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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 | |
15 | * along with this program; if not, write to the Free Software | |
16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
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> | |
44 | #include <linux/percpu.h> | |
45 | #include <linux/notifier.h> | |
46 | #include <linux/cpu.h> | |
47 | #include <linux/mutex.h> | |
48 | #include <linux/time.h> | |
bbad9379 | 49 | #include <linux/kernel_stat.h> |
a26ac245 PM |
50 | #include <linux/wait.h> |
51 | #include <linux/kthread.h> | |
268bb0ce | 52 | #include <linux/prefetch.h> |
3d3b7db0 PM |
53 | #include <linux/delay.h> |
54 | #include <linux/stop_machine.h> | |
661a85dc | 55 | #include <linux/random.h> |
f7f7bac9 | 56 | #include <linux/ftrace_event.h> |
64db4cff | 57 | |
9f77da9f | 58 | #include "rcutree.h" |
29c00b4a PM |
59 | #include <trace/events/rcu.h> |
60 | ||
61 | #include "rcu.h" | |
9f77da9f | 62 | |
f7f7bac9 SRRH |
63 | /* |
64 | * Strings used in tracepoints need to be exported via the | |
65 | * tracing system such that tools like perf and trace-cmd can | |
66 | * translate the string address pointers to actual text. | |
67 | */ | |
68 | #define TPS(x) tracepoint_string(x) | |
69 | ||
64db4cff PM |
70 | /* Data structures. */ |
71 | ||
f885b7f2 | 72 | static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; |
394f2769 | 73 | static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; |
88b91c7c | 74 | |
f7f7bac9 SRRH |
75 | /* |
76 | * In order to export the rcu_state name to the tracing tools, it | |
77 | * needs to be added in the __tracepoint_string section. | |
78 | * This requires defining a separate variable tp_<sname>_varname | |
79 | * that points to the string being used, and this will allow | |
80 | * the tracing userspace tools to be able to decipher the string | |
81 | * address to the matching string. | |
82 | */ | |
a41bfeb2 | 83 | #define RCU_STATE_INITIALIZER(sname, sabbr, cr) \ |
f7f7bac9 SRRH |
84 | static char sname##_varname[] = #sname; \ |
85 | static const char *tp_##sname##_varname __used __tracepoint_string = sname##_varname; \ | |
a41bfeb2 | 86 | struct rcu_state sname##_state = { \ |
6c90cc7b | 87 | .level = { &sname##_state.node[0] }, \ |
037b64ed | 88 | .call = cr, \ |
af446b70 | 89 | .fqs_state = RCU_GP_IDLE, \ |
42c3533e PM |
90 | .gpnum = 0UL - 300UL, \ |
91 | .completed = 0UL - 300UL, \ | |
7b2e6011 | 92 | .orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \ |
6c90cc7b PM |
93 | .orphan_nxttail = &sname##_state.orphan_nxtlist, \ |
94 | .orphan_donetail = &sname##_state.orphan_donelist, \ | |
7be7f0be | 95 | .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \ |
a4fbe35a | 96 | .onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \ |
f7f7bac9 | 97 | .name = sname##_varname, \ |
a4889858 | 98 | .abbr = sabbr, \ |
a41bfeb2 SRRH |
99 | }; \ |
100 | DEFINE_PER_CPU(struct rcu_data, sname##_data) | |
64db4cff | 101 | |
a41bfeb2 SRRH |
102 | RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched); |
103 | RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh); | |
b1f77b05 | 104 | |
27f4d280 | 105 | static struct rcu_state *rcu_state; |
6ce75a23 | 106 | LIST_HEAD(rcu_struct_flavors); |
27f4d280 | 107 | |
f885b7f2 PM |
108 | /* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */ |
109 | static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF; | |
7e5c2dfb | 110 | module_param(rcu_fanout_leaf, int, 0444); |
f885b7f2 PM |
111 | int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; |
112 | static int num_rcu_lvl[] = { /* Number of rcu_nodes at specified level. */ | |
113 | NUM_RCU_LVL_0, | |
114 | NUM_RCU_LVL_1, | |
115 | NUM_RCU_LVL_2, | |
116 | NUM_RCU_LVL_3, | |
117 | NUM_RCU_LVL_4, | |
118 | }; | |
119 | int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ | |
120 | ||
b0d30417 PM |
121 | /* |
122 | * The rcu_scheduler_active variable transitions from zero to one just | |
123 | * before the first task is spawned. So when this variable is zero, RCU | |
124 | * can assume that there is but one task, allowing RCU to (for example) | |
b44f6656 | 125 | * optimize synchronize_sched() to a simple barrier(). When this variable |
b0d30417 PM |
126 | * is one, RCU must actually do all the hard work required to detect real |
127 | * grace periods. This variable is also used to suppress boot-time false | |
128 | * positives from lockdep-RCU error checking. | |
129 | */ | |
bbad9379 PM |
130 | int rcu_scheduler_active __read_mostly; |
131 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
132 | ||
b0d30417 PM |
133 | /* |
134 | * The rcu_scheduler_fully_active variable transitions from zero to one | |
135 | * during the early_initcall() processing, which is after the scheduler | |
136 | * is capable of creating new tasks. So RCU processing (for example, | |
137 | * creating tasks for RCU priority boosting) must be delayed until after | |
138 | * rcu_scheduler_fully_active transitions from zero to one. We also | |
139 | * currently delay invocation of any RCU callbacks until after this point. | |
140 | * | |
141 | * It might later prove better for people registering RCU callbacks during | |
142 | * early boot to take responsibility for these callbacks, but one step at | |
143 | * a time. | |
144 | */ | |
145 | static int rcu_scheduler_fully_active __read_mostly; | |
146 | ||
a46e0899 PM |
147 | #ifdef CONFIG_RCU_BOOST |
148 | ||
a26ac245 PM |
149 | /* |
150 | * Control variables for per-CPU and per-rcu_node kthreads. These | |
151 | * handle all flavors of RCU. | |
152 | */ | |
153 | static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); | |
d71df90e | 154 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); |
5ece5bab | 155 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); |
d71df90e | 156 | DEFINE_PER_CPU(char, rcu_cpu_has_work); |
a26ac245 | 157 | |
a46e0899 PM |
158 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
159 | ||
5d01bbd1 | 160 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); |
a46e0899 PM |
161 | static void invoke_rcu_core(void); |
162 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); | |
a26ac245 | 163 | |
4a298656 PM |
164 | /* |
165 | * Track the rcutorture test sequence number and the update version | |
166 | * number within a given test. The rcutorture_testseq is incremented | |
167 | * on every rcutorture module load and unload, so has an odd value | |
168 | * when a test is running. The rcutorture_vernum is set to zero | |
169 | * when rcutorture starts and is incremented on each rcutorture update. | |
170 | * These variables enable correlating rcutorture output with the | |
171 | * RCU tracing information. | |
172 | */ | |
173 | unsigned long rcutorture_testseq; | |
174 | unsigned long rcutorture_vernum; | |
175 | ||
fc2219d4 PM |
176 | /* |
177 | * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s | |
178 | * permit this function to be invoked without holding the root rcu_node | |
179 | * structure's ->lock, but of course results can be subject to change. | |
180 | */ | |
181 | static int rcu_gp_in_progress(struct rcu_state *rsp) | |
182 | { | |
183 | return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); | |
184 | } | |
185 | ||
b1f77b05 | 186 | /* |
d6714c22 | 187 | * Note a quiescent state. Because we do not need to know |
b1f77b05 | 188 | * how many quiescent states passed, just if there was at least |
d6714c22 | 189 | * one since the start of the grace period, this just sets a flag. |
e4cc1f22 | 190 | * The caller must have disabled preemption. |
b1f77b05 | 191 | */ |
d6714c22 | 192 | void rcu_sched_qs(int cpu) |
b1f77b05 | 193 | { |
25502a6c | 194 | struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); |
f41d911f | 195 | |
e4cc1f22 | 196 | if (rdp->passed_quiesce == 0) |
f7f7bac9 | 197 | trace_rcu_grace_period(TPS("rcu_sched"), rdp->gpnum, TPS("cpuqs")); |
e4cc1f22 | 198 | rdp->passed_quiesce = 1; |
b1f77b05 IM |
199 | } |
200 | ||
d6714c22 | 201 | void rcu_bh_qs(int cpu) |
b1f77b05 | 202 | { |
25502a6c | 203 | struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
f41d911f | 204 | |
e4cc1f22 | 205 | if (rdp->passed_quiesce == 0) |
f7f7bac9 | 206 | trace_rcu_grace_period(TPS("rcu_bh"), rdp->gpnum, TPS("cpuqs")); |
e4cc1f22 | 207 | rdp->passed_quiesce = 1; |
b1f77b05 | 208 | } |
64db4cff | 209 | |
25502a6c PM |
210 | /* |
211 | * Note a context switch. This is a quiescent state for RCU-sched, | |
212 | * and requires special handling for preemptible RCU. | |
e4cc1f22 | 213 | * The caller must have disabled preemption. |
25502a6c PM |
214 | */ |
215 | void rcu_note_context_switch(int cpu) | |
216 | { | |
f7f7bac9 | 217 | trace_rcu_utilization(TPS("Start context switch")); |
25502a6c | 218 | rcu_sched_qs(cpu); |
cba6d0d6 | 219 | rcu_preempt_note_context_switch(cpu); |
f7f7bac9 | 220 | trace_rcu_utilization(TPS("End context switch")); |
25502a6c | 221 | } |
29ce8310 | 222 | EXPORT_SYMBOL_GPL(rcu_note_context_switch); |
25502a6c | 223 | |
90a4d2c0 | 224 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
29e37d81 | 225 | .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, |
23b5c8fa | 226 | .dynticks = ATOMIC_INIT(1), |
2333210b PM |
227 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE |
228 | .dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE, | |
229 | .dynticks_idle = ATOMIC_INIT(1), | |
230 | #endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ | |
90a4d2c0 | 231 | }; |
64db4cff | 232 | |
878d7439 ED |
233 | static long blimit = 10; /* Maximum callbacks per rcu_do_batch. */ |
234 | static long qhimark = 10000; /* If this many pending, ignore blimit. */ | |
235 | static long qlowmark = 100; /* Once only this many pending, use blimit. */ | |
64db4cff | 236 | |
878d7439 ED |
237 | module_param(blimit, long, 0444); |
238 | module_param(qhimark, long, 0444); | |
239 | module_param(qlowmark, long, 0444); | |
3d76c082 | 240 | |
026ad283 PM |
241 | static ulong jiffies_till_first_fqs = ULONG_MAX; |
242 | static ulong jiffies_till_next_fqs = ULONG_MAX; | |
d40011f6 PM |
243 | |
244 | module_param(jiffies_till_first_fqs, ulong, 0644); | |
245 | module_param(jiffies_till_next_fqs, ulong, 0644); | |
246 | ||
910ee45d PM |
247 | static void rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, |
248 | struct rcu_data *rdp); | |
4cdfc175 PM |
249 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)); |
250 | static void force_quiescent_state(struct rcu_state *rsp); | |
a157229c | 251 | static int rcu_pending(int cpu); |
64db4cff PM |
252 | |
253 | /* | |
d6714c22 | 254 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
64db4cff | 255 | */ |
d6714c22 | 256 | long rcu_batches_completed_sched(void) |
64db4cff | 257 | { |
d6714c22 | 258 | return rcu_sched_state.completed; |
64db4cff | 259 | } |
d6714c22 | 260 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
64db4cff PM |
261 | |
262 | /* | |
263 | * Return the number of RCU BH batches processed thus far for debug & stats. | |
264 | */ | |
265 | long rcu_batches_completed_bh(void) | |
266 | { | |
267 | return rcu_bh_state.completed; | |
268 | } | |
269 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
270 | ||
bf66f18e PM |
271 | /* |
272 | * Force a quiescent state for RCU BH. | |
273 | */ | |
274 | void rcu_bh_force_quiescent_state(void) | |
275 | { | |
4cdfc175 | 276 | force_quiescent_state(&rcu_bh_state); |
bf66f18e PM |
277 | } |
278 | EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); | |
279 | ||
4a298656 PM |
280 | /* |
281 | * Record the number of times rcutorture tests have been initiated and | |
282 | * terminated. This information allows the debugfs tracing stats to be | |
283 | * correlated to the rcutorture messages, even when the rcutorture module | |
284 | * is being repeatedly loaded and unloaded. In other words, we cannot | |
285 | * store this state in rcutorture itself. | |
286 | */ | |
287 | void rcutorture_record_test_transition(void) | |
288 | { | |
289 | rcutorture_testseq++; | |
290 | rcutorture_vernum = 0; | |
291 | } | |
292 | EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); | |
293 | ||
294 | /* | |
295 | * Record the number of writer passes through the current rcutorture test. | |
296 | * This is also used to correlate debugfs tracing stats with the rcutorture | |
297 | * messages. | |
298 | */ | |
299 | void rcutorture_record_progress(unsigned long vernum) | |
300 | { | |
301 | rcutorture_vernum++; | |
302 | } | |
303 | EXPORT_SYMBOL_GPL(rcutorture_record_progress); | |
304 | ||
bf66f18e PM |
305 | /* |
306 | * Force a quiescent state for RCU-sched. | |
307 | */ | |
308 | void rcu_sched_force_quiescent_state(void) | |
309 | { | |
4cdfc175 | 310 | force_quiescent_state(&rcu_sched_state); |
bf66f18e PM |
311 | } |
312 | EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); | |
313 | ||
64db4cff PM |
314 | /* |
315 | * Does the CPU have callbacks ready to be invoked? | |
316 | */ | |
317 | static int | |
318 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) | |
319 | { | |
3fbfbf7a PM |
320 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL] && |
321 | rdp->nxttail[RCU_DONE_TAIL] != NULL; | |
64db4cff PM |
322 | } |
323 | ||
324 | /* | |
dc35c893 PM |
325 | * Does the current CPU require a not-yet-started grace period? |
326 | * The caller must have disabled interrupts to prevent races with | |
327 | * normal callback registry. | |
64db4cff PM |
328 | */ |
329 | static int | |
330 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) | |
331 | { | |
dc35c893 | 332 | int i; |
3fbfbf7a | 333 | |
dc35c893 PM |
334 | if (rcu_gp_in_progress(rsp)) |
335 | return 0; /* No, a grace period is already in progress. */ | |
dae6e64d | 336 | if (rcu_nocb_needs_gp(rsp)) |
34ed6246 | 337 | return 1; /* Yes, a no-CBs CPU needs one. */ |
dc35c893 PM |
338 | if (!rdp->nxttail[RCU_NEXT_TAIL]) |
339 | return 0; /* No, this is a no-CBs (or offline) CPU. */ | |
340 | if (*rdp->nxttail[RCU_NEXT_READY_TAIL]) | |
341 | return 1; /* Yes, this CPU has newly registered callbacks. */ | |
342 | for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) | |
343 | if (rdp->nxttail[i - 1] != rdp->nxttail[i] && | |
344 | ULONG_CMP_LT(ACCESS_ONCE(rsp->completed), | |
345 | rdp->nxtcompleted[i])) | |
346 | return 1; /* Yes, CBs for future grace period. */ | |
347 | return 0; /* No grace period needed. */ | |
64db4cff PM |
348 | } |
349 | ||
350 | /* | |
351 | * Return the root node of the specified rcu_state structure. | |
352 | */ | |
353 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) | |
354 | { | |
355 | return &rsp->node[0]; | |
356 | } | |
357 | ||
9b2e4f18 | 358 | /* |
adf5091e | 359 | * rcu_eqs_enter_common - current CPU is moving towards extended quiescent state |
9b2e4f18 PM |
360 | * |
361 | * If the new value of the ->dynticks_nesting counter now is zero, | |
362 | * we really have entered idle, and must do the appropriate accounting. | |
363 | * The caller must have disabled interrupts. | |
364 | */ | |
adf5091e FW |
365 | static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval, |
366 | bool user) | |
9b2e4f18 | 367 | { |
f7f7bac9 | 368 | trace_rcu_dyntick(TPS("Start"), oldval, rdtp->dynticks_nesting); |
cb349ca9 | 369 | if (!user && !is_idle_task(current)) { |
0989cb46 PM |
370 | struct task_struct *idle = idle_task(smp_processor_id()); |
371 | ||
f7f7bac9 | 372 | trace_rcu_dyntick(TPS("Error on entry: not idle task"), oldval, 0); |
bf1304e9 | 373 | ftrace_dump(DUMP_ORIG); |
0989cb46 PM |
374 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
375 | current->pid, current->comm, | |
376 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 | 377 | } |
aea1b35e | 378 | rcu_prepare_for_idle(smp_processor_id()); |
9b2e4f18 PM |
379 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
380 | smp_mb__before_atomic_inc(); /* See above. */ | |
381 | atomic_inc(&rdtp->dynticks); | |
382 | smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */ | |
383 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); | |
c44e2cdd PM |
384 | |
385 | /* | |
adf5091e | 386 | * It is illegal to enter an extended quiescent state while |
c44e2cdd PM |
387 | * in an RCU read-side critical section. |
388 | */ | |
389 | rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), | |
390 | "Illegal idle entry in RCU read-side critical section."); | |
391 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), | |
392 | "Illegal idle entry in RCU-bh read-side critical section."); | |
393 | rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), | |
394 | "Illegal idle entry in RCU-sched read-side critical section."); | |
9b2e4f18 | 395 | } |
64db4cff | 396 | |
adf5091e FW |
397 | /* |
398 | * Enter an RCU extended quiescent state, which can be either the | |
399 | * idle loop or adaptive-tickless usermode execution. | |
64db4cff | 400 | */ |
adf5091e | 401 | static void rcu_eqs_enter(bool user) |
64db4cff | 402 | { |
4145fa7f | 403 | long long oldval; |
64db4cff PM |
404 | struct rcu_dynticks *rdtp; |
405 | ||
64db4cff | 406 | rdtp = &__get_cpu_var(rcu_dynticks); |
4145fa7f | 407 | oldval = rdtp->dynticks_nesting; |
29e37d81 PM |
408 | WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0); |
409 | if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) | |
410 | rdtp->dynticks_nesting = 0; | |
411 | else | |
412 | rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE; | |
adf5091e | 413 | rcu_eqs_enter_common(rdtp, oldval, user); |
64db4cff | 414 | } |
adf5091e FW |
415 | |
416 | /** | |
417 | * rcu_idle_enter - inform RCU that current CPU is entering idle | |
418 | * | |
419 | * Enter idle mode, in other words, -leave- the mode in which RCU | |
420 | * read-side critical sections can occur. (Though RCU read-side | |
421 | * critical sections can occur in irq handlers in idle, a possibility | |
422 | * handled by irq_enter() and irq_exit().) | |
423 | * | |
424 | * We crowbar the ->dynticks_nesting field to zero to allow for | |
425 | * the possibility of usermode upcalls having messed up our count | |
426 | * of interrupt nesting level during the prior busy period. | |
427 | */ | |
428 | void rcu_idle_enter(void) | |
429 | { | |
c5d900bf FW |
430 | unsigned long flags; |
431 | ||
432 | local_irq_save(flags); | |
cb349ca9 | 433 | rcu_eqs_enter(false); |
c5d900bf | 434 | local_irq_restore(flags); |
adf5091e | 435 | } |
8a2ecf47 | 436 | EXPORT_SYMBOL_GPL(rcu_idle_enter); |
64db4cff | 437 | |
2b1d5024 | 438 | #ifdef CONFIG_RCU_USER_QS |
adf5091e FW |
439 | /** |
440 | * rcu_user_enter - inform RCU that we are resuming userspace. | |
441 | * | |
442 | * Enter RCU idle mode right before resuming userspace. No use of RCU | |
443 | * is permitted between this call and rcu_user_exit(). This way the | |
444 | * CPU doesn't need to maintain the tick for RCU maintenance purposes | |
445 | * when the CPU runs in userspace. | |
446 | */ | |
447 | void rcu_user_enter(void) | |
448 | { | |
91d1aa43 | 449 | rcu_eqs_enter(1); |
adf5091e | 450 | } |
2b1d5024 | 451 | #endif /* CONFIG_RCU_USER_QS */ |
19dd1591 | 452 | |
9b2e4f18 PM |
453 | /** |
454 | * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle | |
455 | * | |
456 | * Exit from an interrupt handler, which might possibly result in entering | |
457 | * idle mode, in other words, leaving the mode in which read-side critical | |
458 | * sections can occur. | |
64db4cff | 459 | * |
9b2e4f18 PM |
460 | * This code assumes that the idle loop never does anything that might |
461 | * result in unbalanced calls to irq_enter() and irq_exit(). If your | |
462 | * architecture violates this assumption, RCU will give you what you | |
463 | * deserve, good and hard. But very infrequently and irreproducibly. | |
464 | * | |
465 | * Use things like work queues to work around this limitation. | |
466 | * | |
467 | * You have been warned. | |
64db4cff | 468 | */ |
9b2e4f18 | 469 | void rcu_irq_exit(void) |
64db4cff PM |
470 | { |
471 | unsigned long flags; | |
4145fa7f | 472 | long long oldval; |
64db4cff PM |
473 | struct rcu_dynticks *rdtp; |
474 | ||
475 | local_irq_save(flags); | |
476 | rdtp = &__get_cpu_var(rcu_dynticks); | |
4145fa7f | 477 | oldval = rdtp->dynticks_nesting; |
9b2e4f18 PM |
478 | rdtp->dynticks_nesting--; |
479 | WARN_ON_ONCE(rdtp->dynticks_nesting < 0); | |
b6fc6020 | 480 | if (rdtp->dynticks_nesting) |
f7f7bac9 | 481 | trace_rcu_dyntick(TPS("--="), oldval, rdtp->dynticks_nesting); |
b6fc6020 | 482 | else |
cb349ca9 | 483 | rcu_eqs_enter_common(rdtp, oldval, true); |
9b2e4f18 PM |
484 | local_irq_restore(flags); |
485 | } | |
486 | ||
487 | /* | |
adf5091e | 488 | * rcu_eqs_exit_common - current CPU moving away from extended quiescent state |
9b2e4f18 PM |
489 | * |
490 | * If the new value of the ->dynticks_nesting counter was previously zero, | |
491 | * we really have exited idle, and must do the appropriate accounting. | |
492 | * The caller must have disabled interrupts. | |
493 | */ | |
adf5091e FW |
494 | static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval, |
495 | int user) | |
9b2e4f18 | 496 | { |
23b5c8fa PM |
497 | smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */ |
498 | atomic_inc(&rdtp->dynticks); | |
499 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
500 | smp_mb__after_atomic_inc(); /* See above. */ | |
501 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
7cb92499 | 502 | rcu_cleanup_after_idle(smp_processor_id()); |
f7f7bac9 | 503 | trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting); |
cb349ca9 | 504 | if (!user && !is_idle_task(current)) { |
0989cb46 PM |
505 | struct task_struct *idle = idle_task(smp_processor_id()); |
506 | ||
f7f7bac9 | 507 | trace_rcu_dyntick(TPS("Error on exit: not idle task"), |
4145fa7f | 508 | oldval, rdtp->dynticks_nesting); |
bf1304e9 | 509 | ftrace_dump(DUMP_ORIG); |
0989cb46 PM |
510 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
511 | current->pid, current->comm, | |
512 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 PM |
513 | } |
514 | } | |
515 | ||
adf5091e FW |
516 | /* |
517 | * Exit an RCU extended quiescent state, which can be either the | |
518 | * idle loop or adaptive-tickless usermode execution. | |
9b2e4f18 | 519 | */ |
adf5091e | 520 | static void rcu_eqs_exit(bool user) |
9b2e4f18 | 521 | { |
9b2e4f18 PM |
522 | struct rcu_dynticks *rdtp; |
523 | long long oldval; | |
524 | ||
9b2e4f18 PM |
525 | rdtp = &__get_cpu_var(rcu_dynticks); |
526 | oldval = rdtp->dynticks_nesting; | |
29e37d81 PM |
527 | WARN_ON_ONCE(oldval < 0); |
528 | if (oldval & DYNTICK_TASK_NEST_MASK) | |
529 | rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE; | |
530 | else | |
531 | rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; | |
adf5091e | 532 | rcu_eqs_exit_common(rdtp, oldval, user); |
9b2e4f18 | 533 | } |
adf5091e FW |
534 | |
535 | /** | |
536 | * rcu_idle_exit - inform RCU that current CPU is leaving idle | |
537 | * | |
538 | * Exit idle mode, in other words, -enter- the mode in which RCU | |
539 | * read-side critical sections can occur. | |
540 | * | |
541 | * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to | |
542 | * allow for the possibility of usermode upcalls messing up our count | |
543 | * of interrupt nesting level during the busy period that is just | |
544 | * now starting. | |
545 | */ | |
546 | void rcu_idle_exit(void) | |
547 | { | |
c5d900bf FW |
548 | unsigned long flags; |
549 | ||
550 | local_irq_save(flags); | |
cb349ca9 | 551 | rcu_eqs_exit(false); |
c5d900bf | 552 | local_irq_restore(flags); |
adf5091e | 553 | } |
8a2ecf47 | 554 | EXPORT_SYMBOL_GPL(rcu_idle_exit); |
9b2e4f18 | 555 | |
2b1d5024 | 556 | #ifdef CONFIG_RCU_USER_QS |
adf5091e FW |
557 | /** |
558 | * rcu_user_exit - inform RCU that we are exiting userspace. | |
559 | * | |
560 | * Exit RCU idle mode while entering the kernel because it can | |
561 | * run a RCU read side critical section anytime. | |
562 | */ | |
563 | void rcu_user_exit(void) | |
564 | { | |
91d1aa43 | 565 | rcu_eqs_exit(1); |
adf5091e | 566 | } |
2b1d5024 | 567 | #endif /* CONFIG_RCU_USER_QS */ |
19dd1591 | 568 | |
9b2e4f18 PM |
569 | /** |
570 | * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle | |
571 | * | |
572 | * Enter an interrupt handler, which might possibly result in exiting | |
573 | * idle mode, in other words, entering the mode in which read-side critical | |
574 | * sections can occur. | |
575 | * | |
576 | * Note that the Linux kernel is fully capable of entering an interrupt | |
577 | * handler that it never exits, for example when doing upcalls to | |
578 | * user mode! This code assumes that the idle loop never does upcalls to | |
579 | * user mode. If your architecture does do upcalls from the idle loop (or | |
580 | * does anything else that results in unbalanced calls to the irq_enter() | |
581 | * and irq_exit() functions), RCU will give you what you deserve, good | |
582 | * and hard. But very infrequently and irreproducibly. | |
583 | * | |
584 | * Use things like work queues to work around this limitation. | |
585 | * | |
586 | * You have been warned. | |
587 | */ | |
588 | void rcu_irq_enter(void) | |
589 | { | |
590 | unsigned long flags; | |
591 | struct rcu_dynticks *rdtp; | |
592 | long long oldval; | |
593 | ||
594 | local_irq_save(flags); | |
595 | rdtp = &__get_cpu_var(rcu_dynticks); | |
596 | oldval = rdtp->dynticks_nesting; | |
597 | rdtp->dynticks_nesting++; | |
598 | WARN_ON_ONCE(rdtp->dynticks_nesting == 0); | |
b6fc6020 | 599 | if (oldval) |
f7f7bac9 | 600 | trace_rcu_dyntick(TPS("++="), oldval, rdtp->dynticks_nesting); |
b6fc6020 | 601 | else |
cb349ca9 | 602 | rcu_eqs_exit_common(rdtp, oldval, true); |
64db4cff | 603 | local_irq_restore(flags); |
64db4cff PM |
604 | } |
605 | ||
606 | /** | |
607 | * rcu_nmi_enter - inform RCU of entry to NMI context | |
608 | * | |
609 | * If the CPU was idle with dynamic ticks active, and there is no | |
610 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
611 | * RCU grace-period handling know that the CPU is active. | |
612 | */ | |
613 | void rcu_nmi_enter(void) | |
614 | { | |
615 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
616 | ||
23b5c8fa PM |
617 | if (rdtp->dynticks_nmi_nesting == 0 && |
618 | (atomic_read(&rdtp->dynticks) & 0x1)) | |
64db4cff | 619 | return; |
23b5c8fa PM |
620 | rdtp->dynticks_nmi_nesting++; |
621 | smp_mb__before_atomic_inc(); /* Force delay from prior write. */ | |
622 | atomic_inc(&rdtp->dynticks); | |
623 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
624 | smp_mb__after_atomic_inc(); /* See above. */ | |
625 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
64db4cff PM |
626 | } |
627 | ||
628 | /** | |
629 | * rcu_nmi_exit - inform RCU of exit from NMI context | |
630 | * | |
631 | * If the CPU was idle with dynamic ticks active, and there is no | |
632 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
633 | * RCU grace-period handling know that the CPU is no longer active. | |
634 | */ | |
635 | void rcu_nmi_exit(void) | |
636 | { | |
637 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
638 | ||
23b5c8fa PM |
639 | if (rdtp->dynticks_nmi_nesting == 0 || |
640 | --rdtp->dynticks_nmi_nesting != 0) | |
64db4cff | 641 | return; |
23b5c8fa PM |
642 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
643 | smp_mb__before_atomic_inc(); /* See above. */ | |
644 | atomic_inc(&rdtp->dynticks); | |
645 | smp_mb__after_atomic_inc(); /* Force delay to next write. */ | |
646 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); | |
64db4cff PM |
647 | } |
648 | ||
649 | /** | |
9b2e4f18 | 650 | * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle |
64db4cff | 651 | * |
9b2e4f18 | 652 | * If the current CPU is in its idle loop and is neither in an interrupt |
34240697 | 653 | * or NMI handler, return true. |
64db4cff | 654 | */ |
9b2e4f18 | 655 | int rcu_is_cpu_idle(void) |
64db4cff | 656 | { |
34240697 PM |
657 | int ret; |
658 | ||
659 | preempt_disable(); | |
660 | ret = (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0; | |
661 | preempt_enable(); | |
662 | return ret; | |
64db4cff | 663 | } |
e6b80a3b | 664 | EXPORT_SYMBOL(rcu_is_cpu_idle); |
64db4cff | 665 | |
62fde6ed | 666 | #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) |
c0d6d01b PM |
667 | |
668 | /* | |
669 | * Is the current CPU online? Disable preemption to avoid false positives | |
670 | * that could otherwise happen due to the current CPU number being sampled, | |
671 | * this task being preempted, its old CPU being taken offline, resuming | |
672 | * on some other CPU, then determining that its old CPU is now offline. | |
673 | * It is OK to use RCU on an offline processor during initial boot, hence | |
2036d94a PM |
674 | * the check for rcu_scheduler_fully_active. Note also that it is OK |
675 | * for a CPU coming online to use RCU for one jiffy prior to marking itself | |
676 | * online in the cpu_online_mask. Similarly, it is OK for a CPU going | |
677 | * offline to continue to use RCU for one jiffy after marking itself | |
678 | * offline in the cpu_online_mask. This leniency is necessary given the | |
679 | * non-atomic nature of the online and offline processing, for example, | |
680 | * the fact that a CPU enters the scheduler after completing the CPU_DYING | |
681 | * notifiers. | |
682 | * | |
683 | * This is also why RCU internally marks CPUs online during the | |
684 | * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase. | |
c0d6d01b PM |
685 | * |
686 | * Disable checking if in an NMI handler because we cannot safely report | |
687 | * errors from NMI handlers anyway. | |
688 | */ | |
689 | bool rcu_lockdep_current_cpu_online(void) | |
690 | { | |
2036d94a PM |
691 | struct rcu_data *rdp; |
692 | struct rcu_node *rnp; | |
c0d6d01b PM |
693 | bool ret; |
694 | ||
695 | if (in_nmi()) | |
696 | return 1; | |
697 | preempt_disable(); | |
2036d94a PM |
698 | rdp = &__get_cpu_var(rcu_sched_data); |
699 | rnp = rdp->mynode; | |
700 | ret = (rdp->grpmask & rnp->qsmaskinit) || | |
c0d6d01b PM |
701 | !rcu_scheduler_fully_active; |
702 | preempt_enable(); | |
703 | return ret; | |
704 | } | |
705 | EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); | |
706 | ||
62fde6ed | 707 | #endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */ |
9b2e4f18 | 708 | |
64db4cff | 709 | /** |
9b2e4f18 | 710 | * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle |
64db4cff | 711 | * |
9b2e4f18 PM |
712 | * If the current CPU is idle or running at a first-level (not nested) |
713 | * interrupt from idle, return true. The caller must have at least | |
714 | * disabled preemption. | |
64db4cff | 715 | */ |
62e3cb14 | 716 | static int rcu_is_cpu_rrupt_from_idle(void) |
64db4cff | 717 | { |
9b2e4f18 | 718 | return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1; |
64db4cff PM |
719 | } |
720 | ||
64db4cff PM |
721 | /* |
722 | * Snapshot the specified CPU's dynticks counter so that we can later | |
723 | * credit them with an implicit quiescent state. Return 1 if this CPU | |
1eba8f84 | 724 | * is in dynticks idle mode, which is an extended quiescent state. |
64db4cff PM |
725 | */ |
726 | static int dyntick_save_progress_counter(struct rcu_data *rdp) | |
727 | { | |
23b5c8fa | 728 | rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); |
f0e7c19d | 729 | return (rdp->dynticks_snap & 0x1) == 0; |
64db4cff PM |
730 | } |
731 | ||
732 | /* | |
733 | * Return true if the specified CPU has passed through a quiescent | |
734 | * state by virtue of being in or having passed through an dynticks | |
735 | * idle state since the last call to dyntick_save_progress_counter() | |
a82dcc76 | 736 | * for this same CPU, or by virtue of having been offline. |
64db4cff PM |
737 | */ |
738 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
739 | { | |
7eb4f455 PM |
740 | unsigned int curr; |
741 | unsigned int snap; | |
64db4cff | 742 | |
7eb4f455 PM |
743 | curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks); |
744 | snap = (unsigned int)rdp->dynticks_snap; | |
64db4cff PM |
745 | |
746 | /* | |
747 | * If the CPU passed through or entered a dynticks idle phase with | |
748 | * no active irq/NMI handlers, then we can safely pretend that the CPU | |
749 | * already acknowledged the request to pass through a quiescent | |
750 | * state. Either way, that CPU cannot possibly be in an RCU | |
751 | * read-side critical section that started before the beginning | |
752 | * of the current RCU grace period. | |
753 | */ | |
7eb4f455 | 754 | if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) { |
f7f7bac9 | 755 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti")); |
64db4cff PM |
756 | rdp->dynticks_fqs++; |
757 | return 1; | |
758 | } | |
759 | ||
a82dcc76 PM |
760 | /* |
761 | * Check for the CPU being offline, but only if the grace period | |
762 | * is old enough. We don't need to worry about the CPU changing | |
763 | * state: If we see it offline even once, it has been through a | |
764 | * quiescent state. | |
765 | * | |
766 | * The reason for insisting that the grace period be at least | |
767 | * one jiffy old is that CPUs that are not quite online and that | |
768 | * have just gone offline can still execute RCU read-side critical | |
769 | * sections. | |
770 | */ | |
771 | if (ULONG_CMP_GE(rdp->rsp->gp_start + 2, jiffies)) | |
772 | return 0; /* Grace period is not old enough. */ | |
773 | barrier(); | |
774 | if (cpu_is_offline(rdp->cpu)) { | |
f7f7bac9 | 775 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("ofl")); |
a82dcc76 PM |
776 | rdp->offline_fqs++; |
777 | return 1; | |
778 | } | |
65d798f0 PM |
779 | |
780 | /* | |
781 | * There is a possibility that a CPU in adaptive-ticks state | |
782 | * might run in the kernel with the scheduling-clock tick disabled | |
783 | * for an extended time period. Invoke rcu_kick_nohz_cpu() to | |
784 | * force the CPU to restart the scheduling-clock tick in this | |
785 | * CPU is in this state. | |
786 | */ | |
787 | rcu_kick_nohz_cpu(rdp->cpu); | |
788 | ||
a82dcc76 | 789 | return 0; |
64db4cff PM |
790 | } |
791 | ||
64db4cff PM |
792 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
793 | { | |
794 | rsp->gp_start = jiffies; | |
6bfc09e2 | 795 | rsp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check(); |
64db4cff PM |
796 | } |
797 | ||
b637a328 PM |
798 | /* |
799 | * Dump stacks of all tasks running on stalled CPUs. This is a fallback | |
800 | * for architectures that do not implement trigger_all_cpu_backtrace(). | |
801 | * The NMI-triggered stack traces are more accurate because they are | |
802 | * printed by the target CPU. | |
803 | */ | |
804 | static void rcu_dump_cpu_stacks(struct rcu_state *rsp) | |
805 | { | |
806 | int cpu; | |
807 | unsigned long flags; | |
808 | struct rcu_node *rnp; | |
809 | ||
810 | rcu_for_each_leaf_node(rsp, rnp) { | |
811 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
812 | if (rnp->qsmask != 0) { | |
813 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) | |
814 | if (rnp->qsmask & (1UL << cpu)) | |
815 | dump_cpu_task(rnp->grplo + cpu); | |
816 | } | |
817 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
818 | } | |
819 | } | |
820 | ||
64db4cff PM |
821 | static void print_other_cpu_stall(struct rcu_state *rsp) |
822 | { | |
823 | int cpu; | |
824 | long delta; | |
825 | unsigned long flags; | |
285fe294 | 826 | int ndetected = 0; |
64db4cff | 827 | struct rcu_node *rnp = rcu_get_root(rsp); |
53bb857c | 828 | long totqlen = 0; |
64db4cff PM |
829 | |
830 | /* Only let one CPU complain about others per time interval. */ | |
831 | ||
1304afb2 | 832 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff | 833 | delta = jiffies - rsp->jiffies_stall; |
fc2219d4 | 834 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
1304afb2 | 835 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
836 | return; |
837 | } | |
6bfc09e2 | 838 | rsp->jiffies_stall = jiffies + 3 * rcu_jiffies_till_stall_check() + 3; |
1304afb2 | 839 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 840 | |
8cdd32a9 PM |
841 | /* |
842 | * OK, time to rat on our buddy... | |
843 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
844 | * RCU CPU stall warnings. | |
845 | */ | |
d7f3e207 | 846 | pr_err("INFO: %s detected stalls on CPUs/tasks:", |
4300aa64 | 847 | rsp->name); |
a858af28 | 848 | print_cpu_stall_info_begin(); |
a0b6c9a7 | 849 | rcu_for_each_leaf_node(rsp, rnp) { |
3acd9eb3 | 850 | raw_spin_lock_irqsave(&rnp->lock, flags); |
9bc8b558 | 851 | ndetected += rcu_print_task_stall(rnp); |
c8020a67 PM |
852 | if (rnp->qsmask != 0) { |
853 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) | |
854 | if (rnp->qsmask & (1UL << cpu)) { | |
855 | print_cpu_stall_info(rsp, | |
856 | rnp->grplo + cpu); | |
857 | ndetected++; | |
858 | } | |
859 | } | |
3acd9eb3 | 860 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 861 | } |
a858af28 PM |
862 | |
863 | /* | |
864 | * Now rat on any tasks that got kicked up to the root rcu_node | |
865 | * due to CPU offlining. | |
866 | */ | |
867 | rnp = rcu_get_root(rsp); | |
868 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
285fe294 | 869 | ndetected += rcu_print_task_stall(rnp); |
a858af28 PM |
870 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
871 | ||
872 | print_cpu_stall_info_end(); | |
53bb857c PM |
873 | for_each_possible_cpu(cpu) |
874 | totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen; | |
875 | pr_cont("(detected by %d, t=%ld jiffies, g=%lu, c=%lu, q=%lu)\n", | |
eee05882 | 876 | smp_processor_id(), (long)(jiffies - rsp->gp_start), |
53bb857c | 877 | rsp->gpnum, rsp->completed, totqlen); |
9bc8b558 | 878 | if (ndetected == 0) |
d7f3e207 | 879 | pr_err("INFO: Stall ended before state dump start\n"); |
9bc8b558 | 880 | else if (!trigger_all_cpu_backtrace()) |
b637a328 | 881 | rcu_dump_cpu_stacks(rsp); |
c1dc0b9c | 882 | |
4cdfc175 | 883 | /* Complain about tasks blocking the grace period. */ |
1ed509a2 PM |
884 | |
885 | rcu_print_detail_task_stall(rsp); | |
886 | ||
4cdfc175 | 887 | force_quiescent_state(rsp); /* Kick them all. */ |
64db4cff PM |
888 | } |
889 | ||
890 | static void print_cpu_stall(struct rcu_state *rsp) | |
891 | { | |
53bb857c | 892 | int cpu; |
64db4cff PM |
893 | unsigned long flags; |
894 | struct rcu_node *rnp = rcu_get_root(rsp); | |
53bb857c | 895 | long totqlen = 0; |
64db4cff | 896 | |
8cdd32a9 PM |
897 | /* |
898 | * OK, time to rat on ourselves... | |
899 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
900 | * RCU CPU stall warnings. | |
901 | */ | |
d7f3e207 | 902 | pr_err("INFO: %s self-detected stall on CPU", rsp->name); |
a858af28 PM |
903 | print_cpu_stall_info_begin(); |
904 | print_cpu_stall_info(rsp, smp_processor_id()); | |
905 | print_cpu_stall_info_end(); | |
53bb857c PM |
906 | for_each_possible_cpu(cpu) |
907 | totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen; | |
908 | pr_cont(" (t=%lu jiffies g=%lu c=%lu q=%lu)\n", | |
909 | jiffies - rsp->gp_start, rsp->gpnum, rsp->completed, totqlen); | |
4627e240 PM |
910 | if (!trigger_all_cpu_backtrace()) |
911 | dump_stack(); | |
c1dc0b9c | 912 | |
1304afb2 | 913 | raw_spin_lock_irqsave(&rnp->lock, flags); |
20133cfc | 914 | if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) |
13cfcca0 | 915 | rsp->jiffies_stall = jiffies + |
6bfc09e2 | 916 | 3 * rcu_jiffies_till_stall_check() + 3; |
1304afb2 | 917 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c1dc0b9c | 918 | |
64db4cff PM |
919 | set_need_resched(); /* kick ourselves to get things going. */ |
920 | } | |
921 | ||
922 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
923 | { | |
bad6e139 PM |
924 | unsigned long j; |
925 | unsigned long js; | |
64db4cff PM |
926 | struct rcu_node *rnp; |
927 | ||
742734ee | 928 | if (rcu_cpu_stall_suppress) |
c68de209 | 929 | return; |
bad6e139 PM |
930 | j = ACCESS_ONCE(jiffies); |
931 | js = ACCESS_ONCE(rsp->jiffies_stall); | |
64db4cff | 932 | rnp = rdp->mynode; |
c96ea7cf PM |
933 | if (rcu_gp_in_progress(rsp) && |
934 | (ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) { | |
64db4cff PM |
935 | |
936 | /* We haven't checked in, so go dump stack. */ | |
937 | print_cpu_stall(rsp); | |
938 | ||
bad6e139 PM |
939 | } else if (rcu_gp_in_progress(rsp) && |
940 | ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) { | |
64db4cff | 941 | |
bad6e139 | 942 | /* They had a few time units to dump stack, so complain. */ |
64db4cff PM |
943 | print_other_cpu_stall(rsp); |
944 | } | |
945 | } | |
946 | ||
53d84e00 PM |
947 | /** |
948 | * rcu_cpu_stall_reset - prevent further stall warnings in current grace period | |
949 | * | |
950 | * Set the stall-warning timeout way off into the future, thus preventing | |
951 | * any RCU CPU stall-warning messages from appearing in the current set of | |
952 | * RCU grace periods. | |
953 | * | |
954 | * The caller must disable hard irqs. | |
955 | */ | |
956 | void rcu_cpu_stall_reset(void) | |
957 | { | |
6ce75a23 PM |
958 | struct rcu_state *rsp; |
959 | ||
960 | for_each_rcu_flavor(rsp) | |
961 | rsp->jiffies_stall = jiffies + ULONG_MAX / 2; | |
53d84e00 PM |
962 | } |
963 | ||
3f5d3ea6 PM |
964 | /* |
965 | * Initialize the specified rcu_data structure's callback list to empty. | |
966 | */ | |
967 | static void init_callback_list(struct rcu_data *rdp) | |
968 | { | |
969 | int i; | |
970 | ||
34ed6246 PM |
971 | if (init_nocb_callback_list(rdp)) |
972 | return; | |
3f5d3ea6 PM |
973 | rdp->nxtlist = NULL; |
974 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
975 | rdp->nxttail[i] = &rdp->nxtlist; | |
976 | } | |
977 | ||
dc35c893 PM |
978 | /* |
979 | * Determine the value that ->completed will have at the end of the | |
980 | * next subsequent grace period. This is used to tag callbacks so that | |
981 | * a CPU can invoke callbacks in a timely fashion even if that CPU has | |
982 | * been dyntick-idle for an extended period with callbacks under the | |
983 | * influence of RCU_FAST_NO_HZ. | |
984 | * | |
985 | * The caller must hold rnp->lock with interrupts disabled. | |
986 | */ | |
987 | static unsigned long rcu_cbs_completed(struct rcu_state *rsp, | |
988 | struct rcu_node *rnp) | |
989 | { | |
990 | /* | |
991 | * If RCU is idle, we just wait for the next grace period. | |
992 | * But we can only be sure that RCU is idle if we are looking | |
993 | * at the root rcu_node structure -- otherwise, a new grace | |
994 | * period might have started, but just not yet gotten around | |
995 | * to initializing the current non-root rcu_node structure. | |
996 | */ | |
997 | if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed) | |
998 | return rnp->completed + 1; | |
999 | ||
1000 | /* | |
1001 | * Otherwise, wait for a possible partial grace period and | |
1002 | * then the subsequent full grace period. | |
1003 | */ | |
1004 | return rnp->completed + 2; | |
1005 | } | |
1006 | ||
0446be48 PM |
1007 | /* |
1008 | * Trace-event helper function for rcu_start_future_gp() and | |
1009 | * rcu_nocb_wait_gp(). | |
1010 | */ | |
1011 | static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, | |
e66c33d5 | 1012 | unsigned long c, const char *s) |
0446be48 PM |
1013 | { |
1014 | trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum, | |
1015 | rnp->completed, c, rnp->level, | |
1016 | rnp->grplo, rnp->grphi, s); | |
1017 | } | |
1018 | ||
1019 | /* | |
1020 | * Start some future grace period, as needed to handle newly arrived | |
1021 | * callbacks. The required future grace periods are recorded in each | |
1022 | * rcu_node structure's ->need_future_gp field. | |
1023 | * | |
1024 | * The caller must hold the specified rcu_node structure's ->lock. | |
1025 | */ | |
1026 | static unsigned long __maybe_unused | |
1027 | rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp) | |
1028 | { | |
1029 | unsigned long c; | |
1030 | int i; | |
1031 | struct rcu_node *rnp_root = rcu_get_root(rdp->rsp); | |
1032 | ||
1033 | /* | |
1034 | * Pick up grace-period number for new callbacks. If this | |
1035 | * grace period is already marked as needed, return to the caller. | |
1036 | */ | |
1037 | c = rcu_cbs_completed(rdp->rsp, rnp); | |
f7f7bac9 | 1038 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf")); |
0446be48 | 1039 | if (rnp->need_future_gp[c & 0x1]) { |
f7f7bac9 | 1040 | trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf")); |
0446be48 PM |
1041 | return c; |
1042 | } | |
1043 | ||
1044 | /* | |
1045 | * If either this rcu_node structure or the root rcu_node structure | |
1046 | * believe that a grace period is in progress, then we must wait | |
1047 | * for the one following, which is in "c". Because our request | |
1048 | * will be noticed at the end of the current grace period, we don't | |
1049 | * need to explicitly start one. | |
1050 | */ | |
1051 | if (rnp->gpnum != rnp->completed || | |
1052 | ACCESS_ONCE(rnp->gpnum) != ACCESS_ONCE(rnp->completed)) { | |
1053 | rnp->need_future_gp[c & 0x1]++; | |
f7f7bac9 | 1054 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf")); |
0446be48 PM |
1055 | return c; |
1056 | } | |
1057 | ||
1058 | /* | |
1059 | * There might be no grace period in progress. If we don't already | |
1060 | * hold it, acquire the root rcu_node structure's lock in order to | |
1061 | * start one (if needed). | |
1062 | */ | |
1063 | if (rnp != rnp_root) | |
1064 | raw_spin_lock(&rnp_root->lock); | |
1065 | ||
1066 | /* | |
1067 | * Get a new grace-period number. If there really is no grace | |
1068 | * period in progress, it will be smaller than the one we obtained | |
1069 | * earlier. Adjust callbacks as needed. Note that even no-CBs | |
1070 | * CPUs have a ->nxtcompleted[] array, so no no-CBs checks needed. | |
1071 | */ | |
1072 | c = rcu_cbs_completed(rdp->rsp, rnp_root); | |
1073 | for (i = RCU_DONE_TAIL; i < RCU_NEXT_TAIL; i++) | |
1074 | if (ULONG_CMP_LT(c, rdp->nxtcompleted[i])) | |
1075 | rdp->nxtcompleted[i] = c; | |
1076 | ||
1077 | /* | |
1078 | * If the needed for the required grace period is already | |
1079 | * recorded, trace and leave. | |
1080 | */ | |
1081 | if (rnp_root->need_future_gp[c & 0x1]) { | |
f7f7bac9 | 1082 | trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot")); |
0446be48 PM |
1083 | goto unlock_out; |
1084 | } | |
1085 | ||
1086 | /* Record the need for the future grace period. */ | |
1087 | rnp_root->need_future_gp[c & 0x1]++; | |
1088 | ||
1089 | /* If a grace period is not already in progress, start one. */ | |
1090 | if (rnp_root->gpnum != rnp_root->completed) { | |
f7f7bac9 | 1091 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot")); |
0446be48 | 1092 | } else { |
f7f7bac9 | 1093 | trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot")); |
910ee45d | 1094 | rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp); |
0446be48 PM |
1095 | } |
1096 | unlock_out: | |
1097 | if (rnp != rnp_root) | |
1098 | raw_spin_unlock(&rnp_root->lock); | |
1099 | return c; | |
1100 | } | |
1101 | ||
1102 | /* | |
1103 | * Clean up any old requests for the just-ended grace period. Also return | |
1104 | * whether any additional grace periods have been requested. Also invoke | |
1105 | * rcu_nocb_gp_cleanup() in order to wake up any no-callbacks kthreads | |
1106 | * waiting for this grace period to complete. | |
1107 | */ | |
1108 | static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) | |
1109 | { | |
1110 | int c = rnp->completed; | |
1111 | int needmore; | |
1112 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); | |
1113 | ||
1114 | rcu_nocb_gp_cleanup(rsp, rnp); | |
1115 | rnp->need_future_gp[c & 0x1] = 0; | |
1116 | needmore = rnp->need_future_gp[(c + 1) & 0x1]; | |
f7f7bac9 SRRH |
1117 | trace_rcu_future_gp(rnp, rdp, c, |
1118 | needmore ? TPS("CleanupMore") : TPS("Cleanup")); | |
0446be48 PM |
1119 | return needmore; |
1120 | } | |
1121 | ||
dc35c893 PM |
1122 | /* |
1123 | * If there is room, assign a ->completed number to any callbacks on | |
1124 | * this CPU that have not already been assigned. Also accelerate any | |
1125 | * callbacks that were previously assigned a ->completed number that has | |
1126 | * since proven to be too conservative, which can happen if callbacks get | |
1127 | * assigned a ->completed number while RCU is idle, but with reference to | |
1128 | * a non-root rcu_node structure. This function is idempotent, so it does | |
1129 | * not hurt to call it repeatedly. | |
1130 | * | |
1131 | * The caller must hold rnp->lock with interrupts disabled. | |
1132 | */ | |
1133 | static void rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, | |
1134 | struct rcu_data *rdp) | |
1135 | { | |
1136 | unsigned long c; | |
1137 | int i; | |
1138 | ||
1139 | /* If the CPU has no callbacks, nothing to do. */ | |
1140 | if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL]) | |
1141 | return; | |
1142 | ||
1143 | /* | |
1144 | * Starting from the sublist containing the callbacks most | |
1145 | * recently assigned a ->completed number and working down, find the | |
1146 | * first sublist that is not assignable to an upcoming grace period. | |
1147 | * Such a sublist has something in it (first two tests) and has | |
1148 | * a ->completed number assigned that will complete sooner than | |
1149 | * the ->completed number for newly arrived callbacks (last test). | |
1150 | * | |
1151 | * The key point is that any later sublist can be assigned the | |
1152 | * same ->completed number as the newly arrived callbacks, which | |
1153 | * means that the callbacks in any of these later sublist can be | |
1154 | * grouped into a single sublist, whether or not they have already | |
1155 | * been assigned a ->completed number. | |
1156 | */ | |
1157 | c = rcu_cbs_completed(rsp, rnp); | |
1158 | for (i = RCU_NEXT_TAIL - 1; i > RCU_DONE_TAIL; i--) | |
1159 | if (rdp->nxttail[i] != rdp->nxttail[i - 1] && | |
1160 | !ULONG_CMP_GE(rdp->nxtcompleted[i], c)) | |
1161 | break; | |
1162 | ||
1163 | /* | |
1164 | * If there are no sublist for unassigned callbacks, leave. | |
1165 | * At the same time, advance "i" one sublist, so that "i" will | |
1166 | * index into the sublist where all the remaining callbacks should | |
1167 | * be grouped into. | |
1168 | */ | |
1169 | if (++i >= RCU_NEXT_TAIL) | |
1170 | return; | |
1171 | ||
1172 | /* | |
1173 | * Assign all subsequent callbacks' ->completed number to the next | |
1174 | * full grace period and group them all in the sublist initially | |
1175 | * indexed by "i". | |
1176 | */ | |
1177 | for (; i <= RCU_NEXT_TAIL; i++) { | |
1178 | rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL]; | |
1179 | rdp->nxtcompleted[i] = c; | |
1180 | } | |
910ee45d PM |
1181 | /* Record any needed additional grace periods. */ |
1182 | rcu_start_future_gp(rnp, rdp); | |
6d4b418c PM |
1183 | |
1184 | /* Trace depending on how much we were able to accelerate. */ | |
1185 | if (!*rdp->nxttail[RCU_WAIT_TAIL]) | |
f7f7bac9 | 1186 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccWaitCB")); |
6d4b418c | 1187 | else |
f7f7bac9 | 1188 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccReadyCB")); |
dc35c893 PM |
1189 | } |
1190 | ||
1191 | /* | |
1192 | * Move any callbacks whose grace period has completed to the | |
1193 | * RCU_DONE_TAIL sublist, then compact the remaining sublists and | |
1194 | * assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL | |
1195 | * sublist. This function is idempotent, so it does not hurt to | |
1196 | * invoke it repeatedly. As long as it is not invoked -too- often... | |
1197 | * | |
1198 | * The caller must hold rnp->lock with interrupts disabled. | |
1199 | */ | |
1200 | static void rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp, | |
1201 | struct rcu_data *rdp) | |
1202 | { | |
1203 | int i, j; | |
1204 | ||
1205 | /* If the CPU has no callbacks, nothing to do. */ | |
1206 | if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL]) | |
1207 | return; | |
1208 | ||
1209 | /* | |
1210 | * Find all callbacks whose ->completed numbers indicate that they | |
1211 | * are ready to invoke, and put them into the RCU_DONE_TAIL sublist. | |
1212 | */ | |
1213 | for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) { | |
1214 | if (ULONG_CMP_LT(rnp->completed, rdp->nxtcompleted[i])) | |
1215 | break; | |
1216 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[i]; | |
1217 | } | |
1218 | /* Clean up any sublist tail pointers that were misordered above. */ | |
1219 | for (j = RCU_WAIT_TAIL; j < i; j++) | |
1220 | rdp->nxttail[j] = rdp->nxttail[RCU_DONE_TAIL]; | |
1221 | ||
1222 | /* Copy down callbacks to fill in empty sublists. */ | |
1223 | for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) { | |
1224 | if (rdp->nxttail[j] == rdp->nxttail[RCU_NEXT_TAIL]) | |
1225 | break; | |
1226 | rdp->nxttail[j] = rdp->nxttail[i]; | |
1227 | rdp->nxtcompleted[j] = rdp->nxtcompleted[i]; | |
1228 | } | |
1229 | ||
1230 | /* Classify any remaining callbacks. */ | |
1231 | rcu_accelerate_cbs(rsp, rnp, rdp); | |
1232 | } | |
1233 | ||
d09b62df | 1234 | /* |
ba9fbe95 PM |
1235 | * Update CPU-local rcu_data state to record the beginnings and ends of |
1236 | * grace periods. The caller must hold the ->lock of the leaf rcu_node | |
1237 | * structure corresponding to the current CPU, and must have irqs disabled. | |
d09b62df | 1238 | */ |
ba9fbe95 | 1239 | static void __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
d09b62df | 1240 | { |
ba9fbe95 | 1241 | /* Handle the ends of any preceding grace periods first. */ |
dc35c893 | 1242 | if (rdp->completed == rnp->completed) { |
d09b62df | 1243 | |
ba9fbe95 | 1244 | /* No grace period end, so just accelerate recent callbacks. */ |
dc35c893 | 1245 | rcu_accelerate_cbs(rsp, rnp, rdp); |
d09b62df | 1246 | |
dc35c893 PM |
1247 | } else { |
1248 | ||
1249 | /* Advance callbacks. */ | |
1250 | rcu_advance_cbs(rsp, rnp, rdp); | |
d09b62df PM |
1251 | |
1252 | /* Remember that we saw this grace-period completion. */ | |
1253 | rdp->completed = rnp->completed; | |
f7f7bac9 | 1254 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuend")); |
d09b62df | 1255 | } |
398ebe60 | 1256 | |
6eaef633 PM |
1257 | if (rdp->gpnum != rnp->gpnum) { |
1258 | /* | |
1259 | * If the current grace period is waiting for this CPU, | |
1260 | * set up to detect a quiescent state, otherwise don't | |
1261 | * go looking for one. | |
1262 | */ | |
1263 | rdp->gpnum = rnp->gpnum; | |
f7f7bac9 | 1264 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart")); |
6eaef633 PM |
1265 | rdp->passed_quiesce = 0; |
1266 | rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask); | |
1267 | zero_cpu_stall_ticks(rdp); | |
1268 | } | |
1269 | } | |
1270 | ||
d34ea322 | 1271 | static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp) |
6eaef633 PM |
1272 | { |
1273 | unsigned long flags; | |
1274 | struct rcu_node *rnp; | |
1275 | ||
1276 | local_irq_save(flags); | |
1277 | rnp = rdp->mynode; | |
d34ea322 PM |
1278 | if ((rdp->gpnum == ACCESS_ONCE(rnp->gpnum) && |
1279 | rdp->completed == ACCESS_ONCE(rnp->completed)) || /* w/out lock. */ | |
6eaef633 PM |
1280 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
1281 | local_irq_restore(flags); | |
1282 | return; | |
1283 | } | |
d34ea322 | 1284 | __note_gp_changes(rsp, rnp, rdp); |
6eaef633 PM |
1285 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1286 | } | |
1287 | ||
b3dbec76 | 1288 | /* |
7fdefc10 | 1289 | * Initialize a new grace period. |
b3dbec76 | 1290 | */ |
7fdefc10 | 1291 | static int rcu_gp_init(struct rcu_state *rsp) |
b3dbec76 PM |
1292 | { |
1293 | struct rcu_data *rdp; | |
7fdefc10 | 1294 | struct rcu_node *rnp = rcu_get_root(rsp); |
b3dbec76 | 1295 | |
7fdefc10 | 1296 | raw_spin_lock_irq(&rnp->lock); |
4cdfc175 | 1297 | rsp->gp_flags = 0; /* Clear all flags: New grace period. */ |
b3dbec76 | 1298 | |
7fdefc10 PM |
1299 | if (rcu_gp_in_progress(rsp)) { |
1300 | /* Grace period already in progress, don't start another. */ | |
1301 | raw_spin_unlock_irq(&rnp->lock); | |
1302 | return 0; | |
1303 | } | |
1304 | ||
7fdefc10 PM |
1305 | /* Advance to a new grace period and initialize state. */ |
1306 | rsp->gpnum++; | |
f7f7bac9 | 1307 | trace_rcu_grace_period(rsp->name, rsp->gpnum, TPS("start")); |
7fdefc10 PM |
1308 | record_gp_stall_check_time(rsp); |
1309 | raw_spin_unlock_irq(&rnp->lock); | |
1310 | ||
1311 | /* Exclude any concurrent CPU-hotplug operations. */ | |
a4fbe35a | 1312 | mutex_lock(&rsp->onoff_mutex); |
7fdefc10 PM |
1313 | |
1314 | /* | |
1315 | * Set the quiescent-state-needed bits in all the rcu_node | |
1316 | * structures for all currently online CPUs in breadth-first order, | |
1317 | * starting from the root rcu_node structure, relying on the layout | |
1318 | * of the tree within the rsp->node[] array. Note that other CPUs | |
1319 | * will access only the leaves of the hierarchy, thus seeing that no | |
1320 | * grace period is in progress, at least until the corresponding | |
1321 | * leaf node has been initialized. In addition, we have excluded | |
1322 | * CPU-hotplug operations. | |
1323 | * | |
1324 | * The grace period cannot complete until the initialization | |
1325 | * process finishes, because this kthread handles both. | |
1326 | */ | |
1327 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
b3dbec76 | 1328 | raw_spin_lock_irq(&rnp->lock); |
b3dbec76 | 1329 | rdp = this_cpu_ptr(rsp->rda); |
7fdefc10 PM |
1330 | rcu_preempt_check_blocked_tasks(rnp); |
1331 | rnp->qsmask = rnp->qsmaskinit; | |
0446be48 | 1332 | ACCESS_ONCE(rnp->gpnum) = rsp->gpnum; |
25d30cf4 | 1333 | WARN_ON_ONCE(rnp->completed != rsp->completed); |
0446be48 | 1334 | ACCESS_ONCE(rnp->completed) = rsp->completed; |
7fdefc10 | 1335 | if (rnp == rdp->mynode) |
ce3d9c03 | 1336 | __note_gp_changes(rsp, rnp, rdp); |
7fdefc10 PM |
1337 | rcu_preempt_boost_start_gp(rnp); |
1338 | trace_rcu_grace_period_init(rsp->name, rnp->gpnum, | |
1339 | rnp->level, rnp->grplo, | |
1340 | rnp->grphi, rnp->qsmask); | |
1341 | raw_spin_unlock_irq(&rnp->lock); | |
661a85dc | 1342 | #ifdef CONFIG_PROVE_RCU_DELAY |
971394f3 | 1343 | if ((prandom_u32() % (rcu_num_nodes + 1)) == 0 && |
81e59494 | 1344 | system_state == SYSTEM_RUNNING) |
971394f3 | 1345 | udelay(200); |
661a85dc | 1346 | #endif /* #ifdef CONFIG_PROVE_RCU_DELAY */ |
7fdefc10 PM |
1347 | cond_resched(); |
1348 | } | |
b3dbec76 | 1349 | |
a4fbe35a | 1350 | mutex_unlock(&rsp->onoff_mutex); |
7fdefc10 PM |
1351 | return 1; |
1352 | } | |
b3dbec76 | 1353 | |
4cdfc175 PM |
1354 | /* |
1355 | * Do one round of quiescent-state forcing. | |
1356 | */ | |
1357 | int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in) | |
1358 | { | |
1359 | int fqs_state = fqs_state_in; | |
1360 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1361 | ||
1362 | rsp->n_force_qs++; | |
1363 | if (fqs_state == RCU_SAVE_DYNTICK) { | |
1364 | /* Collect dyntick-idle snapshots. */ | |
1365 | force_qs_rnp(rsp, dyntick_save_progress_counter); | |
1366 | fqs_state = RCU_FORCE_QS; | |
1367 | } else { | |
1368 | /* Handle dyntick-idle and offline CPUs. */ | |
1369 | force_qs_rnp(rsp, rcu_implicit_dynticks_qs); | |
1370 | } | |
1371 | /* Clear flag to prevent immediate re-entry. */ | |
1372 | if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { | |
1373 | raw_spin_lock_irq(&rnp->lock); | |
1374 | rsp->gp_flags &= ~RCU_GP_FLAG_FQS; | |
1375 | raw_spin_unlock_irq(&rnp->lock); | |
1376 | } | |
1377 | return fqs_state; | |
1378 | } | |
1379 | ||
7fdefc10 PM |
1380 | /* |
1381 | * Clean up after the old grace period. | |
1382 | */ | |
4cdfc175 | 1383 | static void rcu_gp_cleanup(struct rcu_state *rsp) |
7fdefc10 PM |
1384 | { |
1385 | unsigned long gp_duration; | |
dae6e64d | 1386 | int nocb = 0; |
7fdefc10 PM |
1387 | struct rcu_data *rdp; |
1388 | struct rcu_node *rnp = rcu_get_root(rsp); | |
b3dbec76 | 1389 | |
7fdefc10 PM |
1390 | raw_spin_lock_irq(&rnp->lock); |
1391 | gp_duration = jiffies - rsp->gp_start; | |
1392 | if (gp_duration > rsp->gp_max) | |
1393 | rsp->gp_max = gp_duration; | |
b3dbec76 | 1394 | |
7fdefc10 PM |
1395 | /* |
1396 | * We know the grace period is complete, but to everyone else | |
1397 | * it appears to still be ongoing. But it is also the case | |
1398 | * that to everyone else it looks like there is nothing that | |
1399 | * they can do to advance the grace period. It is therefore | |
1400 | * safe for us to drop the lock in order to mark the grace | |
1401 | * period as completed in all of the rcu_node structures. | |
7fdefc10 | 1402 | */ |
5d4b8659 | 1403 | raw_spin_unlock_irq(&rnp->lock); |
b3dbec76 | 1404 | |
5d4b8659 PM |
1405 | /* |
1406 | * Propagate new ->completed value to rcu_node structures so | |
1407 | * that other CPUs don't have to wait until the start of the next | |
1408 | * grace period to process their callbacks. This also avoids | |
1409 | * some nasty RCU grace-period initialization races by forcing | |
1410 | * the end of the current grace period to be completely recorded in | |
1411 | * all of the rcu_node structures before the beginning of the next | |
1412 | * grace period is recorded in any of the rcu_node structures. | |
1413 | */ | |
1414 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
755609a9 | 1415 | raw_spin_lock_irq(&rnp->lock); |
0446be48 | 1416 | ACCESS_ONCE(rnp->completed) = rsp->gpnum; |
b11cc576 PM |
1417 | rdp = this_cpu_ptr(rsp->rda); |
1418 | if (rnp == rdp->mynode) | |
470716fc | 1419 | __note_gp_changes(rsp, rnp, rdp); |
0446be48 | 1420 | nocb += rcu_future_gp_cleanup(rsp, rnp); |
5d4b8659 PM |
1421 | raw_spin_unlock_irq(&rnp->lock); |
1422 | cond_resched(); | |
7fdefc10 | 1423 | } |
5d4b8659 PM |
1424 | rnp = rcu_get_root(rsp); |
1425 | raw_spin_lock_irq(&rnp->lock); | |
dae6e64d | 1426 | rcu_nocb_gp_set(rnp, nocb); |
7fdefc10 PM |
1427 | |
1428 | rsp->completed = rsp->gpnum; /* Declare grace period done. */ | |
f7f7bac9 | 1429 | trace_rcu_grace_period(rsp->name, rsp->completed, TPS("end")); |
7fdefc10 | 1430 | rsp->fqs_state = RCU_GP_IDLE; |
5d4b8659 | 1431 | rdp = this_cpu_ptr(rsp->rda); |
b11cc576 | 1432 | rcu_advance_cbs(rsp, rnp, rdp); /* Reduce false positives below. */ |
7fdefc10 PM |
1433 | if (cpu_needs_another_gp(rsp, rdp)) |
1434 | rsp->gp_flags = 1; | |
1435 | raw_spin_unlock_irq(&rnp->lock); | |
7fdefc10 PM |
1436 | } |
1437 | ||
1438 | /* | |
1439 | * Body of kthread that handles grace periods. | |
1440 | */ | |
1441 | static int __noreturn rcu_gp_kthread(void *arg) | |
1442 | { | |
4cdfc175 | 1443 | int fqs_state; |
d40011f6 | 1444 | unsigned long j; |
4cdfc175 | 1445 | int ret; |
7fdefc10 PM |
1446 | struct rcu_state *rsp = arg; |
1447 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1448 | ||
1449 | for (;;) { | |
1450 | ||
1451 | /* Handle grace-period start. */ | |
1452 | for (;;) { | |
4cdfc175 PM |
1453 | wait_event_interruptible(rsp->gp_wq, |
1454 | rsp->gp_flags & | |
1455 | RCU_GP_FLAG_INIT); | |
1456 | if ((rsp->gp_flags & RCU_GP_FLAG_INIT) && | |
1457 | rcu_gp_init(rsp)) | |
7fdefc10 PM |
1458 | break; |
1459 | cond_resched(); | |
1460 | flush_signals(current); | |
1461 | } | |
cabc49c1 | 1462 | |
4cdfc175 PM |
1463 | /* Handle quiescent-state forcing. */ |
1464 | fqs_state = RCU_SAVE_DYNTICK; | |
d40011f6 PM |
1465 | j = jiffies_till_first_fqs; |
1466 | if (j > HZ) { | |
1467 | j = HZ; | |
1468 | jiffies_till_first_fqs = HZ; | |
1469 | } | |
cabc49c1 | 1470 | for (;;) { |
d40011f6 | 1471 | rsp->jiffies_force_qs = jiffies + j; |
4cdfc175 PM |
1472 | ret = wait_event_interruptible_timeout(rsp->gp_wq, |
1473 | (rsp->gp_flags & RCU_GP_FLAG_FQS) || | |
1474 | (!ACCESS_ONCE(rnp->qsmask) && | |
1475 | !rcu_preempt_blocked_readers_cgp(rnp)), | |
d40011f6 | 1476 | j); |
4cdfc175 | 1477 | /* If grace period done, leave loop. */ |
cabc49c1 | 1478 | if (!ACCESS_ONCE(rnp->qsmask) && |
4cdfc175 | 1479 | !rcu_preempt_blocked_readers_cgp(rnp)) |
cabc49c1 | 1480 | break; |
4cdfc175 PM |
1481 | /* If time for quiescent-state forcing, do it. */ |
1482 | if (ret == 0 || (rsp->gp_flags & RCU_GP_FLAG_FQS)) { | |
1483 | fqs_state = rcu_gp_fqs(rsp, fqs_state); | |
1484 | cond_resched(); | |
1485 | } else { | |
1486 | /* Deal with stray signal. */ | |
1487 | cond_resched(); | |
1488 | flush_signals(current); | |
1489 | } | |
d40011f6 PM |
1490 | j = jiffies_till_next_fqs; |
1491 | if (j > HZ) { | |
1492 | j = HZ; | |
1493 | jiffies_till_next_fqs = HZ; | |
1494 | } else if (j < 1) { | |
1495 | j = 1; | |
1496 | jiffies_till_next_fqs = 1; | |
1497 | } | |
cabc49c1 | 1498 | } |
4cdfc175 PM |
1499 | |
1500 | /* Handle grace-period end. */ | |
1501 | rcu_gp_cleanup(rsp); | |
b3dbec76 | 1502 | } |
b3dbec76 PM |
1503 | } |
1504 | ||
016a8d5b SR |
1505 | static void rsp_wakeup(struct irq_work *work) |
1506 | { | |
1507 | struct rcu_state *rsp = container_of(work, struct rcu_state, wakeup_work); | |
1508 | ||
1509 | /* Wake up rcu_gp_kthread() to start the grace period. */ | |
1510 | wake_up(&rsp->gp_wq); | |
1511 | } | |
1512 | ||
64db4cff PM |
1513 | /* |
1514 | * Start a new RCU grace period if warranted, re-initializing the hierarchy | |
1515 | * in preparation for detecting the next grace period. The caller must hold | |
b8462084 | 1516 | * the root node's ->lock and hard irqs must be disabled. |
e5601400 PM |
1517 | * |
1518 | * Note that it is legal for a dying CPU (which is marked as offline) to | |
1519 | * invoke this function. This can happen when the dying CPU reports its | |
1520 | * quiescent state. | |
64db4cff PM |
1521 | */ |
1522 | static void | |
910ee45d PM |
1523 | rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, |
1524 | struct rcu_data *rdp) | |
64db4cff | 1525 | { |
b8462084 | 1526 | if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) { |
afe24b12 | 1527 | /* |
b3dbec76 | 1528 | * Either we have not yet spawned the grace-period |
62da1921 PM |
1529 | * task, this CPU does not need another grace period, |
1530 | * or a grace period is already in progress. | |
b3dbec76 | 1531 | * Either way, don't start a new grace period. |
afe24b12 | 1532 | */ |
afe24b12 PM |
1533 | return; |
1534 | } | |
4cdfc175 | 1535 | rsp->gp_flags = RCU_GP_FLAG_INIT; |
62da1921 | 1536 | |
016a8d5b SR |
1537 | /* |
1538 | * We can't do wakeups while holding the rnp->lock, as that | |
1539 | * could cause possible deadlocks with the rq->lock. Deter | |
1540 | * the wakeup to interrupt context. | |
1541 | */ | |
1542 | irq_work_queue(&rsp->wakeup_work); | |
64db4cff PM |
1543 | } |
1544 | ||
910ee45d PM |
1545 | /* |
1546 | * Similar to rcu_start_gp_advanced(), but also advance the calling CPU's | |
1547 | * callbacks. Note that rcu_start_gp_advanced() cannot do this because it | |
1548 | * is invoked indirectly from rcu_advance_cbs(), which would result in | |
1549 | * endless recursion -- or would do so if it wasn't for the self-deadlock | |
1550 | * that is encountered beforehand. | |
1551 | */ | |
1552 | static void | |
1553 | rcu_start_gp(struct rcu_state *rsp) | |
1554 | { | |
1555 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); | |
1556 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1557 | ||
1558 | /* | |
1559 | * If there is no grace period in progress right now, any | |
1560 | * callbacks we have up to this point will be satisfied by the | |
1561 | * next grace period. Also, advancing the callbacks reduces the | |
1562 | * probability of false positives from cpu_needs_another_gp() | |
1563 | * resulting in pointless grace periods. So, advance callbacks | |
1564 | * then start the grace period! | |
1565 | */ | |
1566 | rcu_advance_cbs(rsp, rnp, rdp); | |
1567 | rcu_start_gp_advanced(rsp, rnp, rdp); | |
1568 | } | |
1569 | ||
f41d911f | 1570 | /* |
d3f6bad3 PM |
1571 | * Report a full set of quiescent states to the specified rcu_state |
1572 | * data structure. This involves cleaning up after the prior grace | |
1573 | * period and letting rcu_start_gp() start up the next grace period | |
b8462084 PM |
1574 | * if one is needed. Note that the caller must hold rnp->lock, which |
1575 | * is released before return. | |
f41d911f | 1576 | */ |
d3f6bad3 | 1577 | static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
fc2219d4 | 1578 | __releases(rcu_get_root(rsp)->lock) |
f41d911f | 1579 | { |
fc2219d4 | 1580 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
cabc49c1 PM |
1581 | raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); |
1582 | wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */ | |
f41d911f PM |
1583 | } |
1584 | ||
64db4cff | 1585 | /* |
d3f6bad3 PM |
1586 | * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
1587 | * Allows quiescent states for a group of CPUs to be reported at one go | |
1588 | * to the specified rcu_node structure, though all the CPUs in the group | |
1589 | * must be represented by the same rcu_node structure (which need not be | |
1590 | * a leaf rcu_node structure, though it often will be). That structure's | |
1591 | * lock must be held upon entry, and it is released before return. | |
64db4cff PM |
1592 | */ |
1593 | static void | |
d3f6bad3 PM |
1594 | rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
1595 | struct rcu_node *rnp, unsigned long flags) | |
64db4cff PM |
1596 | __releases(rnp->lock) |
1597 | { | |
28ecd580 PM |
1598 | struct rcu_node *rnp_c; |
1599 | ||
64db4cff PM |
1600 | /* Walk up the rcu_node hierarchy. */ |
1601 | for (;;) { | |
1602 | if (!(rnp->qsmask & mask)) { | |
1603 | ||
1604 | /* Our bit has already been cleared, so done. */ | |
1304afb2 | 1605 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1606 | return; |
1607 | } | |
1608 | rnp->qsmask &= ~mask; | |
d4c08f2a PM |
1609 | trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum, |
1610 | mask, rnp->qsmask, rnp->level, | |
1611 | rnp->grplo, rnp->grphi, | |
1612 | !!rnp->gp_tasks); | |
27f4d280 | 1613 | if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
64db4cff PM |
1614 | |
1615 | /* Other bits still set at this level, so done. */ | |
1304afb2 | 1616 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1617 | return; |
1618 | } | |
1619 | mask = rnp->grpmask; | |
1620 | if (rnp->parent == NULL) { | |
1621 | ||
1622 | /* No more levels. Exit loop holding root lock. */ | |
1623 | ||
1624 | break; | |
1625 | } | |
1304afb2 | 1626 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
28ecd580 | 1627 | rnp_c = rnp; |
64db4cff | 1628 | rnp = rnp->parent; |
1304afb2 | 1629 | raw_spin_lock_irqsave(&rnp->lock, flags); |
28ecd580 | 1630 | WARN_ON_ONCE(rnp_c->qsmask); |
64db4cff PM |
1631 | } |
1632 | ||
1633 | /* | |
1634 | * Get here if we are the last CPU to pass through a quiescent | |
d3f6bad3 | 1635 | * state for this grace period. Invoke rcu_report_qs_rsp() |
f41d911f | 1636 | * to clean up and start the next grace period if one is needed. |
64db4cff | 1637 | */ |
d3f6bad3 | 1638 | rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
64db4cff PM |
1639 | } |
1640 | ||
1641 | /* | |
d3f6bad3 PM |
1642 | * Record a quiescent state for the specified CPU to that CPU's rcu_data |
1643 | * structure. This must be either called from the specified CPU, or | |
1644 | * called when the specified CPU is known to be offline (and when it is | |
1645 | * also known that no other CPU is concurrently trying to help the offline | |
1646 | * CPU). The lastcomp argument is used to make sure we are still in the | |
1647 | * grace period of interest. We don't want to end the current grace period | |
1648 | * based on quiescent states detected in an earlier grace period! | |
64db4cff PM |
1649 | */ |
1650 | static void | |
d7d6a11e | 1651 | rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
1652 | { |
1653 | unsigned long flags; | |
1654 | unsigned long mask; | |
1655 | struct rcu_node *rnp; | |
1656 | ||
1657 | rnp = rdp->mynode; | |
1304afb2 | 1658 | raw_spin_lock_irqsave(&rnp->lock, flags); |
d7d6a11e PM |
1659 | if (rdp->passed_quiesce == 0 || rdp->gpnum != rnp->gpnum || |
1660 | rnp->completed == rnp->gpnum) { | |
64db4cff PM |
1661 | |
1662 | /* | |
e4cc1f22 PM |
1663 | * The grace period in which this quiescent state was |
1664 | * recorded has ended, so don't report it upwards. | |
1665 | * We will instead need a new quiescent state that lies | |
1666 | * within the current grace period. | |
64db4cff | 1667 | */ |
e4cc1f22 | 1668 | rdp->passed_quiesce = 0; /* need qs for new gp. */ |
1304afb2 | 1669 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1670 | return; |
1671 | } | |
1672 | mask = rdp->grpmask; | |
1673 | if ((rnp->qsmask & mask) == 0) { | |
1304afb2 | 1674 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1675 | } else { |
1676 | rdp->qs_pending = 0; | |
1677 | ||
1678 | /* | |
1679 | * This GP can't end until cpu checks in, so all of our | |
1680 | * callbacks can be processed during the next GP. | |
1681 | */ | |
dc35c893 | 1682 | rcu_accelerate_cbs(rsp, rnp, rdp); |
64db4cff | 1683 | |
d3f6bad3 | 1684 | rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ |
64db4cff PM |
1685 | } |
1686 | } | |
1687 | ||
1688 | /* | |
1689 | * Check to see if there is a new grace period of which this CPU | |
1690 | * is not yet aware, and if so, set up local rcu_data state for it. | |
1691 | * Otherwise, see if this CPU has just passed through its first | |
1692 | * quiescent state for this grace period, and record that fact if so. | |
1693 | */ | |
1694 | static void | |
1695 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) | |
1696 | { | |
05eb552b PM |
1697 | /* Check for grace-period ends and beginnings. */ |
1698 | note_gp_changes(rsp, rdp); | |
64db4cff PM |
1699 | |
1700 | /* | |
1701 | * Does this CPU still need to do its part for current grace period? | |
1702 | * If no, return and let the other CPUs do their part as well. | |
1703 | */ | |
1704 | if (!rdp->qs_pending) | |
1705 | return; | |
1706 | ||
1707 | /* | |
1708 | * Was there a quiescent state since the beginning of the grace | |
1709 | * period? If no, then exit and wait for the next call. | |
1710 | */ | |
e4cc1f22 | 1711 | if (!rdp->passed_quiesce) |
64db4cff PM |
1712 | return; |
1713 | ||
d3f6bad3 PM |
1714 | /* |
1715 | * Tell RCU we are done (but rcu_report_qs_rdp() will be the | |
1716 | * judge of that). | |
1717 | */ | |
d7d6a11e | 1718 | rcu_report_qs_rdp(rdp->cpu, rsp, rdp); |
64db4cff PM |
1719 | } |
1720 | ||
1721 | #ifdef CONFIG_HOTPLUG_CPU | |
1722 | ||
e74f4c45 | 1723 | /* |
b1420f1c PM |
1724 | * Send the specified CPU's RCU callbacks to the orphanage. The |
1725 | * specified CPU must be offline, and the caller must hold the | |
7b2e6011 | 1726 | * ->orphan_lock. |
e74f4c45 | 1727 | */ |
b1420f1c PM |
1728 | static void |
1729 | rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp, | |
1730 | struct rcu_node *rnp, struct rcu_data *rdp) | |
e74f4c45 | 1731 | { |
3fbfbf7a | 1732 | /* No-CBs CPUs do not have orphanable callbacks. */ |
d1e43fa5 | 1733 | if (rcu_is_nocb_cpu(rdp->cpu)) |
3fbfbf7a PM |
1734 | return; |
1735 | ||
b1420f1c PM |
1736 | /* |
1737 | * Orphan the callbacks. First adjust the counts. This is safe | |
abfd6e58 PM |
1738 | * because _rcu_barrier() excludes CPU-hotplug operations, so it |
1739 | * cannot be running now. Thus no memory barrier is required. | |
b1420f1c | 1740 | */ |
a50c3af9 | 1741 | if (rdp->nxtlist != NULL) { |
b1420f1c PM |
1742 | rsp->qlen_lazy += rdp->qlen_lazy; |
1743 | rsp->qlen += rdp->qlen; | |
1744 | rdp->n_cbs_orphaned += rdp->qlen; | |
a50c3af9 | 1745 | rdp->qlen_lazy = 0; |
1d1fb395 | 1746 | ACCESS_ONCE(rdp->qlen) = 0; |
a50c3af9 PM |
1747 | } |
1748 | ||
1749 | /* | |
b1420f1c PM |
1750 | * Next, move those callbacks still needing a grace period to |
1751 | * the orphanage, where some other CPU will pick them up. | |
1752 | * Some of the callbacks might have gone partway through a grace | |
1753 | * period, but that is too bad. They get to start over because we | |
1754 | * cannot assume that grace periods are synchronized across CPUs. | |
1755 | * We don't bother updating the ->nxttail[] array yet, instead | |
1756 | * we just reset the whole thing later on. | |
a50c3af9 | 1757 | */ |
b1420f1c PM |
1758 | if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) { |
1759 | *rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL]; | |
1760 | rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL]; | |
1761 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
a50c3af9 PM |
1762 | } |
1763 | ||
1764 | /* | |
b1420f1c PM |
1765 | * Then move the ready-to-invoke callbacks to the orphanage, |
1766 | * where some other CPU will pick them up. These will not be | |
1767 | * required to pass though another grace period: They are done. | |
a50c3af9 | 1768 | */ |
e5601400 | 1769 | if (rdp->nxtlist != NULL) { |
b1420f1c PM |
1770 | *rsp->orphan_donetail = rdp->nxtlist; |
1771 | rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL]; | |
e5601400 | 1772 | } |
e74f4c45 | 1773 | |
b1420f1c | 1774 | /* Finally, initialize the rcu_data structure's list to empty. */ |
3f5d3ea6 | 1775 | init_callback_list(rdp); |
b1420f1c PM |
1776 | } |
1777 | ||
1778 | /* | |
1779 | * Adopt the RCU callbacks from the specified rcu_state structure's | |
7b2e6011 | 1780 | * orphanage. The caller must hold the ->orphan_lock. |
b1420f1c PM |
1781 | */ |
1782 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) | |
1783 | { | |
1784 | int i; | |
1785 | struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); | |
1786 | ||
3fbfbf7a PM |
1787 | /* No-CBs CPUs are handled specially. */ |
1788 | if (rcu_nocb_adopt_orphan_cbs(rsp, rdp)) | |
1789 | return; | |
1790 | ||
b1420f1c PM |
1791 | /* Do the accounting first. */ |
1792 | rdp->qlen_lazy += rsp->qlen_lazy; | |
1793 | rdp->qlen += rsp->qlen; | |
1794 | rdp->n_cbs_adopted += rsp->qlen; | |
8f5af6f1 PM |
1795 | if (rsp->qlen_lazy != rsp->qlen) |
1796 | rcu_idle_count_callbacks_posted(); | |
b1420f1c PM |
1797 | rsp->qlen_lazy = 0; |
1798 | rsp->qlen = 0; | |
1799 | ||
1800 | /* | |
1801 | * We do not need a memory barrier here because the only way we | |
1802 | * can get here if there is an rcu_barrier() in flight is if | |
1803 | * we are the task doing the rcu_barrier(). | |
1804 | */ | |
1805 | ||
1806 | /* First adopt the ready-to-invoke callbacks. */ | |
1807 | if (rsp->orphan_donelist != NULL) { | |
1808 | *rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL]; | |
1809 | *rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist; | |
1810 | for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--) | |
1811 | if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) | |
1812 | rdp->nxttail[i] = rsp->orphan_donetail; | |
1813 | rsp->orphan_donelist = NULL; | |
1814 | rsp->orphan_donetail = &rsp->orphan_donelist; | |
1815 | } | |
1816 | ||
1817 | /* And then adopt the callbacks that still need a grace period. */ | |
1818 | if (rsp->orphan_nxtlist != NULL) { | |
1819 | *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist; | |
1820 | rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail; | |
1821 | rsp->orphan_nxtlist = NULL; | |
1822 | rsp->orphan_nxttail = &rsp->orphan_nxtlist; | |
1823 | } | |
1824 | } | |
1825 | ||
1826 | /* | |
1827 | * Trace the fact that this CPU is going offline. | |
1828 | */ | |
1829 | static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) | |
1830 | { | |
1831 | RCU_TRACE(unsigned long mask); | |
1832 | RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda)); | |
1833 | RCU_TRACE(struct rcu_node *rnp = rdp->mynode); | |
1834 | ||
1835 | RCU_TRACE(mask = rdp->grpmask); | |
e5601400 PM |
1836 | trace_rcu_grace_period(rsp->name, |
1837 | rnp->gpnum + 1 - !!(rnp->qsmask & mask), | |
f7f7bac9 | 1838 | TPS("cpuofl")); |
64db4cff PM |
1839 | } |
1840 | ||
1841 | /* | |
e5601400 | 1842 | * The CPU has been completely removed, and some other CPU is reporting |
b1420f1c PM |
1843 | * this fact from process context. Do the remainder of the cleanup, |
1844 | * including orphaning the outgoing CPU's RCU callbacks, and also | |
1331e7a1 PM |
1845 | * adopting them. There can only be one CPU hotplug operation at a time, |
1846 | * so no other CPU can be attempting to update rcu_cpu_kthread_task. | |
64db4cff | 1847 | */ |
e5601400 | 1848 | static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
64db4cff | 1849 | { |
2036d94a PM |
1850 | unsigned long flags; |
1851 | unsigned long mask; | |
1852 | int need_report = 0; | |
e5601400 | 1853 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
b1420f1c | 1854 | struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ |
e5601400 | 1855 | |
2036d94a | 1856 | /* Adjust any no-longer-needed kthreads. */ |
5d01bbd1 | 1857 | rcu_boost_kthread_setaffinity(rnp, -1); |
2036d94a | 1858 | |
b1420f1c | 1859 | /* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */ |
2036d94a PM |
1860 | |
1861 | /* Exclude any attempts to start a new grace period. */ | |
a4fbe35a | 1862 | mutex_lock(&rsp->onoff_mutex); |
7b2e6011 | 1863 | raw_spin_lock_irqsave(&rsp->orphan_lock, flags); |
2036d94a | 1864 | |
b1420f1c PM |
1865 | /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */ |
1866 | rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp); | |
1867 | rcu_adopt_orphan_cbs(rsp); | |
1868 | ||
2036d94a PM |
1869 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ |
1870 | mask = rdp->grpmask; /* rnp->grplo is constant. */ | |
1871 | do { | |
1872 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ | |
1873 | rnp->qsmaskinit &= ~mask; | |
1874 | if (rnp->qsmaskinit != 0) { | |
1875 | if (rnp != rdp->mynode) | |
1876 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
1877 | break; | |
1878 | } | |
1879 | if (rnp == rdp->mynode) | |
1880 | need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); | |
1881 | else | |
1882 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
1883 | mask = rnp->grpmask; | |
1884 | rnp = rnp->parent; | |
1885 | } while (rnp != NULL); | |
1886 | ||
1887 | /* | |
1888 | * We still hold the leaf rcu_node structure lock here, and | |
1889 | * irqs are still disabled. The reason for this subterfuge is | |
7b2e6011 | 1890 | * because invoking rcu_report_unblock_qs_rnp() with ->orphan_lock |
2036d94a PM |
1891 | * held leads to deadlock. |
1892 | */ | |
7b2e6011 | 1893 | raw_spin_unlock(&rsp->orphan_lock); /* irqs remain disabled. */ |
2036d94a PM |
1894 | rnp = rdp->mynode; |
1895 | if (need_report & RCU_OFL_TASKS_NORM_GP) | |
1896 | rcu_report_unblock_qs_rnp(rnp, flags); | |
1897 | else | |
1898 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1899 | if (need_report & RCU_OFL_TASKS_EXP_GP) | |
1900 | rcu_report_exp_rnp(rsp, rnp, true); | |
cf01537e PM |
1901 | WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL, |
1902 | "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n", | |
1903 | cpu, rdp->qlen, rdp->nxtlist); | |
0d8ee37e PM |
1904 | init_callback_list(rdp); |
1905 | /* Disallow further callbacks on this CPU. */ | |
1906 | rdp->nxttail[RCU_NEXT_TAIL] = NULL; | |
a4fbe35a | 1907 | mutex_unlock(&rsp->onoff_mutex); |
64db4cff PM |
1908 | } |
1909 | ||
1910 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ | |
1911 | ||
e5601400 | 1912 | static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) |
e74f4c45 PM |
1913 | { |
1914 | } | |
1915 | ||
e5601400 | 1916 | static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
64db4cff PM |
1917 | { |
1918 | } | |
1919 | ||
1920 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ | |
1921 | ||
1922 | /* | |
1923 | * Invoke any RCU callbacks that have made it to the end of their grace | |
1924 | * period. Thottle as specified by rdp->blimit. | |
1925 | */ | |
37c72e56 | 1926 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
1927 | { |
1928 | unsigned long flags; | |
1929 | struct rcu_head *next, *list, **tail; | |
878d7439 ED |
1930 | long bl, count, count_lazy; |
1931 | int i; | |
64db4cff | 1932 | |
dc35c893 | 1933 | /* If no callbacks are ready, just return. */ |
29c00b4a | 1934 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) { |
486e2593 | 1935 | trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0); |
4968c300 PM |
1936 | trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist), |
1937 | need_resched(), is_idle_task(current), | |
1938 | rcu_is_callbacks_kthread()); | |
64db4cff | 1939 | return; |
29c00b4a | 1940 | } |
64db4cff PM |
1941 | |
1942 | /* | |
1943 | * Extract the list of ready callbacks, disabling to prevent | |
1944 | * races with call_rcu() from interrupt handlers. | |
1945 | */ | |
1946 | local_irq_save(flags); | |
8146c4e2 | 1947 | WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); |
29c00b4a | 1948 | bl = rdp->blimit; |
486e2593 | 1949 | trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl); |
64db4cff PM |
1950 | list = rdp->nxtlist; |
1951 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; | |
1952 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
1953 | tail = rdp->nxttail[RCU_DONE_TAIL]; | |
b41772ab PM |
1954 | for (i = RCU_NEXT_SIZE - 1; i >= 0; i--) |
1955 | if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) | |
1956 | rdp->nxttail[i] = &rdp->nxtlist; | |
64db4cff PM |
1957 | local_irq_restore(flags); |
1958 | ||
1959 | /* Invoke callbacks. */ | |
486e2593 | 1960 | count = count_lazy = 0; |
64db4cff PM |
1961 | while (list) { |
1962 | next = list->next; | |
1963 | prefetch(next); | |
551d55a9 | 1964 | debug_rcu_head_unqueue(list); |
486e2593 PM |
1965 | if (__rcu_reclaim(rsp->name, list)) |
1966 | count_lazy++; | |
64db4cff | 1967 | list = next; |
dff1672d PM |
1968 | /* Stop only if limit reached and CPU has something to do. */ |
1969 | if (++count >= bl && | |
1970 | (need_resched() || | |
1971 | (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) | |
64db4cff PM |
1972 | break; |
1973 | } | |
1974 | ||
1975 | local_irq_save(flags); | |
4968c300 PM |
1976 | trace_rcu_batch_end(rsp->name, count, !!list, need_resched(), |
1977 | is_idle_task(current), | |
1978 | rcu_is_callbacks_kthread()); | |
64db4cff PM |
1979 | |
1980 | /* Update count, and requeue any remaining callbacks. */ | |
64db4cff PM |
1981 | if (list != NULL) { |
1982 | *tail = rdp->nxtlist; | |
1983 | rdp->nxtlist = list; | |
b41772ab PM |
1984 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
1985 | if (&rdp->nxtlist == rdp->nxttail[i]) | |
1986 | rdp->nxttail[i] = tail; | |
64db4cff PM |
1987 | else |
1988 | break; | |
1989 | } | |
b1420f1c PM |
1990 | smp_mb(); /* List handling before counting for rcu_barrier(). */ |
1991 | rdp->qlen_lazy -= count_lazy; | |
1d1fb395 | 1992 | ACCESS_ONCE(rdp->qlen) -= count; |
b1420f1c | 1993 | rdp->n_cbs_invoked += count; |
64db4cff PM |
1994 | |
1995 | /* Reinstate batch limit if we have worked down the excess. */ | |
1996 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) | |
1997 | rdp->blimit = blimit; | |
1998 | ||
37c72e56 PM |
1999 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
2000 | if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { | |
2001 | rdp->qlen_last_fqs_check = 0; | |
2002 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
2003 | } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) | |
2004 | rdp->qlen_last_fqs_check = rdp->qlen; | |
cfca9279 | 2005 | WARN_ON_ONCE((rdp->nxtlist == NULL) != (rdp->qlen == 0)); |
37c72e56 | 2006 | |
64db4cff PM |
2007 | local_irq_restore(flags); |
2008 | ||
e0f23060 | 2009 | /* Re-invoke RCU core processing if there are callbacks remaining. */ |
64db4cff | 2010 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
a46e0899 | 2011 | invoke_rcu_core(); |
64db4cff PM |
2012 | } |
2013 | ||
2014 | /* | |
2015 | * Check to see if this CPU is in a non-context-switch quiescent state | |
2016 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). | |
e0f23060 | 2017 | * Also schedule RCU core processing. |
64db4cff | 2018 | * |
9b2e4f18 | 2019 | * This function must be called from hardirq context. It is normally |
64db4cff PM |
2020 | * invoked from the scheduling-clock interrupt. If rcu_pending returns |
2021 | * false, there is no point in invoking rcu_check_callbacks(). | |
2022 | */ | |
2023 | void rcu_check_callbacks(int cpu, int user) | |
2024 | { | |
f7f7bac9 | 2025 | trace_rcu_utilization(TPS("Start scheduler-tick")); |
a858af28 | 2026 | increment_cpu_stall_ticks(); |
9b2e4f18 | 2027 | if (user || rcu_is_cpu_rrupt_from_idle()) { |
64db4cff PM |
2028 | |
2029 | /* | |
2030 | * Get here if this CPU took its interrupt from user | |
2031 | * mode or from the idle loop, and if this is not a | |
2032 | * nested interrupt. In this case, the CPU is in | |
d6714c22 | 2033 | * a quiescent state, so note it. |
64db4cff PM |
2034 | * |
2035 | * No memory barrier is required here because both | |
d6714c22 PM |
2036 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
2037 | * variables that other CPUs neither access nor modify, | |
2038 | * at least not while the corresponding CPU is online. | |
64db4cff PM |
2039 | */ |
2040 | ||
d6714c22 PM |
2041 | rcu_sched_qs(cpu); |
2042 | rcu_bh_qs(cpu); | |
64db4cff PM |
2043 | |
2044 | } else if (!in_softirq()) { | |
2045 | ||
2046 | /* | |
2047 | * Get here if this CPU did not take its interrupt from | |
2048 | * softirq, in other words, if it is not interrupting | |
2049 | * a rcu_bh read-side critical section. This is an _bh | |
d6714c22 | 2050 | * critical section, so note it. |
64db4cff PM |
2051 | */ |
2052 | ||
d6714c22 | 2053 | rcu_bh_qs(cpu); |
64db4cff | 2054 | } |
f41d911f | 2055 | rcu_preempt_check_callbacks(cpu); |
d21670ac | 2056 | if (rcu_pending(cpu)) |
a46e0899 | 2057 | invoke_rcu_core(); |
f7f7bac9 | 2058 | trace_rcu_utilization(TPS("End scheduler-tick")); |
64db4cff PM |
2059 | } |
2060 | ||
64db4cff PM |
2061 | /* |
2062 | * Scan the leaf rcu_node structures, processing dyntick state for any that | |
2063 | * have not yet encountered a quiescent state, using the function specified. | |
27f4d280 PM |
2064 | * Also initiate boosting for any threads blocked on the root rcu_node. |
2065 | * | |
ee47eb9f | 2066 | * The caller must have suppressed start of new grace periods. |
64db4cff | 2067 | */ |
45f014c5 | 2068 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) |
64db4cff PM |
2069 | { |
2070 | unsigned long bit; | |
2071 | int cpu; | |
2072 | unsigned long flags; | |
2073 | unsigned long mask; | |
a0b6c9a7 | 2074 | struct rcu_node *rnp; |
64db4cff | 2075 | |
a0b6c9a7 | 2076 | rcu_for_each_leaf_node(rsp, rnp) { |
b4be093f | 2077 | cond_resched(); |
64db4cff | 2078 | mask = 0; |
1304afb2 | 2079 | raw_spin_lock_irqsave(&rnp->lock, flags); |
ee47eb9f | 2080 | if (!rcu_gp_in_progress(rsp)) { |
1304afb2 | 2081 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
0f10dc82 | 2082 | return; |
64db4cff | 2083 | } |
a0b6c9a7 | 2084 | if (rnp->qsmask == 0) { |
1217ed1b | 2085 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
64db4cff PM |
2086 | continue; |
2087 | } | |
a0b6c9a7 | 2088 | cpu = rnp->grplo; |
64db4cff | 2089 | bit = 1; |
a0b6c9a7 | 2090 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
394f99a9 LJ |
2091 | if ((rnp->qsmask & bit) != 0 && |
2092 | f(per_cpu_ptr(rsp->rda, cpu))) | |
64db4cff PM |
2093 | mask |= bit; |
2094 | } | |
45f014c5 | 2095 | if (mask != 0) { |
64db4cff | 2096 | |
d3f6bad3 PM |
2097 | /* rcu_report_qs_rnp() releases rnp->lock. */ |
2098 | rcu_report_qs_rnp(mask, rsp, rnp, flags); | |
64db4cff PM |
2099 | continue; |
2100 | } | |
1304afb2 | 2101 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 2102 | } |
27f4d280 | 2103 | rnp = rcu_get_root(rsp); |
1217ed1b PM |
2104 | if (rnp->qsmask == 0) { |
2105 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
2106 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ | |
2107 | } | |
64db4cff PM |
2108 | } |
2109 | ||
2110 | /* | |
2111 | * Force quiescent states on reluctant CPUs, and also detect which | |
2112 | * CPUs are in dyntick-idle mode. | |
2113 | */ | |
4cdfc175 | 2114 | static void force_quiescent_state(struct rcu_state *rsp) |
64db4cff PM |
2115 | { |
2116 | unsigned long flags; | |
394f2769 PM |
2117 | bool ret; |
2118 | struct rcu_node *rnp; | |
2119 | struct rcu_node *rnp_old = NULL; | |
2120 | ||
2121 | /* Funnel through hierarchy to reduce memory contention. */ | |
2122 | rnp = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode; | |
2123 | for (; rnp != NULL; rnp = rnp->parent) { | |
2124 | ret = (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) || | |
2125 | !raw_spin_trylock(&rnp->fqslock); | |
2126 | if (rnp_old != NULL) | |
2127 | raw_spin_unlock(&rnp_old->fqslock); | |
2128 | if (ret) { | |
2129 | rsp->n_force_qs_lh++; | |
2130 | return; | |
2131 | } | |
2132 | rnp_old = rnp; | |
2133 | } | |
2134 | /* rnp_old == rcu_get_root(rsp), rnp == NULL. */ | |
64db4cff | 2135 | |
394f2769 PM |
2136 | /* Reached the root of the rcu_node tree, acquire lock. */ |
2137 | raw_spin_lock_irqsave(&rnp_old->lock, flags); | |
2138 | raw_spin_unlock(&rnp_old->fqslock); | |
2139 | if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { | |
2140 | rsp->n_force_qs_lh++; | |
2141 | raw_spin_unlock_irqrestore(&rnp_old->lock, flags); | |
4cdfc175 | 2142 | return; /* Someone beat us to it. */ |
46a1e34e | 2143 | } |
4cdfc175 | 2144 | rsp->gp_flags |= RCU_GP_FLAG_FQS; |
394f2769 | 2145 | raw_spin_unlock_irqrestore(&rnp_old->lock, flags); |
4cdfc175 | 2146 | wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */ |
64db4cff PM |
2147 | } |
2148 | ||
64db4cff | 2149 | /* |
e0f23060 PM |
2150 | * This does the RCU core processing work for the specified rcu_state |
2151 | * and rcu_data structures. This may be called only from the CPU to | |
2152 | * whom the rdp belongs. | |
64db4cff PM |
2153 | */ |
2154 | static void | |
1bca8cf1 | 2155 | __rcu_process_callbacks(struct rcu_state *rsp) |
64db4cff PM |
2156 | { |
2157 | unsigned long flags; | |
1bca8cf1 | 2158 | struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); |
64db4cff | 2159 | |
2e597558 PM |
2160 | WARN_ON_ONCE(rdp->beenonline == 0); |
2161 | ||
64db4cff PM |
2162 | /* Update RCU state based on any recent quiescent states. */ |
2163 | rcu_check_quiescent_state(rsp, rdp); | |
2164 | ||
2165 | /* Does this CPU require a not-yet-started grace period? */ | |
dc35c893 | 2166 | local_irq_save(flags); |
64db4cff | 2167 | if (cpu_needs_another_gp(rsp, rdp)) { |
dc35c893 | 2168 | raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */ |
b8462084 PM |
2169 | rcu_start_gp(rsp); |
2170 | raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); | |
dc35c893 PM |
2171 | } else { |
2172 | local_irq_restore(flags); | |
64db4cff PM |
2173 | } |
2174 | ||
2175 | /* If there are callbacks ready, invoke them. */ | |
09223371 | 2176 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
a46e0899 | 2177 | invoke_rcu_callbacks(rsp, rdp); |
09223371 SL |
2178 | } |
2179 | ||
64db4cff | 2180 | /* |
e0f23060 | 2181 | * Do RCU core processing for the current CPU. |
64db4cff | 2182 | */ |
09223371 | 2183 | static void rcu_process_callbacks(struct softirq_action *unused) |
64db4cff | 2184 | { |
6ce75a23 PM |
2185 | struct rcu_state *rsp; |
2186 | ||
bfa00b4c PM |
2187 | if (cpu_is_offline(smp_processor_id())) |
2188 | return; | |
f7f7bac9 | 2189 | trace_rcu_utilization(TPS("Start RCU core")); |
6ce75a23 PM |
2190 | for_each_rcu_flavor(rsp) |
2191 | __rcu_process_callbacks(rsp); | |
f7f7bac9 | 2192 | trace_rcu_utilization(TPS("End RCU core")); |
64db4cff PM |
2193 | } |
2194 | ||
a26ac245 | 2195 | /* |
e0f23060 PM |
2196 | * Schedule RCU callback invocation. If the specified type of RCU |
2197 | * does not support RCU priority boosting, just do a direct call, | |
2198 | * otherwise wake up the per-CPU kernel kthread. Note that because we | |
2199 | * are running on the current CPU with interrupts disabled, the | |
2200 | * rcu_cpu_kthread_task cannot disappear out from under us. | |
a26ac245 | 2201 | */ |
a46e0899 | 2202 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
a26ac245 | 2203 | { |
b0d30417 PM |
2204 | if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active))) |
2205 | return; | |
a46e0899 PM |
2206 | if (likely(!rsp->boost)) { |
2207 | rcu_do_batch(rsp, rdp); | |
a26ac245 PM |
2208 | return; |
2209 | } | |
a46e0899 | 2210 | invoke_rcu_callbacks_kthread(); |
a26ac245 PM |
2211 | } |
2212 | ||
a46e0899 | 2213 | static void invoke_rcu_core(void) |
09223371 | 2214 | { |
b0f74036 PM |
2215 | if (cpu_online(smp_processor_id())) |
2216 | raise_softirq(RCU_SOFTIRQ); | |
09223371 SL |
2217 | } |
2218 | ||
29154c57 PM |
2219 | /* |
2220 | * Handle any core-RCU processing required by a call_rcu() invocation. | |
2221 | */ | |
2222 | static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, | |
2223 | struct rcu_head *head, unsigned long flags) | |
64db4cff | 2224 | { |
62fde6ed PM |
2225 | /* |
2226 | * If called from an extended quiescent state, invoke the RCU | |
2227 | * core in order to force a re-evaluation of RCU's idleness. | |
2228 | */ | |
a16b7a69 | 2229 | if (rcu_is_cpu_idle() && cpu_online(smp_processor_id())) |
62fde6ed PM |
2230 | invoke_rcu_core(); |
2231 | ||
a16b7a69 | 2232 | /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ |
29154c57 | 2233 | if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) |
2655d57e | 2234 | return; |
64db4cff | 2235 | |
37c72e56 PM |
2236 | /* |
2237 | * Force the grace period if too many callbacks or too long waiting. | |
2238 | * Enforce hysteresis, and don't invoke force_quiescent_state() | |
2239 | * if some other CPU has recently done so. Also, don't bother | |
2240 | * invoking force_quiescent_state() if the newly enqueued callback | |
2241 | * is the only one waiting for a grace period to complete. | |
2242 | */ | |
2655d57e | 2243 | if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { |
b52573d2 PM |
2244 | |
2245 | /* Are we ignoring a completed grace period? */ | |
470716fc | 2246 | note_gp_changes(rsp, rdp); |
b52573d2 PM |
2247 | |
2248 | /* Start a new grace period if one not already started. */ | |
2249 | if (!rcu_gp_in_progress(rsp)) { | |
b52573d2 PM |
2250 | struct rcu_node *rnp_root = rcu_get_root(rsp); |
2251 | ||
b8462084 PM |
2252 | raw_spin_lock(&rnp_root->lock); |
2253 | rcu_start_gp(rsp); | |
2254 | raw_spin_unlock(&rnp_root->lock); | |
b52573d2 PM |
2255 | } else { |
2256 | /* Give the grace period a kick. */ | |
2257 | rdp->blimit = LONG_MAX; | |
2258 | if (rsp->n_force_qs == rdp->n_force_qs_snap && | |
2259 | *rdp->nxttail[RCU_DONE_TAIL] != head) | |
4cdfc175 | 2260 | force_quiescent_state(rsp); |
b52573d2 PM |
2261 | rdp->n_force_qs_snap = rsp->n_force_qs; |
2262 | rdp->qlen_last_fqs_check = rdp->qlen; | |
2263 | } | |
4cdfc175 | 2264 | } |
29154c57 PM |
2265 | } |
2266 | ||
3fbfbf7a PM |
2267 | /* |
2268 | * Helper function for call_rcu() and friends. The cpu argument will | |
2269 | * normally be -1, indicating "currently running CPU". It may specify | |
2270 | * a CPU only if that CPU is a no-CBs CPU. Currently, only _rcu_barrier() | |
2271 | * is expected to specify a CPU. | |
2272 | */ | |
64db4cff PM |
2273 | static void |
2274 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), | |
3fbfbf7a | 2275 | struct rcu_state *rsp, int cpu, bool lazy) |
64db4cff PM |
2276 | { |
2277 | unsigned long flags; | |
2278 | struct rcu_data *rdp; | |
2279 | ||
0bb7b59d | 2280 | WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */ |
551d55a9 | 2281 | debug_rcu_head_queue(head); |
64db4cff PM |
2282 | head->func = func; |
2283 | head->next = NULL; | |
2284 | ||
64db4cff PM |
2285 | /* |
2286 | * Opportunistically note grace-period endings and beginnings. | |
2287 | * Note that we might see a beginning right after we see an | |
2288 | * end, but never vice versa, since this CPU has to pass through | |
2289 | * a quiescent state betweentimes. | |
2290 | */ | |
2291 | local_irq_save(flags); | |
394f99a9 | 2292 | rdp = this_cpu_ptr(rsp->rda); |
64db4cff PM |
2293 | |
2294 | /* Add the callback to our list. */ | |
3fbfbf7a PM |
2295 | if (unlikely(rdp->nxttail[RCU_NEXT_TAIL] == NULL) || cpu != -1) { |
2296 | int offline; | |
2297 | ||
2298 | if (cpu != -1) | |
2299 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
2300 | offline = !__call_rcu_nocb(rdp, head, lazy); | |
2301 | WARN_ON_ONCE(offline); | |
0d8ee37e | 2302 | /* _call_rcu() is illegal on offline CPU; leak the callback. */ |
0d8ee37e PM |
2303 | local_irq_restore(flags); |
2304 | return; | |
2305 | } | |
29154c57 | 2306 | ACCESS_ONCE(rdp->qlen)++; |
486e2593 PM |
2307 | if (lazy) |
2308 | rdp->qlen_lazy++; | |
c57afe80 PM |
2309 | else |
2310 | rcu_idle_count_callbacks_posted(); | |
b1420f1c PM |
2311 | smp_mb(); /* Count before adding callback for rcu_barrier(). */ |
2312 | *rdp->nxttail[RCU_NEXT_TAIL] = head; | |
2313 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; | |
2655d57e | 2314 | |
d4c08f2a PM |
2315 | if (__is_kfree_rcu_offset((unsigned long)func)) |
2316 | trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func, | |
486e2593 | 2317 | rdp->qlen_lazy, rdp->qlen); |
d4c08f2a | 2318 | else |
486e2593 | 2319 | trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen); |
d4c08f2a | 2320 | |
29154c57 PM |
2321 | /* Go handle any RCU core processing required. */ |
2322 | __call_rcu_core(rsp, rdp, head, flags); | |
64db4cff PM |
2323 | local_irq_restore(flags); |
2324 | } | |
2325 | ||
2326 | /* | |
d6714c22 | 2327 | * Queue an RCU-sched callback for invocation after a grace period. |
64db4cff | 2328 | */ |
d6714c22 | 2329 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
64db4cff | 2330 | { |
3fbfbf7a | 2331 | __call_rcu(head, func, &rcu_sched_state, -1, 0); |
64db4cff | 2332 | } |
d6714c22 | 2333 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
64db4cff PM |
2334 | |
2335 | /* | |
486e2593 | 2336 | * Queue an RCU callback for invocation after a quicker grace period. |
64db4cff PM |
2337 | */ |
2338 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
2339 | { | |
3fbfbf7a | 2340 | __call_rcu(head, func, &rcu_bh_state, -1, 0); |
64db4cff PM |
2341 | } |
2342 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
2343 | ||
6d813391 PM |
2344 | /* |
2345 | * Because a context switch is a grace period for RCU-sched and RCU-bh, | |
2346 | * any blocking grace-period wait automatically implies a grace period | |
2347 | * if there is only one CPU online at any point time during execution | |
2348 | * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to | |
2349 | * occasionally incorrectly indicate that there are multiple CPUs online | |
2350 | * when there was in fact only one the whole time, as this just adds | |
2351 | * some overhead: RCU still operates correctly. | |
6d813391 PM |
2352 | */ |
2353 | static inline int rcu_blocking_is_gp(void) | |
2354 | { | |
95f0c1de PM |
2355 | int ret; |
2356 | ||
6d813391 | 2357 | might_sleep(); /* Check for RCU read-side critical section. */ |
95f0c1de PM |
2358 | preempt_disable(); |
2359 | ret = num_online_cpus() <= 1; | |
2360 | preempt_enable(); | |
2361 | return ret; | |
6d813391 PM |
2362 | } |
2363 | ||
6ebb237b PM |
2364 | /** |
2365 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. | |
2366 | * | |
2367 | * Control will return to the caller some time after a full rcu-sched | |
2368 | * grace period has elapsed, in other words after all currently executing | |
2369 | * rcu-sched read-side critical sections have completed. These read-side | |
2370 | * critical sections are delimited by rcu_read_lock_sched() and | |
2371 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), | |
2372 | * local_irq_disable(), and so on may be used in place of | |
2373 | * rcu_read_lock_sched(). | |
2374 | * | |
2375 | * This means that all preempt_disable code sequences, including NMI and | |
f0a0e6f2 PM |
2376 | * non-threaded hardware-interrupt handlers, in progress on entry will |
2377 | * have completed before this primitive returns. However, this does not | |
2378 | * guarantee that softirq handlers will have completed, since in some | |
2379 | * kernels, these handlers can run in process context, and can block. | |
2380 | * | |
2381 | * Note that this guarantee implies further memory-ordering guarantees. | |
2382 | * On systems with more than one CPU, when synchronize_sched() returns, | |
2383 | * each CPU is guaranteed to have executed a full memory barrier since the | |
2384 | * end of its last RCU-sched read-side critical section whose beginning | |
2385 | * preceded the call to synchronize_sched(). In addition, each CPU having | |
2386 | * an RCU read-side critical section that extends beyond the return from | |
2387 | * synchronize_sched() is guaranteed to have executed a full memory barrier | |
2388 | * after the beginning of synchronize_sched() and before the beginning of | |
2389 | * that RCU read-side critical section. Note that these guarantees include | |
2390 | * CPUs that are offline, idle, or executing in user mode, as well as CPUs | |
2391 | * that are executing in the kernel. | |
2392 | * | |
2393 | * Furthermore, if CPU A invoked synchronize_sched(), which returned | |
2394 | * to its caller on CPU B, then both CPU A and CPU B are guaranteed | |
2395 | * to have executed a full memory barrier during the execution of | |
2396 | * synchronize_sched() -- even if CPU A and CPU B are the same CPU (but | |
2397 | * again only if the system has more than one CPU). | |
6ebb237b PM |
2398 | * |
2399 | * This primitive provides the guarantees made by the (now removed) | |
2400 | * synchronize_kernel() API. In contrast, synchronize_rcu() only | |
2401 | * guarantees that rcu_read_lock() sections will have completed. | |
2402 | * In "classic RCU", these two guarantees happen to be one and | |
2403 | * the same, but can differ in realtime RCU implementations. | |
2404 | */ | |
2405 | void synchronize_sched(void) | |
2406 | { | |
fe15d706 PM |
2407 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
2408 | !lock_is_held(&rcu_lock_map) && | |
2409 | !lock_is_held(&rcu_sched_lock_map), | |
2410 | "Illegal synchronize_sched() in RCU-sched read-side critical section"); | |
6ebb237b PM |
2411 | if (rcu_blocking_is_gp()) |
2412 | return; | |
3705b88d AM |
2413 | if (rcu_expedited) |
2414 | synchronize_sched_expedited(); | |
2415 | else | |
2416 | wait_rcu_gp(call_rcu_sched); | |
6ebb237b PM |
2417 | } |
2418 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
2419 | ||
2420 | /** | |
2421 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. | |
2422 | * | |
2423 | * Control will return to the caller some time after a full rcu_bh grace | |
2424 | * period has elapsed, in other words after all currently executing rcu_bh | |
2425 | * read-side critical sections have completed. RCU read-side critical | |
2426 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), | |
2427 | * and may be nested. | |
f0a0e6f2 PM |
2428 | * |
2429 | * See the description of synchronize_sched() for more detailed information | |
2430 | * on memory ordering guarantees. | |
6ebb237b PM |
2431 | */ |
2432 | void synchronize_rcu_bh(void) | |
2433 | { | |
fe15d706 PM |
2434 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
2435 | !lock_is_held(&rcu_lock_map) && | |
2436 | !lock_is_held(&rcu_sched_lock_map), | |
2437 | "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section"); | |
6ebb237b PM |
2438 | if (rcu_blocking_is_gp()) |
2439 | return; | |
3705b88d AM |
2440 | if (rcu_expedited) |
2441 | synchronize_rcu_bh_expedited(); | |
2442 | else | |
2443 | wait_rcu_gp(call_rcu_bh); | |
6ebb237b PM |
2444 | } |
2445 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); | |
2446 | ||
3d3b7db0 PM |
2447 | static int synchronize_sched_expedited_cpu_stop(void *data) |
2448 | { | |
2449 | /* | |
2450 | * There must be a full memory barrier on each affected CPU | |
2451 | * between the time that try_stop_cpus() is called and the | |
2452 | * time that it returns. | |
2453 | * | |
2454 | * In the current initial implementation of cpu_stop, the | |
2455 | * above condition is already met when the control reaches | |
2456 | * this point and the following smp_mb() is not strictly | |
2457 | * necessary. Do smp_mb() anyway for documentation and | |
2458 | * robustness against future implementation changes. | |
2459 | */ | |
2460 | smp_mb(); /* See above comment block. */ | |
2461 | return 0; | |
2462 | } | |
2463 | ||
236fefaf PM |
2464 | /** |
2465 | * synchronize_sched_expedited - Brute-force RCU-sched grace period | |
2466 | * | |
2467 | * Wait for an RCU-sched grace period to elapse, but use a "big hammer" | |
2468 | * approach to force the grace period to end quickly. This consumes | |
2469 | * significant time on all CPUs and is unfriendly to real-time workloads, | |
2470 | * so is thus not recommended for any sort of common-case code. In fact, | |
2471 | * if you are using synchronize_sched_expedited() in a loop, please | |
2472 | * restructure your code to batch your updates, and then use a single | |
2473 | * synchronize_sched() instead. | |
3d3b7db0 | 2474 | * |
236fefaf PM |
2475 | * Note that it is illegal to call this function while holding any lock |
2476 | * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal | |
2477 | * to call this function from a CPU-hotplug notifier. Failing to observe | |
2478 | * these restriction will result in deadlock. | |
3d3b7db0 PM |
2479 | * |
2480 | * This implementation can be thought of as an application of ticket | |
2481 | * locking to RCU, with sync_sched_expedited_started and | |
2482 | * sync_sched_expedited_done taking on the roles of the halves | |
2483 | * of the ticket-lock word. Each task atomically increments | |
2484 | * sync_sched_expedited_started upon entry, snapshotting the old value, | |
2485 | * then attempts to stop all the CPUs. If this succeeds, then each | |
2486 | * CPU will have executed a context switch, resulting in an RCU-sched | |
2487 | * grace period. We are then done, so we use atomic_cmpxchg() to | |
2488 | * update sync_sched_expedited_done to match our snapshot -- but | |
2489 | * only if someone else has not already advanced past our snapshot. | |
2490 | * | |
2491 | * On the other hand, if try_stop_cpus() fails, we check the value | |
2492 | * of sync_sched_expedited_done. If it has advanced past our | |
2493 | * initial snapshot, then someone else must have forced a grace period | |
2494 | * some time after we took our snapshot. In this case, our work is | |
2495 | * done for us, and we can simply return. Otherwise, we try again, | |
2496 | * but keep our initial snapshot for purposes of checking for someone | |
2497 | * doing our work for us. | |
2498 | * | |
2499 | * If we fail too many times in a row, we fall back to synchronize_sched(). | |
2500 | */ | |
2501 | void synchronize_sched_expedited(void) | |
2502 | { | |
1924bcb0 PM |
2503 | long firstsnap, s, snap; |
2504 | int trycount = 0; | |
40694d66 | 2505 | struct rcu_state *rsp = &rcu_sched_state; |
3d3b7db0 | 2506 | |
1924bcb0 PM |
2507 | /* |
2508 | * If we are in danger of counter wrap, just do synchronize_sched(). | |
2509 | * By allowing sync_sched_expedited_started to advance no more than | |
2510 | * ULONG_MAX/8 ahead of sync_sched_expedited_done, we are ensuring | |
2511 | * that more than 3.5 billion CPUs would be required to force a | |
2512 | * counter wrap on a 32-bit system. Quite a few more CPUs would of | |
2513 | * course be required on a 64-bit system. | |
2514 | */ | |
40694d66 PM |
2515 | if (ULONG_CMP_GE((ulong)atomic_long_read(&rsp->expedited_start), |
2516 | (ulong)atomic_long_read(&rsp->expedited_done) + | |
1924bcb0 PM |
2517 | ULONG_MAX / 8)) { |
2518 | synchronize_sched(); | |
a30489c5 | 2519 | atomic_long_inc(&rsp->expedited_wrap); |
1924bcb0 PM |
2520 | return; |
2521 | } | |
3d3b7db0 | 2522 | |
1924bcb0 PM |
2523 | /* |
2524 | * Take a ticket. Note that atomic_inc_return() implies a | |
2525 | * full memory barrier. | |
2526 | */ | |
40694d66 | 2527 | snap = atomic_long_inc_return(&rsp->expedited_start); |
1924bcb0 | 2528 | firstsnap = snap; |
3d3b7db0 | 2529 | get_online_cpus(); |
1cc85961 | 2530 | WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id())); |
3d3b7db0 PM |
2531 | |
2532 | /* | |
2533 | * Each pass through the following loop attempts to force a | |
2534 | * context switch on each CPU. | |
2535 | */ | |
2536 | while (try_stop_cpus(cpu_online_mask, | |
2537 | synchronize_sched_expedited_cpu_stop, | |
2538 | NULL) == -EAGAIN) { | |
2539 | put_online_cpus(); | |
a30489c5 | 2540 | atomic_long_inc(&rsp->expedited_tryfail); |
3d3b7db0 | 2541 | |
1924bcb0 | 2542 | /* Check to see if someone else did our work for us. */ |
40694d66 | 2543 | s = atomic_long_read(&rsp->expedited_done); |
1924bcb0 | 2544 | if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) { |
a30489c5 PM |
2545 | /* ensure test happens before caller kfree */ |
2546 | smp_mb__before_atomic_inc(); /* ^^^ */ | |
2547 | atomic_long_inc(&rsp->expedited_workdone1); | |
1924bcb0 PM |
2548 | return; |
2549 | } | |
3d3b7db0 PM |
2550 | |
2551 | /* No joy, try again later. Or just synchronize_sched(). */ | |
c701d5d9 | 2552 | if (trycount++ < 10) { |
3d3b7db0 | 2553 | udelay(trycount * num_online_cpus()); |
c701d5d9 | 2554 | } else { |
3705b88d | 2555 | wait_rcu_gp(call_rcu_sched); |
a30489c5 | 2556 | atomic_long_inc(&rsp->expedited_normal); |
3d3b7db0 PM |
2557 | return; |
2558 | } | |
2559 | ||
1924bcb0 | 2560 | /* Recheck to see if someone else did our work for us. */ |
40694d66 | 2561 | s = atomic_long_read(&rsp->expedited_done); |
1924bcb0 | 2562 | if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) { |
a30489c5 PM |
2563 | /* ensure test happens before caller kfree */ |
2564 | smp_mb__before_atomic_inc(); /* ^^^ */ | |
2565 | atomic_long_inc(&rsp->expedited_workdone2); | |
3d3b7db0 PM |
2566 | return; |
2567 | } | |
2568 | ||
2569 | /* | |
2570 | * Refetching sync_sched_expedited_started allows later | |
1924bcb0 PM |
2571 | * callers to piggyback on our grace period. We retry |
2572 | * after they started, so our grace period works for them, | |
2573 | * and they started after our first try, so their grace | |
2574 | * period works for us. | |
3d3b7db0 PM |
2575 | */ |
2576 | get_online_cpus(); | |
40694d66 | 2577 | snap = atomic_long_read(&rsp->expedited_start); |
3d3b7db0 PM |
2578 | smp_mb(); /* ensure read is before try_stop_cpus(). */ |
2579 | } | |
a30489c5 | 2580 | atomic_long_inc(&rsp->expedited_stoppedcpus); |
3d3b7db0 PM |
2581 | |
2582 | /* | |
2583 | * Everyone up to our most recent fetch is covered by our grace | |
2584 | * period. Update the counter, but only if our work is still | |
2585 | * relevant -- which it won't be if someone who started later | |
1924bcb0 | 2586 | * than we did already did their update. |
3d3b7db0 PM |
2587 | */ |
2588 | do { | |
a30489c5 | 2589 | atomic_long_inc(&rsp->expedited_done_tries); |
40694d66 | 2590 | s = atomic_long_read(&rsp->expedited_done); |
1924bcb0 | 2591 | if (ULONG_CMP_GE((ulong)s, (ulong)snap)) { |
a30489c5 PM |
2592 | /* ensure test happens before caller kfree */ |
2593 | smp_mb__before_atomic_inc(); /* ^^^ */ | |
2594 | atomic_long_inc(&rsp->expedited_done_lost); | |
3d3b7db0 PM |
2595 | break; |
2596 | } | |
40694d66 | 2597 | } while (atomic_long_cmpxchg(&rsp->expedited_done, s, snap) != s); |
a30489c5 | 2598 | atomic_long_inc(&rsp->expedited_done_exit); |
3d3b7db0 PM |
2599 | |
2600 | put_online_cpus(); | |
2601 | } | |
2602 | EXPORT_SYMBOL_GPL(synchronize_sched_expedited); | |
2603 | ||
64db4cff PM |
2604 | /* |
2605 | * Check to see if there is any immediate RCU-related work to be done | |
2606 | * by the current CPU, for the specified type of RCU, returning 1 if so. | |
2607 | * The checks are in order of increasing expense: checks that can be | |
2608 | * carried out against CPU-local state are performed first. However, | |
2609 | * we must check for CPU stalls first, else we might not get a chance. | |
2610 | */ | |
2611 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) | |
2612 | { | |
2f51f988 PM |
2613 | struct rcu_node *rnp = rdp->mynode; |
2614 | ||
64db4cff PM |
2615 | rdp->n_rcu_pending++; |
2616 | ||
2617 | /* Check for CPU stalls, if enabled. */ | |
2618 | check_cpu_stall(rsp, rdp); | |
2619 | ||
2620 | /* Is the RCU core waiting for a quiescent state from this CPU? */ | |
5c51dd73 PM |
2621 | if (rcu_scheduler_fully_active && |
2622 | rdp->qs_pending && !rdp->passed_quiesce) { | |
d21670ac | 2623 | rdp->n_rp_qs_pending++; |
e4cc1f22 | 2624 | } else if (rdp->qs_pending && rdp->passed_quiesce) { |
d21670ac | 2625 | rdp->n_rp_report_qs++; |
64db4cff | 2626 | return 1; |
7ba5c840 | 2627 | } |
64db4cff PM |
2628 | |
2629 | /* Does this CPU have callbacks ready to invoke? */ | |
7ba5c840 PM |
2630 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
2631 | rdp->n_rp_cb_ready++; | |
64db4cff | 2632 | return 1; |
7ba5c840 | 2633 | } |
64db4cff PM |
2634 | |
2635 | /* Has RCU gone idle with this CPU needing another grace period? */ | |
7ba5c840 PM |
2636 | if (cpu_needs_another_gp(rsp, rdp)) { |
2637 | rdp->n_rp_cpu_needs_gp++; | |
64db4cff | 2638 | return 1; |
7ba5c840 | 2639 | } |
64db4cff PM |
2640 | |
2641 | /* Has another RCU grace period completed? */ | |
2f51f988 | 2642 | if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
7ba5c840 | 2643 | rdp->n_rp_gp_completed++; |
64db4cff | 2644 | return 1; |
7ba5c840 | 2645 | } |
64db4cff PM |
2646 | |
2647 | /* Has a new RCU grace period started? */ | |
2f51f988 | 2648 | if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
7ba5c840 | 2649 | rdp->n_rp_gp_started++; |
64db4cff | 2650 | return 1; |
7ba5c840 | 2651 | } |
64db4cff | 2652 | |
64db4cff | 2653 | /* nothing to do */ |
7ba5c840 | 2654 | rdp->n_rp_need_nothing++; |
64db4cff PM |
2655 | return 0; |
2656 | } | |
2657 | ||
2658 | /* | |
2659 | * Check to see if there is any immediate RCU-related work to be done | |
2660 | * by the current CPU, returning 1 if so. This function is part of the | |
2661 | * RCU implementation; it is -not- an exported member of the RCU API. | |
2662 | */ | |
a157229c | 2663 | static int rcu_pending(int cpu) |
64db4cff | 2664 | { |
6ce75a23 PM |
2665 | struct rcu_state *rsp; |
2666 | ||
2667 | for_each_rcu_flavor(rsp) | |
2668 | if (__rcu_pending(rsp, per_cpu_ptr(rsp->rda, cpu))) | |
2669 | return 1; | |
2670 | return 0; | |
64db4cff PM |
2671 | } |
2672 | ||
2673 | /* | |
c0f4dfd4 PM |
2674 | * Return true if the specified CPU has any callback. If all_lazy is |
2675 | * non-NULL, store an indication of whether all callbacks are lazy. | |
2676 | * (If there are no callbacks, all of them are deemed to be lazy.) | |
64db4cff | 2677 | */ |
c0f4dfd4 | 2678 | static int rcu_cpu_has_callbacks(int cpu, bool *all_lazy) |
64db4cff | 2679 | { |
c0f4dfd4 PM |
2680 | bool al = true; |
2681 | bool hc = false; | |
2682 | struct rcu_data *rdp; | |
6ce75a23 PM |
2683 | struct rcu_state *rsp; |
2684 | ||
c0f4dfd4 PM |
2685 | for_each_rcu_flavor(rsp) { |
2686 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
2687 | if (rdp->qlen != rdp->qlen_lazy) | |
2688 | al = false; | |
2689 | if (rdp->nxtlist) | |
2690 | hc = true; | |
2691 | } | |
2692 | if (all_lazy) | |
2693 | *all_lazy = al; | |
2694 | return hc; | |
64db4cff PM |
2695 | } |
2696 | ||
a83eff0a PM |
2697 | /* |
2698 | * Helper function for _rcu_barrier() tracing. If tracing is disabled, | |
2699 | * the compiler is expected to optimize this away. | |
2700 | */ | |
e66c33d5 | 2701 | static void _rcu_barrier_trace(struct rcu_state *rsp, const char *s, |
a83eff0a PM |
2702 | int cpu, unsigned long done) |
2703 | { | |
2704 | trace_rcu_barrier(rsp->name, s, cpu, | |
2705 | atomic_read(&rsp->barrier_cpu_count), done); | |
2706 | } | |
2707 | ||
b1420f1c PM |
2708 | /* |
2709 | * RCU callback function for _rcu_barrier(). If we are last, wake | |
2710 | * up the task executing _rcu_barrier(). | |
2711 | */ | |
24ebbca8 | 2712 | static void rcu_barrier_callback(struct rcu_head *rhp) |
d0ec774c | 2713 | { |
24ebbca8 PM |
2714 | struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head); |
2715 | struct rcu_state *rsp = rdp->rsp; | |
2716 | ||
a83eff0a PM |
2717 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) { |
2718 | _rcu_barrier_trace(rsp, "LastCB", -1, rsp->n_barrier_done); | |
7db74df8 | 2719 | complete(&rsp->barrier_completion); |
a83eff0a PM |
2720 | } else { |
2721 | _rcu_barrier_trace(rsp, "CB", -1, rsp->n_barrier_done); | |
2722 | } | |
d0ec774c PM |
2723 | } |
2724 | ||
2725 | /* | |
2726 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
2727 | */ | |
2728 | static void rcu_barrier_func(void *type) | |
2729 | { | |
037b64ed | 2730 | struct rcu_state *rsp = type; |
06668efa | 2731 | struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); |
d0ec774c | 2732 | |
a83eff0a | 2733 | _rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done); |
24ebbca8 | 2734 | atomic_inc(&rsp->barrier_cpu_count); |
06668efa | 2735 | rsp->call(&rdp->barrier_head, rcu_barrier_callback); |
d0ec774c PM |
2736 | } |
2737 | ||
d0ec774c PM |
2738 | /* |
2739 | * Orchestrate the specified type of RCU barrier, waiting for all | |
2740 | * RCU callbacks of the specified type to complete. | |
2741 | */ | |
037b64ed | 2742 | static void _rcu_barrier(struct rcu_state *rsp) |
d0ec774c | 2743 | { |
b1420f1c | 2744 | int cpu; |
b1420f1c | 2745 | struct rcu_data *rdp; |
cf3a9c48 PM |
2746 | unsigned long snap = ACCESS_ONCE(rsp->n_barrier_done); |
2747 | unsigned long snap_done; | |
b1420f1c | 2748 | |
a83eff0a | 2749 | _rcu_barrier_trace(rsp, "Begin", -1, snap); |
b1420f1c | 2750 | |
e74f4c45 | 2751 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
7be7f0be | 2752 | mutex_lock(&rsp->barrier_mutex); |
b1420f1c | 2753 | |
cf3a9c48 PM |
2754 | /* |
2755 | * Ensure that all prior references, including to ->n_barrier_done, | |
2756 | * are ordered before the _rcu_barrier() machinery. | |
2757 | */ | |
2758 | smp_mb(); /* See above block comment. */ | |
2759 | ||
2760 | /* | |
2761 | * Recheck ->n_barrier_done to see if others did our work for us. | |
2762 | * This means checking ->n_barrier_done for an even-to-odd-to-even | |
2763 | * transition. The "if" expression below therefore rounds the old | |
2764 | * value up to the next even number and adds two before comparing. | |
2765 | */ | |
2766 | snap_done = ACCESS_ONCE(rsp->n_barrier_done); | |
a83eff0a | 2767 | _rcu_barrier_trace(rsp, "Check", -1, snap_done); |
cf3a9c48 | 2768 | if (ULONG_CMP_GE(snap_done, ((snap + 1) & ~0x1) + 2)) { |
a83eff0a | 2769 | _rcu_barrier_trace(rsp, "EarlyExit", -1, snap_done); |
cf3a9c48 PM |
2770 | smp_mb(); /* caller's subsequent code after above check. */ |
2771 | mutex_unlock(&rsp->barrier_mutex); | |
2772 | return; | |
2773 | } | |
2774 | ||
2775 | /* | |
2776 | * Increment ->n_barrier_done to avoid duplicate work. Use | |
2777 | * ACCESS_ONCE() to prevent the compiler from speculating | |
2778 | * the increment to precede the early-exit check. | |
2779 | */ | |
2780 | ACCESS_ONCE(rsp->n_barrier_done)++; | |
2781 | WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1); | |
a83eff0a | 2782 | _rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done); |
cf3a9c48 | 2783 | smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */ |
b1420f1c | 2784 | |
d0ec774c | 2785 | /* |
b1420f1c PM |
2786 | * Initialize the count to one rather than to zero in order to |
2787 | * avoid a too-soon return to zero in case of a short grace period | |
1331e7a1 PM |
2788 | * (or preemption of this task). Exclude CPU-hotplug operations |
2789 | * to ensure that no offline CPU has callbacks queued. | |
d0ec774c | 2790 | */ |
7db74df8 | 2791 | init_completion(&rsp->barrier_completion); |
24ebbca8 | 2792 | atomic_set(&rsp->barrier_cpu_count, 1); |
1331e7a1 | 2793 | get_online_cpus(); |
b1420f1c PM |
2794 | |
2795 | /* | |
1331e7a1 PM |
2796 | * Force each CPU with callbacks to register a new callback. |
2797 | * When that callback is invoked, we will know that all of the | |
2798 | * corresponding CPU's preceding callbacks have been invoked. | |
b1420f1c | 2799 | */ |
3fbfbf7a | 2800 | for_each_possible_cpu(cpu) { |
d1e43fa5 | 2801 | if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu)) |
3fbfbf7a | 2802 | continue; |
b1420f1c | 2803 | rdp = per_cpu_ptr(rsp->rda, cpu); |
d1e43fa5 | 2804 | if (rcu_is_nocb_cpu(cpu)) { |
3fbfbf7a PM |
2805 | _rcu_barrier_trace(rsp, "OnlineNoCB", cpu, |
2806 | rsp->n_barrier_done); | |
2807 | atomic_inc(&rsp->barrier_cpu_count); | |
2808 | __call_rcu(&rdp->barrier_head, rcu_barrier_callback, | |
2809 | rsp, cpu, 0); | |
2810 | } else if (ACCESS_ONCE(rdp->qlen)) { | |
a83eff0a PM |
2811 | _rcu_barrier_trace(rsp, "OnlineQ", cpu, |
2812 | rsp->n_barrier_done); | |
037b64ed | 2813 | smp_call_function_single(cpu, rcu_barrier_func, rsp, 1); |
b1420f1c | 2814 | } else { |
a83eff0a PM |
2815 | _rcu_barrier_trace(rsp, "OnlineNQ", cpu, |
2816 | rsp->n_barrier_done); | |
b1420f1c PM |
2817 | } |
2818 | } | |
1331e7a1 | 2819 | put_online_cpus(); |
b1420f1c PM |
2820 | |
2821 | /* | |
2822 | * Now that we have an rcu_barrier_callback() callback on each | |
2823 | * CPU, and thus each counted, remove the initial count. | |
2824 | */ | |
24ebbca8 | 2825 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) |
7db74df8 | 2826 | complete(&rsp->barrier_completion); |
b1420f1c | 2827 | |
cf3a9c48 PM |
2828 | /* Increment ->n_barrier_done to prevent duplicate work. */ |
2829 | smp_mb(); /* Keep increment after above mechanism. */ | |
2830 | ACCESS_ONCE(rsp->n_barrier_done)++; | |
2831 | WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0); | |
a83eff0a | 2832 | _rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done); |
cf3a9c48 PM |
2833 | smp_mb(); /* Keep increment before caller's subsequent code. */ |
2834 | ||
b1420f1c | 2835 | /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ |
7db74df8 | 2836 | wait_for_completion(&rsp->barrier_completion); |
b1420f1c PM |
2837 | |
2838 | /* Other rcu_barrier() invocations can now safely proceed. */ | |
7be7f0be | 2839 | mutex_unlock(&rsp->barrier_mutex); |
d0ec774c | 2840 | } |
d0ec774c PM |
2841 | |
2842 | /** | |
2843 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. | |
2844 | */ | |
2845 | void rcu_barrier_bh(void) | |
2846 | { | |
037b64ed | 2847 | _rcu_barrier(&rcu_bh_state); |
d0ec774c PM |
2848 | } |
2849 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); | |
2850 | ||
2851 | /** | |
2852 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. | |
2853 | */ | |
2854 | void rcu_barrier_sched(void) | |
2855 | { | |
037b64ed | 2856 | _rcu_barrier(&rcu_sched_state); |
d0ec774c PM |
2857 | } |
2858 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); | |
2859 | ||
64db4cff | 2860 | /* |
27569620 | 2861 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
64db4cff | 2862 | */ |
27569620 PM |
2863 | static void __init |
2864 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) | |
64db4cff PM |
2865 | { |
2866 | unsigned long flags; | |
394f99a9 | 2867 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
27569620 PM |
2868 | struct rcu_node *rnp = rcu_get_root(rsp); |
2869 | ||
2870 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 2871 | raw_spin_lock_irqsave(&rnp->lock, flags); |
27569620 | 2872 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
3f5d3ea6 | 2873 | init_callback_list(rdp); |
486e2593 | 2874 | rdp->qlen_lazy = 0; |
1d1fb395 | 2875 | ACCESS_ONCE(rdp->qlen) = 0; |
27569620 | 2876 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
29e37d81 | 2877 | WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); |
9b2e4f18 | 2878 | WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1); |
27569620 | 2879 | rdp->cpu = cpu; |
d4c08f2a | 2880 | rdp->rsp = rsp; |
3fbfbf7a | 2881 | rcu_boot_init_nocb_percpu_data(rdp); |
1304afb2 | 2882 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27569620 PM |
2883 | } |
2884 | ||
2885 | /* | |
2886 | * Initialize a CPU's per-CPU RCU data. Note that only one online or | |
2887 | * offline event can be happening at a given time. Note also that we | |
2888 | * can accept some slop in the rsp->completed access due to the fact | |
2889 | * that this CPU cannot possibly have any RCU callbacks in flight yet. | |
64db4cff | 2890 | */ |
49fb4c62 | 2891 | static void |
6cc68793 | 2892 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) |
64db4cff PM |
2893 | { |
2894 | unsigned long flags; | |
64db4cff | 2895 | unsigned long mask; |
394f99a9 | 2896 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
64db4cff PM |
2897 | struct rcu_node *rnp = rcu_get_root(rsp); |
2898 | ||
a4fbe35a PM |
2899 | /* Exclude new grace periods. */ |
2900 | mutex_lock(&rsp->onoff_mutex); | |
2901 | ||
64db4cff | 2902 | /* Set up local state, ensuring consistent view of global state. */ |
1304afb2 | 2903 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff | 2904 | rdp->beenonline = 1; /* We have now been online. */ |
6cc68793 | 2905 | rdp->preemptible = preemptible; |
37c72e56 PM |
2906 | rdp->qlen_last_fqs_check = 0; |
2907 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
64db4cff | 2908 | rdp->blimit = blimit; |
0d8ee37e | 2909 | init_callback_list(rdp); /* Re-enable callbacks on this CPU. */ |
29e37d81 | 2910 | rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
2333210b | 2911 | rcu_sysidle_init_percpu_data(rdp->dynticks); |
c92b131b PM |
2912 | atomic_set(&rdp->dynticks->dynticks, |
2913 | (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1); | |
1304afb2 | 2914 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff | 2915 | |
64db4cff PM |
2916 | /* Add CPU to rcu_node bitmasks. */ |
2917 | rnp = rdp->mynode; | |
2918 | mask = rdp->grpmask; | |
2919 | do { | |
2920 | /* Exclude any attempts to start a new GP on small systems. */ | |
1304afb2 | 2921 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
2922 | rnp->qsmaskinit |= mask; |
2923 | mask = rnp->grpmask; | |
d09b62df | 2924 | if (rnp == rdp->mynode) { |
06ae115a PM |
2925 | /* |
2926 | * If there is a grace period in progress, we will | |
2927 | * set up to wait for it next time we run the | |
2928 | * RCU core code. | |
2929 | */ | |
2930 | rdp->gpnum = rnp->completed; | |
d09b62df | 2931 | rdp->completed = rnp->completed; |
06ae115a PM |
2932 | rdp->passed_quiesce = 0; |
2933 | rdp->qs_pending = 0; | |
f7f7bac9 | 2934 | trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl")); |
d09b62df | 2935 | } |
1304afb2 | 2936 | raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
2937 | rnp = rnp->parent; |
2938 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); | |
a4fbe35a | 2939 | local_irq_restore(flags); |
64db4cff | 2940 | |
a4fbe35a | 2941 | mutex_unlock(&rsp->onoff_mutex); |
64db4cff PM |
2942 | } |
2943 | ||
49fb4c62 | 2944 | static void rcu_prepare_cpu(int cpu) |
64db4cff | 2945 | { |
6ce75a23 PM |
2946 | struct rcu_state *rsp; |
2947 | ||
2948 | for_each_rcu_flavor(rsp) | |
2949 | rcu_init_percpu_data(cpu, rsp, | |
2950 | strcmp(rsp->name, "rcu_preempt") == 0); | |
64db4cff PM |
2951 | } |
2952 | ||
2953 | /* | |
f41d911f | 2954 | * Handle CPU online/offline notification events. |
64db4cff | 2955 | */ |
49fb4c62 | 2956 | static int rcu_cpu_notify(struct notifier_block *self, |
9f680ab4 | 2957 | unsigned long action, void *hcpu) |
64db4cff PM |
2958 | { |
2959 | long cpu = (long)hcpu; | |
27f4d280 | 2960 | struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); |
a26ac245 | 2961 | struct rcu_node *rnp = rdp->mynode; |
6ce75a23 | 2962 | struct rcu_state *rsp; |
64db4cff | 2963 | |
f7f7bac9 | 2964 | trace_rcu_utilization(TPS("Start CPU hotplug")); |
64db4cff PM |
2965 | switch (action) { |
2966 | case CPU_UP_PREPARE: | |
2967 | case CPU_UP_PREPARE_FROZEN: | |
d72bce0e PZ |
2968 | rcu_prepare_cpu(cpu); |
2969 | rcu_prepare_kthreads(cpu); | |
a26ac245 PM |
2970 | break; |
2971 | case CPU_ONLINE: | |
0f962a5e | 2972 | case CPU_DOWN_FAILED: |
5d01bbd1 | 2973 | rcu_boost_kthread_setaffinity(rnp, -1); |
0f962a5e PM |
2974 | break; |
2975 | case CPU_DOWN_PREPARE: | |
34ed6246 | 2976 | rcu_boost_kthread_setaffinity(rnp, cpu); |
64db4cff | 2977 | break; |
d0ec774c PM |
2978 | case CPU_DYING: |
2979 | case CPU_DYING_FROZEN: | |
6ce75a23 PM |
2980 | for_each_rcu_flavor(rsp) |
2981 | rcu_cleanup_dying_cpu(rsp); | |
d0ec774c | 2982 | break; |
64db4cff PM |
2983 | case CPU_DEAD: |
2984 | case CPU_DEAD_FROZEN: | |
2985 | case CPU_UP_CANCELED: | |
2986 | case CPU_UP_CANCELED_FROZEN: | |
6ce75a23 PM |
2987 | for_each_rcu_flavor(rsp) |
2988 | rcu_cleanup_dead_cpu(cpu, rsp); | |
64db4cff PM |
2989 | break; |
2990 | default: | |
2991 | break; | |
2992 | } | |
f7f7bac9 | 2993 | trace_rcu_utilization(TPS("End CPU hotplug")); |
34ed6246 | 2994 | return NOTIFY_OK; |
64db4cff PM |
2995 | } |
2996 | ||
b3dbec76 PM |
2997 | /* |
2998 | * Spawn the kthread that handles this RCU flavor's grace periods. | |
2999 | */ | |
3000 | static int __init rcu_spawn_gp_kthread(void) | |
3001 | { | |
3002 | unsigned long flags; | |
3003 | struct rcu_node *rnp; | |
3004 | struct rcu_state *rsp; | |
3005 | struct task_struct *t; | |
3006 | ||
3007 | for_each_rcu_flavor(rsp) { | |
f170168b | 3008 | t = kthread_run(rcu_gp_kthread, rsp, "%s", rsp->name); |
b3dbec76 PM |
3009 | BUG_ON(IS_ERR(t)); |
3010 | rnp = rcu_get_root(rsp); | |
3011 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
3012 | rsp->gp_kthread = t; | |
3013 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
3fbfbf7a | 3014 | rcu_spawn_nocb_kthreads(rsp); |
b3dbec76 PM |
3015 | } |
3016 | return 0; | |
3017 | } | |
3018 | early_initcall(rcu_spawn_gp_kthread); | |
3019 | ||
bbad9379 PM |
3020 | /* |
3021 | * This function is invoked towards the end of the scheduler's initialization | |
3022 | * process. Before this is called, the idle task might contain | |
3023 | * RCU read-side critical sections (during which time, this idle | |
3024 | * task is booting the system). After this function is called, the | |
3025 | * idle tasks are prohibited from containing RCU read-side critical | |
3026 | * sections. This function also enables RCU lockdep checking. | |
3027 | */ | |
3028 | void rcu_scheduler_starting(void) | |
3029 | { | |
3030 | WARN_ON(num_online_cpus() != 1); | |
3031 | WARN_ON(nr_context_switches() > 0); | |
3032 | rcu_scheduler_active = 1; | |
3033 | } | |
3034 | ||
64db4cff PM |
3035 | /* |
3036 | * Compute the per-level fanout, either using the exact fanout specified | |
3037 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. | |
3038 | */ | |
3039 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
3040 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
3041 | { | |
3042 | int i; | |
3043 | ||
f885b7f2 | 3044 | for (i = rcu_num_lvls - 1; i > 0; i--) |
64db4cff | 3045 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
f885b7f2 | 3046 | rsp->levelspread[0] = rcu_fanout_leaf; |
64db4cff PM |
3047 | } |
3048 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
3049 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
3050 | { | |
3051 | int ccur; | |
3052 | int cprv; | |
3053 | int i; | |
3054 | ||
4dbd6bb3 | 3055 | cprv = nr_cpu_ids; |
f885b7f2 | 3056 | for (i = rcu_num_lvls - 1; i >= 0; i--) { |
64db4cff PM |
3057 | ccur = rsp->levelcnt[i]; |
3058 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; | |
3059 | cprv = ccur; | |
3060 | } | |
3061 | } | |
3062 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
3063 | ||
3064 | /* | |
3065 | * Helper function for rcu_init() that initializes one rcu_state structure. | |
3066 | */ | |
394f99a9 LJ |
3067 | static void __init rcu_init_one(struct rcu_state *rsp, |
3068 | struct rcu_data __percpu *rda) | |
64db4cff | 3069 | { |
394f2769 PM |
3070 | static char *buf[] = { "rcu_node_0", |
3071 | "rcu_node_1", | |
3072 | "rcu_node_2", | |
3073 | "rcu_node_3" }; /* Match MAX_RCU_LVLS */ | |
3074 | static char *fqs[] = { "rcu_node_fqs_0", | |
3075 | "rcu_node_fqs_1", | |
3076 | "rcu_node_fqs_2", | |
3077 | "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */ | |
64db4cff PM |
3078 | int cpustride = 1; |
3079 | int i; | |
3080 | int j; | |
3081 | struct rcu_node *rnp; | |
3082 | ||
b6407e86 PM |
3083 | BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
3084 | ||
4930521a PM |
3085 | /* Silence gcc 4.8 warning about array index out of range. */ |
3086 | if (rcu_num_lvls > RCU_NUM_LVLS) | |
3087 | panic("rcu_init_one: rcu_num_lvls overflow"); | |
3088 | ||
64db4cff PM |
3089 | /* Initialize the level-tracking arrays. */ |
3090 | ||
f885b7f2 PM |
3091 | for (i = 0; i < rcu_num_lvls; i++) |
3092 | rsp->levelcnt[i] = num_rcu_lvl[i]; | |
3093 | for (i = 1; i < rcu_num_lvls; i++) | |
64db4cff PM |
3094 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; |
3095 | rcu_init_levelspread(rsp); | |
3096 | ||
3097 | /* Initialize the elements themselves, starting from the leaves. */ | |
3098 | ||
f885b7f2 | 3099 | for (i = rcu_num_lvls - 1; i >= 0; i--) { |
64db4cff PM |
3100 | cpustride *= rsp->levelspread[i]; |
3101 | rnp = rsp->level[i]; | |
3102 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { | |
1304afb2 | 3103 | raw_spin_lock_init(&rnp->lock); |
b6407e86 PM |
3104 | lockdep_set_class_and_name(&rnp->lock, |
3105 | &rcu_node_class[i], buf[i]); | |
394f2769 PM |
3106 | raw_spin_lock_init(&rnp->fqslock); |
3107 | lockdep_set_class_and_name(&rnp->fqslock, | |
3108 | &rcu_fqs_class[i], fqs[i]); | |
25d30cf4 PM |
3109 | rnp->gpnum = rsp->gpnum; |
3110 | rnp->completed = rsp->completed; | |
64db4cff PM |
3111 | rnp->qsmask = 0; |
3112 | rnp->qsmaskinit = 0; | |
3113 | rnp->grplo = j * cpustride; | |
3114 | rnp->grphi = (j + 1) * cpustride - 1; | |
3115 | if (rnp->grphi >= NR_CPUS) | |
3116 | rnp->grphi = NR_CPUS - 1; | |
3117 | if (i == 0) { | |
3118 | rnp->grpnum = 0; | |
3119 | rnp->grpmask = 0; | |
3120 | rnp->parent = NULL; | |
3121 | } else { | |
3122 | rnp->grpnum = j % rsp->levelspread[i - 1]; | |
3123 | rnp->grpmask = 1UL << rnp->grpnum; | |
3124 | rnp->parent = rsp->level[i - 1] + | |
3125 | j / rsp->levelspread[i - 1]; | |
3126 | } | |
3127 | rnp->level = i; | |
12f5f524 | 3128 | INIT_LIST_HEAD(&rnp->blkd_tasks); |
dae6e64d | 3129 | rcu_init_one_nocb(rnp); |
64db4cff PM |
3130 | } |
3131 | } | |
0c34029a | 3132 | |
394f99a9 | 3133 | rsp->rda = rda; |
b3dbec76 | 3134 | init_waitqueue_head(&rsp->gp_wq); |
016a8d5b | 3135 | init_irq_work(&rsp->wakeup_work, rsp_wakeup); |
f885b7f2 | 3136 | rnp = rsp->level[rcu_num_lvls - 1]; |
0c34029a | 3137 | for_each_possible_cpu(i) { |
4a90a068 | 3138 | while (i > rnp->grphi) |
0c34029a | 3139 | rnp++; |
394f99a9 | 3140 | per_cpu_ptr(rsp->rda, i)->mynode = rnp; |
0c34029a LJ |
3141 | rcu_boot_init_percpu_data(i, rsp); |
3142 | } | |
6ce75a23 | 3143 | list_add(&rsp->flavors, &rcu_struct_flavors); |
64db4cff PM |
3144 | } |
3145 | ||
f885b7f2 PM |
3146 | /* |
3147 | * Compute the rcu_node tree geometry from kernel parameters. This cannot | |
3148 | * replace the definitions in rcutree.h because those are needed to size | |
3149 | * the ->node array in the rcu_state structure. | |
3150 | */ | |
3151 | static void __init rcu_init_geometry(void) | |
3152 | { | |
026ad283 | 3153 | ulong d; |
f885b7f2 PM |
3154 | int i; |
3155 | int j; | |
cca6f393 | 3156 | int n = nr_cpu_ids; |
f885b7f2 PM |
3157 | int rcu_capacity[MAX_RCU_LVLS + 1]; |
3158 | ||
026ad283 PM |
3159 | /* |
3160 | * Initialize any unspecified boot parameters. | |
3161 | * The default values of jiffies_till_first_fqs and | |
3162 | * jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS | |
3163 | * value, which is a function of HZ, then adding one for each | |
3164 | * RCU_JIFFIES_FQS_DIV CPUs that might be on the system. | |
3165 | */ | |
3166 | d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV; | |
3167 | if (jiffies_till_first_fqs == ULONG_MAX) | |
3168 | jiffies_till_first_fqs = d; | |
3169 | if (jiffies_till_next_fqs == ULONG_MAX) | |
3170 | jiffies_till_next_fqs = d; | |
3171 | ||
f885b7f2 | 3172 | /* If the compile-time values are accurate, just leave. */ |
b17c7035 PM |
3173 | if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF && |
3174 | nr_cpu_ids == NR_CPUS) | |
f885b7f2 PM |
3175 | return; |
3176 | ||
3177 | /* | |
3178 | * Compute number of nodes that can be handled an rcu_node tree | |
3179 | * with the given number of levels. Setting rcu_capacity[0] makes | |
3180 | * some of the arithmetic easier. | |
3181 | */ | |
3182 | rcu_capacity[0] = 1; | |
3183 | rcu_capacity[1] = rcu_fanout_leaf; | |
3184 | for (i = 2; i <= MAX_RCU_LVLS; i++) | |
3185 | rcu_capacity[i] = rcu_capacity[i - 1] * CONFIG_RCU_FANOUT; | |
3186 | ||
3187 | /* | |
3188 | * The boot-time rcu_fanout_leaf parameter is only permitted | |
3189 | * to increase the leaf-level fanout, not decrease it. Of course, | |
3190 | * the leaf-level fanout cannot exceed the number of bits in | |
3191 | * the rcu_node masks. Finally, the tree must be able to accommodate | |
3192 | * the configured number of CPUs. Complain and fall back to the | |
3193 | * compile-time values if these limits are exceeded. | |
3194 | */ | |
3195 | if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF || | |
3196 | rcu_fanout_leaf > sizeof(unsigned long) * 8 || | |
3197 | n > rcu_capacity[MAX_RCU_LVLS]) { | |
3198 | WARN_ON(1); | |
3199 | return; | |
3200 | } | |
3201 | ||
3202 | /* Calculate the number of rcu_nodes at each level of the tree. */ | |
3203 | for (i = 1; i <= MAX_RCU_LVLS; i++) | |
3204 | if (n <= rcu_capacity[i]) { | |
3205 | for (j = 0; j <= i; j++) | |
3206 | num_rcu_lvl[j] = | |
3207 | DIV_ROUND_UP(n, rcu_capacity[i - j]); | |
3208 | rcu_num_lvls = i; | |
3209 | for (j = i + 1; j <= MAX_RCU_LVLS; j++) | |
3210 | num_rcu_lvl[j] = 0; | |
3211 | break; | |
3212 | } | |
3213 | ||
3214 | /* Calculate the total number of rcu_node structures. */ | |
3215 | rcu_num_nodes = 0; | |
3216 | for (i = 0; i <= MAX_RCU_LVLS; i++) | |
3217 | rcu_num_nodes += num_rcu_lvl[i]; | |
3218 | rcu_num_nodes -= n; | |
3219 | } | |
3220 | ||
9f680ab4 | 3221 | void __init rcu_init(void) |
64db4cff | 3222 | { |
017c4261 | 3223 | int cpu; |
9f680ab4 | 3224 | |
f41d911f | 3225 | rcu_bootup_announce(); |
f885b7f2 | 3226 | rcu_init_geometry(); |
394f99a9 LJ |
3227 | rcu_init_one(&rcu_sched_state, &rcu_sched_data); |
3228 | rcu_init_one(&rcu_bh_state, &rcu_bh_data); | |
f41d911f | 3229 | __rcu_init_preempt(); |
b5b39360 | 3230 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
9f680ab4 PM |
3231 | |
3232 | /* | |
3233 | * We don't need protection against CPU-hotplug here because | |
3234 | * this is called early in boot, before either interrupts | |
3235 | * or the scheduler are operational. | |
3236 | */ | |
3237 | cpu_notifier(rcu_cpu_notify, 0); | |
017c4261 PM |
3238 | for_each_online_cpu(cpu) |
3239 | rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); | |
64db4cff PM |
3240 | } |
3241 | ||
1eba8f84 | 3242 | #include "rcutree_plugin.h" |