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 rcu_idle_enter() and rcu_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  */
rcu_read_lock_held_common(bool * ret)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 
rcu_read_lock_sched_held(void)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  */
rcu_gp_is_normal(void)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_expedited_nesting = ATOMIC_INIT(1);
148 
149 /*
150  * Should normal grace-period primitives be expedited?  Intended for
151  * use within RCU.  Note that this function takes the rcu_expedited
152  * sysfs/boot variable and rcu_scheduler_active into account as well
153  * as the rcu_expedite_gp() nesting.  So looping on rcu_unexpedite_gp()
154  * until rcu_gp_is_expedited() returns false is a -really- bad idea.
155  */
rcu_gp_is_expedited(void)156 bool rcu_gp_is_expedited(void)
157 {
158 	return rcu_expedited || atomic_read(&rcu_expedited_nesting);
159 }
160 EXPORT_SYMBOL_GPL(rcu_gp_is_expedited);
161 
162 /**
163  * rcu_expedite_gp - Expedite future RCU grace periods
164  *
165  * After a call to this function, future calls to synchronize_rcu() and
166  * friends act as the corresponding synchronize_rcu_expedited() function
167  * had instead been called.
168  */
rcu_expedite_gp(void)169 void rcu_expedite_gp(void)
170 {
171 	atomic_inc(&rcu_expedited_nesting);
172 }
173 EXPORT_SYMBOL_GPL(rcu_expedite_gp);
174 
175 /**
176  * rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation
177  *
178  * Undo a prior call to rcu_expedite_gp().  If all prior calls to
179  * rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(),
180  * and if the rcu_expedited sysfs/boot parameter is not set, then all
181  * subsequent calls to synchronize_rcu() and friends will return to
182  * their normal non-expedited behavior.
183  */
rcu_unexpedite_gp(void)184 void rcu_unexpedite_gp(void)
185 {
186 	atomic_dec(&rcu_expedited_nesting);
187 }
188 EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
189 
190 static bool rcu_boot_ended __read_mostly;
191 
192 /*
193  * Inform RCU of the end of the in-kernel boot sequence.
194  */
rcu_end_inkernel_boot(void)195 void rcu_end_inkernel_boot(void)
196 {
197 	rcu_unexpedite_gp();
198 	if (rcu_normal_after_boot)
199 		WRITE_ONCE(rcu_normal, 1);
200 	rcu_boot_ended = true;
201 }
202 
203 /*
204  * Let rcutorture know when it is OK to turn it up to eleven.
205  */
rcu_inkernel_boot_has_ended(void)206 bool rcu_inkernel_boot_has_ended(void)
207 {
208 	return rcu_boot_ended;
209 }
210 EXPORT_SYMBOL_GPL(rcu_inkernel_boot_has_ended);
211 
212 #endif /* #ifndef CONFIG_TINY_RCU */
213 
214 /*
215  * Test each non-SRCU synchronous grace-period wait API.  This is
216  * useful just after a change in mode for these primitives, and
217  * during early boot.
218  */
rcu_test_sync_prims(void)219 void rcu_test_sync_prims(void)
220 {
221 	if (!IS_ENABLED(CONFIG_PROVE_RCU))
222 		return;
223 	synchronize_rcu();
224 	synchronize_rcu_expedited();
225 }
226 
227 #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU)
228 
229 /*
230  * Switch to run-time mode once RCU has fully initialized.
231  */
rcu_set_runtime_mode(void)232 static int __init rcu_set_runtime_mode(void)
233 {
234 	rcu_test_sync_prims();
235 	rcu_scheduler_active = RCU_SCHEDULER_RUNNING;
236 	kfree_rcu_scheduler_running();
237 	rcu_test_sync_prims();
238 	return 0;
239 }
240 core_initcall(rcu_set_runtime_mode);
241 
242 #endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */
243 
244 #ifdef CONFIG_DEBUG_LOCK_ALLOC
245 static struct lock_class_key rcu_lock_key;
246 struct lockdep_map rcu_lock_map = {
247 	.name = "rcu_read_lock",
248 	.key = &rcu_lock_key,
249 	.wait_type_outer = LD_WAIT_FREE,
250 	.wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT implies PREEMPT_RCU */
251 };
252 EXPORT_SYMBOL_GPL(rcu_lock_map);
253 
254 static struct lock_class_key rcu_bh_lock_key;
255 struct lockdep_map rcu_bh_lock_map = {
256 	.name = "rcu_read_lock_bh",
257 	.key = &rcu_bh_lock_key,
258 	.wait_type_outer = LD_WAIT_FREE,
259 	.wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT makes BH preemptible. */
260 };
261 EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
262 
263 static struct lock_class_key rcu_sched_lock_key;
264 struct lockdep_map rcu_sched_lock_map = {
265 	.name = "rcu_read_lock_sched",
266 	.key = &rcu_sched_lock_key,
267 	.wait_type_outer = LD_WAIT_FREE,
268 	.wait_type_inner = LD_WAIT_SPIN,
269 };
270 EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
271 
272 // Tell lockdep when RCU callbacks are being invoked.
273 static struct lock_class_key rcu_callback_key;
274 struct lockdep_map rcu_callback_map =
275 	STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key);
276 EXPORT_SYMBOL_GPL(rcu_callback_map);
277 
debug_lockdep_rcu_enabled(void)278 noinstr int notrace debug_lockdep_rcu_enabled(void)
279 {
280 	return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && READ_ONCE(debug_locks) &&
281 	       current->lockdep_recursion == 0;
282 }
283 EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
284 
285 /**
286  * rcu_read_lock_held() - might we be in RCU read-side critical section?
287  *
288  * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU
289  * read-side critical section.  In absence of CONFIG_DEBUG_LOCK_ALLOC,
290  * this assumes we are in an RCU read-side critical section unless it can
291  * prove otherwise.  This is useful for debug checks in functions that
292  * require that they be called within an RCU read-side critical section.
293  *
294  * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
295  * and while lockdep is disabled.
296  *
297  * Note that rcu_read_lock() and the matching rcu_read_unlock() must
298  * occur in the same context, for example, it is illegal to invoke
299  * rcu_read_unlock() in process context if the matching rcu_read_lock()
300  * was invoked from within an irq handler.
301  *
302  * Note that rcu_read_lock() is disallowed if the CPU is either idle or
303  * offline from an RCU perspective, so check for those as well.
304  */
rcu_read_lock_held(void)305 int rcu_read_lock_held(void)
306 {
307 	bool ret;
308 
309 	if (rcu_read_lock_held_common(&ret))
310 		return ret;
311 	return lock_is_held(&rcu_lock_map);
312 }
313 EXPORT_SYMBOL_GPL(rcu_read_lock_held);
314 
315 /**
316  * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
317  *
318  * Check for bottom half being disabled, which covers both the
319  * CONFIG_PROVE_RCU and not cases.  Note that if someone uses
320  * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
321  * will show the situation.  This is useful for debug checks in functions
322  * that require that they be called within an RCU read-side critical
323  * section.
324  *
325  * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
326  *
327  * Note that rcu_read_lock_bh() is disallowed if the CPU is either idle or
328  * offline from an RCU perspective, so check for those as well.
329  */
rcu_read_lock_bh_held(void)330 int rcu_read_lock_bh_held(void)
331 {
332 	bool ret;
333 
334 	if (rcu_read_lock_held_common(&ret))
335 		return ret;
336 	return in_softirq() || irqs_disabled();
337 }
338 EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
339 
rcu_read_lock_any_held(void)340 int rcu_read_lock_any_held(void)
341 {
342 	bool ret;
343 
344 	if (rcu_read_lock_held_common(&ret))
345 		return ret;
346 	if (lock_is_held(&rcu_lock_map) ||
347 	    lock_is_held(&rcu_bh_lock_map) ||
348 	    lock_is_held(&rcu_sched_lock_map))
349 		return 1;
350 	return !preemptible();
351 }
352 EXPORT_SYMBOL_GPL(rcu_read_lock_any_held);
353 
354 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
355 
356 /**
357  * wakeme_after_rcu() - Callback function to awaken a task after grace period
358  * @head: Pointer to rcu_head member within rcu_synchronize structure
359  *
360  * Awaken the corresponding task now that a grace period has elapsed.
361  */
wakeme_after_rcu(struct rcu_head * head)362 void wakeme_after_rcu(struct rcu_head *head)
363 {
364 	struct rcu_synchronize *rcu;
365 
366 	rcu = container_of(head, struct rcu_synchronize, head);
367 	complete(&rcu->completion);
368 }
369 EXPORT_SYMBOL_GPL(wakeme_after_rcu);
370 
__wait_rcu_gp(bool checktiny,int n,call_rcu_func_t * crcu_array,struct rcu_synchronize * rs_array)371 void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
372 		   struct rcu_synchronize *rs_array)
373 {
374 	int i;
375 	int j;
376 
377 	/* Initialize and register callbacks for each crcu_array element. */
378 	for (i = 0; i < n; i++) {
379 		if (checktiny &&
380 		    (crcu_array[i] == call_rcu)) {
381 			might_sleep();
382 			continue;
383 		}
384 		for (j = 0; j < i; j++)
385 			if (crcu_array[j] == crcu_array[i])
386 				break;
387 		if (j == i) {
388 			init_rcu_head_on_stack(&rs_array[i].head);
389 			init_completion(&rs_array[i].completion);
390 			(crcu_array[i])(&rs_array[i].head, wakeme_after_rcu);
391 		}
392 	}
393 
394 	/* Wait for all callbacks to be invoked. */
395 	for (i = 0; i < n; i++) {
396 		if (checktiny &&
397 		    (crcu_array[i] == call_rcu))
398 			continue;
399 		for (j = 0; j < i; j++)
400 			if (crcu_array[j] == crcu_array[i])
401 				break;
402 		if (j == i) {
403 			wait_for_completion(&rs_array[i].completion);
404 			destroy_rcu_head_on_stack(&rs_array[i].head);
405 		}
406 	}
407 }
408 EXPORT_SYMBOL_GPL(__wait_rcu_gp);
409 
finish_rcuwait(struct rcuwait * w)410 void finish_rcuwait(struct rcuwait *w)
411 {
412 	rcu_assign_pointer(w->task, NULL);
413 	__set_current_state(TASK_RUNNING);
414 }
415 EXPORT_SYMBOL_GPL(finish_rcuwait);
416 
417 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
init_rcu_head(struct rcu_head * head)418 void init_rcu_head(struct rcu_head *head)
419 {
420 	debug_object_init(head, &rcuhead_debug_descr);
421 }
422 EXPORT_SYMBOL_GPL(init_rcu_head);
423 
destroy_rcu_head(struct rcu_head * head)424 void destroy_rcu_head(struct rcu_head *head)
425 {
426 	debug_object_free(head, &rcuhead_debug_descr);
427 }
428 EXPORT_SYMBOL_GPL(destroy_rcu_head);
429 
rcuhead_is_static_object(void * addr)430 static bool rcuhead_is_static_object(void *addr)
431 {
432 	return true;
433 }
434 
435 /**
436  * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
437  * @head: pointer to rcu_head structure to be initialized
438  *
439  * This function informs debugobjects of a new rcu_head structure that
440  * has been allocated as an auto variable on the stack.  This function
441  * is not required for rcu_head structures that are statically defined or
442  * that are dynamically allocated on the heap.  This function has no
443  * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
444  */
init_rcu_head_on_stack(struct rcu_head * head)445 void init_rcu_head_on_stack(struct rcu_head *head)
446 {
447 	debug_object_init_on_stack(head, &rcuhead_debug_descr);
448 }
449 EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
450 
451 /**
452  * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
453  * @head: pointer to rcu_head structure to be initialized
454  *
455  * This function informs debugobjects that an on-stack rcu_head structure
456  * is about to go out of scope.  As with init_rcu_head_on_stack(), this
457  * function is not required for rcu_head structures that are statically
458  * defined or that are dynamically allocated on the heap.  Also as with
459  * init_rcu_head_on_stack(), this function has no effect for
460  * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
461  */
destroy_rcu_head_on_stack(struct rcu_head * head)462 void destroy_rcu_head_on_stack(struct rcu_head *head)
463 {
464 	debug_object_free(head, &rcuhead_debug_descr);
465 }
466 EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
467 
468 const struct debug_obj_descr rcuhead_debug_descr = {
469 	.name = "rcu_head",
470 	.is_static_object = rcuhead_is_static_object,
471 };
472 EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
473 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
474 
475 #if defined(CONFIG_TREE_RCU) || defined(CONFIG_RCU_TRACE)
do_trace_rcu_torture_read(const char * rcutorturename,struct rcu_head * rhp,unsigned long secs,unsigned long c_old,unsigned long c)476 void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp,
477 			       unsigned long secs,
478 			       unsigned long c_old, unsigned long c)
479 {
480 	trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c);
481 }
482 EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
483 #else
484 #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
485 	do { } while (0)
486 #endif
487 
488 #if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST)
489 /* Get rcutorture access to sched_setaffinity(). */
rcutorture_sched_setaffinity(pid_t pid,const struct cpumask * in_mask)490 long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
491 {
492 	int ret;
493 
494 	ret = sched_setaffinity(pid, in_mask);
495 	WARN_ONCE(ret, "%s: sched_setaffinity() returned %d\n", __func__, ret);
496 	return ret;
497 }
498 EXPORT_SYMBOL_GPL(rcutorture_sched_setaffinity);
499 #endif
500 
501 #ifdef CONFIG_RCU_STALL_COMMON
502 int rcu_cpu_stall_ftrace_dump __read_mostly;
503 module_param(rcu_cpu_stall_ftrace_dump, int, 0644);
504 int rcu_cpu_stall_suppress __read_mostly; // !0 = suppress stall warnings.
505 EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress);
506 module_param(rcu_cpu_stall_suppress, int, 0644);
507 int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
508 module_param(rcu_cpu_stall_timeout, int, 0644);
509 int rcu_exp_cpu_stall_timeout __read_mostly = CONFIG_RCU_EXP_CPU_STALL_TIMEOUT;
510 module_param(rcu_exp_cpu_stall_timeout, int, 0644);
511 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
512 
513 // Suppress boot-time RCU CPU stall warnings and rcutorture writer stall
514 // warnings.  Also used by rcutorture even if stall warnings are excluded.
515 int rcu_cpu_stall_suppress_at_boot __read_mostly; // !0 = suppress boot stalls.
516 EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress_at_boot);
517 module_param(rcu_cpu_stall_suppress_at_boot, int, 0444);
518 
519 #ifdef CONFIG_PROVE_RCU
520 
521 /*
522  * Early boot self test parameters.
523  */
524 static bool rcu_self_test;
525 module_param(rcu_self_test, bool, 0444);
526 
527 static int rcu_self_test_counter;
528 
test_callback(struct rcu_head * r)529 static void test_callback(struct rcu_head *r)
530 {
531 	rcu_self_test_counter++;
532 	pr_info("RCU test callback executed %d\n", rcu_self_test_counter);
533 }
534 
535 DEFINE_STATIC_SRCU(early_srcu);
536 static unsigned long early_srcu_cookie;
537 
538 struct early_boot_kfree_rcu {
539 	struct rcu_head rh;
540 };
541 
early_boot_test_call_rcu(void)542 static void early_boot_test_call_rcu(void)
543 {
544 	static struct rcu_head head;
545 	static struct rcu_head shead;
546 	struct early_boot_kfree_rcu *rhp;
547 
548 	call_rcu(&head, test_callback);
549 	if (IS_ENABLED(CONFIG_SRCU)) {
550 		early_srcu_cookie = start_poll_synchronize_srcu(&early_srcu);
551 		call_srcu(&early_srcu, &shead, test_callback);
552 	}
553 	rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
554 	if (!WARN_ON_ONCE(!rhp))
555 		kfree_rcu(rhp, rh);
556 }
557 
rcu_early_boot_tests(void)558 void rcu_early_boot_tests(void)
559 {
560 	pr_info("Running RCU self tests\n");
561 
562 	if (rcu_self_test)
563 		early_boot_test_call_rcu();
564 	rcu_test_sync_prims();
565 }
566 
rcu_verify_early_boot_tests(void)567 static int rcu_verify_early_boot_tests(void)
568 {
569 	int ret = 0;
570 	int early_boot_test_counter = 0;
571 
572 	if (rcu_self_test) {
573 		early_boot_test_counter++;
574 		rcu_barrier();
575 		if (IS_ENABLED(CONFIG_SRCU)) {
576 			early_boot_test_counter++;
577 			srcu_barrier(&early_srcu);
578 			WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_srcu_cookie));
579 		}
580 	}
581 	if (rcu_self_test_counter != early_boot_test_counter) {
582 		WARN_ON(1);
583 		ret = -1;
584 	}
585 
586 	return ret;
587 }
588 late_initcall(rcu_verify_early_boot_tests);
589 #else
rcu_early_boot_tests(void)590 void rcu_early_boot_tests(void) {}
591 #endif /* CONFIG_PROVE_RCU */
592 
593 #include "tasks.h"
594 
595 #ifndef CONFIG_TINY_RCU
596 
597 /*
598  * Print any significant non-default boot-time settings.
599  */
rcupdate_announce_bootup_oddness(void)600 void __init rcupdate_announce_bootup_oddness(void)
601 {
602 	if (rcu_normal)
603 		pr_info("\tNo expedited grace period (rcu_normal).\n");
604 	else if (rcu_normal_after_boot)
605 		pr_info("\tNo expedited grace period (rcu_normal_after_boot).\n");
606 	else if (rcu_expedited)
607 		pr_info("\tAll grace periods are expedited (rcu_expedited).\n");
608 	if (rcu_cpu_stall_suppress)
609 		pr_info("\tRCU CPU stall warnings suppressed (rcu_cpu_stall_suppress).\n");
610 	if (rcu_cpu_stall_timeout != CONFIG_RCU_CPU_STALL_TIMEOUT)
611 		pr_info("\tRCU CPU stall warnings timeout set to %d (rcu_cpu_stall_timeout).\n", rcu_cpu_stall_timeout);
612 	rcu_tasks_bootup_oddness();
613 }
614 
615 #endif /* #ifndef CONFIG_TINY_RCU */
616