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1da177e4 LT |
1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2 of the License, or | |
7 | * (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
87de1cfd PM |
15 | * along with this program; if not, you can access it online at |
16 | * http://www.gnu.org/licenses/gpl-2.0.html. | |
1da177e4 | 17 | * |
01c1c660 | 18 | * Copyright IBM Corporation, 2001 |
1da177e4 LT |
19 | * |
20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> | |
21 | * Manfred Spraul <manfred@colorfullife.com> | |
a71fca58 | 22 | * |
1da177e4 LT |
23 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
24 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. | |
25 | * Papers: | |
26 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf | |
27 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) | |
28 | * | |
29 | * For detailed explanation of Read-Copy Update mechanism see - | |
a71fca58 | 30 | * http://lse.sourceforge.net/locking/rcupdate.html |
1da177e4 LT |
31 | * |
32 | */ | |
33 | #include <linux/types.h> | |
34 | #include <linux/kernel.h> | |
35 | #include <linux/init.h> | |
36 | #include <linux/spinlock.h> | |
37 | #include <linux/smp.h> | |
38 | #include <linux/interrupt.h> | |
3f07c014 | 39 | #include <linux/sched/signal.h> |
b17b0153 | 40 | #include <linux/sched/debug.h> |
60063497 | 41 | #include <linux/atomic.h> |
1da177e4 | 42 | #include <linux/bitops.h> |
1da177e4 LT |
43 | #include <linux/percpu.h> |
44 | #include <linux/notifier.h> | |
1da177e4 | 45 | #include <linux/cpu.h> |
9331b315 | 46 | #include <linux/mutex.h> |
9984de1a | 47 | #include <linux/export.h> |
e3818b8d | 48 | #include <linux/hardirq.h> |
e3ebfb96 | 49 | #include <linux/delay.h> |
e77b7041 | 50 | #include <linux/moduleparam.h> |
8315f422 | 51 | #include <linux/kthread.h> |
4ff475ed | 52 | #include <linux/tick.h> |
f9411ebe | 53 | #include <linux/rcupdate_wait.h> |
78634061 | 54 | #include <linux/sched/isolation.h> |
1da177e4 | 55 | |
29c00b4a | 56 | #define CREATE_TRACE_POINTS |
29c00b4a PM |
57 | |
58 | #include "rcu.h" | |
59 | ||
4102adab PM |
60 | #ifdef MODULE_PARAM_PREFIX |
61 | #undef MODULE_PARAM_PREFIX | |
62 | #endif | |
63 | #define MODULE_PARAM_PREFIX "rcupdate." | |
64 | ||
79cfea02 | 65 | #ifndef CONFIG_TINY_RCU |
3caec62f | 66 | extern int rcu_expedited; /* from sysctl */ |
3705b88d | 67 | module_param(rcu_expedited, int, 0); |
3caec62f | 68 | extern int rcu_normal; /* from sysctl */ |
5a9be7c6 | 69 | module_param(rcu_normal, int, 0); |
3e42ec1a PM |
70 | static int rcu_normal_after_boot; |
71 | module_param(rcu_normal_after_boot, int, 0); | |
79cfea02 | 72 | #endif /* #ifndef CONFIG_TINY_RCU */ |
3e42ec1a | 73 | |
293e2421 | 74 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
d5671f6b DV |
75 | /** |
76 | * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section? | |
77 | * | |
78 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an | |
79 | * RCU-sched read-side critical section. In absence of | |
80 | * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side | |
81 | * critical section unless it can prove otherwise. Note that disabling | |
82 | * of preemption (including disabling irqs) counts as an RCU-sched | |
83 | * read-side critical section. This is useful for debug checks in functions | |
84 | * that required that they be called within an RCU-sched read-side | |
85 | * critical section. | |
86 | * | |
87 | * Check debug_lockdep_rcu_enabled() to prevent false positives during boot | |
88 | * and while lockdep is disabled. | |
89 | * | |
90 | * Note that if the CPU is in the idle loop from an RCU point of | |
91 | * view (ie: that we are in the section between rcu_idle_enter() and | |
92 | * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU | |
93 | * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs | |
94 | * that are in such a section, considering these as in extended quiescent | |
95 | * state, so such a CPU is effectively never in an RCU read-side critical | |
96 | * section regardless of what RCU primitives it invokes. This state of | |
97 | * affairs is required --- we need to keep an RCU-free window in idle | |
98 | * where the CPU may possibly enter into low power mode. This way we can | |
99 | * notice an extended quiescent state to other CPUs that started a grace | |
100 | * period. Otherwise we would delay any grace period as long as we run in | |
101 | * the idle task. | |
102 | * | |
103 | * Similarly, we avoid claiming an SRCU read lock held if the current | |
104 | * CPU is offline. | |
105 | */ | |
106 | int rcu_read_lock_sched_held(void) | |
107 | { | |
108 | int lockdep_opinion = 0; | |
109 | ||
110 | if (!debug_lockdep_rcu_enabled()) | |
111 | return 1; | |
112 | if (!rcu_is_watching()) | |
113 | return 0; | |
114 | if (!rcu_lockdep_current_cpu_online()) | |
115 | return 0; | |
116 | if (debug_locks) | |
117 | lockdep_opinion = lock_is_held(&rcu_sched_lock_map); | |
293e2421 | 118 | return lockdep_opinion || !preemptible(); |
d5671f6b DV |
119 | } |
120 | EXPORT_SYMBOL(rcu_read_lock_sched_held); | |
121 | #endif | |
122 | ||
0d39482c PM |
123 | #ifndef CONFIG_TINY_RCU |
124 | ||
5a9be7c6 PM |
125 | /* |
126 | * Should expedited grace-period primitives always fall back to their | |
127 | * non-expedited counterparts? Intended for use within RCU. Note | |
128 | * that if the user specifies both rcu_expedited and rcu_normal, then | |
52d7e48b | 129 | * rcu_normal wins. (Except during the time period during boot from |
900b1028 | 130 | * when the first task is spawned until the rcu_set_runtime_mode() |
52d7e48b | 131 | * core_initcall() is invoked, at which point everything is expedited.) |
5a9be7c6 PM |
132 | */ |
133 | bool rcu_gp_is_normal(void) | |
134 | { | |
52d7e48b PM |
135 | return READ_ONCE(rcu_normal) && |
136 | rcu_scheduler_active != RCU_SCHEDULER_INIT; | |
5a9be7c6 | 137 | } |
4f2a848c | 138 | EXPORT_SYMBOL_GPL(rcu_gp_is_normal); |
5a9be7c6 | 139 | |
7c6094db | 140 | static atomic_t rcu_expedited_nesting = ATOMIC_INIT(1); |
0d39482c PM |
141 | |
142 | /* | |
143 | * Should normal grace-period primitives be expedited? Intended for | |
144 | * use within RCU. Note that this function takes the rcu_expedited | |
52d7e48b PM |
145 | * sysfs/boot variable and rcu_scheduler_active into account as well |
146 | * as the rcu_expedite_gp() nesting. So looping on rcu_unexpedite_gp() | |
147 | * until rcu_gp_is_expedited() returns false is a -really- bad idea. | |
0d39482c PM |
148 | */ |
149 | bool rcu_gp_is_expedited(void) | |
150 | { | |
52d7e48b PM |
151 | return rcu_expedited || atomic_read(&rcu_expedited_nesting) || |
152 | rcu_scheduler_active == RCU_SCHEDULER_INIT; | |
0d39482c PM |
153 | } |
154 | EXPORT_SYMBOL_GPL(rcu_gp_is_expedited); | |
155 | ||
156 | /** | |
157 | * rcu_expedite_gp - Expedite future RCU grace periods | |
158 | * | |
159 | * After a call to this function, future calls to synchronize_rcu() and | |
160 | * friends act as the corresponding synchronize_rcu_expedited() function | |
161 | * had instead been called. | |
162 | */ | |
163 | void rcu_expedite_gp(void) | |
164 | { | |
165 | atomic_inc(&rcu_expedited_nesting); | |
166 | } | |
167 | EXPORT_SYMBOL_GPL(rcu_expedite_gp); | |
168 | ||
169 | /** | |
170 | * rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation | |
171 | * | |
172 | * Undo a prior call to rcu_expedite_gp(). If all prior calls to | |
173 | * rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(), | |
174 | * and if the rcu_expedited sysfs/boot parameter is not set, then all | |
175 | * subsequent calls to synchronize_rcu() and friends will return to | |
176 | * their normal non-expedited behavior. | |
177 | */ | |
178 | void rcu_unexpedite_gp(void) | |
179 | { | |
180 | atomic_dec(&rcu_expedited_nesting); | |
181 | } | |
182 | EXPORT_SYMBOL_GPL(rcu_unexpedite_gp); | |
183 | ||
ee42571f PM |
184 | /* |
185 | * Inform RCU of the end of the in-kernel boot sequence. | |
186 | */ | |
187 | void rcu_end_inkernel_boot(void) | |
188 | { | |
7c6094db | 189 | rcu_unexpedite_gp(); |
3e42ec1a PM |
190 | if (rcu_normal_after_boot) |
191 | WRITE_ONCE(rcu_normal, 1); | |
ee42571f | 192 | } |
0d39482c | 193 | |
79cfea02 PM |
194 | #endif /* #ifndef CONFIG_TINY_RCU */ |
195 | ||
900b1028 PM |
196 | /* |
197 | * Test each non-SRCU synchronous grace-period wait API. This is | |
198 | * useful just after a change in mode for these primitives, and | |
199 | * during early boot. | |
200 | */ | |
201 | void rcu_test_sync_prims(void) | |
202 | { | |
203 | if (!IS_ENABLED(CONFIG_PROVE_RCU)) | |
204 | return; | |
205 | synchronize_rcu(); | |
206 | synchronize_rcu_bh(); | |
207 | synchronize_sched(); | |
208 | synchronize_rcu_expedited(); | |
209 | synchronize_rcu_bh_expedited(); | |
210 | synchronize_sched_expedited(); | |
211 | } | |
212 | ||
213 | #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) | |
214 | ||
215 | /* | |
216 | * Switch to run-time mode once RCU has fully initialized. | |
217 | */ | |
218 | static int __init rcu_set_runtime_mode(void) | |
219 | { | |
220 | rcu_test_sync_prims(); | |
221 | rcu_scheduler_active = RCU_SCHEDULER_RUNNING; | |
222 | rcu_test_sync_prims(); | |
223 | return 0; | |
224 | } | |
225 | core_initcall(rcu_set_runtime_mode); | |
226 | ||
227 | #endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */ | |
228 | ||
9dd8fb16 PM |
229 | #ifdef CONFIG_PREEMPT_RCU |
230 | ||
2a3fa843 PM |
231 | /* |
232 | * Preemptible RCU implementation for rcu_read_lock(). | |
233 | * Just increment ->rcu_read_lock_nesting, shared state will be updated | |
234 | * if we block. | |
235 | */ | |
236 | void __rcu_read_lock(void) | |
237 | { | |
238 | current->rcu_read_lock_nesting++; | |
239 | barrier(); /* critical section after entry code. */ | |
240 | } | |
241 | EXPORT_SYMBOL_GPL(__rcu_read_lock); | |
242 | ||
243 | /* | |
244 | * Preemptible RCU implementation for rcu_read_unlock(). | |
245 | * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost | |
246 | * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then | |
247 | * invoke rcu_read_unlock_special() to clean up after a context switch | |
248 | * in an RCU read-side critical section and other special cases. | |
249 | */ | |
250 | void __rcu_read_unlock(void) | |
251 | { | |
252 | struct task_struct *t = current; | |
253 | ||
254 | if (t->rcu_read_lock_nesting != 1) { | |
255 | --t->rcu_read_lock_nesting; | |
256 | } else { | |
257 | barrier(); /* critical section before exit code. */ | |
258 | t->rcu_read_lock_nesting = INT_MIN; | |
259 | barrier(); /* assign before ->rcu_read_unlock_special load */ | |
7d0ae808 | 260 | if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s))) |
2a3fa843 PM |
261 | rcu_read_unlock_special(t); |
262 | barrier(); /* ->rcu_read_unlock_special load before assign */ | |
263 | t->rcu_read_lock_nesting = 0; | |
264 | } | |
265 | #ifdef CONFIG_PROVE_LOCKING | |
266 | { | |
7d0ae808 | 267 | int rrln = READ_ONCE(t->rcu_read_lock_nesting); |
2a3fa843 PM |
268 | |
269 | WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2); | |
270 | } | |
271 | #endif /* #ifdef CONFIG_PROVE_LOCKING */ | |
272 | } | |
273 | EXPORT_SYMBOL_GPL(__rcu_read_unlock); | |
274 | ||
2439b696 | 275 | #endif /* #ifdef CONFIG_PREEMPT_RCU */ |
9dd8fb16 | 276 | |
162cc279 PM |
277 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
278 | static struct lock_class_key rcu_lock_key; | |
279 | struct lockdep_map rcu_lock_map = | |
280 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); | |
281 | EXPORT_SYMBOL_GPL(rcu_lock_map); | |
632ee200 PM |
282 | |
283 | static struct lock_class_key rcu_bh_lock_key; | |
284 | struct lockdep_map rcu_bh_lock_map = | |
285 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key); | |
286 | EXPORT_SYMBOL_GPL(rcu_bh_lock_map); | |
287 | ||
288 | static struct lock_class_key rcu_sched_lock_key; | |
289 | struct lockdep_map rcu_sched_lock_map = | |
290 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key); | |
291 | EXPORT_SYMBOL_GPL(rcu_sched_lock_map); | |
e3818b8d | 292 | |
24ef659a PM |
293 | static struct lock_class_key rcu_callback_key; |
294 | struct lockdep_map rcu_callback_map = | |
295 | STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key); | |
296 | EXPORT_SYMBOL_GPL(rcu_callback_map); | |
297 | ||
a0a5a056 | 298 | int notrace debug_lockdep_rcu_enabled(void) |
bc293d62 | 299 | { |
52d7e48b | 300 | return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && debug_locks && |
bc293d62 PM |
301 | current->lockdep_recursion == 0; |
302 | } | |
303 | EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); | |
304 | ||
85b39d30 ON |
305 | /** |
306 | * rcu_read_lock_held() - might we be in RCU read-side critical section? | |
307 | * | |
308 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU | |
309 | * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, | |
310 | * this assumes we are in an RCU read-side critical section unless it can | |
311 | * prove otherwise. This is useful for debug checks in functions that | |
312 | * require that they be called within an RCU read-side critical section. | |
313 | * | |
314 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot | |
315 | * and while lockdep is disabled. | |
316 | * | |
317 | * Note that rcu_read_lock() and the matching rcu_read_unlock() must | |
318 | * occur in the same context, for example, it is illegal to invoke | |
319 | * rcu_read_unlock() in process context if the matching rcu_read_lock() | |
320 | * was invoked from within an irq handler. | |
321 | * | |
322 | * Note that rcu_read_lock() is disallowed if the CPU is either idle or | |
323 | * offline from an RCU perspective, so check for those as well. | |
324 | */ | |
325 | int rcu_read_lock_held(void) | |
326 | { | |
327 | if (!debug_lockdep_rcu_enabled()) | |
328 | return 1; | |
329 | if (!rcu_is_watching()) | |
330 | return 0; | |
331 | if (!rcu_lockdep_current_cpu_online()) | |
332 | return 0; | |
333 | return lock_is_held(&rcu_lock_map); | |
334 | } | |
335 | EXPORT_SYMBOL_GPL(rcu_read_lock_held); | |
336 | ||
e3818b8d | 337 | /** |
ca5ecddf | 338 | * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section? |
e3818b8d PM |
339 | * |
340 | * Check for bottom half being disabled, which covers both the | |
341 | * CONFIG_PROVE_RCU and not cases. Note that if someone uses | |
342 | * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled) | |
ca5ecddf PM |
343 | * will show the situation. This is useful for debug checks in functions |
344 | * that require that they be called within an RCU read-side critical | |
345 | * section. | |
e3818b8d PM |
346 | * |
347 | * Check debug_lockdep_rcu_enabled() to prevent false positives during boot. | |
c0d6d01b PM |
348 | * |
349 | * Note that rcu_read_lock() is disallowed if the CPU is either idle or | |
350 | * offline from an RCU perspective, so check for those as well. | |
e3818b8d PM |
351 | */ |
352 | int rcu_read_lock_bh_held(void) | |
353 | { | |
354 | if (!debug_lockdep_rcu_enabled()) | |
355 | return 1; | |
5c173eb8 | 356 | if (!rcu_is_watching()) |
e6b80a3b | 357 | return 0; |
c0d6d01b PM |
358 | if (!rcu_lockdep_current_cpu_online()) |
359 | return 0; | |
773e3f93 | 360 | return in_softirq() || irqs_disabled(); |
e3818b8d PM |
361 | } |
362 | EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); | |
363 | ||
364 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
365 | ||
ee376dbd PM |
366 | /** |
367 | * wakeme_after_rcu() - Callback function to awaken a task after grace period | |
368 | * @head: Pointer to rcu_head member within rcu_synchronize structure | |
369 | * | |
370 | * Awaken the corresponding task now that a grace period has elapsed. | |
fbf6bfca | 371 | */ |
ee376dbd | 372 | void wakeme_after_rcu(struct rcu_head *head) |
21a1ea9e | 373 | { |
01c1c660 PM |
374 | struct rcu_synchronize *rcu; |
375 | ||
376 | rcu = container_of(head, struct rcu_synchronize, head); | |
377 | complete(&rcu->completion); | |
21a1ea9e | 378 | } |
ec90a194 | 379 | EXPORT_SYMBOL_GPL(wakeme_after_rcu); |
ee84b824 | 380 | |
ec90a194 PM |
381 | void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array, |
382 | struct rcu_synchronize *rs_array) | |
2c42818e | 383 | { |
ec90a194 | 384 | int i; |
68ab0b42 | 385 | int j; |
ec90a194 PM |
386 | |
387 | /* Initialize and register callbacks for each flavor specified. */ | |
388 | for (i = 0; i < n; i++) { | |
389 | if (checktiny && | |
390 | (crcu_array[i] == call_rcu || | |
391 | crcu_array[i] == call_rcu_bh)) { | |
392 | might_sleep(); | |
393 | continue; | |
394 | } | |
395 | init_rcu_head_on_stack(&rs_array[i].head); | |
396 | init_completion(&rs_array[i].completion); | |
68ab0b42 PM |
397 | for (j = 0; j < i; j++) |
398 | if (crcu_array[j] == crcu_array[i]) | |
399 | break; | |
400 | if (j == i) | |
401 | (crcu_array[i])(&rs_array[i].head, wakeme_after_rcu); | |
ec90a194 PM |
402 | } |
403 | ||
404 | /* Wait for all callbacks to be invoked. */ | |
405 | for (i = 0; i < n; i++) { | |
406 | if (checktiny && | |
407 | (crcu_array[i] == call_rcu || | |
408 | crcu_array[i] == call_rcu_bh)) | |
409 | continue; | |
68ab0b42 PM |
410 | for (j = 0; j < i; j++) |
411 | if (crcu_array[j] == crcu_array[i]) | |
412 | break; | |
413 | if (j == i) | |
414 | wait_for_completion(&rs_array[i].completion); | |
ec90a194 PM |
415 | destroy_rcu_head_on_stack(&rs_array[i].head); |
416 | } | |
2c42818e | 417 | } |
ec90a194 | 418 | EXPORT_SYMBOL_GPL(__wait_rcu_gp); |
2c42818e | 419 | |
551d55a9 | 420 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD |
546a9d85 | 421 | void init_rcu_head(struct rcu_head *head) |
551d55a9 MD |
422 | { |
423 | debug_object_init(head, &rcuhead_debug_descr); | |
424 | } | |
425 | ||
546a9d85 | 426 | void destroy_rcu_head(struct rcu_head *head) |
551d55a9 MD |
427 | { |
428 | debug_object_free(head, &rcuhead_debug_descr); | |
429 | } | |
430 | ||
b9fdac7f | 431 | static bool rcuhead_is_static_object(void *addr) |
551d55a9 | 432 | { |
b9fdac7f | 433 | return true; |
551d55a9 MD |
434 | } |
435 | ||
436 | /** | |
437 | * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects | |
438 | * @head: pointer to rcu_head structure to be initialized | |
439 | * | |
440 | * This function informs debugobjects of a new rcu_head structure that | |
441 | * has been allocated as an auto variable on the stack. This function | |
442 | * is not required for rcu_head structures that are statically defined or | |
443 | * that are dynamically allocated on the heap. This function has no | |
444 | * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. | |
445 | */ | |
446 | void init_rcu_head_on_stack(struct rcu_head *head) | |
447 | { | |
448 | debug_object_init_on_stack(head, &rcuhead_debug_descr); | |
449 | } | |
450 | EXPORT_SYMBOL_GPL(init_rcu_head_on_stack); | |
451 | ||
452 | /** | |
453 | * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects | |
454 | * @head: pointer to rcu_head structure to be initialized | |
455 | * | |
456 | * This function informs debugobjects that an on-stack rcu_head structure | |
457 | * is about to go out of scope. As with init_rcu_head_on_stack(), this | |
458 | * function is not required for rcu_head structures that are statically | |
459 | * defined or that are dynamically allocated on the heap. Also as with | |
460 | * init_rcu_head_on_stack(), this function has no effect for | |
461 | * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. | |
462 | */ | |
463 | void destroy_rcu_head_on_stack(struct rcu_head *head) | |
464 | { | |
465 | debug_object_free(head, &rcuhead_debug_descr); | |
466 | } | |
467 | EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack); | |
468 | ||
469 | struct debug_obj_descr rcuhead_debug_descr = { | |
470 | .name = "rcu_head", | |
b9fdac7f | 471 | .is_static_object = rcuhead_is_static_object, |
551d55a9 MD |
472 | }; |
473 | EXPORT_SYMBOL_GPL(rcuhead_debug_descr); | |
474 | #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ | |
91afaf30 | 475 | |
28f6569a | 476 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE) |
e66c33d5 | 477 | void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, |
52494535 PM |
478 | unsigned long secs, |
479 | unsigned long c_old, unsigned long c) | |
91afaf30 | 480 | { |
52494535 | 481 | trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c); |
91afaf30 PM |
482 | } |
483 | EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read); | |
484 | #else | |
52494535 PM |
485 | #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ |
486 | do { } while (0) | |
91afaf30 | 487 | #endif |
6bfc09e2 PM |
488 | |
489 | #ifdef CONFIG_RCU_STALL_COMMON | |
490 | ||
491 | #ifdef CONFIG_PROVE_RCU | |
492 | #define RCU_STALL_DELAY_DELTA (5 * HZ) | |
493 | #else | |
494 | #define RCU_STALL_DELAY_DELTA 0 | |
495 | #endif | |
496 | ||
497 | int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */ | |
01896f7e | 498 | static int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; |
6bfc09e2 PM |
499 | |
500 | module_param(rcu_cpu_stall_suppress, int, 0644); | |
501 | module_param(rcu_cpu_stall_timeout, int, 0644); | |
502 | ||
503 | int rcu_jiffies_till_stall_check(void) | |
504 | { | |
7d0ae808 | 505 | int till_stall_check = READ_ONCE(rcu_cpu_stall_timeout); |
6bfc09e2 PM |
506 | |
507 | /* | |
508 | * Limit check must be consistent with the Kconfig limits | |
509 | * for CONFIG_RCU_CPU_STALL_TIMEOUT. | |
510 | */ | |
511 | if (till_stall_check < 3) { | |
7d0ae808 | 512 | WRITE_ONCE(rcu_cpu_stall_timeout, 3); |
6bfc09e2 PM |
513 | till_stall_check = 3; |
514 | } else if (till_stall_check > 300) { | |
7d0ae808 | 515 | WRITE_ONCE(rcu_cpu_stall_timeout, 300); |
6bfc09e2 PM |
516 | till_stall_check = 300; |
517 | } | |
518 | return till_stall_check * HZ + RCU_STALL_DELAY_DELTA; | |
519 | } | |
520 | ||
61f38db3 RR |
521 | void rcu_sysrq_start(void) |
522 | { | |
523 | if (!rcu_cpu_stall_suppress) | |
524 | rcu_cpu_stall_suppress = 2; | |
525 | } | |
526 | ||
527 | void rcu_sysrq_end(void) | |
528 | { | |
529 | if (rcu_cpu_stall_suppress == 2) | |
530 | rcu_cpu_stall_suppress = 0; | |
531 | } | |
532 | ||
6bfc09e2 PM |
533 | static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) |
534 | { | |
535 | rcu_cpu_stall_suppress = 1; | |
536 | return NOTIFY_DONE; | |
537 | } | |
538 | ||
539 | static struct notifier_block rcu_panic_block = { | |
540 | .notifier_call = rcu_panic, | |
541 | }; | |
542 | ||
543 | static int __init check_cpu_stall_init(void) | |
544 | { | |
545 | atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); | |
546 | return 0; | |
547 | } | |
548 | early_initcall(check_cpu_stall_init); | |
549 | ||
550 | #endif /* #ifdef CONFIG_RCU_STALL_COMMON */ | |
8315f422 PM |
551 | |
552 | #ifdef CONFIG_TASKS_RCU | |
553 | ||
554 | /* | |
555 | * Simple variant of RCU whose quiescent states are voluntary context switch, | |
556 | * user-space execution, and idle. As such, grace periods can take one good | |
557 | * long time. There are no read-side primitives similar to rcu_read_lock() | |
558 | * and rcu_read_unlock() because this implementation is intended to get | |
559 | * the system into a safe state for some of the manipulations involved in | |
560 | * tracing and the like. Finally, this implementation does not support | |
561 | * high call_rcu_tasks() rates from multiple CPUs. If this is required, | |
562 | * per-CPU callback lists will be needed. | |
563 | */ | |
564 | ||
565 | /* Global list of callbacks and associated lock. */ | |
566 | static struct rcu_head *rcu_tasks_cbs_head; | |
567 | static struct rcu_head **rcu_tasks_cbs_tail = &rcu_tasks_cbs_head; | |
c7b24d2b | 568 | static DECLARE_WAIT_QUEUE_HEAD(rcu_tasks_cbs_wq); |
8315f422 PM |
569 | static DEFINE_RAW_SPINLOCK(rcu_tasks_cbs_lock); |
570 | ||
3f95aa81 | 571 | /* Track exiting tasks in order to allow them to be waited for. */ |
ccdd29ff | 572 | DEFINE_STATIC_SRCU(tasks_rcu_exit_srcu); |
3f95aa81 PM |
573 | |
574 | /* Control stall timeouts. Disable with <= 0, otherwise jiffies till stall. */ | |
59d80fd8 PM |
575 | #define RCU_TASK_STALL_TIMEOUT (HZ * 60 * 10) |
576 | static int rcu_task_stall_timeout __read_mostly = RCU_TASK_STALL_TIMEOUT; | |
3f95aa81 PM |
577 | module_param(rcu_task_stall_timeout, int, 0644); |
578 | ||
84a8f446 | 579 | static void rcu_spawn_tasks_kthread(void); |
4929c913 | 580 | static struct task_struct *rcu_tasks_kthread_ptr; |
84a8f446 | 581 | |
a68a2bb2 PM |
582 | /** |
583 | * call_rcu_tasks() - Queue an RCU for invocation task-based grace period | |
584 | * @rhp: structure to be used for queueing the RCU updates. | |
585 | * @func: actual callback function to be invoked after the grace period | |
586 | * | |
587 | * The callback function will be invoked some time after a full grace | |
588 | * period elapses, in other words after all currently executing RCU | |
589 | * read-side critical sections have completed. call_rcu_tasks() assumes | |
590 | * that the read-side critical sections end at a voluntary context | |
591 | * switch (not a preemption!), entry into idle, or transition to usermode | |
592 | * execution. As such, there are no read-side primitives analogous to | |
593 | * rcu_read_lock() and rcu_read_unlock() because this primitive is intended | |
594 | * to determine that all tasks have passed through a safe state, not so | |
595 | * much for data-strcuture synchronization. | |
596 | * | |
597 | * See the description of call_rcu() for more detailed information on | |
598 | * memory ordering guarantees. | |
84a8f446 | 599 | */ |
b6a4ae76 | 600 | void call_rcu_tasks(struct rcu_head *rhp, rcu_callback_t func) |
8315f422 PM |
601 | { |
602 | unsigned long flags; | |
c7b24d2b | 603 | bool needwake; |
4929c913 | 604 | bool havetask = READ_ONCE(rcu_tasks_kthread_ptr); |
8315f422 PM |
605 | |
606 | rhp->next = NULL; | |
607 | rhp->func = func; | |
608 | raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags); | |
c7b24d2b | 609 | needwake = !rcu_tasks_cbs_head; |
8315f422 PM |
610 | *rcu_tasks_cbs_tail = rhp; |
611 | rcu_tasks_cbs_tail = &rhp->next; | |
612 | raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags); | |
4929c913 PM |
613 | /* We can't create the thread unless interrupts are enabled. */ |
614 | if ((needwake && havetask) || | |
615 | (!havetask && !irqs_disabled_flags(flags))) { | |
84a8f446 | 616 | rcu_spawn_tasks_kthread(); |
c7b24d2b | 617 | wake_up(&rcu_tasks_cbs_wq); |
84a8f446 | 618 | } |
8315f422 PM |
619 | } |
620 | EXPORT_SYMBOL_GPL(call_rcu_tasks); | |
621 | ||
53c6d4ed PM |
622 | /** |
623 | * synchronize_rcu_tasks - wait until an rcu-tasks grace period has elapsed. | |
624 | * | |
625 | * Control will return to the caller some time after a full rcu-tasks | |
626 | * grace period has elapsed, in other words after all currently | |
627 | * executing rcu-tasks read-side critical sections have elapsed. These | |
628 | * read-side critical sections are delimited by calls to schedule(), | |
629 | * cond_resched_rcu_qs(), idle execution, userspace execution, calls | |
630 | * to synchronize_rcu_tasks(), and (in theory, anyway) cond_resched(). | |
631 | * | |
632 | * This is a very specialized primitive, intended only for a few uses in | |
633 | * tracing and other situations requiring manipulation of function | |
634 | * preambles and profiling hooks. The synchronize_rcu_tasks() function | |
635 | * is not (yet) intended for heavy use from multiple CPUs. | |
636 | * | |
637 | * Note that this guarantee implies further memory-ordering guarantees. | |
638 | * On systems with more than one CPU, when synchronize_rcu_tasks() returns, | |
639 | * each CPU is guaranteed to have executed a full memory barrier since the | |
640 | * end of its last RCU-tasks read-side critical section whose beginning | |
641 | * preceded the call to synchronize_rcu_tasks(). In addition, each CPU | |
642 | * having an RCU-tasks read-side critical section that extends beyond | |
643 | * the return from synchronize_rcu_tasks() is guaranteed to have executed | |
644 | * a full memory barrier after the beginning of synchronize_rcu_tasks() | |
645 | * and before the beginning of that RCU-tasks read-side critical section. | |
646 | * Note that these guarantees include CPUs that are offline, idle, or | |
647 | * executing in user mode, as well as CPUs that are executing in the kernel. | |
648 | * | |
649 | * Furthermore, if CPU A invoked synchronize_rcu_tasks(), which returned | |
650 | * to its caller on CPU B, then both CPU A and CPU B are guaranteed | |
651 | * to have executed a full memory barrier during the execution of | |
652 | * synchronize_rcu_tasks() -- even if CPU A and CPU B are the same CPU | |
653 | * (but again only if the system has more than one CPU). | |
654 | */ | |
655 | void synchronize_rcu_tasks(void) | |
656 | { | |
657 | /* Complain if the scheduler has not started. */ | |
52d7e48b | 658 | RCU_LOCKDEP_WARN(rcu_scheduler_active == RCU_SCHEDULER_INACTIVE, |
f78f5b90 | 659 | "synchronize_rcu_tasks called too soon"); |
53c6d4ed PM |
660 | |
661 | /* Wait for the grace period. */ | |
662 | wait_rcu_gp(call_rcu_tasks); | |
663 | } | |
06c2a923 | 664 | EXPORT_SYMBOL_GPL(synchronize_rcu_tasks); |
53c6d4ed PM |
665 | |
666 | /** | |
667 | * rcu_barrier_tasks - Wait for in-flight call_rcu_tasks() callbacks. | |
668 | * | |
669 | * Although the current implementation is guaranteed to wait, it is not | |
670 | * obligated to, for example, if there are no pending callbacks. | |
671 | */ | |
672 | void rcu_barrier_tasks(void) | |
673 | { | |
674 | /* There is only one callback queue, so this is easy. ;-) */ | |
675 | synchronize_rcu_tasks(); | |
676 | } | |
06c2a923 | 677 | EXPORT_SYMBOL_GPL(rcu_barrier_tasks); |
53c6d4ed | 678 | |
52db30ab PM |
679 | /* See if tasks are still holding out, complain if so. */ |
680 | static void check_holdout_task(struct task_struct *t, | |
681 | bool needreport, bool *firstreport) | |
8315f422 | 682 | { |
4ff475ed PM |
683 | int cpu; |
684 | ||
7d0ae808 PM |
685 | if (!READ_ONCE(t->rcu_tasks_holdout) || |
686 | t->rcu_tasks_nvcsw != READ_ONCE(t->nvcsw) || | |
687 | !READ_ONCE(t->on_rq) || | |
176f8f7a PM |
688 | (IS_ENABLED(CONFIG_NO_HZ_FULL) && |
689 | !is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) { | |
7d0ae808 | 690 | WRITE_ONCE(t->rcu_tasks_holdout, false); |
8f20a5e8 | 691 | list_del_init(&t->rcu_tasks_holdout_list); |
8315f422 | 692 | put_task_struct(t); |
52db30ab | 693 | return; |
8315f422 | 694 | } |
bcbfdd01 | 695 | rcu_request_urgent_qs_task(t); |
52db30ab PM |
696 | if (!needreport) |
697 | return; | |
698 | if (*firstreport) { | |
699 | pr_err("INFO: rcu_tasks detected stalls on tasks:\n"); | |
700 | *firstreport = false; | |
701 | } | |
4ff475ed PM |
702 | cpu = task_cpu(t); |
703 | pr_alert("%p: %c%c nvcsw: %lu/%lu holdout: %d idle_cpu: %d/%d\n", | |
704 | t, ".I"[is_idle_task(t)], | |
705 | "N."[cpu < 0 || !tick_nohz_full_cpu(cpu)], | |
706 | t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout, | |
707 | t->rcu_tasks_idle_cpu, cpu); | |
52db30ab | 708 | sched_show_task(t); |
8315f422 PM |
709 | } |
710 | ||
711 | /* RCU-tasks kthread that detects grace periods and invokes callbacks. */ | |
712 | static int __noreturn rcu_tasks_kthread(void *arg) | |
713 | { | |
714 | unsigned long flags; | |
715 | struct task_struct *g, *t; | |
52db30ab | 716 | unsigned long lastreport; |
8315f422 PM |
717 | struct rcu_head *list; |
718 | struct rcu_head *next; | |
719 | LIST_HEAD(rcu_tasks_holdouts); | |
720 | ||
60ced495 PM |
721 | /* Run on housekeeping CPUs by default. Sysadm can move if desired. */ |
722 | housekeeping_affine(current); | |
8315f422 PM |
723 | |
724 | /* | |
725 | * Each pass through the following loop makes one check for | |
726 | * newly arrived callbacks, and, if there are some, waits for | |
727 | * one RCU-tasks grace period and then invokes the callbacks. | |
728 | * This loop is terminated by the system going down. ;-) | |
729 | */ | |
730 | for (;;) { | |
731 | ||
732 | /* Pick up any new callbacks. */ | |
733 | raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags); | |
734 | list = rcu_tasks_cbs_head; | |
735 | rcu_tasks_cbs_head = NULL; | |
736 | rcu_tasks_cbs_tail = &rcu_tasks_cbs_head; | |
737 | raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags); | |
738 | ||
739 | /* If there were none, wait a bit and start over. */ | |
740 | if (!list) { | |
c7b24d2b PM |
741 | wait_event_interruptible(rcu_tasks_cbs_wq, |
742 | rcu_tasks_cbs_head); | |
743 | if (!rcu_tasks_cbs_head) { | |
744 | WARN_ON(signal_pending(current)); | |
745 | schedule_timeout_interruptible(HZ/10); | |
746 | } | |
8315f422 PM |
747 | continue; |
748 | } | |
749 | ||
750 | /* | |
751 | * Wait for all pre-existing t->on_rq and t->nvcsw | |
752 | * transitions to complete. Invoking synchronize_sched() | |
753 | * suffices because all these transitions occur with | |
754 | * interrupts disabled. Without this synchronize_sched(), | |
755 | * a read-side critical section that started before the | |
756 | * grace period might be incorrectly seen as having started | |
757 | * after the grace period. | |
758 | * | |
759 | * This synchronize_sched() also dispenses with the | |
760 | * need for a memory barrier on the first store to | |
761 | * ->rcu_tasks_holdout, as it forces the store to happen | |
762 | * after the beginning of the grace period. | |
763 | */ | |
764 | synchronize_sched(); | |
765 | ||
766 | /* | |
767 | * There were callbacks, so we need to wait for an | |
768 | * RCU-tasks grace period. Start off by scanning | |
769 | * the task list for tasks that are not already | |
770 | * voluntarily blocked. Mark these tasks and make | |
771 | * a list of them in rcu_tasks_holdouts. | |
772 | */ | |
773 | rcu_read_lock(); | |
774 | for_each_process_thread(g, t) { | |
7d0ae808 | 775 | if (t != current && READ_ONCE(t->on_rq) && |
8315f422 PM |
776 | !is_idle_task(t)) { |
777 | get_task_struct(t); | |
7d0ae808 PM |
778 | t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw); |
779 | WRITE_ONCE(t->rcu_tasks_holdout, true); | |
8315f422 PM |
780 | list_add(&t->rcu_tasks_holdout_list, |
781 | &rcu_tasks_holdouts); | |
782 | } | |
783 | } | |
784 | rcu_read_unlock(); | |
785 | ||
3f95aa81 PM |
786 | /* |
787 | * Wait for tasks that are in the process of exiting. | |
788 | * This does only part of the job, ensuring that all | |
789 | * tasks that were previously exiting reach the point | |
790 | * where they have disabled preemption, allowing the | |
791 | * later synchronize_sched() to finish the job. | |
792 | */ | |
793 | synchronize_srcu(&tasks_rcu_exit_srcu); | |
794 | ||
8315f422 PM |
795 | /* |
796 | * Each pass through the following loop scans the list | |
797 | * of holdout tasks, removing any that are no longer | |
798 | * holdouts. When the list is empty, we are done. | |
799 | */ | |
52db30ab | 800 | lastreport = jiffies; |
8315f422 | 801 | while (!list_empty(&rcu_tasks_holdouts)) { |
52db30ab PM |
802 | bool firstreport; |
803 | bool needreport; | |
804 | int rtst; | |
8f20a5e8 | 805 | struct task_struct *t1; |
52db30ab | 806 | |
8315f422 | 807 | schedule_timeout_interruptible(HZ); |
7d0ae808 | 808 | rtst = READ_ONCE(rcu_task_stall_timeout); |
52db30ab PM |
809 | needreport = rtst > 0 && |
810 | time_after(jiffies, lastreport + rtst); | |
811 | if (needreport) | |
812 | lastreport = jiffies; | |
813 | firstreport = true; | |
8315f422 | 814 | WARN_ON(signal_pending(current)); |
8f20a5e8 PM |
815 | list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts, |
816 | rcu_tasks_holdout_list) { | |
52db30ab | 817 | check_holdout_task(t, needreport, &firstreport); |
8f20a5e8 PM |
818 | cond_resched(); |
819 | } | |
8315f422 PM |
820 | } |
821 | ||
822 | /* | |
823 | * Because ->on_rq and ->nvcsw are not guaranteed | |
824 | * to have a full memory barriers prior to them in the | |
825 | * schedule() path, memory reordering on other CPUs could | |
826 | * cause their RCU-tasks read-side critical sections to | |
827 | * extend past the end of the grace period. However, | |
828 | * because these ->nvcsw updates are carried out with | |
829 | * interrupts disabled, we can use synchronize_sched() | |
830 | * to force the needed ordering on all such CPUs. | |
831 | * | |
832 | * This synchronize_sched() also confines all | |
833 | * ->rcu_tasks_holdout accesses to be within the grace | |
834 | * period, avoiding the need for memory barriers for | |
835 | * ->rcu_tasks_holdout accesses. | |
3f95aa81 PM |
836 | * |
837 | * In addition, this synchronize_sched() waits for exiting | |
838 | * tasks to complete their final preempt_disable() region | |
839 | * of execution, cleaning up after the synchronize_srcu() | |
840 | * above. | |
8315f422 PM |
841 | */ |
842 | synchronize_sched(); | |
843 | ||
844 | /* Invoke the callbacks. */ | |
845 | while (list) { | |
846 | next = list->next; | |
847 | local_bh_disable(); | |
848 | list->func(list); | |
849 | local_bh_enable(); | |
850 | list = next; | |
851 | cond_resched(); | |
852 | } | |
c7b24d2b | 853 | schedule_timeout_uninterruptible(HZ/10); |
8315f422 PM |
854 | } |
855 | } | |
856 | ||
84a8f446 PM |
857 | /* Spawn rcu_tasks_kthread() at first call to call_rcu_tasks(). */ |
858 | static void rcu_spawn_tasks_kthread(void) | |
8315f422 | 859 | { |
84a8f446 | 860 | static DEFINE_MUTEX(rcu_tasks_kthread_mutex); |
84a8f446 | 861 | struct task_struct *t; |
8315f422 | 862 | |
7d0ae808 | 863 | if (READ_ONCE(rcu_tasks_kthread_ptr)) { |
84a8f446 PM |
864 | smp_mb(); /* Ensure caller sees full kthread. */ |
865 | return; | |
866 | } | |
867 | mutex_lock(&rcu_tasks_kthread_mutex); | |
868 | if (rcu_tasks_kthread_ptr) { | |
869 | mutex_unlock(&rcu_tasks_kthread_mutex); | |
870 | return; | |
871 | } | |
8315f422 PM |
872 | t = kthread_run(rcu_tasks_kthread, NULL, "rcu_tasks_kthread"); |
873 | BUG_ON(IS_ERR(t)); | |
84a8f446 | 874 | smp_mb(); /* Ensure others see full kthread. */ |
7d0ae808 | 875 | WRITE_ONCE(rcu_tasks_kthread_ptr, t); |
84a8f446 | 876 | mutex_unlock(&rcu_tasks_kthread_mutex); |
8315f422 | 877 | } |
8315f422 | 878 | |
ccdd29ff PM |
879 | /* Do the srcu_read_lock() for the above synchronize_srcu(). */ |
880 | void exit_tasks_rcu_start(void) | |
881 | { | |
882 | preempt_disable(); | |
883 | current->rcu_tasks_idx = __srcu_read_lock(&tasks_rcu_exit_srcu); | |
884 | preempt_enable(); | |
885 | } | |
886 | ||
887 | /* Do the srcu_read_unlock() for the above synchronize_srcu(). */ | |
888 | void exit_tasks_rcu_finish(void) | |
889 | { | |
890 | preempt_disable(); | |
891 | __srcu_read_unlock(&tasks_rcu_exit_srcu, current->rcu_tasks_idx); | |
892 | preempt_enable(); | |
893 | } | |
894 | ||
8315f422 | 895 | #endif /* #ifdef CONFIG_TASKS_RCU */ |
aa23c6fb | 896 | |
59d80fd8 PM |
897 | #ifndef CONFIG_TINY_RCU |
898 | ||
899 | /* | |
900 | * Print any non-default Tasks RCU settings. | |
901 | */ | |
902 | static void __init rcu_tasks_bootup_oddness(void) | |
903 | { | |
904 | #ifdef CONFIG_TASKS_RCU | |
905 | if (rcu_task_stall_timeout != RCU_TASK_STALL_TIMEOUT) | |
906 | pr_info("\tTasks-RCU CPU stall warnings timeout set to %d (rcu_task_stall_timeout).\n", rcu_task_stall_timeout); | |
907 | else | |
908 | pr_info("\tTasks RCU enabled.\n"); | |
909 | #endif /* #ifdef CONFIG_TASKS_RCU */ | |
910 | } | |
911 | ||
912 | #endif /* #ifndef CONFIG_TINY_RCU */ | |
913 | ||
aa23c6fb PK |
914 | #ifdef CONFIG_PROVE_RCU |
915 | ||
916 | /* | |
917 | * Early boot self test parameters, one for each flavor | |
918 | */ | |
919 | static bool rcu_self_test; | |
920 | static bool rcu_self_test_bh; | |
921 | static bool rcu_self_test_sched; | |
922 | ||
923 | module_param(rcu_self_test, bool, 0444); | |
924 | module_param(rcu_self_test_bh, bool, 0444); | |
925 | module_param(rcu_self_test_sched, bool, 0444); | |
926 | ||
927 | static int rcu_self_test_counter; | |
928 | ||
929 | static void test_callback(struct rcu_head *r) | |
930 | { | |
931 | rcu_self_test_counter++; | |
932 | pr_info("RCU test callback executed %d\n", rcu_self_test_counter); | |
933 | } | |
934 | ||
935 | static void early_boot_test_call_rcu(void) | |
936 | { | |
937 | static struct rcu_head head; | |
938 | ||
939 | call_rcu(&head, test_callback); | |
940 | } | |
941 | ||
942 | static void early_boot_test_call_rcu_bh(void) | |
943 | { | |
944 | static struct rcu_head head; | |
945 | ||
946 | call_rcu_bh(&head, test_callback); | |
947 | } | |
948 | ||
949 | static void early_boot_test_call_rcu_sched(void) | |
950 | { | |
951 | static struct rcu_head head; | |
952 | ||
953 | call_rcu_sched(&head, test_callback); | |
954 | } | |
955 | ||
956 | void rcu_early_boot_tests(void) | |
957 | { | |
958 | pr_info("Running RCU self tests\n"); | |
959 | ||
960 | if (rcu_self_test) | |
961 | early_boot_test_call_rcu(); | |
962 | if (rcu_self_test_bh) | |
963 | early_boot_test_call_rcu_bh(); | |
964 | if (rcu_self_test_sched) | |
965 | early_boot_test_call_rcu_sched(); | |
52d7e48b | 966 | rcu_test_sync_prims(); |
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967 | } |
968 | ||
969 | static int rcu_verify_early_boot_tests(void) | |
970 | { | |
971 | int ret = 0; | |
972 | int early_boot_test_counter = 0; | |
973 | ||
974 | if (rcu_self_test) { | |
975 | early_boot_test_counter++; | |
976 | rcu_barrier(); | |
977 | } | |
978 | if (rcu_self_test_bh) { | |
979 | early_boot_test_counter++; | |
980 | rcu_barrier_bh(); | |
981 | } | |
982 | if (rcu_self_test_sched) { | |
983 | early_boot_test_counter++; | |
984 | rcu_barrier_sched(); | |
985 | } | |
986 | ||
987 | if (rcu_self_test_counter != early_boot_test_counter) { | |
988 | WARN_ON(1); | |
989 | ret = -1; | |
990 | } | |
991 | ||
992 | return ret; | |
993 | } | |
994 | late_initcall(rcu_verify_early_boot_tests); | |
995 | #else | |
996 | void rcu_early_boot_tests(void) {} | |
997 | #endif /* CONFIG_PROVE_RCU */ | |
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998 | |
999 | #ifndef CONFIG_TINY_RCU | |
1000 | ||
1001 | /* | |
1002 | * Print any significant non-default boot-time settings. | |
1003 | */ | |
1004 | void __init rcupdate_announce_bootup_oddness(void) | |
1005 | { | |
1006 | if (rcu_normal) | |
1007 | pr_info("\tNo expedited grace period (rcu_normal).\n"); | |
1008 | else if (rcu_normal_after_boot) | |
1009 | pr_info("\tNo expedited grace period (rcu_normal_after_boot).\n"); | |
1010 | else if (rcu_expedited) | |
1011 | pr_info("\tAll grace periods are expedited (rcu_expedited).\n"); | |
1012 | if (rcu_cpu_stall_suppress) | |
1013 | pr_info("\tRCU CPU stall warnings suppressed (rcu_cpu_stall_suppress).\n"); | |
1014 | if (rcu_cpu_stall_timeout != CONFIG_RCU_CPU_STALL_TIMEOUT) | |
1015 | pr_info("\tRCU CPU stall warnings timeout set to %d (rcu_cpu_stall_timeout).\n", rcu_cpu_stall_timeout); | |
1016 | rcu_tasks_bootup_oddness(); | |
1017 | } | |
1018 | ||
1019 | #endif /* #ifndef CONFIG_TINY_RCU */ |