Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0+
2 : /*
3 : * Read-Copy Update mechanism for mutual exclusion
4 : *
5 : * Copyright IBM Corporation, 2001
6 : *
7 : * Authors: Dipankar Sarma <dipankar@in.ibm.com>
8 : * Manfred Spraul <manfred@colorfullife.com>
9 : *
10 : * Based on the original work by Paul McKenney <paulmck@linux.ibm.com>
11 : * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
12 : * Papers:
13 : * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
14 : * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
15 : *
16 : * For detailed explanation of Read-Copy Update mechanism see -
17 : * http://lse.sourceforge.net/locking/rcupdate.html
18 : *
19 : */
20 : #include <linux/types.h>
21 : #include <linux/kernel.h>
22 : #include <linux/init.h>
23 : #include <linux/spinlock.h>
24 : #include <linux/smp.h>
25 : #include <linux/interrupt.h>
26 : #include <linux/sched/signal.h>
27 : #include <linux/sched/debug.h>
28 : #include <linux/atomic.h>
29 : #include <linux/bitops.h>
30 : #include <linux/percpu.h>
31 : #include <linux/notifier.h>
32 : #include <linux/cpu.h>
33 : #include <linux/mutex.h>
34 : #include <linux/export.h>
35 : #include <linux/hardirq.h>
36 : #include <linux/delay.h>
37 : #include <linux/moduleparam.h>
38 : #include <linux/kthread.h>
39 : #include <linux/tick.h>
40 : #include <linux/rcupdate_wait.h>
41 : #include <linux/sched/isolation.h>
42 : #include <linux/kprobes.h>
43 : #include <linux/slab.h>
44 : #include <linux/irq_work.h>
45 : #include <linux/rcupdate_trace.h>
46 :
47 : #define CREATE_TRACE_POINTS
48 :
49 : #include "rcu.h"
50 :
51 : #ifdef MODULE_PARAM_PREFIX
52 : #undef MODULE_PARAM_PREFIX
53 : #endif
54 : #define MODULE_PARAM_PREFIX "rcupdate."
55 :
56 : #ifndef CONFIG_TINY_RCU
57 : module_param(rcu_expedited, int, 0444);
58 : module_param(rcu_normal, int, 0444);
59 : static int rcu_normal_after_boot = IS_ENABLED(CONFIG_PREEMPT_RT);
60 : #if !defined(CONFIG_PREEMPT_RT) || defined(CONFIG_NO_HZ_FULL)
61 : module_param(rcu_normal_after_boot, int, 0444);
62 : #endif
63 : #endif /* #ifndef CONFIG_TINY_RCU */
64 :
65 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
66 : /**
67 : * rcu_read_lock_held_common() - might we be in RCU-sched read-side critical section?
68 : * @ret: Best guess answer if lockdep cannot be relied on
69 : *
70 : * Returns true if lockdep must be ignored, in which case ``*ret`` contains
71 : * the best guess described below. Otherwise returns false, in which
72 : * case ``*ret`` tells the caller nothing and the caller should instead
73 : * consult lockdep.
74 : *
75 : * If CONFIG_DEBUG_LOCK_ALLOC is selected, set ``*ret`` to nonzero iff in an
76 : * RCU-sched read-side critical section. In absence of
77 : * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
78 : * critical section unless it can prove otherwise. Note that disabling
79 : * of preemption (including disabling irqs) counts as an RCU-sched
80 : * read-side critical section. This is useful for debug checks in functions
81 : * that required that they be called within an RCU-sched read-side
82 : * critical section.
83 : *
84 : * Check debug_lockdep_rcu_enabled() to prevent false positives during boot
85 : * and while lockdep is disabled.
86 : *
87 : * Note that if the CPU is in the idle loop from an RCU point of view (ie:
88 : * that we are in the section between ct_idle_enter() and ct_idle_exit())
89 : * then rcu_read_lock_held() sets ``*ret`` to false even if the CPU did an
90 : * rcu_read_lock(). The reason for this is that RCU ignores CPUs that are
91 : * in such a section, considering these as in extended quiescent state,
92 : * so such a CPU is effectively never in an RCU read-side critical section
93 : * regardless of what RCU primitives it invokes. This state of affairs is
94 : * required --- we need to keep an RCU-free window in idle where the CPU may
95 : * possibly enter into low power mode. This way we can notice an extended
96 : * quiescent state to other CPUs that started a grace period. Otherwise
97 : * we would delay any grace period as long as we run in the idle task.
98 : *
99 : * Similarly, we avoid claiming an RCU read lock held if the current
100 : * CPU is offline.
101 : */
102 : static bool rcu_read_lock_held_common(bool *ret)
103 : {
104 : if (!debug_lockdep_rcu_enabled()) {
105 : *ret = true;
106 : return true;
107 : }
108 : if (!rcu_is_watching()) {
109 : *ret = false;
110 : return true;
111 : }
112 : if (!rcu_lockdep_current_cpu_online()) {
113 : *ret = false;
114 : return true;
115 : }
116 : return false;
117 : }
118 :
119 : int rcu_read_lock_sched_held(void)
120 : {
121 : bool ret;
122 :
123 : if (rcu_read_lock_held_common(&ret))
124 : return ret;
125 : return lock_is_held(&rcu_sched_lock_map) || !preemptible();
126 : }
127 : EXPORT_SYMBOL(rcu_read_lock_sched_held);
128 : #endif
129 :
130 : #ifndef CONFIG_TINY_RCU
131 :
132 : /*
133 : * Should expedited grace-period primitives always fall back to their
134 : * non-expedited counterparts? Intended for use within RCU. Note
135 : * that if the user specifies both rcu_expedited and rcu_normal, then
136 : * rcu_normal wins. (Except during the time period during boot from
137 : * when the first task is spawned until the rcu_set_runtime_mode()
138 : * core_initcall() is invoked, at which point everything is expedited.)
139 : */
140 : bool rcu_gp_is_normal(void)
141 : {
142 : return READ_ONCE(rcu_normal) &&
143 : rcu_scheduler_active != RCU_SCHEDULER_INIT;
144 : }
145 : EXPORT_SYMBOL_GPL(rcu_gp_is_normal);
146 :
147 : static atomic_t rcu_async_hurry_nesting = ATOMIC_INIT(1);
148 : /*
149 : * Should call_rcu() callbacks be processed with urgency or are
150 : * they OK being executed with arbitrary delays?
151 : */
152 : bool rcu_async_should_hurry(void)
153 : {
154 : return !IS_ENABLED(CONFIG_RCU_LAZY) ||
155 : atomic_read(&rcu_async_hurry_nesting);
156 : }
157 : EXPORT_SYMBOL_GPL(rcu_async_should_hurry);
158 :
159 : /**
160 : * rcu_async_hurry - Make future async RCU callbacks not lazy.
161 : *
162 : * After a call to this function, future calls to call_rcu()
163 : * will be processed in a timely fashion.
164 : */
165 : void rcu_async_hurry(void)
166 : {
167 : if (IS_ENABLED(CONFIG_RCU_LAZY))
168 : atomic_inc(&rcu_async_hurry_nesting);
169 : }
170 : EXPORT_SYMBOL_GPL(rcu_async_hurry);
171 :
172 : /**
173 : * rcu_async_relax - Make future async RCU callbacks lazy.
174 : *
175 : * After a call to this function, future calls to call_rcu()
176 : * will be processed in a lazy fashion.
177 : */
178 : void rcu_async_relax(void)
179 : {
180 : if (IS_ENABLED(CONFIG_RCU_LAZY))
181 : atomic_dec(&rcu_async_hurry_nesting);
182 : }
183 : EXPORT_SYMBOL_GPL(rcu_async_relax);
184 :
185 : static atomic_t rcu_expedited_nesting = ATOMIC_INIT(1);
186 : /*
187 : * Should normal grace-period primitives be expedited? Intended for
188 : * use within RCU. Note that this function takes the rcu_expedited
189 : * sysfs/boot variable and rcu_scheduler_active into account as well
190 : * as the rcu_expedite_gp() nesting. So looping on rcu_unexpedite_gp()
191 : * until rcu_gp_is_expedited() returns false is a -really- bad idea.
192 : */
193 : bool rcu_gp_is_expedited(void)
194 : {
195 : return rcu_expedited || atomic_read(&rcu_expedited_nesting);
196 : }
197 : EXPORT_SYMBOL_GPL(rcu_gp_is_expedited);
198 :
199 : /**
200 : * rcu_expedite_gp - Expedite future RCU grace periods
201 : *
202 : * After a call to this function, future calls to synchronize_rcu() and
203 : * friends act as the corresponding synchronize_rcu_expedited() function
204 : * had instead been called.
205 : */
206 : void rcu_expedite_gp(void)
207 : {
208 : atomic_inc(&rcu_expedited_nesting);
209 : }
210 : EXPORT_SYMBOL_GPL(rcu_expedite_gp);
211 :
212 : /**
213 : * rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation
214 : *
215 : * Undo a prior call to rcu_expedite_gp(). If all prior calls to
216 : * rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(),
217 : * and if the rcu_expedited sysfs/boot parameter is not set, then all
218 : * subsequent calls to synchronize_rcu() and friends will return to
219 : * their normal non-expedited behavior.
220 : */
221 : void rcu_unexpedite_gp(void)
222 : {
223 : atomic_dec(&rcu_expedited_nesting);
224 : }
225 : EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
226 :
227 : static bool rcu_boot_ended __read_mostly;
228 :
229 : /*
230 : * Inform RCU of the end of the in-kernel boot sequence.
231 : */
232 : void rcu_end_inkernel_boot(void)
233 : {
234 : rcu_unexpedite_gp();
235 : rcu_async_relax();
236 : if (rcu_normal_after_boot)
237 : WRITE_ONCE(rcu_normal, 1);
238 : rcu_boot_ended = true;
239 : }
240 :
241 : /*
242 : * Let rcutorture know when it is OK to turn it up to eleven.
243 : */
244 : bool rcu_inkernel_boot_has_ended(void)
245 : {
246 : return rcu_boot_ended;
247 : }
248 : EXPORT_SYMBOL_GPL(rcu_inkernel_boot_has_ended);
249 :
250 : #endif /* #ifndef CONFIG_TINY_RCU */
251 :
252 : /*
253 : * Test each non-SRCU synchronous grace-period wait API. This is
254 : * useful just after a change in mode for these primitives, and
255 : * during early boot.
256 : */
257 0 : void rcu_test_sync_prims(void)
258 : {
259 : if (!IS_ENABLED(CONFIG_PROVE_RCU))
260 : return;
261 : pr_info("Running RCU synchronous self tests\n");
262 : synchronize_rcu();
263 : synchronize_rcu_expedited();
264 : }
265 :
266 : #if !defined(CONFIG_TINY_RCU)
267 :
268 : /*
269 : * Switch to run-time mode once RCU has fully initialized.
270 : */
271 : static int __init rcu_set_runtime_mode(void)
272 : {
273 : rcu_test_sync_prims();
274 : rcu_scheduler_active = RCU_SCHEDULER_RUNNING;
275 : kfree_rcu_scheduler_running();
276 : rcu_test_sync_prims();
277 : return 0;
278 : }
279 : core_initcall(rcu_set_runtime_mode);
280 :
281 : #endif /* #if !defined(CONFIG_TINY_RCU) */
282 :
283 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
284 : static struct lock_class_key rcu_lock_key;
285 : struct lockdep_map rcu_lock_map = {
286 : .name = "rcu_read_lock",
287 : .key = &rcu_lock_key,
288 : .wait_type_outer = LD_WAIT_FREE,
289 : .wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT implies PREEMPT_RCU */
290 : };
291 : EXPORT_SYMBOL_GPL(rcu_lock_map);
292 :
293 : static struct lock_class_key rcu_bh_lock_key;
294 : struct lockdep_map rcu_bh_lock_map = {
295 : .name = "rcu_read_lock_bh",
296 : .key = &rcu_bh_lock_key,
297 : .wait_type_outer = LD_WAIT_FREE,
298 : .wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT makes BH preemptible. */
299 : };
300 : EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
301 :
302 : static struct lock_class_key rcu_sched_lock_key;
303 : struct lockdep_map rcu_sched_lock_map = {
304 : .name = "rcu_read_lock_sched",
305 : .key = &rcu_sched_lock_key,
306 : .wait_type_outer = LD_WAIT_FREE,
307 : .wait_type_inner = LD_WAIT_SPIN,
308 : };
309 : EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
310 :
311 : // Tell lockdep when RCU callbacks are being invoked.
312 : static struct lock_class_key rcu_callback_key;
313 : struct lockdep_map rcu_callback_map =
314 : STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key);
315 : EXPORT_SYMBOL_GPL(rcu_callback_map);
316 :
317 : noinstr int notrace debug_lockdep_rcu_enabled(void)
318 : {
319 : return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && READ_ONCE(debug_locks) &&
320 : current->lockdep_recursion == 0;
321 : }
322 : EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
323 :
324 : /**
325 : * rcu_read_lock_held() - might we be in RCU read-side critical section?
326 : *
327 : * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU
328 : * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
329 : * this assumes we are in an RCU read-side critical section unless it can
330 : * prove otherwise. This is useful for debug checks in functions that
331 : * require that they be called within an RCU read-side critical section.
332 : *
333 : * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
334 : * and while lockdep is disabled.
335 : *
336 : * Note that rcu_read_lock() and the matching rcu_read_unlock() must
337 : * occur in the same context, for example, it is illegal to invoke
338 : * rcu_read_unlock() in process context if the matching rcu_read_lock()
339 : * was invoked from within an irq handler.
340 : *
341 : * Note that rcu_read_lock() is disallowed if the CPU is either idle or
342 : * offline from an RCU perspective, so check for those as well.
343 : */
344 : int rcu_read_lock_held(void)
345 : {
346 : bool ret;
347 :
348 : if (rcu_read_lock_held_common(&ret))
349 : return ret;
350 : return lock_is_held(&rcu_lock_map);
351 : }
352 : EXPORT_SYMBOL_GPL(rcu_read_lock_held);
353 :
354 : /**
355 : * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
356 : *
357 : * Check for bottom half being disabled, which covers both the
358 : * CONFIG_PROVE_RCU and not cases. Note that if someone uses
359 : * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
360 : * will show the situation. This is useful for debug checks in functions
361 : * that require that they be called within an RCU read-side critical
362 : * section.
363 : *
364 : * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
365 : *
366 : * Note that rcu_read_lock_bh() is disallowed if the CPU is either idle or
367 : * offline from an RCU perspective, so check for those as well.
368 : */
369 : int rcu_read_lock_bh_held(void)
370 : {
371 : bool ret;
372 :
373 : if (rcu_read_lock_held_common(&ret))
374 : return ret;
375 : return in_softirq() || irqs_disabled();
376 : }
377 : EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
378 :
379 : int rcu_read_lock_any_held(void)
380 : {
381 : bool ret;
382 :
383 : if (rcu_read_lock_held_common(&ret))
384 : return ret;
385 : if (lock_is_held(&rcu_lock_map) ||
386 : lock_is_held(&rcu_bh_lock_map) ||
387 : lock_is_held(&rcu_sched_lock_map))
388 : return 1;
389 : return !preemptible();
390 : }
391 : EXPORT_SYMBOL_GPL(rcu_read_lock_any_held);
392 :
393 : #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
394 :
395 : /**
396 : * wakeme_after_rcu() - Callback function to awaken a task after grace period
397 : * @head: Pointer to rcu_head member within rcu_synchronize structure
398 : *
399 : * Awaken the corresponding task now that a grace period has elapsed.
400 : */
401 0 : void wakeme_after_rcu(struct rcu_head *head)
402 : {
403 : struct rcu_synchronize *rcu;
404 :
405 0 : rcu = container_of(head, struct rcu_synchronize, head);
406 0 : complete(&rcu->completion);
407 0 : }
408 : EXPORT_SYMBOL_GPL(wakeme_after_rcu);
409 :
410 0 : void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
411 : struct rcu_synchronize *rs_array)
412 : {
413 : int i;
414 : int j;
415 :
416 : /* Initialize and register callbacks for each crcu_array element. */
417 0 : for (i = 0; i < n; i++) {
418 0 : if (checktiny &&
419 0 : (crcu_array[i] == call_rcu)) {
420 : might_sleep();
421 0 : continue;
422 : }
423 0 : for (j = 0; j < i; j++)
424 0 : if (crcu_array[j] == crcu_array[i])
425 : break;
426 0 : if (j == i) {
427 0 : init_rcu_head_on_stack(&rs_array[i].head);
428 0 : init_completion(&rs_array[i].completion);
429 0 : (crcu_array[i])(&rs_array[i].head, wakeme_after_rcu);
430 : }
431 : }
432 :
433 : /* Wait for all callbacks to be invoked. */
434 0 : for (i = 0; i < n; i++) {
435 0 : if (checktiny &&
436 0 : (crcu_array[i] == call_rcu))
437 0 : continue;
438 0 : for (j = 0; j < i; j++)
439 0 : if (crcu_array[j] == crcu_array[i])
440 : break;
441 0 : if (j == i) {
442 0 : wait_for_completion(&rs_array[i].completion);
443 0 : destroy_rcu_head_on_stack(&rs_array[i].head);
444 : }
445 : }
446 0 : }
447 : EXPORT_SYMBOL_GPL(__wait_rcu_gp);
448 :
449 0 : void finish_rcuwait(struct rcuwait *w)
450 : {
451 0 : rcu_assign_pointer(w->task, NULL);
452 0 : __set_current_state(TASK_RUNNING);
453 0 : }
454 : EXPORT_SYMBOL_GPL(finish_rcuwait);
455 :
456 : #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
457 : void init_rcu_head(struct rcu_head *head)
458 : {
459 : debug_object_init(head, &rcuhead_debug_descr);
460 : }
461 : EXPORT_SYMBOL_GPL(init_rcu_head);
462 :
463 : void destroy_rcu_head(struct rcu_head *head)
464 : {
465 : debug_object_free(head, &rcuhead_debug_descr);
466 : }
467 : EXPORT_SYMBOL_GPL(destroy_rcu_head);
468 :
469 : static bool rcuhead_is_static_object(void *addr)
470 : {
471 : return true;
472 : }
473 :
474 : /**
475 : * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
476 : * @head: pointer to rcu_head structure to be initialized
477 : *
478 : * This function informs debugobjects of a new rcu_head structure that
479 : * has been allocated as an auto variable on the stack. This function
480 : * is not required for rcu_head structures that are statically defined or
481 : * that are dynamically allocated on the heap. This function has no
482 : * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
483 : */
484 : void init_rcu_head_on_stack(struct rcu_head *head)
485 : {
486 : debug_object_init_on_stack(head, &rcuhead_debug_descr);
487 : }
488 : EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
489 :
490 : /**
491 : * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
492 : * @head: pointer to rcu_head structure to be initialized
493 : *
494 : * This function informs debugobjects that an on-stack rcu_head structure
495 : * is about to go out of scope. As with init_rcu_head_on_stack(), this
496 : * function is not required for rcu_head structures that are statically
497 : * defined or that are dynamically allocated on the heap. Also as with
498 : * init_rcu_head_on_stack(), this function has no effect for
499 : * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
500 : */
501 : void destroy_rcu_head_on_stack(struct rcu_head *head)
502 : {
503 : debug_object_free(head, &rcuhead_debug_descr);
504 : }
505 : EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
506 :
507 : const struct debug_obj_descr rcuhead_debug_descr = {
508 : .name = "rcu_head",
509 : .is_static_object = rcuhead_is_static_object,
510 : };
511 : EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
512 : #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
513 :
514 : #if defined(CONFIG_TREE_RCU) || defined(CONFIG_RCU_TRACE)
515 : void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp,
516 : unsigned long secs,
517 : unsigned long c_old, unsigned long c)
518 : {
519 : trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c);
520 : }
521 : EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
522 : #else
523 : #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
524 : do { } while (0)
525 : #endif
526 :
527 : #if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST)
528 : /* Get rcutorture access to sched_setaffinity(). */
529 : long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
530 : {
531 : int ret;
532 :
533 : ret = sched_setaffinity(pid, in_mask);
534 : WARN_ONCE(ret, "%s: sched_setaffinity() returned %d\n", __func__, ret);
535 : return ret;
536 : }
537 : EXPORT_SYMBOL_GPL(rcutorture_sched_setaffinity);
538 : #endif
539 :
540 : #ifdef CONFIG_RCU_STALL_COMMON
541 : int rcu_cpu_stall_ftrace_dump __read_mostly;
542 : module_param(rcu_cpu_stall_ftrace_dump, int, 0644);
543 : int rcu_cpu_stall_suppress __read_mostly; // !0 = suppress stall warnings.
544 : EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress);
545 : module_param(rcu_cpu_stall_suppress, int, 0644);
546 : int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
547 : module_param(rcu_cpu_stall_timeout, int, 0644);
548 : int rcu_exp_cpu_stall_timeout __read_mostly = CONFIG_RCU_EXP_CPU_STALL_TIMEOUT;
549 : module_param(rcu_exp_cpu_stall_timeout, int, 0644);
550 : int rcu_cpu_stall_cputime __read_mostly = IS_ENABLED(CONFIG_RCU_CPU_STALL_CPUTIME);
551 : module_param(rcu_cpu_stall_cputime, int, 0644);
552 : bool rcu_exp_stall_task_details __read_mostly;
553 : module_param(rcu_exp_stall_task_details, bool, 0644);
554 : #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
555 :
556 : // Suppress boot-time RCU CPU stall warnings and rcutorture writer stall
557 : // warnings. Also used by rcutorture even if stall warnings are excluded.
558 : int rcu_cpu_stall_suppress_at_boot __read_mostly; // !0 = suppress boot stalls.
559 : EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress_at_boot);
560 : module_param(rcu_cpu_stall_suppress_at_boot, int, 0444);
561 :
562 : /**
563 : * get_completed_synchronize_rcu - Return a pre-completed polled state cookie
564 : *
565 : * Returns a value that will always be treated by functions like
566 : * poll_state_synchronize_rcu() as a cookie whose grace period has already
567 : * completed.
568 : */
569 0 : unsigned long get_completed_synchronize_rcu(void)
570 : {
571 0 : return RCU_GET_STATE_COMPLETED;
572 : }
573 : EXPORT_SYMBOL_GPL(get_completed_synchronize_rcu);
574 :
575 : #ifdef CONFIG_PROVE_RCU
576 :
577 : /*
578 : * Early boot self test parameters.
579 : */
580 : static bool rcu_self_test;
581 : module_param(rcu_self_test, bool, 0444);
582 :
583 : static int rcu_self_test_counter;
584 :
585 : static void test_callback(struct rcu_head *r)
586 : {
587 : rcu_self_test_counter++;
588 : pr_info("RCU test callback executed %d\n", rcu_self_test_counter);
589 : }
590 :
591 : DEFINE_STATIC_SRCU(early_srcu);
592 : static unsigned long early_srcu_cookie;
593 :
594 : struct early_boot_kfree_rcu {
595 : struct rcu_head rh;
596 : };
597 :
598 : static void early_boot_test_call_rcu(void)
599 : {
600 : static struct rcu_head head;
601 : int idx;
602 : static struct rcu_head shead;
603 : struct early_boot_kfree_rcu *rhp;
604 :
605 : idx = srcu_down_read(&early_srcu);
606 : srcu_up_read(&early_srcu, idx);
607 : call_rcu(&head, test_callback);
608 : early_srcu_cookie = start_poll_synchronize_srcu(&early_srcu);
609 : call_srcu(&early_srcu, &shead, test_callback);
610 : rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
611 : if (!WARN_ON_ONCE(!rhp))
612 : kfree_rcu(rhp, rh);
613 : }
614 :
615 : void rcu_early_boot_tests(void)
616 : {
617 : pr_info("Running RCU self tests\n");
618 :
619 : if (rcu_self_test)
620 : early_boot_test_call_rcu();
621 : rcu_test_sync_prims();
622 : }
623 :
624 : static int rcu_verify_early_boot_tests(void)
625 : {
626 : int ret = 0;
627 : int early_boot_test_counter = 0;
628 :
629 : if (rcu_self_test) {
630 : early_boot_test_counter++;
631 : rcu_barrier();
632 : early_boot_test_counter++;
633 : srcu_barrier(&early_srcu);
634 : WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_srcu_cookie));
635 : cleanup_srcu_struct(&early_srcu);
636 : }
637 : if (rcu_self_test_counter != early_boot_test_counter) {
638 : WARN_ON(1);
639 : ret = -1;
640 : }
641 :
642 : return ret;
643 : }
644 : late_initcall(rcu_verify_early_boot_tests);
645 : #else
646 1 : void rcu_early_boot_tests(void) {}
647 : #endif /* CONFIG_PROVE_RCU */
648 :
649 : #include "tasks.h"
650 :
651 : #ifndef CONFIG_TINY_RCU
652 :
653 : /*
654 : * Print any significant non-default boot-time settings.
655 : */
656 : void __init rcupdate_announce_bootup_oddness(void)
657 : {
658 : if (rcu_normal)
659 : pr_info("\tNo expedited grace period (rcu_normal).\n");
660 : else if (rcu_normal_after_boot)
661 : pr_info("\tNo expedited grace period (rcu_normal_after_boot).\n");
662 : else if (rcu_expedited)
663 : pr_info("\tAll grace periods are expedited (rcu_expedited).\n");
664 : if (rcu_cpu_stall_suppress)
665 : pr_info("\tRCU CPU stall warnings suppressed (rcu_cpu_stall_suppress).\n");
666 : if (rcu_cpu_stall_timeout != CONFIG_RCU_CPU_STALL_TIMEOUT)
667 : pr_info("\tRCU CPU stall warnings timeout set to %d (rcu_cpu_stall_timeout).\n", rcu_cpu_stall_timeout);
668 : rcu_tasks_bootup_oddness();
669 : }
670 :
671 : #endif /* #ifndef CONFIG_TINY_RCU */
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