 PM |
1504 | { |
1505 | struct rcu_data *rdp; | |
7fdefc10 | 1506 | struct rcu_node *rnp = rcu_get_root(rsp); |
b3dbec76 | 1507 | |
eb75767b | 1508 | rcu_bind_gp_kthread(); |
7fdefc10 | 1509 | raw_spin_lock_irq(&rnp->lock); |
6303b9c8 | 1510 | smp_mb__after_unlock_lock(); |
91dc9542 | 1511 | if (!ACCESS_ONCE(rsp->gp_flags)) { |
f7be8209 PM |
1512 | /* Spurious wakeup, tell caller to go back to sleep. */ |
1513 | raw_spin_unlock_irq(&rnp->lock); | |
1514 | return 0; | |
1515 | } | |
91dc9542 | 1516 | ACCESS_ONCE(rsp->gp_flags) = 0; /* Clear all flags: New grace period. */ |
b3dbec76 | 1517 | |
f7be8209 PM |
1518 | if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) { |
1519 | /* | |
1520 | * Grace period already in progress, don't start another. | |
1521 | * Not supposed to be able to happen. | |
1522 | */ | |
7fdefc10 PM |
1523 | raw_spin_unlock_irq(&rnp->lock); |
1524 | return 0; | |
1525 | } | |
1526 | ||
7fdefc10 | 1527 | /* Advance to a new grace period and initialize state. */ |
26cdfedf | 1528 | record_gp_stall_check_time(rsp); |
765a3f4f PM |
1529 | /* Record GP times before starting GP, hence smp_store_release(). */ |
1530 | smp_store_release(&rsp->gpnum, rsp->gpnum + 1); | |
f7f7bac9 | 1531 | trace_rcu_grace_period(rsp->name, rsp->gpnum, TPS("start")); |
7fdefc10 PM |
1532 | raw_spin_unlock_irq(&rnp->lock); |
1533 | ||
1534 | /* Exclude any concurrent CPU-hotplug operations. */ | |
a4fbe35a | 1535 | mutex_lock(&rsp->onoff_mutex); |
765a3f4f | 1536 | smp_mb__after_unlock_lock(); /* ->gpnum increment before GP! */ |
7fdefc10 PM |
1537 | |
1538 | /* | |
1539 | * Set the quiescent-state-needed bits in all the rcu_node | |
1540 | * structures for all currently online CPUs in breadth-first order, | |
1541 | * starting from the root rcu_node structure, relying on the layout | |
1542 | * of the tree within the rsp->node[] array. Note that other CPUs | |
1543 | * will access only the leaves of the hierarchy, thus seeing that no | |
1544 | * grace period is in progress, at least until the corresponding | |
1545 | * leaf node has been initialized. In addition, we have excluded | |
1546 | * CPU-hotplug operations. | |
1547 | * | |
1548 | * The grace period cannot complete until the initialization | |
1549 | * process finishes, because this kthread handles both. | |
1550 | */ | |
1551 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
b3dbec76 | 1552 | raw_spin_lock_irq(&rnp->lock); |
6303b9c8 | 1553 | smp_mb__after_unlock_lock(); |
b3dbec76 | 1554 | rdp = this_cpu_ptr(rsp->rda); |
7fdefc10 PM |
1555 | rcu_preempt_check_blocked_tasks(rnp); |
1556 | rnp->qsmask = rnp->qsmaskinit; | |
0446be48 | 1557 | ACCESS_ONCE(rnp->gpnum) = rsp->gpnum; |
25d30cf4 | 1558 | WARN_ON_ONCE(rnp->completed != rsp->completed); |
0446be48 | 1559 | ACCESS_ONCE(rnp->completed) = rsp->completed; |
7fdefc10 | 1560 | if (rnp == rdp->mynode) |
48a7639c | 1561 | (void)__note_gp_changes(rsp, rnp, rdp); |
7fdefc10 PM |
1562 | rcu_preempt_boost_start_gp(rnp); |
1563 | trace_rcu_grace_period_init(rsp->name, rnp->gpnum, | |
1564 | rnp->level, rnp->grplo, | |
1565 | rnp->grphi, rnp->qsmask); | |
1566 | raw_spin_unlock_irq(&rnp->lock); | |
661a85dc | 1567 | #ifdef CONFIG_PROVE_RCU_DELAY |
971394f3 | 1568 | if ((prandom_u32() % (rcu_num_nodes + 1)) == 0 && |
81e59494 | 1569 | system_state == SYSTEM_RUNNING) |
971394f3 | 1570 | udelay(200); |
661a85dc | 1571 | #endif /* #ifdef CONFIG_PROVE_RCU_DELAY */ |
7fdefc10 PM |
1572 | cond_resched(); |
1573 | } | |
b3dbec76 | 1574 | |
a4fbe35a | 1575 | mutex_unlock(&rsp->onoff_mutex); |
7fdefc10 PM |
1576 | return 1; |
1577 | } | |
b3dbec76 | 1578 | |
4cdfc175 PM |
1579 | /* |
1580 | * Do one round of quiescent-state forcing. | |
1581 | */ | |
01896f7e | 1582 | static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in) |
4cdfc175 PM |
1583 | { |
1584 | int fqs_state = fqs_state_in; | |
217af2a2 PM |
1585 | bool isidle = false; |
1586 | unsigned long maxj; | |
4cdfc175 PM |
1587 | struct rcu_node *rnp = rcu_get_root(rsp); |
1588 | ||
1589 | rsp->n_force_qs++; | |
1590 | if (fqs_state == RCU_SAVE_DYNTICK) { | |
1591 | /* Collect dyntick-idle snapshots. */ | |
0edd1b17 PM |
1592 | if (is_sysidle_rcu_state(rsp)) { |
1593 | isidle = 1; | |
1594 | maxj = jiffies - ULONG_MAX / 4; | |
1595 | } | |
217af2a2 PM |
1596 | force_qs_rnp(rsp, dyntick_save_progress_counter, |
1597 | &isidle, &maxj); | |
0edd1b17 | 1598 | rcu_sysidle_report_gp(rsp, isidle, maxj); |
4cdfc175 PM |
1599 | fqs_state = RCU_FORCE_QS; |
1600 | } else { | |
1601 | /* Handle dyntick-idle and offline CPUs. */ | |
0edd1b17 | 1602 | isidle = 0; |
217af2a2 | 1603 | force_qs_rnp(rsp, rcu_implicit_dynticks_qs, &isidle, &maxj); |
4cdfc175 PM |
1604 | } |
1605 | /* Clear flag to prevent immediate re-entry. */ | |
1606 | if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { | |
1607 | raw_spin_lock_irq(&rnp->lock); | |
6303b9c8 | 1608 | smp_mb__after_unlock_lock(); |
91dc9542 | 1609 | ACCESS_ONCE(rsp->gp_flags) &= ~RCU_GP_FLAG_FQS; |
4cdfc175 PM |
1610 | raw_spin_unlock_irq(&rnp->lock); |
1611 | } | |
1612 | return fqs_state; | |
1613 | } | |
1614 | ||
7fdefc10 PM |
1615 | /* |
1616 | * Clean up after the old grace period. | |
1617 | */ | |
4cdfc175 | 1618 | static void rcu_gp_cleanup(struct rcu_state *rsp) |
7fdefc10 PM |
1619 | { |
1620 | unsigned long gp_duration; | |
48a7639c | 1621 | bool needgp = false; |
dae6e64d | 1622 | int nocb = 0; |
7fdefc10 PM |
1623 | struct rcu_data *rdp; |
1624 | struct rcu_node *rnp = rcu_get_root(rsp); | |
b3dbec76 | 1625 | |
7fdefc10 | 1626 | raw_spin_lock_irq(&rnp->lock); |
6303b9c8 | 1627 | smp_mb__after_unlock_lock(); |
7fdefc10 PM |
1628 | gp_duration = jiffies - rsp->gp_start; |
1629 | if (gp_duration > rsp->gp_max) | |
1630 | rsp->gp_max = gp_duration; | |
b3dbec76 | 1631 | |
7fdefc10 PM |
1632 | /* |
1633 | * We know the grace period is complete, but to everyone else | |
1634 | * it appears to still be ongoing. But it is also the case | |
1635 | * that to everyone else it looks like there is nothing that | |
1636 | * they can do to advance the grace period. It is therefore | |
1637 | * safe for us to drop the lock in order to mark the grace | |
1638 | * period as completed in all of the rcu_node structures. | |
7fdefc10 | 1639 | */ |
5d4b8659 | 1640 | raw_spin_unlock_irq(&rnp->lock); |
b3dbec76 | 1641 | |
5d4b8659 PM |
1642 | /* |
1643 | * Propagate new ->completed value to rcu_node structures so | |
1644 | * that other CPUs don't have to wait until the start of the next | |
1645 | * grace period to process their callbacks. This also avoids | |
1646 | * some nasty RCU grace-period initialization races by forcing | |
1647 | * the end of the current grace period to be completely recorded in | |
1648 | * all of the rcu_node structures before the beginning of the next | |
1649 | * grace period is recorded in any of the rcu_node structures. | |
1650 | */ | |
1651 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
755609a9 | 1652 | raw_spin_lock_irq(&rnp->lock); |
6303b9c8 | 1653 | smp_mb__after_unlock_lock(); |
0446be48 | 1654 | ACCESS_ONCE(rnp->completed) = rsp->gpnum; |
b11cc576 PM |
1655 | rdp = this_cpu_ptr(rsp->rda); |
1656 | if (rnp == rdp->mynode) | |
48a7639c | 1657 | needgp = __note_gp_changes(rsp, rnp, rdp) || needgp; |
78e4bc34 | 1658 | /* smp_mb() provided by prior unlock-lock pair. */ |
0446be48 | 1659 | nocb += rcu_future_gp_cleanup(rsp, rnp); |
5d4b8659 PM |
1660 | raw_spin_unlock_irq(&rnp->lock); |
1661 | cond_resched(); | |
7fdefc10 | 1662 | } |
5d4b8659 PM |
1663 | rnp = rcu_get_root(rsp); |
1664 | raw_spin_lock_irq(&rnp->lock); | |
765a3f4f | 1665 | smp_mb__after_unlock_lock(); /* Order GP before ->completed update. */ |
dae6e64d | 1666 | rcu_nocb_gp_set(rnp, nocb); |
7fdefc10 | 1667 | |
765a3f4f PM |
1668 | /* Declare grace period done. */ |
1669 | ACCESS_ONCE(rsp->completed) = rsp->gpnum; | |
f7f7bac9 | 1670 | trace_rcu_grace_period(rsp->name, rsp->completed, TPS("end")); |
7fdefc10 | 1671 | rsp->fqs_state = RCU_GP_IDLE; |
5d4b8659 | 1672 | rdp = this_cpu_ptr(rsp->rda); |
48a7639c PM |
1673 | /* Advance CBs to reduce false positives below. */ |
1674 | needgp = rcu_advance_cbs(rsp, rnp, rdp) || needgp; | |
1675 | if (needgp || cpu_needs_another_gp(rsp, rdp)) { | |
91dc9542 | 1676 | ACCESS_ONCE(rsp->gp_flags) = RCU_GP_FLAG_INIT; |
bb311ecc PM |
1677 | trace_rcu_grace_period(rsp->name, |
1678 | ACCESS_ONCE(rsp->gpnum), | |
1679 | TPS("newreq")); | |
1680 | } | |
7fdefc10 | 1681 | raw_spin_unlock_irq(&rnp->lock); |
7fdefc10 PM |
1682 | } |
1683 | ||
1684 | /* | |
1685 | * Body of kthread that handles grace periods. | |
1686 | */ | |
1687 | static int __noreturn rcu_gp_kthread(void *arg) | |
1688 | { | |
4cdfc175 | 1689 | int fqs_state; |
88d6df61 | 1690 | int gf; |
d40011f6 | 1691 | unsigned long j; |
4cdfc175 | 1692 | int ret; |
7fdefc10 PM |
1693 | struct rcu_state *rsp = arg; |
1694 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1695 | ||
1696 | for (;;) { | |
1697 | ||
1698 | /* Handle grace-period start. */ | |
1699 | for (;;) { | |
63c4db78 PM |
1700 | trace_rcu_grace_period(rsp->name, |
1701 | ACCESS_ONCE(rsp->gpnum), | |
1702 | TPS("reqwait")); | |
afea227f | 1703 | rsp->gp_state = RCU_GP_WAIT_GPS; |
4cdfc175 | 1704 | wait_event_interruptible(rsp->gp_wq, |
591c6d17 | 1705 | ACCESS_ONCE(rsp->gp_flags) & |
4cdfc175 | 1706 | RCU_GP_FLAG_INIT); |
78e4bc34 | 1707 | /* Locking provides needed memory barrier. */ |
f7be8209 | 1708 | if (rcu_gp_init(rsp)) |
7fdefc10 PM |
1709 | break; |
1710 | cond_resched(); | |
1711 | flush_signals(current); | |
63c4db78 PM |
1712 | trace_rcu_grace_period(rsp->name, |
1713 | ACCESS_ONCE(rsp->gpnum), | |
1714 | TPS("reqwaitsig")); | |
7fdefc10 | 1715 | } |
cabc49c1 | 1716 | |
4cdfc175 PM |
1717 | /* Handle quiescent-state forcing. */ |
1718 | fqs_state = RCU_SAVE_DYNTICK; | |
d40011f6 PM |
1719 | j = jiffies_till_first_fqs; |
1720 | if (j > HZ) { | |
1721 | j = HZ; | |
1722 | jiffies_till_first_fqs = HZ; | |
1723 | } | |
88d6df61 | 1724 | ret = 0; |
cabc49c1 | 1725 | for (;;) { |
88d6df61 PM |
1726 | if (!ret) |
1727 | rsp->jiffies_force_qs = jiffies + j; | |
63c4db78 PM |
1728 | trace_rcu_grace_period(rsp->name, |
1729 | ACCESS_ONCE(rsp->gpnum), | |
1730 | TPS("fqswait")); | |
afea227f | 1731 | rsp->gp_state = RCU_GP_WAIT_FQS; |
4cdfc175 | 1732 | ret = wait_event_interruptible_timeout(rsp->gp_wq, |
88d6df61 PM |
1733 | ((gf = ACCESS_ONCE(rsp->gp_flags)) & |
1734 | RCU_GP_FLAG_FQS) || | |
4cdfc175 PM |
1735 | (!ACCESS_ONCE(rnp->qsmask) && |
1736 | !rcu_preempt_blocked_readers_cgp(rnp)), | |
d40011f6 | 1737 | j); |
78e4bc34 | 1738 | /* Locking provides needed memory barriers. */ |
4cdfc175 | 1739 | /* If grace period done, leave loop. */ |
cabc49c1 | 1740 | if (!ACCESS_ONCE(rnp->qsmask) && |
4cdfc175 | 1741 | !rcu_preempt_blocked_readers_cgp(rnp)) |
cabc49c1 | 1742 | break; |
4cdfc175 | 1743 | /* If time for quiescent-state forcing, do it. */ |
88d6df61 PM |
1744 | if (ULONG_CMP_GE(jiffies, rsp->jiffies_force_qs) || |
1745 | (gf & RCU_GP_FLAG_FQS)) { | |
63c4db78 PM |
1746 | trace_rcu_grace_period(rsp->name, |
1747 | ACCESS_ONCE(rsp->gpnum), | |
1748 | TPS("fqsstart")); | |
4cdfc175 | 1749 | fqs_state = rcu_gp_fqs(rsp, fqs_state); |
63c4db78 PM |
1750 | trace_rcu_grace_period(rsp->name, |
1751 | ACCESS_ONCE(rsp->gpnum), | |
1752 | TPS("fqsend")); | |
4cdfc175 PM |
1753 | cond_resched(); |
1754 | } else { | |
1755 | /* Deal with stray signal. */ | |
1756 | cond_resched(); | |
1757 | flush_signals(current); | |
63c4db78 PM |
1758 | trace_rcu_grace_period(rsp->name, |
1759 | ACCESS_ONCE(rsp->gpnum), | |
1760 | TPS("fqswaitsig")); | |
4cdfc175 | 1761 | } |
d40011f6 PM |
1762 | j = jiffies_till_next_fqs; |
1763 | if (j > HZ) { | |
1764 | j = HZ; | |
1765 | jiffies_till_next_fqs = HZ; | |
1766 | } else if (j < 1) { | |
1767 | j = 1; | |
1768 | jiffies_till_next_fqs = 1; | |
1769 | } | |
cabc49c1 | 1770 | } |
4cdfc175 PM |
1771 | |
1772 | /* Handle grace-period end. */ | |
1773 | rcu_gp_cleanup(rsp); | |
b3dbec76 | 1774 | } |
b3dbec76 PM |
1775 | } |
1776 | ||
64db4cff PM |
1777 | /* |
1778 | * Start a new RCU grace period if warranted, re-initializing the hierarchy | |
1779 | * in preparation for detecting the next grace period. The caller must hold | |
b8462084 | 1780 | * the root node's ->lock and hard irqs must be disabled. |
e5601400 PM |
1781 | * |
1782 | * Note that it is legal for a dying CPU (which is marked as offline) to | |
1783 | * invoke this function. This can happen when the dying CPU reports its | |
1784 | * quiescent state. | |
48a7639c PM |
1785 | * |
1786 | * Returns true if the grace-period kthread must be awakened. | |
64db4cff | 1787 | */ |
48a7639c | 1788 | static bool |
910ee45d PM |
1789 | rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, |
1790 | struct rcu_data *rdp) | |
64db4cff | 1791 | { |
b8462084 | 1792 | if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) { |
afe24b12 | 1793 | /* |
b3dbec76 | 1794 | * Either we have not yet spawned the grace-period |
62da1921 PM |
1795 | * task, this CPU does not need another grace period, |
1796 | * or a grace period is already in progress. | |
b3dbec76 | 1797 | * Either way, don't start a new grace period. |
afe24b12 | 1798 | */ |
48a7639c | 1799 | return false; |
afe24b12 | 1800 | } |
91dc9542 | 1801 | ACCESS_ONCE(rsp->gp_flags) = RCU_GP_FLAG_INIT; |
bb311ecc PM |
1802 | trace_rcu_grace_period(rsp->name, ACCESS_ONCE(rsp->gpnum), |
1803 | TPS("newreq")); | |
62da1921 | 1804 | |
016a8d5b SR |
1805 | /* |
1806 | * We can't do wakeups while holding the rnp->lock, as that | |
1eafd31c | 1807 | * could cause possible deadlocks with the rq->lock. Defer |
48a7639c | 1808 | * the wakeup to our caller. |
016a8d5b | 1809 | */ |
48a7639c | 1810 | return true; |
64db4cff PM |
1811 | } |
1812 | ||
910ee45d PM |
1813 | /* |
1814 | * Similar to rcu_start_gp_advanced(), but also advance the calling CPU's | |
1815 | * callbacks. Note that rcu_start_gp_advanced() cannot do this because it | |
1816 | * is invoked indirectly from rcu_advance_cbs(), which would result in | |
1817 | * endless recursion -- or would do so if it wasn't for the self-deadlock | |
1818 | * that is encountered beforehand. | |
48a7639c PM |
1819 | * |
1820 | * Returns true if the grace-period kthread needs to be awakened. | |
910ee45d | 1821 | */ |
48a7639c | 1822 | static bool rcu_start_gp(struct rcu_state *rsp) |
910ee45d PM |
1823 | { |
1824 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); | |
1825 | struct rcu_node *rnp = rcu_get_root(rsp); | |
48a7639c | 1826 | bool ret = false; |
910ee45d PM |
1827 | |
1828 | /* | |
1829 | * If there is no grace period in progress right now, any | |
1830 | * callbacks we have up to this point will be satisfied by the | |
1831 | * next grace period. Also, advancing the callbacks reduces the | |
1832 | * probability of false positives from cpu_needs_another_gp() | |
1833 | * resulting in pointless grace periods. So, advance callbacks | |
1834 | * then start the grace period! | |
1835 | */ | |
48a7639c PM |
1836 | ret = rcu_advance_cbs(rsp, rnp, rdp) || ret; |
1837 | ret = rcu_start_gp_advanced(rsp, rnp, rdp) || ret; | |
1838 | return ret; | |
910ee45d PM |
1839 | } |
1840 | ||
f41d911f | 1841 | /* |
d3f6bad3 PM |
1842 | * Report a full set of quiescent states to the specified rcu_state |
1843 | * data structure. This involves cleaning up after the prior grace | |
1844 | * period and letting rcu_start_gp() start up the next grace period | |
b8462084 PM |
1845 | * if one is needed. Note that the caller must hold rnp->lock, which |
1846 | * is released before return. | |
f41d911f | 1847 | */ |
d3f6bad3 | 1848 | static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
fc2219d4 | 1849 | __releases(rcu_get_root(rsp)->lock) |
f41d911f | 1850 | { |
fc2219d4 | 1851 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
cabc49c1 PM |
1852 | raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); |
1853 | wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */ | |
f41d911f PM |
1854 | } |
1855 | ||
64db4cff | 1856 | /* |
d3f6bad3 PM |
1857 | * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
1858 | * Allows quiescent states for a group of CPUs to be reported at one go | |
1859 | * to the specified rcu_node structure, though all the CPUs in the group | |
1860 | * must be represented by the same rcu_node structure (which need not be | |
1861 | * a leaf rcu_node structure, though it often will be). That structure's | |
1862 | * lock must be held upon entry, and it is released before return. | |
64db4cff PM |
1863 | */ |
1864 | static void | |
d3f6bad3 PM |
1865 | rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
1866 | struct rcu_node *rnp, unsigned long flags) | |
64db4cff PM |
1867 | __releases(rnp->lock) |
1868 | { | |
28ecd580 PM |
1869 | struct rcu_node *rnp_c; |
1870 | ||
64db4cff PM |
1871 | /* Walk up the rcu_node hierarchy. */ |
1872 | for (;;) { | |
1873 | if (!(rnp->qsmask & mask)) { | |
1874 | ||
1875 | /* Our bit has already been cleared, so done. */ | |
1304afb2 | 1876 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1877 | return; |
1878 | } | |
1879 | rnp->qsmask &= ~mask; | |
d4c08f2a PM |
1880 | trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum, |
1881 | mask, rnp->qsmask, rnp->level, | |
1882 | rnp->grplo, rnp->grphi, | |
1883 | !!rnp->gp_tasks); | |
27f4d280 | 1884 | if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
64db4cff PM |
1885 | |
1886 | /* Other bits still set at this level, so done. */ | |
1304afb2 | 1887 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1888 | return; |
1889 | } | |
1890 | mask = rnp->grpmask; | |
1891 | if (rnp->parent == NULL) { | |
1892 | ||
1893 | /* No more levels. Exit loop holding root lock. */ | |
1894 | ||
1895 | break; | |
1896 | } | |
1304afb2 | 1897 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
28ecd580 | 1898 | rnp_c = rnp; |
64db4cff | 1899 | rnp = rnp->parent; |
1304afb2 | 1900 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 1901 | smp_mb__after_unlock_lock(); |
28ecd580 | 1902 | WARN_ON_ONCE(rnp_c->qsmask); |
64db4cff PM |
1903 | } |
1904 | ||
1905 | /* | |
1906 | * Get here if we are the last CPU to pass through a quiescent | |
d3f6bad3 | 1907 | * state for this grace period. Invoke rcu_report_qs_rsp() |
f41d911f | 1908 | * to clean up and start the next grace period if one is needed. |
64db4cff | 1909 | */ |
d3f6bad3 | 1910 | rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
64db4cff PM |
1911 | } |
1912 | ||
1913 | /* | |
d3f6bad3 PM |
1914 | * Record a quiescent state for the specified CPU to that CPU's rcu_data |
1915 | * structure. This must be either called from the specified CPU, or | |
1916 | * called when the specified CPU is known to be offline (and when it is | |
1917 | * also known that no other CPU is concurrently trying to help the offline | |
1918 | * CPU). The lastcomp argument is used to make sure we are still in the | |
1919 | * grace period of interest. We don't want to end the current grace period | |
1920 | * based on quiescent states detected in an earlier grace period! | |
64db4cff PM |
1921 | */ |
1922 | static void | |
d7d6a11e | 1923 | rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
1924 | { |
1925 | unsigned long flags; | |
1926 | unsigned long mask; | |
48a7639c | 1927 | bool needwake; |
64db4cff PM |
1928 | struct rcu_node *rnp; |
1929 | ||
1930 | rnp = rdp->mynode; | |
1304afb2 | 1931 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 1932 | smp_mb__after_unlock_lock(); |
d7d6a11e PM |
1933 | if (rdp->passed_quiesce == 0 || rdp->gpnum != rnp->gpnum || |
1934 | rnp->completed == rnp->gpnum) { | |
64db4cff PM |
1935 | |
1936 | /* | |
e4cc1f22 PM |
1937 | * The grace period in which this quiescent state was |
1938 | * recorded has ended, so don't report it upwards. | |
1939 | * We will instead need a new quiescent state that lies | |
1940 | * within the current grace period. | |
64db4cff | 1941 | */ |
e4cc1f22 | 1942 | rdp->passed_quiesce = 0; /* need qs for new gp. */ |
1304afb2 | 1943 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1944 | return; |
1945 | } | |
1946 | mask = rdp->grpmask; | |
1947 | if ((rnp->qsmask & mask) == 0) { | |
1304afb2 | 1948 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1949 | } else { |
1950 | rdp->qs_pending = 0; | |
1951 | ||
1952 | /* | |
1953 | * This GP can't end until cpu checks in, so all of our | |
1954 | * callbacks can be processed during the next GP. | |
1955 | */ | |
48a7639c | 1956 | needwake = rcu_accelerate_cbs(rsp, rnp, rdp); |
64db4cff | 1957 | |
d3f6bad3 | 1958 | rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ |
48a7639c PM |
1959 | if (needwake) |
1960 | rcu_gp_kthread_wake(rsp); | |
64db4cff PM |
1961 | } |
1962 | } | |
1963 | ||
1964 | /* | |
1965 | * Check to see if there is a new grace period of which this CPU | |
1966 | * is not yet aware, and if so, set up local rcu_data state for it. | |
1967 | * Otherwise, see if this CPU has just passed through its first | |
1968 | * quiescent state for this grace period, and record that fact if so. | |
1969 | */ | |
1970 | static void | |
1971 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) | |
1972 | { | |
05eb552b PM |
1973 | /* Check for grace-period ends and beginnings. */ |
1974 | note_gp_changes(rsp, rdp); | |
64db4cff PM |
1975 | |
1976 | /* | |
1977 | * Does this CPU still need to do its part for current grace period? | |
1978 | * If no, return and let the other CPUs do their part as well. | |
1979 | */ | |
1980 | if (!rdp->qs_pending) | |
1981 | return; | |
1982 | ||
1983 | /* | |
1984 | * Was there a quiescent state since the beginning of the grace | |
1985 | * period? If no, then exit and wait for the next call. | |
1986 | */ | |
e4cc1f22 | 1987 | if (!rdp->passed_quiesce) |
64db4cff PM |
1988 | return; |
1989 | ||
d3f6bad3 PM |
1990 | /* |
1991 | * Tell RCU we are done (but rcu_report_qs_rdp() will be the | |
1992 | * judge of that). | |
1993 | */ | |
d7d6a11e | 1994 | rcu_report_qs_rdp(rdp->cpu, rsp, rdp); |
64db4cff PM |
1995 | } |
1996 | ||
1997 | #ifdef CONFIG_HOTPLUG_CPU | |
1998 | ||
e74f4c45 | 1999 | /* |
b1420f1c PM |
2000 | * Send the specified CPU's RCU callbacks to the orphanage. The |
2001 | * specified CPU must be offline, and the caller must hold the | |
7b2e6011 | 2002 | * ->orphan_lock. |
e74f4c45 | 2003 | */ |
b1420f1c PM |
2004 | static void |
2005 | rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp, | |
2006 | struct rcu_node *rnp, struct rcu_data *rdp) | |
e74f4c45 | 2007 | { |
3fbfbf7a | 2008 | /* No-CBs CPUs do not have orphanable callbacks. */ |
d1e43fa5 | 2009 | if (rcu_is_nocb_cpu(rdp->cpu)) |
3fbfbf7a PM |
2010 | return; |
2011 | ||
b1420f1c PM |
2012 | /* |
2013 | * Orphan the callbacks. First adjust the counts. This is safe | |
abfd6e58 PM |
2014 | * because _rcu_barrier() excludes CPU-hotplug operations, so it |
2015 | * cannot be running now. Thus no memory barrier is required. | |
b1420f1c | 2016 | */ |
a50c3af9 | 2017 | if (rdp->nxtlist != NULL) { |
b1420f1c PM |
2018 | rsp->qlen_lazy += rdp->qlen_lazy; |
2019 | rsp->qlen += rdp->qlen; | |
2020 | rdp->n_cbs_orphaned += rdp->qlen; | |
a50c3af9 | 2021 | rdp->qlen_lazy = 0; |
1d1fb395 | 2022 | ACCESS_ONCE(rdp->qlen) = 0; |
a50c3af9 PM |
2023 | } |
2024 | ||
2025 | /* | |
b1420f1c PM |
2026 | * Next, move those callbacks still needing a grace period to |
2027 | * the orphanage, where some other CPU will pick them up. | |
2028 | * Some of the callbacks might have gone partway through a grace | |
2029 | * period, but that is too bad. They get to start over because we | |
2030 | * cannot assume that grace periods are synchronized across CPUs. | |
2031 | * We don't bother updating the ->nxttail[] array yet, instead | |
2032 | * we just reset the whole thing later on. | |
a50c3af9 | 2033 | */ |
b1420f1c PM |
2034 | if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) { |
2035 | *rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL]; | |
2036 | rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL]; | |
2037 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
a50c3af9 PM |
2038 | } |
2039 | ||
2040 | /* | |
b1420f1c PM |
2041 | * Then move the ready-to-invoke callbacks to the orphanage, |
2042 | * where some other CPU will pick them up. These will not be | |
2043 | * required to pass though another grace period: They are done. | |
a50c3af9 | 2044 | */ |
e5601400 | 2045 | if (rdp->nxtlist != NULL) { |
b1420f1c PM |
2046 | *rsp->orphan_donetail = rdp->nxtlist; |
2047 | rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL]; | |
e5601400 | 2048 | } |
e74f4c45 | 2049 | |
b1420f1c | 2050 | /* Finally, initialize the rcu_data structure's list to empty. */ |
3f5d3ea6 | 2051 | init_callback_list(rdp); |
b1420f1c PM |
2052 | } |
2053 | ||
2054 | /* | |
2055 | * Adopt the RCU callbacks from the specified rcu_state structure's | |
7b2e6011 | 2056 | * orphanage. The caller must hold the ->orphan_lock. |
b1420f1c | 2057 | */ |
96d3fd0d | 2058 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags) |
b1420f1c PM |
2059 | { |
2060 | int i; | |
fa07a58f | 2061 | struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); |
b1420f1c | 2062 | |
3fbfbf7a | 2063 | /* No-CBs CPUs are handled specially. */ |
96d3fd0d | 2064 | if (rcu_nocb_adopt_orphan_cbs(rsp, rdp, flags)) |
3fbfbf7a PM |
2065 | return; |
2066 | ||
b1420f1c PM |
2067 | /* Do the accounting first. */ |
2068 | rdp->qlen_lazy += rsp->qlen_lazy; | |
2069 | rdp->qlen += rsp->qlen; | |
2070 | rdp->n_cbs_adopted += rsp->qlen; | |
8f5af6f1 PM |
2071 | if (rsp->qlen_lazy != rsp->qlen) |
2072 | rcu_idle_count_callbacks_posted(); | |
b1420f1c PM |
2073 | rsp->qlen_lazy = 0; |
2074 | rsp->qlen = 0; | |
2075 | ||
2076 | /* | |
2077 | * We do not need a memory barrier here because the only way we | |
2078 | * can get here if there is an rcu_barrier() in flight is if | |
2079 | * we are the task doing the rcu_barrier(). | |
2080 | */ | |
2081 | ||
2082 | /* First adopt the ready-to-invoke callbacks. */ | |
2083 | if (rsp->orphan_donelist != NULL) { | |
2084 | *rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL]; | |
2085 | *rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist; | |
2086 | for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--) | |
2087 | if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) | |
2088 | rdp->nxttail[i] = rsp->orphan_donetail; | |
2089 | rsp->orphan_donelist = NULL; | |
2090 | rsp->orphan_donetail = &rsp->orphan_donelist; | |
2091 | } | |
2092 | ||
2093 | /* And then adopt the callbacks that still need a grace period. */ | |
2094 | if (rsp->orphan_nxtlist != NULL) { | |
2095 | *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist; | |
2096 | rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail; | |
2097 | rsp->orphan_nxtlist = NULL; | |
2098 | rsp->orphan_nxttail = &rsp->orphan_nxtlist; | |
2099 | } | |
2100 | } | |
2101 | ||
2102 | /* | |
2103 | * Trace the fact that this CPU is going offline. | |
2104 | */ | |
2105 | static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) | |
2106 | { | |
2107 | RCU_TRACE(unsigned long mask); | |
2108 | RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda)); | |
2109 | RCU_TRACE(struct rcu_node *rnp = rdp->mynode); | |
2110 | ||
2111 | RCU_TRACE(mask = rdp->grpmask); | |
e5601400 PM |
2112 | trace_rcu_grace_period(rsp->name, |
2113 | rnp->gpnum + 1 - !!(rnp->qsmask & mask), | |
f7f7bac9 | 2114 | TPS("cpuofl")); |
64db4cff PM |
2115 | } |
2116 | ||
2117 | /* | |
e5601400 | 2118 | * The CPU has been completely removed, and some other CPU is reporting |
b1420f1c PM |
2119 | * this fact from process context. Do the remainder of the cleanup, |
2120 | * including orphaning the outgoing CPU's RCU callbacks, and also | |
1331e7a1 PM |
2121 | * adopting them. There can only be one CPU hotplug operation at a time, |
2122 | * so no other CPU can be attempting to update rcu_cpu_kthread_task. | |
64db4cff | 2123 | */ |
e5601400 | 2124 | static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
64db4cff | 2125 | { |
2036d94a PM |
2126 | unsigned long flags; |
2127 | unsigned long mask; | |
2128 | int need_report = 0; | |
e5601400 | 2129 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
b1420f1c | 2130 | struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ |
e5601400 | 2131 | |
2036d94a | 2132 | /* Adjust any no-longer-needed kthreads. */ |
5d01bbd1 | 2133 | rcu_boost_kthread_setaffinity(rnp, -1); |
2036d94a | 2134 | |
b1420f1c | 2135 | /* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */ |
2036d94a PM |
2136 | |
2137 | /* Exclude any attempts to start a new grace period. */ | |
a4fbe35a | 2138 | mutex_lock(&rsp->onoff_mutex); |
7b2e6011 | 2139 | raw_spin_lock_irqsave(&rsp->orphan_lock, flags); |
2036d94a | 2140 | |
b1420f1c PM |
2141 | /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */ |
2142 | rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp); | |
96d3fd0d | 2143 | rcu_adopt_orphan_cbs(rsp, flags); |
b1420f1c | 2144 | |
2036d94a PM |
2145 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ |
2146 | mask = rdp->grpmask; /* rnp->grplo is constant. */ | |
2147 | do { | |
2148 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ | |
6303b9c8 | 2149 | smp_mb__after_unlock_lock(); |
2036d94a PM |
2150 | rnp->qsmaskinit &= ~mask; |
2151 | if (rnp->qsmaskinit != 0) { | |
2152 | if (rnp != rdp->mynode) | |
2153 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
2154 | break; | |
2155 | } | |
2156 | if (rnp == rdp->mynode) | |
2157 | need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); | |
2158 | else | |
2159 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
2160 | mask = rnp->grpmask; | |
2161 | rnp = rnp->parent; | |
2162 | } while (rnp != NULL); | |
2163 | ||
2164 | /* | |
2165 | * We still hold the leaf rcu_node structure lock here, and | |
2166 | * irqs are still disabled. The reason for this subterfuge is | |
7b2e6011 | 2167 | * because invoking rcu_report_unblock_qs_rnp() with ->orphan_lock |
2036d94a PM |
2168 | * held leads to deadlock. |
2169 | */ | |
7b2e6011 | 2170 | raw_spin_unlock(&rsp->orphan_lock); /* irqs remain disabled. */ |
2036d94a PM |
2171 | rnp = rdp->mynode; |
2172 | if (need_report & RCU_OFL_TASKS_NORM_GP) | |
2173 | rcu_report_unblock_qs_rnp(rnp, flags); | |
2174 | else | |
2175 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
2176 | if (need_report & RCU_OFL_TASKS_EXP_GP) | |
2177 | rcu_report_exp_rnp(rsp, rnp, true); | |
cf01537e PM |
2178 | WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL, |
2179 | "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n", | |
2180 | cpu, rdp->qlen, rdp->nxtlist); | |
0d8ee37e PM |
2181 | init_callback_list(rdp); |
2182 | /* Disallow further callbacks on this CPU. */ | |
2183 | rdp->nxttail[RCU_NEXT_TAIL] = NULL; | |
a4fbe35a | 2184 | mutex_unlock(&rsp->onoff_mutex); |
64db4cff PM |
2185 | } |
2186 | ||
2187 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ | |
2188 | ||
e5601400 | 2189 | static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) |
e74f4c45 PM |
2190 | { |
2191 | } | |
2192 | ||
e5601400 | 2193 | static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
64db4cff PM |
2194 | { |
2195 | } | |
2196 | ||
2197 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ | |
2198 | ||
2199 | /* | |
2200 | * Invoke any RCU callbacks that have made it to the end of their grace | |
2201 | * period. Thottle as specified by rdp->blimit. | |
2202 | */ | |
37c72e56 | 2203 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
2204 | { |
2205 | unsigned long flags; | |
2206 | struct rcu_head *next, *list, **tail; | |
878d7439 ED |
2207 | long bl, count, count_lazy; |
2208 | int i; | |
64db4cff | 2209 | |
dc35c893 | 2210 | /* If no callbacks are ready, just return. */ |
29c00b4a | 2211 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) { |
486e2593 | 2212 | trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0); |
4968c300 PM |
2213 | trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist), |
2214 | need_resched(), is_idle_task(current), | |
2215 | rcu_is_callbacks_kthread()); | |
64db4cff | 2216 | return; |
29c00b4a | 2217 | } |
64db4cff PM |
2218 | |
2219 | /* | |
2220 | * Extract the list of ready callbacks, disabling to prevent | |
2221 | * races with call_rcu() from interrupt handlers. | |
2222 | */ | |
2223 | local_irq_save(flags); | |
8146c4e2 | 2224 | WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); |
29c00b4a | 2225 | bl = rdp->blimit; |
486e2593 | 2226 | trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl); |
64db4cff PM |
2227 | list = rdp->nxtlist; |
2228 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; | |
2229 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
2230 | tail = rdp->nxttail[RCU_DONE_TAIL]; | |
b41772ab PM |
2231 | for (i = RCU_NEXT_SIZE - 1; i >= 0; i--) |
2232 | if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) | |
2233 | rdp->nxttail[i] = &rdp->nxtlist; | |
64db4cff PM |
2234 | local_irq_restore(flags); |
2235 | ||
2236 | /* Invoke callbacks. */ | |
486e2593 | 2237 | count = count_lazy = 0; |
64db4cff PM |
2238 | while (list) { |
2239 | next = list->next; | |
2240 | prefetch(next); | |
551d55a9 | 2241 | debug_rcu_head_unqueue(list); |
486e2593 PM |
2242 | if (__rcu_reclaim(rsp->name, list)) |
2243 | count_lazy++; | |
64db4cff | 2244 | list = next; |
dff1672d PM |
2245 | /* Stop only if limit reached and CPU has something to do. */ |
2246 | if (++count >= bl && | |
2247 | (need_resched() || | |
2248 | (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) | |
64db4cff PM |
2249 | break; |
2250 | } | |
2251 | ||
2252 | local_irq_save(flags); | |
4968c300 PM |
2253 | trace_rcu_batch_end(rsp->name, count, !!list, need_resched(), |
2254 | is_idle_task(current), | |
2255 | rcu_is_callbacks_kthread()); | |
64db4cff PM |
2256 | |
2257 | /* Update count, and requeue any remaining callbacks. */ | |
64db4cff PM |
2258 | if (list != NULL) { |
2259 | *tail = rdp->nxtlist; | |
2260 | rdp->nxtlist = list; | |
b41772ab PM |
2261 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
2262 | if (&rdp->nxtlist == rdp->nxttail[i]) | |
2263 | rdp->nxttail[i] = tail; | |
64db4cff PM |
2264 | else |
2265 | break; | |
2266 | } | |
b1420f1c PM |
2267 | smp_mb(); /* List handling before counting for rcu_barrier(). */ |
2268 | rdp->qlen_lazy -= count_lazy; | |
1d1fb395 | 2269 | ACCESS_ONCE(rdp->qlen) -= count; |
b1420f1c | 2270 | rdp->n_cbs_invoked += count; |
64db4cff PM |
2271 | |
2272 | /* Reinstate batch limit if we have worked down the excess. */ | |
2273 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) | |
2274 | rdp->blimit = blimit; | |
2275 | ||
37c72e56 PM |
2276 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
2277 | if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { | |
2278 | rdp->qlen_last_fqs_check = 0; | |
2279 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
2280 | } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) | |
2281 | rdp->qlen_last_fqs_check = rdp->qlen; | |
cfca9279 | 2282 | WARN_ON_ONCE((rdp->nxtlist == NULL) != (rdp->qlen == 0)); |
37c72e56 | 2283 | |
64db4cff PM |
2284 | local_irq_restore(flags); |
2285 | ||
e0f23060 | 2286 | /* Re-invoke RCU core processing if there are callbacks remaining. */ |
64db4cff | 2287 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
a46e0899 | 2288 | invoke_rcu_core(); |
64db4cff PM |
2289 | } |
2290 | ||
2291 | /* | |
2292 | * Check to see if this CPU is in a non-context-switch quiescent state | |
2293 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). | |
e0f23060 | 2294 | * Also schedule RCU core processing. |
64db4cff | 2295 | * |
9b2e4f18 | 2296 | * This function must be called from hardirq context. It is normally |
64db4cff PM |
2297 | * invoked from the scheduling-clock interrupt. If rcu_pending returns |
2298 | * false, there is no point in invoking rcu_check_callbacks(). | |
2299 | */ | |
2300 | void rcu_check_callbacks(int cpu, int user) | |
2301 | { | |
f7f7bac9 | 2302 | trace_rcu_utilization(TPS("Start scheduler-tick")); |
a858af28 | 2303 | increment_cpu_stall_ticks(); |
9b2e4f18 | 2304 | if (user || rcu_is_cpu_rrupt_from_idle()) { |
64db4cff PM |
2305 | |
2306 | /* | |
2307 | * Get here if this CPU took its interrupt from user | |
2308 | * mode or from the idle loop, and if this is not a | |
2309 | * nested interrupt. In this case, the CPU is in | |
d6714c22 | 2310 | * a quiescent state, so note it. |
64db4cff PM |
2311 | * |
2312 | * No memory barrier is required here because both | |
d6714c22 PM |
2313 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
2314 | * variables that other CPUs neither access nor modify, | |
2315 | * at least not while the corresponding CPU is online. | |
64db4cff PM |
2316 | */ |
2317 | ||
d6714c22 PM |
2318 | rcu_sched_qs(cpu); |
2319 | rcu_bh_qs(cpu); | |
64db4cff PM |
2320 | |
2321 | } else if (!in_softirq()) { | |
2322 | ||
2323 | /* | |
2324 | * Get here if this CPU did not take its interrupt from | |
2325 | * softirq, in other words, if it is not interrupting | |
2326 | * a rcu_bh read-side critical section. This is an _bh | |
d6714c22 | 2327 | * critical section, so note it. |
64db4cff PM |
2328 | */ |
2329 | ||
d6714c22 | 2330 | rcu_bh_qs(cpu); |
64db4cff | 2331 | } |
f41d911f | 2332 | rcu_preempt_check_callbacks(cpu); |
d21670ac | 2333 | if (rcu_pending(cpu)) |
a46e0899 | 2334 | invoke_rcu_core(); |
f7f7bac9 | 2335 | trace_rcu_utilization(TPS("End scheduler-tick")); |
64db4cff PM |
2336 | } |
2337 | ||
64db4cff PM |
2338 | /* |
2339 | * Scan the leaf rcu_node structures, processing dyntick state for any that | |
2340 | * have not yet encountered a quiescent state, using the function specified. | |
27f4d280 PM |
2341 | * Also initiate boosting for any threads blocked on the root rcu_node. |
2342 | * | |
ee47eb9f | 2343 | * The caller must have suppressed start of new grace periods. |
64db4cff | 2344 | */ |
217af2a2 PM |
2345 | static void force_qs_rnp(struct rcu_state *rsp, |
2346 | int (*f)(struct rcu_data *rsp, bool *isidle, | |
2347 | unsigned long *maxj), | |
2348 | bool *isidle, unsigned long *maxj) | |
64db4cff PM |
2349 | { |
2350 | unsigned long bit; | |
2351 | int cpu; | |
2352 | unsigned long flags; | |
2353 | unsigned long mask; | |
a0b6c9a7 | 2354 | struct rcu_node *rnp; |
64db4cff | 2355 | |
a0b6c9a7 | 2356 | rcu_for_each_leaf_node(rsp, rnp) { |
b4be093f | 2357 | cond_resched(); |
64db4cff | 2358 | mask = 0; |
1304afb2 | 2359 | raw_spin_lock_irqsave(&rnp->lock, flags); |
6303b9c8 | 2360 | smp_mb__after_unlock_lock(); |
ee47eb9f | 2361 | if (!rcu_gp_in_progress(rsp)) { |
1304afb2 | 2362 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
0f10dc82 | 2363 | return; |
64db4cff | 2364 | } |
a0b6c9a7 | 2365 | if (rnp->qsmask == 0) { |
1217ed1b | 2366 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
64db4cff PM |
2367 | continue; |
2368 | } | |
a0b6c9a7 | 2369 | cpu = rnp->grplo; |
64db4cff | 2370 | bit = 1; |
a0b6c9a7 | 2371 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
0edd1b17 PM |
2372 | if ((rnp->qsmask & bit) != 0) { |
2373 | if ((rnp->qsmaskinit & bit) != 0) | |
2374 | *isidle = 0; | |
2375 | if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj)) | |
2376 | mask |= bit; | |
2377 | } | |
64db4cff | 2378 | } |
45f014c5 | 2379 | if (mask != 0) { |
64db4cff | 2380 | |
d3f6bad3 PM |
2381 | /* rcu_report_qs_rnp() releases rnp->lock. */ |
2382 | rcu_report_qs_rnp(mask, rsp, rnp, flags); | |
64db4cff PM |
2383 | continue; |
2384 | } | |
1304afb2 | 2385 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 2386 | } |
27f4d280 | 2387 | rnp = rcu_get_root(rsp); |
1217ed1b PM |
2388 | if (rnp->qsmask == 0) { |
2389 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
6303b9c8 | 2390 | smp_mb__after_unlock_lock(); |
1217ed1b PM |
2391 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ |
2392 | } | |
64db4cff PM |
2393 | } |
2394 | ||
2395 | /* | |
2396 | * Force quiescent states on reluctant CPUs, and also detect which | |
2397 | * CPUs are in dyntick-idle mode. | |
2398 | */ | |
4cdfc175 | 2399 | static void force_quiescent_state(struct rcu_state *rsp) |
64db4cff PM |
2400 | { |
2401 | unsigned long flags; | |
394f2769 PM |
2402 | bool ret; |
2403 | struct rcu_node *rnp; | |
2404 | struct rcu_node *rnp_old = NULL; | |
2405 | ||
2406 | /* Funnel through hierarchy to reduce memory contention. */ | |
2407 | rnp = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode; | |
2408 | for (; rnp != NULL; rnp = rnp->parent) { | |
2409 | ret = (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) || | |
2410 | !raw_spin_trylock(&rnp->fqslock); | |
2411 | if (rnp_old != NULL) | |
2412 | raw_spin_unlock(&rnp_old->fqslock); | |
2413 | if (ret) { | |
3660c281 | 2414 | ACCESS_ONCE(rsp->n_force_qs_lh)++; |
394f2769 PM |
2415 | return; |
2416 | } | |
2417 | rnp_old = rnp; | |
2418 | } | |
2419 | /* rnp_old == rcu_get_root(rsp), rnp == NULL. */ | |
64db4cff | 2420 | |
394f2769 PM |
2421 | /* Reached the root of the rcu_node tree, acquire lock. */ |
2422 | raw_spin_lock_irqsave(&rnp_old->lock, flags); | |
6303b9c8 | 2423 | smp_mb__after_unlock_lock(); |
394f2769 PM |
2424 | raw_spin_unlock(&rnp_old->fqslock); |
2425 | if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { | |
3660c281 | 2426 | ACCESS_ONCE(rsp->n_force_qs_lh)++; |
394f2769 | 2427 | raw_spin_unlock_irqrestore(&rnp_old->lock, flags); |
4cdfc175 | 2428 | return; /* Someone beat us to it. */ |
46a1e34e | 2429 | } |
91dc9542 | 2430 | ACCESS_ONCE(rsp->gp_flags) |= RCU_GP_FLAG_FQS; |
394f2769 | 2431 | raw_spin_unlock_irqrestore(&rnp_old->lock, flags); |
4cdfc175 | 2432 | wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */ |
64db4cff PM |
2433 | } |
2434 | ||
64db4cff | 2435 | /* |
e0f23060 PM |
2436 | * This does the RCU core processing work for the specified rcu_state |
2437 | * and rcu_data structures. This may be called only from the CPU to | |
2438 | * whom the rdp belongs. | |
64db4cff PM |
2439 | */ |
2440 | static void | |
1bca8cf1 | 2441 | __rcu_process_callbacks(struct rcu_state *rsp) |
64db4cff PM |
2442 | { |
2443 | unsigned long flags; | |
48a7639c | 2444 | bool needwake; |
fa07a58f | 2445 | struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); |
64db4cff | 2446 | |
2e597558 PM |
2447 | WARN_ON_ONCE(rdp->beenonline == 0); |
2448 | ||
64db4cff PM |
2449 | /* Update RCU state based on any recent quiescent states. */ |
2450 | rcu_check_quiescent_state(rsp, rdp); | |
2451 | ||
2452 | /* Does this CPU require a not-yet-started grace period? */ | |
dc35c893 | 2453 | local_irq_save(flags); |
64db4cff | 2454 | if (cpu_needs_another_gp(rsp, rdp)) { |
dc35c893 | 2455 | raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */ |
48a7639c | 2456 | needwake = rcu_start_gp(rsp); |
b8462084 | 2457 | raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); |
48a7639c PM |
2458 | if (needwake) |
2459 | rcu_gp_kthread_wake(rsp); | |
dc35c893 PM |
2460 | } else { |
2461 | local_irq_restore(flags); | |
64db4cff PM |
2462 | } |
2463 | ||
2464 | /* If there are callbacks ready, invoke them. */ | |
09223371 | 2465 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
a46e0899 | 2466 | invoke_rcu_callbacks(rsp, rdp); |
96d3fd0d PM |
2467 | |
2468 | /* Do any needed deferred wakeups of rcuo kthreads. */ | |
2469 | do_nocb_deferred_wakeup(rdp); | |
09223371 SL |
2470 | } |
2471 | ||
64db4cff | 2472 | /* |
e0f23060 | 2473 | * Do RCU core processing for the current CPU. |
64db4cff | 2474 | */ |
09223371 | 2475 | static void rcu_process_callbacks(struct softirq_action *unused) |
64db4cff | 2476 | { |
6ce75a23 PM |
2477 | struct rcu_state *rsp; |
2478 | ||
bfa00b4c PM |
2479 | if (cpu_is_offline(smp_processor_id())) |
2480 | return; | |
f7f7bac9 | 2481 | trace_rcu_utilization(TPS("Start RCU core")); |
6ce75a23 PM |
2482 | for_each_rcu_flavor(rsp) |
2483 | __rcu_process_callbacks(rsp); | |
f7f7bac9 | 2484 | trace_rcu_utilization(TPS("End RCU core")); |
64db4cff PM |
2485 | } |
2486 | ||
a26ac245 | 2487 | /* |
e0f23060 PM |
2488 | * Schedule RCU callback invocation. If the specified type of RCU |
2489 | * does not support RCU priority boosting, just do a direct call, | |
2490 | * otherwise wake up the per-CPU kernel kthread. Note that because we | |
2491 | * are running on the current CPU with interrupts disabled, the | |
2492 | * rcu_cpu_kthread_task cannot disappear out from under us. | |
a26ac245 | 2493 | */ |
a46e0899 | 2494 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
a26ac245 | 2495 | { |
b0d30417 PM |
2496 | if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active))) |
2497 | return; | |
a46e0899 PM |
2498 | if (likely(!rsp->boost)) { |
2499 | rcu_do_batch(rsp, rdp); | |
a26ac245 PM |
2500 | return; |
2501 | } | |
a46e0899 | 2502 | invoke_rcu_callbacks_kthread(); |
a26ac245 PM |
2503 | } |
2504 | ||
a46e0899 | 2505 | static void invoke_rcu_core(void) |
09223371 | 2506 | { |
b0f74036 PM |
2507 | if (cpu_online(smp_processor_id())) |
2508 | raise_softirq(RCU_SOFTIRQ); | |
09223371 SL |
2509 | } |
2510 | ||
29154c57 PM |
2511 | /* |
2512 | * Handle any core-RCU processing required by a call_rcu() invocation. | |
2513 | */ | |
2514 | static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, | |
2515 | struct rcu_head *head, unsigned long flags) | |
64db4cff | 2516 | { |
48a7639c PM |
2517 | bool needwake; |
2518 | ||
62fde6ed PM |
2519 | /* |
2520 | * If called from an extended quiescent state, invoke the RCU | |
2521 | * core in order to force a re-evaluation of RCU's idleness. | |
2522 | */ | |
5c173eb8 | 2523 | if (!rcu_is_watching() && cpu_online(smp_processor_id())) |
62fde6ed PM |
2524 | invoke_rcu_core(); |
2525 | ||
a16b7a69 | 2526 | /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ |
29154c57 | 2527 | if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) |
2655d57e | 2528 | return; |
64db4cff | 2529 | |
37c72e56 PM |
2530 | /* |
2531 | * Force the grace period if too many callbacks or too long waiting. | |
2532 | * Enforce hysteresis, and don't invoke force_quiescent_state() | |
2533 | * if some other CPU has recently done so. Also, don't bother | |
2534 | * invoking force_quiescent_state() if the newly enqueued callback | |
2535 | * is the only one waiting for a grace period to complete. | |
2536 | */ | |
2655d57e | 2537 | if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { |
b52573d2 PM |
2538 | |
2539 | /* Are we ignoring a completed grace period? */ | |
470716fc | 2540 | note_gp_changes(rsp, rdp); |
b52573d2 PM |
2541 | |
2542 | /* Start a new grace period if one not already started. */ | |
2543 | if (!rcu_gp_in_progress(rsp)) { | |
b52573d2 PM |
2544 | struct rcu_node *rnp_root = rcu_get_root(rsp); |
2545 | ||
b8462084 | 2546 | raw_spin_lock(&rnp_root->lock); |
6303b9c8 | 2547 | smp_mb__after_unlock_lock(); |
48a7639c | 2548 | needwake = rcu_start_gp(rsp); |
b8462084 | 2549 | raw_spin_unlock(&rnp_root->lock); |
48a7639c PM |
2550 | if (needwake) |
2551 | rcu_gp_kthread_wake(rsp); | |
b52573d2 PM |
2552 | } else { |
2553 | /* Give the grace period a kick. */ | |
2554 | rdp->blimit = LONG_MAX; | |
2555 | if (rsp->n_force_qs == rdp->n_force_qs_snap && | |
2556 | *rdp->nxttail[RCU_DONE_TAIL] != head) | |
4cdfc175 | 2557 | force_quiescent_state(rsp); |
b52573d2 PM |
2558 | rdp->n_force_qs_snap = rsp->n_force_qs; |
2559 | rdp->qlen_last_fqs_check = rdp->qlen; | |
2560 | } | |
4cdfc175 | 2561 | } |
29154c57 PM |
2562 | } |
2563 | ||
ae150184 PM |
2564 | /* |
2565 | * RCU callback function to leak a callback. | |
2566 | */ | |
2567 | static void rcu_leak_callback(struct rcu_head *rhp) | |
2568 | { | |
2569 | } | |
2570 | ||
3fbfbf7a PM |
2571 | /* |
2572 | * Helper function for call_rcu() and friends. The cpu argument will | |
2573 | * normally be -1, indicating "currently running CPU". It may specify | |
2574 | * a CPU only if that CPU is a no-CBs CPU. Currently, only _rcu_barrier() | |
2575 | * is expected to specify a CPU. | |
2576 | */ | |
64db4cff PM |
2577 | static void |
2578 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), | |
3fbfbf7a | 2579 | struct rcu_state *rsp, int cpu, bool lazy) |
64db4cff PM |
2580 | { |
2581 | unsigned long flags; | |
2582 | struct rcu_data *rdp; | |
2583 | ||
0bb7b59d | 2584 | WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */ |
ae150184 PM |
2585 | if (debug_rcu_head_queue(head)) { |
2586 | /* Probable double call_rcu(), so leak the callback. */ | |
2587 | ACCESS_ONCE(head->func) = rcu_leak_callback; | |
2588 | WARN_ONCE(1, "__call_rcu(): Leaked duplicate callback\n"); | |
2589 | return; | |
2590 | } | |
64db4cff PM |
2591 | head->func = func; |
2592 | head->next = NULL; | |
2593 | ||
64db4cff PM |
2594 | /* |
2595 | * Opportunistically note grace-period endings and beginnings. | |
2596 | * Note that we might see a beginning right after we see an | |
2597 | * end, but never vice versa, since this CPU has to pass through | |
2598 | * a quiescent state betweentimes. | |
2599 | */ | |
2600 | local_irq_save(flags); | |
394f99a9 | 2601 | rdp = this_cpu_ptr(rsp->rda); |
64db4cff PM |
2602 | |
2603 | /* Add the callback to our list. */ | |
3fbfbf7a PM |
2604 | if (unlikely(rdp->nxttail[RCU_NEXT_TAIL] == NULL) || cpu != -1) { |
2605 | int offline; | |
2606 | ||
2607 | if (cpu != -1) | |
2608 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
96d3fd0d | 2609 | offline = !__call_rcu_nocb(rdp, head, lazy, flags); |
3fbfbf7a | 2610 | WARN_ON_ONCE(offline); |
0d8ee37e | 2611 | /* _call_rcu() is illegal on offline CPU; leak the callback. */ |
0d8ee37e PM |
2612 | local_irq_restore(flags); |
2613 | return; | |
2614 | } | |
29154c57 | 2615 | ACCESS_ONCE(rdp->qlen)++; |
486e2593 PM |
2616 | if (lazy) |
2617 | rdp->qlen_lazy++; | |
c57afe80 PM |
2618 | else |
2619 | rcu_idle_count_callbacks_posted(); | |
b1420f1c PM |
2620 | smp_mb(); /* Count before adding callback for rcu_barrier(). */ |
2621 | *rdp->nxttail[RCU_NEXT_TAIL] = head; | |
2622 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; | |
2655d57e | 2623 | |
d4c08f2a PM |
2624 | if (__is_kfree_rcu_offset((unsigned long)func)) |
2625 | trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func, | |
486e2593 | 2626 | rdp->qlen_lazy, rdp->qlen); |
d4c08f2a | 2627 | else |
486e2593 | 2628 | trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen); |
d4c08f2a | 2629 | |
29154c57 PM |
2630 | /* Go handle any RCU core processing required. */ |
2631 | __call_rcu_core(rsp, rdp, head, flags); | |
64db4cff PM |
2632 | local_irq_restore(flags); |
2633 | } | |
2634 | ||
2635 | /* | |
d6714c22 | 2636 | * Queue an RCU-sched callback for invocation after a grace period. |
64db4cff | 2637 | */ |
d6714c22 | 2638 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
64db4cff | 2639 | { |
3fbfbf7a | 2640 | __call_rcu(head, func, &rcu_sched_state, -1, 0); |
64db4cff | 2641 | } |
d6714c22 | 2642 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
64db4cff PM |
2643 | |
2644 | /* | |
486e2593 | 2645 | * Queue an RCU callback for invocation after a quicker grace period. |
64db4cff PM |
2646 | */ |
2647 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
2648 | { | |
3fbfbf7a | 2649 | __call_rcu(head, func, &rcu_bh_state, -1, 0); |
64db4cff PM |
2650 | } |
2651 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
2652 | ||
495aa969 ACB |
2653 | /* |
2654 | * Queue an RCU callback for lazy invocation after a grace period. | |
2655 | * This will likely be later named something like "call_rcu_lazy()", | |
2656 | * but this change will require some way of tagging the lazy RCU | |
2657 | * callbacks in the list of pending callbacks. Until then, this | |
2658 | * function may only be called from __kfree_rcu(). | |
2659 | */ | |
2660 | void kfree_call_rcu(struct rcu_head *head, | |
2661 | void (*func)(struct rcu_head *rcu)) | |
2662 | { | |
e534165b | 2663 | __call_rcu(head, func, rcu_state_p, -1, 1); |
495aa969 ACB |
2664 | } |
2665 | EXPORT_SYMBOL_GPL(kfree_call_rcu); | |
2666 | ||
6d813391 PM |
2667 | /* |
2668 | * Because a context switch is a grace period for RCU-sched and RCU-bh, | |
2669 | * any blocking grace-period wait automatically implies a grace period | |
2670 | * if there is only one CPU online at any point time during execution | |
2671 | * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to | |
2672 | * occasionally incorrectly indicate that there are multiple CPUs online | |
2673 | * when there was in fact only one the whole time, as this just adds | |
2674 | * some overhead: RCU still operates correctly. | |
6d813391 PM |
2675 | */ |
2676 | static inline int rcu_blocking_is_gp(void) | |
2677 | { | |
95f0c1de PM |
2678 | int ret; |
2679 | ||
6d813391 | 2680 | might_sleep(); /* Check for RCU read-side critical section. */ |
95f0c1de PM |
2681 | preempt_disable(); |
2682 | ret = num_online_cpus() <= 1; | |
2683 | preempt_enable(); | |
2684 | return ret; | |
6d813391 PM |
2685 | } |
2686 | ||
6ebb237b PM |
2687 | /** |
2688 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. | |
2689 | * | |
2690 | * Control will return to the caller some time after a full rcu-sched | |
2691 | * grace period has elapsed, in other words after all currently executing | |
2692 | * rcu-sched read-side critical sections have completed. These read-side | |
2693 | * critical sections are delimited by rcu_read_lock_sched() and | |
2694 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), | |
2695 | * local_irq_disable(), and so on may be used in place of | |
2696 | * rcu_read_lock_sched(). | |
2697 | * | |
2698 | * This means that all preempt_disable code sequences, including NMI and | |
f0a0e6f2 PM |
2699 | * non-threaded hardware-interrupt handlers, in progress on entry will |
2700 | * have completed before this primitive returns. However, this does not | |
2701 | * guarantee that softirq handlers will have completed, since in some | |
2702 | * kernels, these handlers can run in process context, and can block. | |
2703 | * | |
2704 | * Note that this guarantee implies further memory-ordering guarantees. | |
2705 | * On systems with more than one CPU, when synchronize_sched() returns, | |
2706 | * each CPU is guaranteed to have executed a full memory barrier since the | |
2707 | * end of its last RCU-sched read-side critical section whose beginning | |
2708 | * preceded the call to synchronize_sched(). In addition, each CPU having | |
2709 | * an RCU read-side critical section that extends beyond the return from | |
2710 | * synchronize_sched() is guaranteed to have executed a full memory barrier | |
2711 | * after the beginning of synchronize_sched() and before the beginning of | |
2712 | * that RCU read-side critical section. Note that these guarantees include | |
2713 | * CPUs that are offline, idle, or executing in user mode, as well as CPUs | |
2714 | * that are executing in the kernel. | |
2715 | * | |
2716 | * Furthermore, if CPU A invoked synchronize_sched(), which returned | |
2717 | * to its caller on CPU B, then both CPU A and CPU B are guaranteed | |
2718 | * to have executed a full memory barrier during the execution of | |
2719 | * synchronize_sched() -- even if CPU A and CPU B are the same CPU (but | |
2720 | * again only if the system has more than one CPU). | |
6ebb237b PM |
2721 | * |
2722 | * This primitive provides the guarantees made by the (now removed) | |
2723 | * synchronize_kernel() API. In contrast, synchronize_rcu() only | |
2724 | * guarantees that rcu_read_lock() sections will have completed. | |
2725 | * In "classic RCU", these two guarantees happen to be one and | |
2726 | * the same, but can differ in realtime RCU implementations. | |
2727 | */ | |
2728 | void synchronize_sched(void) | |
2729 | { | |
fe15d706 PM |
2730 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
2731 | !lock_is_held(&rcu_lock_map) && | |
2732 | !lock_is_held(&rcu_sched_lock_map), | |
2733 | "Illegal synchronize_sched() in RCU-sched read-side critical section"); | |
6ebb237b PM |
2734 | if (rcu_blocking_is_gp()) |
2735 | return; | |
3705b88d AM |
2736 | if (rcu_expedited) |
2737 | synchronize_sched_expedited(); | |
2738 | else | |
2739 | wait_rcu_gp(call_rcu_sched); | |
6ebb237b PM |
2740 | } |
2741 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
2742 | ||
2743 | /** | |
2744 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. | |
2745 | * | |
2746 | * Control will return to the caller some time after a full rcu_bh grace | |
2747 | * period has elapsed, in other words after all currently executing rcu_bh | |
2748 | * read-side critical sections have completed. RCU read-side critical | |
2749 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), | |
2750 | * and may be nested. | |
f0a0e6f2 PM |
2751 | * |
2752 | * See the description of synchronize_sched() for more detailed information | |
2753 | * on memory ordering guarantees. | |
6ebb237b PM |
2754 | */ |
2755 | void synchronize_rcu_bh(void) | |
2756 | { | |
fe15d706 PM |
2757 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
2758 | !lock_is_held(&rcu_lock_map) && | |
2759 | !lock_is_held(&rcu_sched_lock_map), | |
2760 | "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section"); | |
6ebb237b PM |
2761 | if (rcu_blocking_is_gp()) |
2762 | return; | |
3705b88d AM |
2763 | if (rcu_expedited) |
2764 | synchronize_rcu_bh_expedited(); | |
2765 | else | |
2766 | wait_rcu_gp(call_rcu_bh); | |
6ebb237b PM |
2767 | } |
2768 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); | |
2769 | ||
765a3f4f PM |
2770 | /** |
2771 | * get_state_synchronize_rcu - Snapshot current RCU state | |
2772 | * | |
2773 | * Returns a cookie that is used by a later call to cond_synchronize_rcu() | |
2774 | * to determine whether or not a full grace period has elapsed in the | |
2775 | * meantime. | |
2776 | */ | |
2777 | unsigned long get_state_synchronize_rcu(void) | |
2778 | { | |
2779 | /* | |
2780 | * Any prior manipulation of RCU-protected data must happen | |
2781 | * before the load from ->gpnum. | |
2782 | */ | |
2783 | smp_mb(); /* ^^^ */ | |
2784 | ||
2785 | /* | |
2786 | * Make sure this load happens before the purportedly | |
2787 | * time-consuming work between get_state_synchronize_rcu() | |
2788 | * and cond_synchronize_rcu(). | |
2789 | */ | |
e534165b | 2790 | return smp_load_acquire(&rcu_state_p->gpnum); |
765a3f4f PM |
2791 | } |
2792 | EXPORT_SYMBOL_GPL(get_state_synchronize_rcu); | |
2793 | ||
2794 | /** | |
2795 | * cond_synchronize_rcu - Conditionally wait for an RCU grace period | |
2796 | * | |
2797 | * @oldstate: return value from earlier call to get_state_synchronize_rcu() | |
2798 | * | |
2799 | * If a full RCU grace period has elapsed since the earlier call to | |
2800 | * get_state_synchronize_rcu(), just return. Otherwise, invoke | |
2801 | * synchronize_rcu() to wait for a full grace period. | |
2802 | * | |
2803 | * Yes, this function does not take counter wrap into account. But | |
2804 | * counter wrap is harmless. If the counter wraps, we have waited for | |
2805 | * more than 2 billion grace periods (and way more on a 64-bit system!), | |
2806 | * so waiting for one additional grace period should be just fine. | |
2807 | */ | |
2808 | void cond_synchronize_rcu(unsigned long oldstate) | |
2809 | { | |
2810 | unsigned long newstate; | |
2811 | ||
2812 | /* | |
2813 | * Ensure that this load happens before any RCU-destructive | |
2814 | * actions the caller might carry out after we return. | |
2815 | */ | |
e534165b | 2816 | newstate = smp_load_acquire(&rcu_state_p->completed); |
765a3f4f PM |
2817 | if (ULONG_CMP_GE(oldstate, newstate)) |
2818 | synchronize_rcu(); | |
2819 | } | |
2820 | EXPORT_SYMBOL_GPL(cond_synchronize_rcu); | |
2821 | ||
3d3b7db0 PM |
2822 | static int synchronize_sched_expedited_cpu_stop(void *data) |
2823 | { | |
2824 | /* | |
2825 | * There must be a full memory barrier on each affected CPU | |
2826 | * between the time that try_stop_cpus() is called and the | |
2827 | * time that it returns. | |
2828 | * | |
2829 | * In the current initial implementation of cpu_stop, the | |
2830 | * above condition is already met when the control reaches | |
2831 | * this point and the following smp_mb() is not strictly | |
2832 | * necessary. Do smp_mb() anyway for documentation and | |
2833 | * robustness against future implementation changes. | |
2834 | */ | |
2835 | smp_mb(); /* See above comment block. */ | |
2836 | return 0; | |
2837 | } | |
2838 | ||
236fefaf PM |
2839 | /** |
2840 | * synchronize_sched_expedited - Brute-force RCU-sched grace period | |
2841 | * | |
2842 | * Wait for an RCU-sched grace period to elapse, but use a "big hammer" | |
2843 | * approach to force the grace period to end quickly. This consumes | |
2844 | * significant time on all CPUs and is unfriendly to real-time workloads, | |
2845 | * so is thus not recommended for any sort of common-case code. In fact, | |
2846 | * if you are using synchronize_sched_expedited() in a loop, please | |
2847 | * restructure your code to batch your updates, and then use a single | |
2848 | * synchronize_sched() instead. | |
3d3b7db0 | 2849 | * |
236fefaf PM |
2850 | * Note that it is illegal to call this function while holding any lock |
2851 | * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal | |
2852 | * to call this function from a CPU-hotplug notifier. Failing to observe | |
2853 | * these restriction will result in deadlock. | |
3d3b7db0 PM |
2854 | * |
2855 | * This implementation can be thought of as an application of ticket | |
2856 | * locking to RCU, with sync_sched_expedited_started and | |
2857 | * sync_sched_expedited_done taking on the roles of the halves | |
2858 | * of the ticket-lock word. Each task atomically increments | |
2859 | * sync_sched_expedited_started upon entry, snapshotting the old value, | |
2860 | * then attempts to stop all the CPUs. If this succeeds, then each | |
2861 | * CPU will have executed a context switch, resulting in an RCU-sched | |
2862 | * grace period. We are then done, so we use atomic_cmpxchg() to | |
2863 | * update sync_sched_expedited_done to match our snapshot -- but | |
2864 | * only if someone else has not already advanced past our snapshot. | |
2865 | * | |
2866 | * On the other hand, if try_stop_cpus() fails, we check the value | |
2867 | * of sync_sched_expedited_done. If it has advanced past our | |
2868 | * initial snapshot, then someone else must have forced a grace period | |
2869 | * some time after we took our snapshot. In this case, our work is | |
2870 | * done for us, and we can simply return. Otherwise, we try again, | |
2871 | * but keep our initial snapshot for purposes of checking for someone | |
2872 | * doing our work for us. | |
2873 | * | |
2874 | * If we fail too many times in a row, we fall back to synchronize_sched(). | |
2875 | */ | |
2876 | void synchronize_sched_expedited(void) | |
2877 | { | |
1924bcb0 PM |
2878 | long firstsnap, s, snap; |
2879 | int trycount = 0; | |
40694d66 | 2880 | struct rcu_state *rsp = &rcu_sched_state; |
3d3b7db0 | 2881 | |
1924bcb0 PM |
2882 | /* |
2883 | * If we are in danger of counter wrap, just do synchronize_sched(). | |
2884 | * By allowing sync_sched_expedited_started to advance no more than | |
2885 | * ULONG_MAX/8 ahead of sync_sched_expedited_done, we are ensuring | |
2886 | * that more than 3.5 billion CPUs would be required to force a | |
2887 | * counter wrap on a 32-bit system. Quite a few more CPUs would of | |
2888 | * course be required on a 64-bit system. | |
2889 | */ | |
40694d66 PM |
2890 | if (ULONG_CMP_GE((ulong)atomic_long_read(&rsp->expedited_start), |
2891 | (ulong)atomic_long_read(&rsp->expedited_done) + | |
1924bcb0 PM |
2892 | ULONG_MAX / 8)) { |
2893 | synchronize_sched(); | |
a30489c5 | 2894 | atomic_long_inc(&rsp->expedited_wrap); |
1924bcb0 PM |
2895 | return; |
2896 | } | |
3d3b7db0 | 2897 | |
1924bcb0 PM |
2898 | /* |
2899 | * Take a ticket. Note that atomic_inc_return() implies a | |
2900 | * full memory barrier. | |
2901 | */ | |
40694d66 | 2902 | snap = atomic_long_inc_return(&rsp->expedited_start); |
1924bcb0 | 2903 | firstsnap = snap; |
3d3b7db0 | 2904 | get_online_cpus(); |
1cc85961 | 2905 | WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id())); |
3d3b7db0 PM |
2906 | |
2907 | /* | |
2908 | * Each pass through the following loop attempts to force a | |
2909 | * context switch on each CPU. | |
2910 | */ | |
2911 | while (try_stop_cpus(cpu_online_mask, | |
2912 | synchronize_sched_expedited_cpu_stop, | |
2913 | NULL) == -EAGAIN) { | |
2914 | put_online_cpus(); | |
a30489c5 | 2915 | atomic_long_inc(&rsp->expedited_tryfail); |
3d3b7db0 | 2916 | |
1924bcb0 | 2917 | /* Check to see if someone else did our work for us. */ |
40694d66 | 2918 | s = atomic_long_read(&rsp->expedited_done); |
1924bcb0 | 2919 | if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) { |
a30489c5 | 2920 | /* ensure test happens before caller kfree */ |
4e857c58 | 2921 | smp_mb__before_atomic(); /* ^^^ */ |
a30489c5 | 2922 | atomic_long_inc(&rsp->expedited_workdone1); |
1924bcb0 PM |
2923 | return; |
2924 | } | |
3d3b7db0 PM |
2925 | |
2926 | /* No joy, try again later. Or just synchronize_sched(). */ | |
c701d5d9 | 2927 | if (trycount++ < 10) { |
3d3b7db0 | 2928 | udelay(trycount * num_online_cpus()); |
c701d5d9 | 2929 | } else { |
3705b88d | 2930 | wait_rcu_gp(call_rcu_sched); |
a30489c5 | 2931 | atomic_long_inc(&rsp->expedited_normal); |
3d3b7db0 PM |
2932 | return; |
2933 | } | |
2934 | ||
1924bcb0 | 2935 | /* Recheck to see if someone else did our work for us. */ |
40694d66 | 2936 | s = atomic_long_read(&rsp->expedited_done); |
1924bcb0 | 2937 | if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) { |
a30489c5 | 2938 | /* ensure test happens before caller kfree */ |
4e857c58 | 2939 | smp_mb__before_atomic(); /* ^^^ */ |
a30489c5 | 2940 | atomic_long_inc(&rsp->expedited_workdone2); |
3d3b7db0 PM |
2941 | return; |
2942 | } | |
2943 | ||
2944 | /* | |
2945 | * Refetching sync_sched_expedited_started allows later | |
1924bcb0 PM |
2946 | * callers to piggyback on our grace period. We retry |
2947 | * after they started, so our grace period works for them, | |
2948 | * and they started after our first try, so their grace | |
2949 | * period works for us. | |
3d3b7db0 PM |
2950 | */ |
2951 | get_online_cpus(); | |
40694d66 | 2952 | snap = atomic_long_read(&rsp->expedited_start); |
3d3b7db0 PM |
2953 | smp_mb(); /* ensure read is before try_stop_cpus(). */ |
2954 | } | |
a30489c5 | 2955 | atomic_long_inc(&rsp->expedited_stoppedcpus); |
3d3b7db0 PM |
2956 | |
2957 | /* | |
2958 | * Everyone up to our most recent fetch is covered by our grace | |
2959 | * period. Update the counter, but only if our work is still | |
2960 | * relevant -- which it won't be if someone who started later | |
1924bcb0 | 2961 | * than we did already did their update. |
3d3b7db0 PM |
2962 | */ |
2963 | do { | |
a30489c5 | 2964 | atomic_long_inc(&rsp->expedited_done_tries); |
40694d66 | 2965 | s = atomic_long_read(&rsp->expedited_done); |
1924bcb0 | 2966 | if (ULONG_CMP_GE((ulong)s, (ulong)snap)) { |
a30489c5 | 2967 | /* ensure test happens before caller kfree */ |
4e857c58 | 2968 | smp_mb__before_atomic(); /* ^^^ */ |
a30489c5 | 2969 | atomic_long_inc(&rsp->expedited_done_lost); |
3d3b7db0 PM |
2970 | break; |
2971 | } | |
40694d66 | 2972 | } while (atomic_long_cmpxchg(&rsp->expedited_done, s, snap) != s); |
a30489c5 | 2973 | atomic_long_inc(&rsp->expedited_done_exit); |
3d3b7db0 PM |
2974 | |
2975 | put_online_cpus(); | |
2976 | } | |
2977 | EXPORT_SYMBOL_GPL(synchronize_sched_expedited); | |
2978 | ||
64db4cff PM |
2979 | /* |
2980 | * Check to see if there is any immediate RCU-related work to be done | |
2981 | * by the current CPU, for the specified type of RCU, returning 1 if so. | |
2982 | * The checks are in order of increasing expense: checks that can be | |
2983 | * carried out against CPU-local state are performed first. However, | |
2984 | * we must check for CPU stalls first, else we might not get a chance. | |
2985 | */ | |
2986 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) | |
2987 | { | |
2f51f988 PM |
2988 | struct rcu_node *rnp = rdp->mynode; |
2989 | ||
64db4cff PM |
2990 | rdp->n_rcu_pending++; |
2991 | ||
2992 | /* Check for CPU stalls, if enabled. */ | |
2993 | check_cpu_stall(rsp, rdp); | |
2994 | ||
a096932f PM |
2995 | /* Is this CPU a NO_HZ_FULL CPU that should ignore RCU? */ |
2996 | if (rcu_nohz_full_cpu(rsp)) | |
2997 | return 0; | |
2998 | ||
64db4cff | 2999 | /* Is the RCU core waiting for a quiescent state from this CPU? */ |
5c51dd73 PM |
3000 | if (rcu_scheduler_fully_active && |
3001 | rdp->qs_pending && !rdp->passed_quiesce) { | |
d21670ac | 3002 | rdp->n_rp_qs_pending++; |
e4cc1f22 | 3003 | } else if (rdp->qs_pending && rdp->passed_quiesce) { |
d21670ac | 3004 | rdp->n_rp_report_qs++; |
64db4cff | 3005 | return 1; |
7ba5c840 | 3006 | } |
64db4cff PM |
3007 | |
3008 | /* Does this CPU have callbacks ready to invoke? */ | |
7ba5c840 PM |
3009 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
3010 | rdp->n_rp_cb_ready++; | |
64db4cff | 3011 | return 1; |
7ba5c840 | 3012 | } |
64db4cff PM |
3013 | |
3014 | /* Has RCU gone idle with this CPU needing another grace period? */ | |
7ba5c840 PM |
3015 | if (cpu_needs_another_gp(rsp, rdp)) { |
3016 | rdp->n_rp_cpu_needs_gp++; | |
64db4cff | 3017 | return 1; |
7ba5c840 | 3018 | } |
64db4cff PM |
3019 | |
3020 | /* Has another RCU grace period completed? */ | |
2f51f988 | 3021 | if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
7ba5c840 | 3022 | rdp->n_rp_gp_completed++; |
64db4cff | 3023 | return 1; |
7ba5c840 | 3024 | } |
64db4cff PM |
3025 | |
3026 | /* Has a new RCU grace period started? */ | |
2f51f988 | 3027 | if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
7ba5c840 | 3028 | rdp->n_rp_gp_started++; |
64db4cff | 3029 | return 1; |
7ba5c840 | 3030 | } |
64db4cff | 3031 | |
96d3fd0d PM |
3032 | /* Does this CPU need a deferred NOCB wakeup? */ |
3033 | if (rcu_nocb_need_deferred_wakeup(rdp)) { | |
3034 | rdp->n_rp_nocb_defer_wakeup++; | |
3035 | return 1; | |
3036 | } | |
3037 | ||
64db4cff | 3038 | /* nothing to do */ |
7ba5c840 | 3039 | rdp->n_rp_need_nothing++; |
64db4cff PM |
3040 | return 0; |
3041 | } | |
3042 | ||
3043 | /* | |
3044 | * Check to see if there is any immediate RCU-related work to be done | |
3045 | * by the current CPU, returning 1 if so. This function is part of the | |
3046 | * RCU implementation; it is -not- an exported member of the RCU API. | |
3047 | */ | |
a157229c | 3048 | static int rcu_pending(int cpu) |
64db4cff | 3049 | { |
6ce75a23 PM |
3050 | struct rcu_state *rsp; |
3051 | ||
3052 | for_each_rcu_flavor(rsp) | |
3053 | if (__rcu_pending(rsp, per_cpu_ptr(rsp->rda, cpu))) | |
3054 | return 1; | |
3055 | return 0; | |
64db4cff PM |
3056 | } |
3057 | ||
3058 | /* | |
c0f4dfd4 PM |
3059 | * Return true if the specified CPU has any callback. If all_lazy is |
3060 | * non-NULL, store an indication of whether all callbacks are lazy. | |
3061 | * (If there are no callbacks, all of them are deemed to be lazy.) | |
64db4cff | 3062 | */ |
ffa83fb5 | 3063 | static int __maybe_unused rcu_cpu_has_callbacks(int cpu, bool *all_lazy) |
64db4cff | 3064 | { |
c0f4dfd4 PM |
3065 | bool al = true; |
3066 | bool hc = false; | |
3067 | struct rcu_data *rdp; | |
6ce75a23 PM |
3068 | struct rcu_state *rsp; |
3069 | ||
c0f4dfd4 PM |
3070 | for_each_rcu_flavor(rsp) { |
3071 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
69c8d28c PM |
3072 | if (!rdp->nxtlist) |
3073 | continue; | |
3074 | hc = true; | |
3075 | if (rdp->qlen != rdp->qlen_lazy || !all_lazy) { | |
c0f4dfd4 | 3076 | al = false; |
69c8d28c PM |
3077 | break; |
3078 | } | |
c0f4dfd4 PM |
3079 | } |
3080 | if (all_lazy) | |
3081 | *all_lazy = al; | |
3082 | return hc; | |
64db4cff PM |
3083 | } |
3084 | ||
a83eff0a PM |
3085 | /* |
3086 | * Helper function for _rcu_barrier() tracing. If tracing is disabled, | |
3087 | * the compiler is expected to optimize this away. | |
3088 | */ | |
e66c33d5 | 3089 | static void _rcu_barrier_trace(struct rcu_state *rsp, const char *s, |
a83eff0a PM |
3090 | int cpu, unsigned long done) |
3091 | { | |
3092 | trace_rcu_barrier(rsp->name, s, cpu, | |
3093 | atomic_read(&rsp->barrier_cpu_count), done); | |
3094 | } | |
3095 | ||
b1420f1c PM |
3096 | /* |
3097 | * RCU callback function for _rcu_barrier(). If we are last, wake | |
3098 | * up the task executing _rcu_barrier(). | |
3099 | */ | |
24ebbca8 | 3100 | static void rcu_barrier_callback(struct rcu_head *rhp) |
d0ec774c | 3101 | { |
24ebbca8 PM |
3102 | struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head); |
3103 | struct rcu_state *rsp = rdp->rsp; | |
3104 | ||
a83eff0a PM |
3105 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) { |
3106 | _rcu_barrier_trace(rsp, "LastCB", -1, rsp->n_barrier_done); | |
7db74df8 | 3107 | complete(&rsp->barrier_completion); |
a83eff0a PM |
3108 | } else { |
3109 | _rcu_barrier_trace(rsp, "CB", -1, rsp->n_barrier_done); | |
3110 | } | |
d0ec774c PM |
3111 | } |
3112 | ||
3113 | /* | |
3114 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
3115 | */ | |
3116 | static void rcu_barrier_func(void *type) | |
3117 | { | |
037b64ed | 3118 | struct rcu_state *rsp = type; |
fa07a58f | 3119 | struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); |
d0ec774c | 3120 | |
a83eff0a | 3121 | _rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done); |
24ebbca8 | 3122 | atomic_inc(&rsp->barrier_cpu_count); |
06668efa | 3123 | rsp->call(&rdp->barrier_head, rcu_barrier_callback); |
d0ec774c PM |
3124 | } |
3125 | ||
d0ec774c PM |
3126 | /* |
3127 | * Orchestrate the specified type of RCU barrier, waiting for all | |
3128 | * RCU callbacks of the specified type to complete. | |
3129 | */ | |
037b64ed | 3130 | static void _rcu_barrier(struct rcu_state *rsp) |
d0ec774c | 3131 | { |
b1420f1c | 3132 | int cpu; |
b1420f1c | 3133 | struct rcu_data *rdp; |
cf3a9c48 PM |
3134 | unsigned long snap = ACCESS_ONCE(rsp->n_barrier_done); |
3135 | unsigned long snap_done; | |
b1420f1c | 3136 | |
a83eff0a | 3137 | _rcu_barrier_trace(rsp, "Begin", -1, snap); |
b1420f1c | 3138 | |
e74f4c45 | 3139 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
7be7f0be | 3140 | mutex_lock(&rsp->barrier_mutex); |
b1420f1c | 3141 | |
cf3a9c48 PM |
3142 | /* |
3143 | * Ensure that all prior references, including to ->n_barrier_done, | |
3144 | * are ordered before the _rcu_barrier() machinery. | |
3145 | */ | |
3146 | smp_mb(); /* See above block comment. */ | |
3147 | ||
3148 | /* | |
3149 | * Recheck ->n_barrier_done to see if others did our work for us. | |
3150 | * This means checking ->n_barrier_done for an even-to-odd-to-even | |
3151 | * transition. The "if" expression below therefore rounds the old | |
3152 | * value up to the next even number and adds two before comparing. | |
3153 | */ | |
458fb381 | 3154 | snap_done = rsp->n_barrier_done; |
a83eff0a | 3155 | _rcu_barrier_trace(rsp, "Check", -1, snap_done); |
458fb381 PM |
3156 | |
3157 | /* | |
3158 | * If the value in snap is odd, we needed to wait for the current | |
3159 | * rcu_barrier() to complete, then wait for the next one, in other | |
3160 | * words, we need the value of snap_done to be three larger than | |
3161 | * the value of snap. On the other hand, if the value in snap is | |
3162 | * even, we only had to wait for the next rcu_barrier() to complete, | |
3163 | * in other words, we need the value of snap_done to be only two | |
3164 | * greater than the value of snap. The "(snap + 3) & ~0x1" computes | |
3165 | * this for us (thank you, Linus!). | |
3166 | */ | |
3167 | if (ULONG_CMP_GE(snap_done, (snap + 3) & ~0x1)) { | |
a83eff0a | 3168 | _rcu_barrier_trace(rsp, "EarlyExit", -1, snap_done); |
cf3a9c48 PM |
3169 | smp_mb(); /* caller's subsequent code after above check. */ |
3170 | mutex_unlock(&rsp->barrier_mutex); | |
3171 | return; | |
3172 | } | |
3173 | ||
3174 | /* | |
3175 | * Increment ->n_barrier_done to avoid duplicate work. Use | |
3176 | * ACCESS_ONCE() to prevent the compiler from speculating | |
3177 | * the increment to precede the early-exit check. | |
3178 | */ | |
3179 | ACCESS_ONCE(rsp->n_barrier_done)++; | |
3180 | WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1); | |
a83eff0a | 3181 | _rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done); |
cf3a9c48 | 3182 | smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */ |
b1420f1c | 3183 | |
d0ec774c | 3184 | /* |
b1420f1c PM |
3185 | * Initialize the count to one rather than to zero in order to |
3186 | * avoid a too-soon return to zero in case of a short grace period | |
1331e7a1 PM |
3187 | * (or preemption of this task). Exclude CPU-hotplug operations |
3188 | * to ensure that no offline CPU has callbacks queued. | |
d0ec774c | 3189 | */ |
7db74df8 | 3190 | init_completion(&rsp->barrier_completion); |
24ebbca8 | 3191 | atomic_set(&rsp->barrier_cpu_count, 1); |
1331e7a1 | 3192 | get_online_cpus(); |
b1420f1c PM |
3193 | |
3194 | /* | |
1331e7a1 PM |
3195 | * Force each CPU with callbacks to register a new callback. |
3196 | * When that callback is invoked, we will know that all of the | |
3197 | * corresponding CPU's preceding callbacks have been invoked. | |
b1420f1c | 3198 | */ |
3fbfbf7a | 3199 | for_each_possible_cpu(cpu) { |
d1e43fa5 | 3200 | if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu)) |
3fbfbf7a | 3201 | continue; |
b1420f1c | 3202 | rdp = per_cpu_ptr(rsp->rda, cpu); |
d1e43fa5 | 3203 | if (rcu_is_nocb_cpu(cpu)) { |
3fbfbf7a PM |
3204 | _rcu_barrier_trace(rsp, "OnlineNoCB", cpu, |
3205 | rsp->n_barrier_done); | |
3206 | atomic_inc(&rsp->barrier_cpu_count); | |
3207 | __call_rcu(&rdp->barrier_head, rcu_barrier_callback, | |
3208 | rsp, cpu, 0); | |
3209 | } else if (ACCESS_ONCE(rdp->qlen)) { | |
a83eff0a PM |
3210 | _rcu_barrier_trace(rsp, "OnlineQ", cpu, |
3211 | rsp->n_barrier_done); | |
037b64ed | 3212 | smp_call_function_single(cpu, rcu_barrier_func, rsp, 1); |
b1420f1c | 3213 | } else { |
a83eff0a PM |
3214 | _rcu_barrier_trace(rsp, "OnlineNQ", cpu, |
3215 | rsp->n_barrier_done); | |
b1420f1c PM |
3216 | } |
3217 | } | |
1331e7a1 | 3218 | put_online_cpus(); |
b1420f1c PM |
3219 | |
3220 | /* | |
3221 | * Now that we have an rcu_barrier_callback() callback on each | |
3222 | * CPU, and thus each counted, remove the initial count. | |
3223 | */ | |
24ebbca8 | 3224 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) |
7db74df8 | 3225 | complete(&rsp->barrier_completion); |
b1420f1c | 3226 | |
cf3a9c48 PM |
3227 | /* Increment ->n_barrier_done to prevent duplicate work. */ |
3228 | smp_mb(); /* Keep increment after above mechanism. */ | |
3229 | ACCESS_ONCE(rsp->n_barrier_done)++; | |
3230 | WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0); | |
a83eff0a | 3231 | _rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done); |
cf3a9c48 PM |
3232 | smp_mb(); /* Keep increment before caller's subsequent code. */ |
3233 | ||
b1420f1c | 3234 | /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ |
7db74df8 | 3235 | wait_for_completion(&rsp->barrier_completion); |
b1420f1c PM |
3236 | |
3237 | /* Other rcu_barrier() invocations can now safely proceed. */ | |
7be7f0be | 3238 | mutex_unlock(&rsp->barrier_mutex); |
d0ec774c | 3239 | } |
d0ec774c PM |
3240 | |
3241 | /** | |
3242 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. | |
3243 | */ | |
3244 | void rcu_barrier_bh(void) | |
3245 | { | |
037b64ed | 3246 | _rcu_barrier(&rcu_bh_state); |
d0ec774c PM |
3247 | } |
3248 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); | |
3249 | ||
3250 | /** | |
3251 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. | |
3252 | */ | |
3253 | void rcu_barrier_sched(void) | |
3254 | { | |
037b64ed | 3255 | _rcu_barrier(&rcu_sched_state); |
d0ec774c PM |
3256 | } |
3257 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); | |
3258 | ||
64db4cff | 3259 | /* |
27569620 | 3260 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
64db4cff | 3261 | */ |
27569620 PM |
3262 | static void __init |
3263 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) | |
64db4cff PM |
3264 | { |
3265 | unsigned long flags; | |
394f99a9 | 3266 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
27569620 PM |
3267 | struct rcu_node *rnp = rcu_get_root(rsp); |
3268 | ||
3269 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 3270 | raw_spin_lock_irqsave(&rnp->lock, flags); |
27569620 | 3271 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
3f5d3ea6 | 3272 | init_callback_list(rdp); |
486e2593 | 3273 | rdp->qlen_lazy = 0; |
1d1fb395 | 3274 | ACCESS_ONCE(rdp->qlen) = 0; |
27569620 | 3275 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
29e37d81 | 3276 | WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); |
9b2e4f18 | 3277 | WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1); |
27569620 | 3278 | rdp->cpu = cpu; |
d4c08f2a | 3279 | rdp->rsp = rsp; |
3fbfbf7a | 3280 | rcu_boot_init_nocb_percpu_data(rdp); |
1304afb2 | 3281 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27569620 PM |
3282 | } |
3283 | ||
3284 | /* | |
3285 | * Initialize a CPU's per-CPU RCU data. Note that only one online or | |
3286 | * offline event can be happening at a given time. Note also that we | |
3287 | * can accept some slop in the rsp->completed access due to the fact | |
3288 | * that this CPU cannot possibly have any RCU callbacks in flight yet. | |
64db4cff | 3289 | */ |
49fb4c62 | 3290 | static void |
9b67122a | 3291 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp) |
64db4cff PM |
3292 | { |
3293 | unsigned long flags; | |
64db4cff | 3294 | unsigned long mask; |
394f99a9 | 3295 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
64db4cff PM |
3296 | struct rcu_node *rnp = rcu_get_root(rsp); |
3297 | ||
a4fbe35a PM |
3298 | /* Exclude new grace periods. */ |
3299 | mutex_lock(&rsp->onoff_mutex); | |
3300 | ||
64db4cff | 3301 | /* Set up local state, ensuring consistent view of global state. */ |
1304afb2 | 3302 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff | 3303 | rdp->beenonline = 1; /* We have now been online. */ |
37c72e56 PM |
3304 | rdp->qlen_last_fqs_check = 0; |
3305 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
64db4cff | 3306 | rdp->blimit = blimit; |
0d8ee37e | 3307 | init_callback_list(rdp); /* Re-enable callbacks on this CPU. */ |
29e37d81 | 3308 | rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
2333210b | 3309 | rcu_sysidle_init_percpu_data(rdp->dynticks); |
c92b131b PM |
3310 | atomic_set(&rdp->dynticks->dynticks, |
3311 | (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1); | |
1304afb2 | 3312 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff | 3313 | |
64db4cff PM |
3314 | /* Add CPU to rcu_node bitmasks. */ |
3315 | rnp = rdp->mynode; | |
3316 | mask = rdp->grpmask; | |
3317 | do { | |
3318 | /* Exclude any attempts to start a new GP on small systems. */ | |
1304afb2 | 3319 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
3320 | rnp->qsmaskinit |= mask; |
3321 | mask = rnp->grpmask; | |
d09b62df | 3322 | if (rnp == rdp->mynode) { |
06ae115a PM |
3323 | /* |
3324 | * If there is a grace period in progress, we will | |
3325 | * set up to wait for it next time we run the | |
3326 | * RCU core code. | |
3327 | */ | |
3328 | rdp->gpnum = rnp->completed; | |
d09b62df | 3329 | rdp->completed = rnp->completed; |
06ae115a PM |
3330 | rdp->passed_quiesce = 0; |
3331 | rdp->qs_pending = 0; | |
f7f7bac9 | 3332 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl")); |
d09b62df | 3333 | } |
1304afb2 | 3334 | raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
3335 | rnp = rnp->parent; |
3336 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); | |
a4fbe35a | 3337 | local_irq_restore(flags); |
64db4cff | 3338 | |
a4fbe35a | 3339 | mutex_unlock(&rsp->onoff_mutex); |
64db4cff PM |
3340 | } |
3341 | ||
49fb4c62 | 3342 | static void rcu_prepare_cpu(int cpu) |
64db4cff | 3343 | { |
6ce75a23 PM |
3344 | struct rcu_state *rsp; |
3345 | ||
3346 | for_each_rcu_flavor(rsp) | |
9b67122a | 3347 | rcu_init_percpu_data(cpu, rsp); |
64db4cff PM |
3348 | } |
3349 | ||
3350 | /* | |
f41d911f | 3351 | * Handle CPU online/offline notification events. |
64db4cff | 3352 | */ |
49fb4c62 | 3353 | static int rcu_cpu_notify(struct notifier_block *self, |
9f680ab4 | 3354 | unsigned long action, void *hcpu) |
64db4cff PM |
3355 | { |
3356 | long cpu = (long)hcpu; | |
e534165b | 3357 | struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); |
a26ac245 | 3358 | struct rcu_node *rnp = rdp->mynode; |
6ce75a23 | 3359 | struct rcu_state *rsp; |
64db4cff | 3360 | |
f7f7bac9 | 3361 | trace_rcu_utilization(TPS("Start CPU hotplug")); |
64db4cff PM |
3362 | switch (action) { |
3363 | case CPU_UP_PREPARE: | |
3364 | case CPU_UP_PREPARE_FROZEN: | |
d72bce0e PZ |
3365 | rcu_prepare_cpu(cpu); |
3366 | rcu_prepare_kthreads(cpu); | |
a26ac245 PM |
3367 | break; |
3368 | case CPU_ONLINE: | |
0f962a5e | 3369 | case CPU_DOWN_FAILED: |
5d01bbd1 | 3370 | rcu_boost_kthread_setaffinity(rnp, -1); |
0f962a5e PM |
3371 | break; |
3372 | case CPU_DOWN_PREPARE: | |
34ed6246 | 3373 | rcu_boost_kthread_setaffinity(rnp, cpu); |
64db4cff | 3374 | break; |
d0ec774c PM |
3375 | case CPU_DYING: |
3376 | case CPU_DYING_FROZEN: | |
6ce75a23 PM |
3377 | for_each_rcu_flavor(rsp) |
3378 | rcu_cleanup_dying_cpu(rsp); | |
d0ec774c | 3379 | break; |
64db4cff PM |
3380 | case CPU_DEAD: |
3381 | case CPU_DEAD_FROZEN: | |
3382 | case CPU_UP_CANCELED: | |
3383 | case CPU_UP_CANCELED_FROZEN: | |
6ce75a23 PM |
3384 | for_each_rcu_flavor(rsp) |
3385 | rcu_cleanup_dead_cpu(cpu, rsp); | |
64db4cff PM |
3386 | break; |
3387 | default: | |
3388 | break; | |
3389 | } | |
f7f7bac9 | 3390 | trace_rcu_utilization(TPS("End CPU hotplug")); |
34ed6246 | 3391 | return NOTIFY_OK; |
64db4cff PM |
3392 | } |
3393 | ||
d1d74d14 BP |
3394 | static int rcu_pm_notify(struct notifier_block *self, |
3395 | unsigned long action, void *hcpu) | |
3396 | { | |
3397 | switch (action) { | |
3398 | case PM_HIBERNATION_PREPARE: | |
3399 | case PM_SUSPEND_PREPARE: | |
3400 | if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ | |
3401 | rcu_expedited = 1; | |
3402 | break; | |
3403 | case PM_POST_HIBERNATION: | |
3404 | case PM_POST_SUSPEND: | |
3405 | rcu_expedited = 0; | |
3406 | break; | |
3407 | default: | |
3408 | break; | |
3409 | } | |
3410 | return NOTIFY_OK; | |
3411 | } | |
3412 | ||
b3dbec76 PM |
3413 | /* |
3414 | * Spawn the kthread that handles this RCU flavor's grace periods. | |
3415 | */ | |
3416 | static int __init rcu_spawn_gp_kthread(void) | |
3417 | { | |
3418 | unsigned long flags; | |
3419 | struct rcu_node *rnp; | |
3420 | struct rcu_state *rsp; | |
3421 | struct task_struct *t; | |
3422 | ||
3423 | for_each_rcu_flavor(rsp) { | |
f170168b | 3424 | t = kthread_run(rcu_gp_kthread, rsp, "%s", rsp->name); |
b3dbec76 PM |
3425 | BUG_ON(IS_ERR(t)); |
3426 | rnp = rcu_get_root(rsp); | |
3427 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
3428 | rsp->gp_kthread = t; | |
3429 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
3fbfbf7a | 3430 | rcu_spawn_nocb_kthreads(rsp); |
b3dbec76 PM |
3431 | } |
3432 | return 0; | |
3433 | } | |
3434 | early_initcall(rcu_spawn_gp_kthread); | |
3435 | ||
bbad9379 PM |
3436 | /* |
3437 | * This function is invoked towards the end of the scheduler's initialization | |
3438 | * process. Before this is called, the idle task might contain | |
3439 | * RCU read-side critical sections (during which time, this idle | |
3440 | * task is booting the system). After this function is called, the | |
3441 | * idle tasks are prohibited from containing RCU read-side critical | |
3442 | * sections. This function also enables RCU lockdep checking. | |
3443 | */ | |
3444 | void rcu_scheduler_starting(void) | |
3445 | { | |
3446 | WARN_ON(num_online_cpus() != 1); | |
3447 | WARN_ON(nr_context_switches() > 0); | |
3448 | rcu_scheduler_active = 1; | |
3449 | } | |
3450 | ||
64db4cff PM |
3451 | /* |
3452 | * Compute the per-level fanout, either using the exact fanout specified | |
3453 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. | |
3454 | */ | |
3455 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
3456 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
3457 | { | |
3458 | int i; | |
3459 | ||
04f34650 PM |
3460 | rsp->levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf; |
3461 | for (i = rcu_num_lvls - 2; i >= 0; i--) | |
64db4cff PM |
3462 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
3463 | } | |
3464 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
3465 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
3466 | { | |
3467 | int ccur; | |
3468 | int cprv; | |
3469 | int i; | |
3470 | ||
4dbd6bb3 | 3471 | cprv = nr_cpu_ids; |
f885b7f2 | 3472 | for (i = rcu_num_lvls - 1; i >= 0; i--) { |
64db4cff PM |
3473 | ccur = rsp->levelcnt[i]; |
3474 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; | |
3475 | cprv = ccur; | |
3476 | } | |
3477 | } | |
3478 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
3479 | ||
3480 | /* | |
3481 | * Helper function for rcu_init() that initializes one rcu_state structure. | |
3482 | */ | |
394f99a9 LJ |
3483 | static void __init rcu_init_one(struct rcu_state *rsp, |
3484 | struct rcu_data __percpu *rda) | |
64db4cff | 3485 | { |
394f2769 PM |
3486 | static char *buf[] = { "rcu_node_0", |
3487 | "rcu_node_1", | |
3488 | "rcu_node_2", | |
3489 | "rcu_node_3" }; /* Match MAX_RCU_LVLS */ | |
3490 | static char *fqs[] = { "rcu_node_fqs_0", | |
3491 | "rcu_node_fqs_1", | |
3492 | "rcu_node_fqs_2", | |
3493 | "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */ | |
64db4cff PM |
3494 | int cpustride = 1; |
3495 | int i; | |
3496 | int j; | |
3497 | struct rcu_node *rnp; | |
3498 | ||
b6407e86 PM |
3499 | BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
3500 | ||
4930521a PM |
3501 | /* Silence gcc 4.8 warning about array index out of range. */ |
3502 | if (rcu_num_lvls > RCU_NUM_LVLS) | |
3503 | panic("rcu_init_one: rcu_num_lvls overflow"); | |
3504 | ||
64db4cff PM |
3505 | /* Initialize the level-tracking arrays. */ |
3506 | ||
f885b7f2 PM |
3507 | for (i = 0; i < rcu_num_lvls; i++) |
3508 | rsp->levelcnt[i] = num_rcu_lvl[i]; | |
3509 | for (i = 1; i < rcu_num_lvls; i++) | |
64db4cff PM |
3510 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; |
3511 | rcu_init_levelspread(rsp); | |
3512 | ||
3513 | /* Initialize the elements themselves, starting from the leaves. */ | |
3514 | ||
f885b7f2 | 3515 | for (i = rcu_num_lvls - 1; i >= 0; i--) { |
64db4cff PM |
3516 | cpustride *= rsp->levelspread[i]; |
3517 | rnp = rsp->level[i]; | |
3518 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { | |
1304afb2 | 3519 | raw_spin_lock_init(&rnp->lock); |
b6407e86 PM |
3520 | lockdep_set_class_and_name(&rnp->lock, |
3521 | &rcu_node_class[i], buf[i]); | |
394f2769 PM |
3522 | raw_spin_lock_init(&rnp->fqslock); |
3523 | lockdep_set_class_and_name(&rnp->fqslock, | |
3524 | &rcu_fqs_class[i], fqs[i]); | |
25d30cf4 PM |
3525 | rnp->gpnum = rsp->gpnum; |
3526 | rnp->completed = rsp->completed; | |
64db4cff PM |
3527 | rnp->qsmask = 0; |
3528 | rnp->qsmaskinit = 0; | |
3529 | rnp->grplo = j * cpustride; | |
3530 | rnp->grphi = (j + 1) * cpustride - 1; | |
595f3900 HS |
3531 | if (rnp->grphi >= nr_cpu_ids) |
3532 | rnp->grphi = nr_cpu_ids - 1; | |
64db4cff PM |
3533 | if (i == 0) { |
3534 | rnp->grpnum = 0; | |
3535 | rnp->grpmask = 0; | |
3536 | rnp->parent = NULL; | |
3537 | } else { | |
3538 | rnp->grpnum = j % rsp->levelspread[i - 1]; | |
3539 | rnp->grpmask = 1UL << rnp->grpnum; | |
3540 | rnp->parent = rsp->level[i - 1] + | |
3541 | j / rsp->levelspread[i - 1]; | |
3542 | } | |
3543 | rnp->level = i; | |
12f5f524 | 3544 | INIT_LIST_HEAD(&rnp->blkd_tasks); |
dae6e64d | 3545 | rcu_init_one_nocb(rnp); |
64db4cff PM |
3546 | } |
3547 | } | |
0c34029a | 3548 | |
394f99a9 | 3549 | rsp->rda = rda; |
b3dbec76 | 3550 | init_waitqueue_head(&rsp->gp_wq); |
f885b7f2 | 3551 | rnp = rsp->level[rcu_num_lvls - 1]; |
0c34029a | 3552 | for_each_possible_cpu(i) { |
4a90a068 | 3553 | while (i > rnp->grphi) |
0c34029a | 3554 | rnp++; |
394f99a9 | 3555 | per_cpu_ptr(rsp->rda, i)->mynode = rnp; |
0c34029a LJ |
3556 | rcu_boot_init_percpu_data(i, rsp); |
3557 | } | |
6ce75a23 | 3558 | list_add(&rsp->flavors, &rcu_struct_flavors); |
64db4cff PM |
3559 | } |
3560 | ||
f885b7f2 PM |
3561 | /* |
3562 | * Compute the rcu_node tree geometry from kernel parameters. This cannot | |
4102adab | 3563 | * replace the definitions in tree.h because those are needed to size |
f885b7f2 PM |
3564 | * the ->node array in the rcu_state structure. |
3565 | */ | |
3566 | static void __init rcu_init_geometry(void) | |
3567 | { | |
026ad283 | 3568 | ulong d; |
f885b7f2 PM |
3569 | int i; |
3570 | int j; | |
cca6f393 | 3571 | int n = nr_cpu_ids; |
f885b7f2 PM |
3572 | int rcu_capacity[MAX_RCU_LVLS + 1]; |
3573 | ||
026ad283 PM |
3574 | /* |
3575 | * Initialize any unspecified boot parameters. | |
3576 | * The default values of jiffies_till_first_fqs and | |
3577 | * jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS | |
3578 | * value, which is a function of HZ, then adding one for each | |
3579 | * RCU_JIFFIES_FQS_DIV CPUs that might be on the system. | |
3580 | */ | |
3581 | d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV; | |
3582 | if (jiffies_till_first_fqs == ULONG_MAX) | |
3583 | jiffies_till_first_fqs = d; | |
3584 | if (jiffies_till_next_fqs == ULONG_MAX) | |
3585 | jiffies_till_next_fqs = d; | |
3586 | ||
f885b7f2 | 3587 | /* If the compile-time values are accurate, just leave. */ |
b17c7035 PM |
3588 | if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF && |
3589 | nr_cpu_ids == NR_CPUS) | |
f885b7f2 | 3590 | return; |
39479098 PM |
3591 | pr_info("RCU: Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%d\n", |
3592 | rcu_fanout_leaf, nr_cpu_ids); | |
f885b7f2 PM |
3593 | |
3594 | /* | |
3595 | * Compute number of nodes that can be handled an rcu_node tree | |
3596 | * with the given number of levels. Setting rcu_capacity[0] makes | |
3597 | * some of the arithmetic easier. | |
3598 | */ | |
3599 | rcu_capacity[0] = 1; | |
3600 | rcu_capacity[1] = rcu_fanout_leaf; | |
3601 | for (i = 2; i <= MAX_RCU_LVLS; i++) | |
3602 | rcu_capacity[i] = rcu_capacity[i - 1] * CONFIG_RCU_FANOUT; | |
3603 | ||
3604 | /* | |
3605 | * The boot-time rcu_fanout_leaf parameter is only permitted | |
3606 | * to increase the leaf-level fanout, not decrease it. Of course, | |
3607 | * the leaf-level fanout cannot exceed the number of bits in | |
3608 | * the rcu_node masks. Finally, the tree must be able to accommodate | |
3609 | * the configured number of CPUs. Complain and fall back to the | |
3610 | * compile-time values if these limits are exceeded. | |
3611 | */ | |
3612 | if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF || | |
3613 | rcu_fanout_leaf > sizeof(unsigned long) * 8 || | |
3614 | n > rcu_capacity[MAX_RCU_LVLS]) { | |
3615 | WARN_ON(1); | |
3616 | return; | |
3617 | } | |
3618 | ||
3619 | /* Calculate the number of rcu_nodes at each level of the tree. */ | |
3620 | for (i = 1; i <= MAX_RCU_LVLS; i++) | |
3621 | if (n <= rcu_capacity[i]) { | |
3622 | for (j = 0; j <= i; j++) | |
3623 | num_rcu_lvl[j] = | |
3624 | DIV_ROUND_UP(n, rcu_capacity[i - j]); | |
3625 | rcu_num_lvls = i; | |
3626 | for (j = i + 1; j <= MAX_RCU_LVLS; j++) | |
3627 | num_rcu_lvl[j] = 0; | |
3628 | break; | |
3629 | } | |
3630 | ||
3631 | /* Calculate the total number of rcu_node structures. */ | |
3632 | rcu_num_nodes = 0; | |
3633 | for (i = 0; i <= MAX_RCU_LVLS; i++) | |
3634 | rcu_num_nodes += num_rcu_lvl[i]; | |
3635 | rcu_num_nodes -= n; | |
3636 | } | |
3637 | ||
9f680ab4 | 3638 | void __init rcu_init(void) |
64db4cff | 3639 | { |
017c4261 | 3640 | int cpu; |
9f680ab4 | 3641 | |
f41d911f | 3642 | rcu_bootup_announce(); |
f885b7f2 | 3643 | rcu_init_geometry(); |
394f99a9 | 3644 | rcu_init_one(&rcu_bh_state, &rcu_bh_data); |
69c8d28c | 3645 | rcu_init_one(&rcu_sched_state, &rcu_sched_data); |
f41d911f | 3646 | __rcu_init_preempt(); |
b5b39360 | 3647 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
9f680ab4 PM |
3648 | |
3649 | /* | |
3650 | * We don't need protection against CPU-hotplug here because | |
3651 | * this is called early in boot, before either interrupts | |
3652 | * or the scheduler are operational. | |
3653 | */ | |
3654 | cpu_notifier(rcu_cpu_notify, 0); | |
d1d74d14 | 3655 | pm_notifier(rcu_pm_notify, 0); |
017c4261 PM |
3656 | for_each_online_cpu(cpu) |
3657 | rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); | |
64db4cff PM |
3658 | } |
3659 | ||
4102adab | 3660 | #include "tree_plugin.h" |