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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Paul E. McKenneya71fca52009-09-18 10:28:19 -07002 * Read-Copy Update mechanism for mutual exclusion
Linus Torvalds1da177e2005-04-16 15:20:36 -07003 *
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
Paul E. McKenney87de1cf2013-12-03 10:02:52 -080015 * along with this program; if not, you can access it online at
16 * http://www.gnu.org/licenses/gpl-2.0.html.
Linus Torvalds1da177e2005-04-16 15:20:36 -070017 *
Paul E. McKenney01c1c662008-01-25 21:08:24 +010018 * Copyright IBM Corporation, 2001
Linus Torvalds1da177e2005-04-16 15:20:36 -070019 *
20 * Author: Dipankar Sarma <dipankar@in.ibm.com>
Paul E. McKenneya71fca52009-09-18 10:28:19 -070021 *
Josh Triplett595182b2006-10-04 02:17:21 -070022 * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
Linus Torvalds1da177e2005-04-16 15:20:36 -070023 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
24 * Papers:
25 * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
26 * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
27 *
28 * For detailed explanation of Read-Copy Update mechanism see -
Paul E. McKenneya71fca52009-09-18 10:28:19 -070029 * http://lse.sourceforge.net/locking/rcupdate.html
Linus Torvalds1da177e2005-04-16 15:20:36 -070030 *
31 */
32
33#ifndef __LINUX_RCUPDATE_H
34#define __LINUX_RCUPDATE_H
35
Paul E. McKenney99098752011-05-31 21:03:55 -070036#include <linux/types.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070037#include <linux/cache.h>
38#include <linux/spinlock.h>
39#include <linux/threads.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070040#include <linux/cpumask.h>
41#include <linux/seqlock.h>
Peter Zijlstra851a67b2007-10-11 22:11:12 +020042#include <linux/lockdep.h>
Paul E. McKenney4446a362008-05-12 21:21:05 +020043#include <linux/completion.h>
Mathieu Desnoyers551d55a2010-04-17 08:48:42 -040044#include <linux/debugobjects.h>
Paul Gortmaker187f1882011-11-23 20:12:59 -050045#include <linux/bug.h>
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -070046#include <linux/compiler.h>
Paul E. McKenney88c18632013-12-16 13:24:32 -080047#include <asm/barrier.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070048
Paul Gortmaker7a754742014-02-11 16:10:12 -050049extern int rcu_expedited; /* for sysctl */
Dave Younge5ab6772010-03-10 15:24:05 -080050
Paul E. McKenney0d394822015-02-18 12:24:30 -080051#ifdef CONFIG_TINY_RCU
52/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
53static inline bool rcu_gp_is_expedited(void) /* Internal RCU use. */
54{
55 return false;
56}
57
58static inline void rcu_expedite_gp(void)
59{
60}
61
62static inline void rcu_unexpedite_gp(void)
63{
64}
65#else /* #ifdef CONFIG_TINY_RCU */
66bool rcu_gp_is_expedited(void); /* Internal RCU use. */
67void rcu_expedite_gp(void);
68void rcu_unexpedite_gp(void);
69#endif /* #else #ifdef CONFIG_TINY_RCU */
70
Paul E. McKenneyad0dc7f2014-02-19 10:51:42 -080071enum rcutorture_type {
72 RCU_FLAVOR,
73 RCU_BH_FLAVOR,
74 RCU_SCHED_FLAVOR,
Paul E. McKenney69c60452014-07-01 11:59:36 -070075 RCU_TASKS_FLAVOR,
Paul E. McKenneyad0dc7f2014-02-19 10:51:42 -080076 SRCU_FLAVOR,
77 INVALID_RCU_FLAVOR
78};
79
Pranith Kumar28f65692014-09-22 14:00:48 -040080#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
Paul E. McKenneyad0dc7f2014-02-19 10:51:42 -080081void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
82 unsigned long *gpnum, unsigned long *completed);
Teodora Baluta584dc4c2013-11-11 17:11:23 +020083void rcutorture_record_test_transition(void);
84void rcutorture_record_progress(unsigned long vernum);
85void do_trace_rcu_torture_read(const char *rcutorturename,
86 struct rcu_head *rhp,
87 unsigned long secs,
88 unsigned long c_old,
89 unsigned long c);
Paul E. McKenney4a298652011-04-03 21:33:51 -070090#else
Paul E. McKenneyad0dc7f2014-02-19 10:51:42 -080091static inline void rcutorture_get_gp_data(enum rcutorture_type test_type,
92 int *flags,
93 unsigned long *gpnum,
94 unsigned long *completed)
95{
96 *flags = 0;
97 *gpnum = 0;
98 *completed = 0;
99}
Paul E. McKenney4a298652011-04-03 21:33:51 -0700100static inline void rcutorture_record_test_transition(void)
101{
102}
103static inline void rcutorture_record_progress(unsigned long vernum)
104{
105}
Paul E. McKenney91afaf32011-10-02 07:44:32 -0700106#ifdef CONFIG_RCU_TRACE
Teodora Baluta584dc4c2013-11-11 17:11:23 +0200107void do_trace_rcu_torture_read(const char *rcutorturename,
108 struct rcu_head *rhp,
109 unsigned long secs,
110 unsigned long c_old,
111 unsigned long c);
Paul E. McKenney91afaf32011-10-02 07:44:32 -0700112#else
Paul E. McKenney52494532012-11-14 16:26:40 -0800113#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
114 do { } while (0)
Paul E. McKenney91afaf32011-10-02 07:44:32 -0700115#endif
Paul E. McKenney4a298652011-04-03 21:33:51 -0700116#endif
117
Tejun Heoe27fc962010-11-22 21:36:11 -0800118#define UINT_CMP_GE(a, b) (UINT_MAX / 2 >= (a) - (b))
119#define UINT_CMP_LT(a, b) (UINT_MAX / 2 < (a) - (b))
Paul E. McKenneya3dc3fb2010-08-13 16:16:25 -0700120#define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b))
121#define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b))
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -0800122#define ulong2long(a) (*(long *)(&(a)))
Paul E. McKenneya3dc3fb2010-08-13 16:16:25 -0700123
Paul E. McKenney03b042b2009-06-25 09:08:16 -0700124/* Exported common interfaces */
Paul E. McKenney2c428182011-05-26 22:14:36 -0700125
126#ifdef CONFIG_PREEMPT_RCU
127
128/**
129 * call_rcu() - Queue an RCU callback for invocation after a grace period.
130 * @head: structure to be used for queueing the RCU updates.
131 * @func: actual callback function to be invoked after the grace period
132 *
133 * The callback function will be invoked some time after a full grace
134 * period elapses, in other words after all pre-existing RCU read-side
135 * critical sections have completed. However, the callback function
136 * might well execute concurrently with RCU read-side critical sections
137 * that started after call_rcu() was invoked. RCU read-side critical
138 * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
139 * and may be nested.
Paul E. McKenneyf0a0e6f2012-10-23 13:47:01 -0700140 *
141 * Note that all CPUs must agree that the grace period extended beyond
142 * all pre-existing RCU read-side critical section. On systems with more
143 * than one CPU, this means that when "func()" is invoked, each CPU is
144 * guaranteed to have executed a full memory barrier since the end of its
145 * last RCU read-side critical section whose beginning preceded the call
146 * to call_rcu(). It also means that each CPU executing an RCU read-side
147 * critical section that continues beyond the start of "func()" must have
148 * executed a memory barrier after the call_rcu() but before the beginning
149 * of that RCU read-side critical section. Note that these guarantees
150 * include CPUs that are offline, idle, or executing in user mode, as
151 * well as CPUs that are executing in the kernel.
152 *
153 * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the
154 * resulting RCU callback function "func()", then both CPU A and CPU B are
155 * guaranteed to execute a full memory barrier during the time interval
156 * between the call to call_rcu() and the invocation of "func()" -- even
157 * if CPU A and CPU B are the same CPU (but again only if the system has
158 * more than one CPU).
Paul E. McKenney2c428182011-05-26 22:14:36 -0700159 */
Teodora Baluta584dc4c2013-11-11 17:11:23 +0200160void call_rcu(struct rcu_head *head,
161 void (*func)(struct rcu_head *head));
Paul E. McKenney2c428182011-05-26 22:14:36 -0700162
163#else /* #ifdef CONFIG_PREEMPT_RCU */
164
165/* In classic RCU, call_rcu() is just call_rcu_sched(). */
166#define call_rcu call_rcu_sched
167
168#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
169
170/**
171 * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period.
172 * @head: structure to be used for queueing the RCU updates.
173 * @func: actual callback function to be invoked after the grace period
174 *
175 * The callback function will be invoked some time after a full grace
176 * period elapses, in other words after all currently executing RCU
177 * read-side critical sections have completed. call_rcu_bh() assumes
178 * that the read-side critical sections end on completion of a softirq
179 * handler. This means that read-side critical sections in process
180 * context must not be interrupted by softirqs. This interface is to be
181 * used when most of the read-side critical sections are in softirq context.
182 * RCU read-side critical sections are delimited by :
183 * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context.
184 * OR
185 * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context.
186 * These may be nested.
Paul E. McKenneyf0a0e6f2012-10-23 13:47:01 -0700187 *
188 * See the description of call_rcu() for more detailed information on
189 * memory ordering guarantees.
Paul E. McKenney2c428182011-05-26 22:14:36 -0700190 */
Teodora Baluta584dc4c2013-11-11 17:11:23 +0200191void call_rcu_bh(struct rcu_head *head,
192 void (*func)(struct rcu_head *head));
Paul E. McKenney2c428182011-05-26 22:14:36 -0700193
194/**
195 * call_rcu_sched() - Queue an RCU for invocation after sched grace period.
196 * @head: structure to be used for queueing the RCU updates.
197 * @func: actual callback function to be invoked after the grace period
198 *
199 * The callback function will be invoked some time after a full grace
200 * period elapses, in other words after all currently executing RCU
201 * read-side critical sections have completed. call_rcu_sched() assumes
202 * that the read-side critical sections end on enabling of preemption
203 * or on voluntary preemption.
204 * RCU read-side critical sections are delimited by :
205 * - rcu_read_lock_sched() and rcu_read_unlock_sched(),
206 * OR
207 * anything that disables preemption.
208 * These may be nested.
Paul E. McKenneyf0a0e6f2012-10-23 13:47:01 -0700209 *
210 * See the description of call_rcu() for more detailed information on
211 * memory ordering guarantees.
Paul E. McKenney2c428182011-05-26 22:14:36 -0700212 */
Teodora Baluta584dc4c2013-11-11 17:11:23 +0200213void call_rcu_sched(struct rcu_head *head,
214 void (*func)(struct rcu_head *rcu));
Paul E. McKenney2c428182011-05-26 22:14:36 -0700215
Teodora Baluta584dc4c2013-11-11 17:11:23 +0200216void synchronize_sched(void);
Paul E. McKenney03b042b2009-06-25 09:08:16 -0700217
Paul E. McKenneyee376db2015-01-10 19:47:10 -0800218/*
219 * Structure allowing asynchronous waiting on RCU.
220 */
221struct rcu_synchronize {
222 struct rcu_head head;
223 struct completion completion;
224};
225void wakeme_after_rcu(struct rcu_head *head);
226
Paul E. McKenney8315f422014-06-27 13:42:20 -0700227/**
228 * call_rcu_tasks() - Queue an RCU for invocation task-based grace period
229 * @head: structure to be used for queueing the RCU updates.
230 * @func: actual callback function to be invoked after the grace period
231 *
232 * The callback function will be invoked some time after a full grace
233 * period elapses, in other words after all currently executing RCU
234 * read-side critical sections have completed. call_rcu_tasks() assumes
235 * that the read-side critical sections end at a voluntary context
236 * switch (not a preemption!), entry into idle, or transition to usermode
237 * execution. As such, there are no read-side primitives analogous to
238 * rcu_read_lock() and rcu_read_unlock() because this primitive is intended
239 * to determine that all tasks have passed through a safe state, not so
240 * much for data-strcuture synchronization.
241 *
242 * See the description of call_rcu() for more detailed information on
243 * memory ordering guarantees.
244 */
245void call_rcu_tasks(struct rcu_head *head, void (*func)(struct rcu_head *head));
Paul E. McKenney53c6d4e2014-07-01 12:22:23 -0700246void synchronize_rcu_tasks(void);
247void rcu_barrier_tasks(void);
Paul E. McKenney8315f422014-06-27 13:42:20 -0700248
Paul E. McKenneya3dc3fb2010-08-13 16:16:25 -0700249#ifdef CONFIG_PREEMPT_RCU
250
Teodora Baluta584dc4c2013-11-11 17:11:23 +0200251void __rcu_read_lock(void);
252void __rcu_read_unlock(void);
253void rcu_read_unlock_special(struct task_struct *t);
Paul E. McKenney7b0b7592010-08-17 14:18:46 -0700254void synchronize_rcu(void);
255
Paul E. McKenneya3dc3fb2010-08-13 16:16:25 -0700256/*
257 * Defined as a macro as it is a very low level header included from
258 * areas that don't even know about current. This gives the rcu_read_lock()
259 * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other
260 * types of kernel builds, the rcu_read_lock() nesting depth is unknowable.
261 */
262#define rcu_preempt_depth() (current->rcu_read_lock_nesting)
263
Paul E. McKenney7b0b7592010-08-17 14:18:46 -0700264#else /* #ifdef CONFIG_PREEMPT_RCU */
265
266static inline void __rcu_read_lock(void)
267{
268 preempt_disable();
269}
270
271static inline void __rcu_read_unlock(void)
272{
273 preempt_enable();
274}
275
276static inline void synchronize_rcu(void)
277{
278 synchronize_sched();
279}
280
281static inline int rcu_preempt_depth(void)
282{
283 return 0;
284}
285
286#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
287
288/* Internal to kernel */
Teodora Baluta584dc4c2013-11-11 17:11:23 +0200289void rcu_init(void);
Paul E. McKenneyee425712015-02-19 10:51:32 -0800290void rcu_end_inkernel_boot(void);
Paul E. McKenney284a8c92014-08-14 16:38:46 -0700291void rcu_sched_qs(void);
292void rcu_bh_qs(void);
Paul E. McKenneyc3377c2d2014-10-21 07:53:02 -0700293void rcu_check_callbacks(int user);
Paul E. McKenney7b0b7592010-08-17 14:18:46 -0700294struct notifier_block;
Teodora Baluta584dc4c2013-11-11 17:11:23 +0200295void rcu_idle_enter(void);
296void rcu_idle_exit(void);
297void rcu_irq_enter(void);
298void rcu_irq_exit(void);
Paul E. McKenney88428cc2015-01-28 14:42:09 -0800299int rcu_cpu_notify(struct notifier_block *self,
300 unsigned long action, void *hcpu);
Frederic Weisbecker2b1d5022012-07-11 20:26:30 +0200301
Rik van Riel61f38db2014-04-26 23:15:35 -0700302#ifdef CONFIG_RCU_STALL_COMMON
303void rcu_sysrq_start(void);
304void rcu_sysrq_end(void);
305#else /* #ifdef CONFIG_RCU_STALL_COMMON */
306static inline void rcu_sysrq_start(void)
307{
308}
309static inline void rcu_sysrq_end(void)
310{
311}
312#endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */
313
Frederic Weisbecker2b1d5022012-07-11 20:26:30 +0200314#ifdef CONFIG_RCU_USER_QS
Teodora Baluta584dc4c2013-11-11 17:11:23 +0200315void rcu_user_enter(void);
316void rcu_user_exit(void);
Frederic Weisbecker2b1d5022012-07-11 20:26:30 +0200317#else
318static inline void rcu_user_enter(void) { }
319static inline void rcu_user_exit(void) { }
Frederic Weisbecker4d9a5d42012-10-11 01:47:16 +0200320static inline void rcu_user_hooks_switch(struct task_struct *prev,
321 struct task_struct *next) { }
Frederic Weisbecker2b1d5022012-07-11 20:26:30 +0200322#endif /* CONFIG_RCU_USER_QS */
323
Paul E. McKenneyf4579fc2014-07-25 11:21:47 -0700324#ifdef CONFIG_RCU_NOCB_CPU
325void rcu_init_nohz(void);
326#else /* #ifdef CONFIG_RCU_NOCB_CPU */
327static inline void rcu_init_nohz(void)
328{
329}
330#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
331
Paul E. McKenney8a2ecf42012-02-02 15:42:04 -0800332/**
333 * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers
334 * @a: Code that RCU needs to pay attention to.
335 *
336 * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden
337 * in the inner idle loop, that is, between the rcu_idle_enter() and
338 * the rcu_idle_exit() -- RCU will happily ignore any such read-side
339 * critical sections. However, things like powertop need tracepoints
340 * in the inner idle loop.
341 *
342 * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU())
343 * will tell RCU that it needs to pay attending, invoke its argument
344 * (in this example, a call to the do_something_with_RCU() function),
345 * and then tell RCU to go back to ignoring this CPU. It is permissible
346 * to nest RCU_NONIDLE() wrappers, but the nesting level is currently
347 * quite limited. If deeper nesting is required, it will be necessary
348 * to adjust DYNTICK_TASK_NESTING_VALUE accordingly.
Paul E. McKenney8a2ecf42012-02-02 15:42:04 -0800349 */
350#define RCU_NONIDLE(a) \
351 do { \
Paul E. McKenneyb4270ee2012-07-31 10:12:48 -0700352 rcu_irq_enter(); \
Paul E. McKenney8a2ecf42012-02-02 15:42:04 -0800353 do { a; } while (0); \
Paul E. McKenneyb4270ee2012-07-31 10:12:48 -0700354 rcu_irq_exit(); \
Paul E. McKenney8a2ecf42012-02-02 15:42:04 -0800355 } while (0)
356
Paul E. McKenney8315f422014-06-27 13:42:20 -0700357/*
358 * Note a voluntary context switch for RCU-tasks benefit. This is a
359 * macro rather than an inline function to avoid #include hell.
360 */
361#ifdef CONFIG_TASKS_RCU
Paul E. McKenney3f95aa82014-08-04 06:10:23 -0700362#define TASKS_RCU(x) x
363extern struct srcu_struct tasks_rcu_exit_srcu;
Paul E. McKenney8315f422014-06-27 13:42:20 -0700364#define rcu_note_voluntary_context_switch(t) \
365 do { \
Paul E. McKenney5cd37192014-12-13 20:32:04 -0800366 rcu_all_qs(); \
Paul E. McKenney8315f422014-06-27 13:42:20 -0700367 if (ACCESS_ONCE((t)->rcu_tasks_holdout)) \
368 ACCESS_ONCE((t)->rcu_tasks_holdout) = false; \
Paul E. McKenney8315f422014-06-27 13:42:20 -0700369 } while (0)
370#else /* #ifdef CONFIG_TASKS_RCU */
Paul E. McKenney3f95aa82014-08-04 06:10:23 -0700371#define TASKS_RCU(x) do { } while (0)
Paul E. McKenney5cd37192014-12-13 20:32:04 -0800372#define rcu_note_voluntary_context_switch(t) rcu_all_qs()
Paul E. McKenney8315f422014-06-27 13:42:20 -0700373#endif /* #else #ifdef CONFIG_TASKS_RCU */
374
Paul E. McKenneybde6c3a2014-07-01 11:26:57 -0700375/**
376 * cond_resched_rcu_qs - Report potential quiescent states to RCU
377 *
378 * This macro resembles cond_resched(), except that it is defined to
379 * report potential quiescent states to RCU-tasks even if the cond_resched()
380 * machinery were to be shut off, as some advocate for PREEMPT kernels.
381 */
382#define cond_resched_rcu_qs() \
383do { \
Paul E. McKenneyb6331ae2014-10-04 03:43:41 -0700384 if (!cond_resched()) \
385 rcu_note_voluntary_context_switch(current); \
Paul E. McKenneybde6c3a2014-07-01 11:26:57 -0700386} while (0)
387
Paul E. McKenneycc6783f2013-09-06 17:39:49 -0700388#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP)
Teodora Baluta584dc4c2013-11-11 17:11:23 +0200389bool __rcu_is_watching(void);
Paul E. McKenneycc6783f2013-09-06 17:39:49 -0700390#endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) */
391
Paul E. McKenney2c428182011-05-26 22:14:36 -0700392/*
393 * Infrastructure to implement the synchronize_() primitives in
394 * TREE_RCU and rcu_barrier_() primitives in TINY_RCU.
395 */
396
397typedef void call_rcu_func_t(struct rcu_head *head,
398 void (*func)(struct rcu_head *head));
399void wait_rcu_gp(call_rcu_func_t crf);
400
Pranith Kumar28f65692014-09-22 14:00:48 -0400401#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100402#include <linux/rcutree.h>
Paul E. McKenney127781d2013-03-27 08:44:00 -0700403#elif defined(CONFIG_TINY_RCU)
Paul E. McKenney9b1d82f2009-10-25 19:03:50 -0700404#include <linux/rcutiny.h>
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100405#else
406#error "Unknown RCU implementation specified to kernel configuration"
Paul E. McKenney6b3ef482009-08-22 13:56:53 -0700407#endif
Paul E. McKenney01c1c662008-01-25 21:08:24 +0100408
Mathieu Desnoyers551d55a2010-04-17 08:48:42 -0400409/*
410 * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic
411 * initialization and destruction of rcu_head on the stack. rcu_head structures
412 * allocated dynamically in the heap or defined statically don't need any
413 * initialization.
414 */
415#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
Paul E. McKenney546a9d82014-06-19 14:57:10 -0700416void init_rcu_head(struct rcu_head *head);
417void destroy_rcu_head(struct rcu_head *head);
Teodora Baluta584dc4c2013-11-11 17:11:23 +0200418void init_rcu_head_on_stack(struct rcu_head *head);
419void destroy_rcu_head_on_stack(struct rcu_head *head);
Mathieu Desnoyers551d55a2010-04-17 08:48:42 -0400420#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
Paul E. McKenney546a9d82014-06-19 14:57:10 -0700421static inline void init_rcu_head(struct rcu_head *head)
422{
423}
424
425static inline void destroy_rcu_head(struct rcu_head *head)
426{
427}
428
Mathieu Desnoyers43760302010-04-17 08:48:39 -0400429static inline void init_rcu_head_on_stack(struct rcu_head *head)
430{
431}
432
433static inline void destroy_rcu_head_on_stack(struct rcu_head *head)
434{
435}
Mathieu Desnoyers551d55a2010-04-17 08:48:42 -0400436#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
Mathieu Desnoyers43760302010-04-17 08:48:39 -0400437
Paul E. McKenneyc0d6d012012-01-23 12:41:26 -0800438#if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU)
439bool rcu_lockdep_current_cpu_online(void);
440#else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */
441static inline bool rcu_lockdep_current_cpu_online(void)
442{
Pranith Kumar521d24e2014-07-08 18:26:18 -0400443 return true;
Paul E. McKenneyc0d6d012012-01-23 12:41:26 -0800444}
445#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */
446
Paul E. McKenneybc33f242009-08-22 13:56:47 -0700447#ifdef CONFIG_DEBUG_LOCK_ALLOC
Paul E. McKenney632ee202010-02-22 17:04:45 -0800448
Frederic Weisbecker00f49e52011-10-07 18:22:02 +0200449static inline void rcu_lock_acquire(struct lockdep_map *map)
450{
Oleg Nesterovfb9edbe2014-01-20 19:20:06 +0100451 lock_acquire(map, 0, 0, 2, 0, NULL, _THIS_IP_);
Frederic Weisbecker00f49e52011-10-07 18:22:02 +0200452}
453
454static inline void rcu_lock_release(struct lockdep_map *map)
455{
Frederic Weisbecker00f49e52011-10-07 18:22:02 +0200456 lock_release(map, 1, _THIS_IP_);
457}
458
Paul E. McKenneybc33f242009-08-22 13:56:47 -0700459extern struct lockdep_map rcu_lock_map;
Paul E. McKenney632ee202010-02-22 17:04:45 -0800460extern struct lockdep_map rcu_bh_lock_map;
Paul E. McKenney632ee202010-02-22 17:04:45 -0800461extern struct lockdep_map rcu_sched_lock_map;
Paul E. McKenney24ef6592013-10-28 09:22:24 -0700462extern struct lockdep_map rcu_callback_map;
Iulia Mandaa235c092014-03-12 18:37:24 +0200463int debug_lockdep_rcu_enabled(void);
Paul E. McKenney54dbf962010-03-03 07:46:57 -0800464
Oleg Nesterov85b39d32014-07-08 15:17:59 -0700465int rcu_read_lock_held(void);
Teodora Baluta584dc4c2013-11-11 17:11:23 +0200466int rcu_read_lock_bh_held(void);
Paul E. McKenney632ee202010-02-22 17:04:45 -0800467
468/**
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700469 * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section?
Paul E. McKenney632ee202010-02-22 17:04:45 -0800470 *
Paul E. McKenneyd20200b2010-03-30 10:52:21 -0700471 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an
472 * RCU-sched read-side critical section. In absence of
473 * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
474 * critical section unless it can prove otherwise. Note that disabling
475 * of preemption (including disabling irqs) counts as an RCU-sched
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700476 * read-side critical section. This is useful for debug checks in functions
477 * that required that they be called within an RCU-sched read-side
478 * critical section.
Paul E. McKenney54dbf962010-03-03 07:46:57 -0800479 *
Paul E. McKenney32c141a2010-03-30 10:59:28 -0700480 * Check debug_lockdep_rcu_enabled() to prevent false positives during boot
481 * and while lockdep is disabled.
Frederic Weisbeckere6b80a32011-10-07 16:25:18 -0700482 *
483 * Note that if the CPU is in the idle loop from an RCU point of
484 * view (ie: that we are in the section between rcu_idle_enter() and
485 * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU
486 * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs
487 * that are in such a section, considering these as in extended quiescent
488 * state, so such a CPU is effectively never in an RCU read-side critical
489 * section regardless of what RCU primitives it invokes. This state of
490 * affairs is required --- we need to keep an RCU-free window in idle
491 * where the CPU may possibly enter into low power mode. This way we can
492 * notice an extended quiescent state to other CPUs that started a grace
493 * period. Otherwise we would delay any grace period as long as we run in
494 * the idle task.
Paul E. McKenneyc0d6d012012-01-23 12:41:26 -0800495 *
496 * Similarly, we avoid claiming an SRCU read lock held if the current
497 * CPU is offline.
Paul E. McKenney632ee202010-02-22 17:04:45 -0800498 */
Frederic Weisbeckerbdd4e852011-06-08 01:13:27 +0200499#ifdef CONFIG_PREEMPT_COUNT
Paul E. McKenney632ee202010-02-22 17:04:45 -0800500static inline int rcu_read_lock_sched_held(void)
501{
502 int lockdep_opinion = 0;
503
Paul E. McKenney54dbf962010-03-03 07:46:57 -0800504 if (!debug_lockdep_rcu_enabled())
505 return 1;
Paul E. McKenney5c173eb2013-09-13 17:20:11 -0700506 if (!rcu_is_watching())
Frederic Weisbeckere6b80a32011-10-07 16:25:18 -0700507 return 0;
Paul E. McKenneyc0d6d012012-01-23 12:41:26 -0800508 if (!rcu_lockdep_current_cpu_online())
509 return 0;
Paul E. McKenney632ee202010-02-22 17:04:45 -0800510 if (debug_locks)
511 lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
Lai Jiangshan0cff8102010-03-18 12:25:33 -0700512 return lockdep_opinion || preempt_count() != 0 || irqs_disabled();
Paul E. McKenney632ee202010-02-22 17:04:45 -0800513}
Frederic Weisbeckerbdd4e852011-06-08 01:13:27 +0200514#else /* #ifdef CONFIG_PREEMPT_COUNT */
Paul E. McKenneye6033e32010-03-03 17:50:16 -0800515static inline int rcu_read_lock_sched_held(void)
516{
517 return 1;
518}
Frederic Weisbeckerbdd4e852011-06-08 01:13:27 +0200519#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */
Paul E. McKenney632ee202010-02-22 17:04:45 -0800520
521#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
522
Paul E. McKenneyd8ab29f2011-10-07 18:22:03 +0200523# define rcu_lock_acquire(a) do { } while (0)
524# define rcu_lock_release(a) do { } while (0)
Paul E. McKenney632ee202010-02-22 17:04:45 -0800525
526static inline int rcu_read_lock_held(void)
527{
528 return 1;
529}
530
531static inline int rcu_read_lock_bh_held(void)
532{
533 return 1;
534}
535
Frederic Weisbeckerbdd4e852011-06-08 01:13:27 +0200536#ifdef CONFIG_PREEMPT_COUNT
Paul E. McKenney632ee202010-02-22 17:04:45 -0800537static inline int rcu_read_lock_sched_held(void)
538{
Paul E. McKenneybbad9372010-04-02 16:17:17 -0700539 return preempt_count() != 0 || irqs_disabled();
Paul E. McKenney632ee202010-02-22 17:04:45 -0800540}
Frederic Weisbeckerbdd4e852011-06-08 01:13:27 +0200541#else /* #ifdef CONFIG_PREEMPT_COUNT */
Paul E. McKenneye6033e32010-03-03 17:50:16 -0800542static inline int rcu_read_lock_sched_held(void)
543{
544 return 1;
545}
Frederic Weisbeckerbdd4e852011-06-08 01:13:27 +0200546#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */
Paul E. McKenney632ee202010-02-22 17:04:45 -0800547
548#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
549
550#ifdef CONFIG_PROVE_RCU
551
Tetsuo Handa4221a992010-06-26 01:08:19 +0900552/**
553 * rcu_lockdep_assert - emit lockdep splat if specified condition not met
554 * @c: condition to check
Paul E. McKenneyb3fbab02011-05-24 08:31:09 -0700555 * @s: informative message
Tetsuo Handa4221a992010-06-26 01:08:19 +0900556 */
Paul E. McKenneyb3fbab02011-05-24 08:31:09 -0700557#define rcu_lockdep_assert(c, s) \
Lai Jiangshan2b3fc352010-04-20 16:23:07 +0800558 do { \
Jan Beulich7ccaba52012-03-23 15:01:52 -0700559 static bool __section(.data.unlikely) __warned; \
Lai Jiangshan2b3fc352010-04-20 16:23:07 +0800560 if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \
561 __warned = true; \
Paul E. McKenneyb3fbab02011-05-24 08:31:09 -0700562 lockdep_rcu_suspicious(__FILE__, __LINE__, s); \
Lai Jiangshan2b3fc352010-04-20 16:23:07 +0800563 } \
564 } while (0)
565
Paul E. McKenney50406b92012-01-12 13:49:19 -0800566#if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU)
567static inline void rcu_preempt_sleep_check(void)
568{
569 rcu_lockdep_assert(!lock_is_held(&rcu_lock_map),
Paul E. McKenney5cf05ad2012-05-17 15:12:45 -0700570 "Illegal context switch in RCU read-side critical section");
Paul E. McKenney50406b92012-01-12 13:49:19 -0800571}
572#else /* #ifdef CONFIG_PROVE_RCU */
573static inline void rcu_preempt_sleep_check(void)
574{
575}
576#endif /* #else #ifdef CONFIG_PROVE_RCU */
577
Paul E. McKenneyb3fbab02011-05-24 08:31:09 -0700578#define rcu_sleep_check() \
579 do { \
Paul E. McKenney50406b92012-01-12 13:49:19 -0800580 rcu_preempt_sleep_check(); \
Paul E. McKenneyb3fbab02011-05-24 08:31:09 -0700581 rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), \
Joe Perches41f4abd2013-12-05 15:10:23 -0800582 "Illegal context switch in RCU-bh read-side critical section"); \
Paul E. McKenneyb3fbab02011-05-24 08:31:09 -0700583 rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), \
Joe Perches41f4abd2013-12-05 15:10:23 -0800584 "Illegal context switch in RCU-sched read-side critical section"); \
Paul E. McKenneyb3fbab02011-05-24 08:31:09 -0700585 } while (0)
586
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700587#else /* #ifdef CONFIG_PROVE_RCU */
588
Paul E. McKenneyb3fbab02011-05-24 08:31:09 -0700589#define rcu_lockdep_assert(c, s) do { } while (0)
590#define rcu_sleep_check() do { } while (0)
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700591
592#endif /* #else #ifdef CONFIG_PROVE_RCU */
593
594/*
595 * Helper functions for rcu_dereference_check(), rcu_dereference_protected()
596 * and rcu_assign_pointer(). Some of these could be folded into their
597 * callers, but they are left separate in order to ease introduction of
598 * multiple flavors of pointers to match the multiple flavors of RCU
599 * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in
600 * the future.
601 */
Paul E. McKenney53ecfba2010-09-13 17:24:21 -0700602
603#ifdef __CHECKER__
604#define rcu_dereference_sparse(p, space) \
605 ((void)(((typeof(*p) space *)p) == p))
606#else /* #ifdef __CHECKER__ */
607#define rcu_dereference_sparse(p, space)
608#endif /* #else #ifdef __CHECKER__ */
609
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700610#define __rcu_access_pointer(p, space) \
Joe Perches0adab9b2013-12-05 16:19:15 -0800611({ \
612 typeof(*p) *_________p1 = (typeof(*p) *__force)ACCESS_ONCE(p); \
613 rcu_dereference_sparse(p, space); \
614 ((typeof(*p) __force __kernel *)(_________p1)); \
615})
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700616#define __rcu_dereference_check(p, c, space) \
Joe Perches0adab9b2013-12-05 16:19:15 -0800617({ \
Pranith Kumarac598532014-11-13 14:24:14 -0500618 /* Dependency order vs. p above. */ \
619 typeof(*p) *________p1 = (typeof(*p) *__force)lockless_dereference(p); \
Joe Perches0adab9b2013-12-05 16:19:15 -0800620 rcu_lockdep_assert(c, "suspicious rcu_dereference_check() usage"); \
621 rcu_dereference_sparse(p, space); \
Pranith Kumarac598532014-11-13 14:24:14 -0500622 ((typeof(*p) __force __kernel *)(________p1)); \
Joe Perches0adab9b2013-12-05 16:19:15 -0800623})
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700624#define __rcu_dereference_protected(p, c, space) \
Joe Perches0adab9b2013-12-05 16:19:15 -0800625({ \
626 rcu_lockdep_assert(c, "suspicious rcu_dereference_protected() usage"); \
627 rcu_dereference_sparse(p, space); \
628 ((typeof(*p) __force __kernel *)(p)); \
629})
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700630
Paul E. McKenneya4dd9922011-04-01 07:15:14 -0700631#define __rcu_access_index(p, space) \
Joe Perches0adab9b2013-12-05 16:19:15 -0800632({ \
633 typeof(p) _________p1 = ACCESS_ONCE(p); \
634 rcu_dereference_sparse(p, space); \
635 (_________p1); \
636})
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700637#define __rcu_dereference_index_check(p, c) \
Joe Perches0adab9b2013-12-05 16:19:15 -0800638({ \
Pranith Kumarac598532014-11-13 14:24:14 -0500639 /* Dependency order vs. p above. */ \
640 typeof(p) _________p1 = lockless_dereference(p); \
Joe Perches0adab9b2013-12-05 16:19:15 -0800641 rcu_lockdep_assert(c, \
642 "suspicious rcu_dereference_index_check() usage"); \
Joe Perches0adab9b2013-12-05 16:19:15 -0800643 (_________p1); \
644})
Paul E. McKenney462225ae2013-11-11 09:59:34 -0800645
646/**
647 * RCU_INITIALIZER() - statically initialize an RCU-protected global variable
648 * @v: The value to statically initialize with.
649 */
650#define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v)
651
652/**
Paul E. McKenney54ef6df2014-10-27 21:11:27 -0700653 * lockless_dereference() - safely load a pointer for later dereference
654 * @p: The pointer to load
655 *
656 * Similar to rcu_dereference(), but for situations where the pointed-to
657 * object's lifetime is managed by something other than RCU. That
658 * "something other" might be reference counting or simple immortality.
659 */
660#define lockless_dereference(p) \
661({ \
662 typeof(p) _________p1 = ACCESS_ONCE(p); \
663 smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
664 (_________p1); \
665})
666
667/**
Paul E. McKenney462225ae2013-11-11 09:59:34 -0800668 * rcu_assign_pointer() - assign to RCU-protected pointer
669 * @p: pointer to assign to
670 * @v: value to assign (publish)
671 *
672 * Assigns the specified value to the specified RCU-protected
673 * pointer, ensuring that any concurrent RCU readers will see
674 * any prior initialization.
675 *
676 * Inserts memory barriers on architectures that require them
677 * (which is most of them), and also prevents the compiler from
678 * reordering the code that initializes the structure after the pointer
679 * assignment. More importantly, this call documents which pointers
680 * will be dereferenced by RCU read-side code.
681 *
682 * In some special cases, you may use RCU_INIT_POINTER() instead
683 * of rcu_assign_pointer(). RCU_INIT_POINTER() is a bit faster due
684 * to the fact that it does not constrain either the CPU or the compiler.
685 * That said, using RCU_INIT_POINTER() when you should have used
686 * rcu_assign_pointer() is a very bad thing that results in
687 * impossible-to-diagnose memory corruption. So please be careful.
688 * See the RCU_INIT_POINTER() comment header for details.
689 *
690 * Note that rcu_assign_pointer() evaluates each of its arguments only
691 * once, appearances notwithstanding. One of the "extra" evaluations
692 * is in typeof() and the other visible only to sparse (__CHECKER__),
693 * neither of which actually execute the argument. As with most cpp
694 * macros, this execute-arguments-only-once property is important, so
695 * please be careful when making changes to rcu_assign_pointer() and the
696 * other macros that it invokes.
697 */
Paul E. McKenney88c18632013-12-16 13:24:32 -0800698#define rcu_assign_pointer(p, v) smp_store_release(&p, RCU_INITIALIZER(v))
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700699
Paul E. McKenney632ee202010-02-22 17:04:45 -0800700/**
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700701 * rcu_access_pointer() - fetch RCU pointer with no dereferencing
702 * @p: The pointer to read
703 *
704 * Return the value of the specified RCU-protected pointer, but omit the
705 * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful
706 * when the value of this pointer is accessed, but the pointer is not
707 * dereferenced, for example, when testing an RCU-protected pointer against
708 * NULL. Although rcu_access_pointer() may also be used in cases where
709 * update-side locks prevent the value of the pointer from changing, you
710 * should instead use rcu_dereference_protected() for this use case.
Paul E. McKenney5e1ee6e2012-01-12 17:21:20 -0800711 *
712 * It is also permissible to use rcu_access_pointer() when read-side
713 * access to the pointer was removed at least one grace period ago, as
714 * is the case in the context of the RCU callback that is freeing up
715 * the data, or after a synchronize_rcu() returns. This can be useful
716 * when tearing down multi-linked structures after a grace period
717 * has elapsed.
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700718 */
719#define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu)
720
721/**
722 * rcu_dereference_check() - rcu_dereference with debug checking
David Howellsc08c68d2010-04-09 15:39:11 -0700723 * @p: The pointer to read, prior to dereferencing
724 * @c: The conditions under which the dereference will take place
Paul E. McKenney632ee202010-02-22 17:04:45 -0800725 *
David Howellsc08c68d2010-04-09 15:39:11 -0700726 * Do an rcu_dereference(), but check that the conditions under which the
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700727 * dereference will take place are correct. Typically the conditions
728 * indicate the various locking conditions that should be held at that
729 * point. The check should return true if the conditions are satisfied.
730 * An implicit check for being in an RCU read-side critical section
731 * (rcu_read_lock()) is included.
David Howellsc08c68d2010-04-09 15:39:11 -0700732 *
733 * For example:
734 *
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700735 * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock));
David Howellsc08c68d2010-04-09 15:39:11 -0700736 *
737 * could be used to indicate to lockdep that foo->bar may only be dereferenced
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700738 * if either rcu_read_lock() is held, or that the lock required to replace
David Howellsc08c68d2010-04-09 15:39:11 -0700739 * the bar struct at foo->bar is held.
740 *
741 * Note that the list of conditions may also include indications of when a lock
742 * need not be held, for example during initialisation or destruction of the
743 * target struct:
744 *
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700745 * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) ||
David Howellsc08c68d2010-04-09 15:39:11 -0700746 * atomic_read(&foo->usage) == 0);
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700747 *
748 * Inserts memory barriers on architectures that require them
749 * (currently only the Alpha), prevents the compiler from refetching
750 * (and from merging fetches), and, more importantly, documents exactly
751 * which pointers are protected by RCU and checks that the pointer is
752 * annotated as __rcu.
Paul E. McKenney632ee202010-02-22 17:04:45 -0800753 */
754#define rcu_dereference_check(p, c) \
Paul E. McKenneyb826565a2015-02-02 11:46:33 -0800755 __rcu_dereference_check((p), (c) || rcu_read_lock_held(), __rcu)
Paul E. McKenney632ee202010-02-22 17:04:45 -0800756
Paul E. McKenneyb62730b2010-04-09 15:39:10 -0700757/**
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700758 * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking
759 * @p: The pointer to read, prior to dereferencing
760 * @c: The conditions under which the dereference will take place
761 *
762 * This is the RCU-bh counterpart to rcu_dereference_check().
763 */
764#define rcu_dereference_bh_check(p, c) \
Paul E. McKenneyb826565a2015-02-02 11:46:33 -0800765 __rcu_dereference_check((p), (c) || rcu_read_lock_bh_held(), __rcu)
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700766
767/**
768 * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking
769 * @p: The pointer to read, prior to dereferencing
770 * @c: The conditions under which the dereference will take place
771 *
772 * This is the RCU-sched counterpart to rcu_dereference_check().
773 */
774#define rcu_dereference_sched_check(p, c) \
Paul E. McKenneyb826565a2015-02-02 11:46:33 -0800775 __rcu_dereference_check((p), (c) || rcu_read_lock_sched_held(), \
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700776 __rcu)
777
778#define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/
779
Steven Rostedt12bcbe62013-05-28 14:38:42 -0400780/*
781 * The tracing infrastructure traces RCU (we want that), but unfortunately
782 * some of the RCU checks causes tracing to lock up the system.
783 *
784 * The tracing version of rcu_dereference_raw() must not call
785 * rcu_read_lock_held().
786 */
787#define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu)
788
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700789/**
Paul E. McKenneya4dd9922011-04-01 07:15:14 -0700790 * rcu_access_index() - fetch RCU index with no dereferencing
791 * @p: The index to read
792 *
793 * Return the value of the specified RCU-protected index, but omit the
794 * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful
795 * when the value of this index is accessed, but the index is not
796 * dereferenced, for example, when testing an RCU-protected index against
797 * -1. Although rcu_access_index() may also be used in cases where
798 * update-side locks prevent the value of the index from changing, you
799 * should instead use rcu_dereference_index_protected() for this use case.
800 */
801#define rcu_access_index(p) __rcu_access_index((p), __rcu)
802
803/**
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700804 * rcu_dereference_index_check() - rcu_dereference for indices with debug checking
805 * @p: The pointer to read, prior to dereferencing
806 * @c: The conditions under which the dereference will take place
807 *
808 * Similar to rcu_dereference_check(), but omits the sparse checking.
809 * This allows rcu_dereference_index_check() to be used on integers,
810 * which can then be used as array indices. Attempting to use
811 * rcu_dereference_check() on an integer will give compiler warnings
812 * because the sparse address-space mechanism relies on dereferencing
813 * the RCU-protected pointer. Dereferencing integers is not something
814 * that even gcc will put up with.
815 *
816 * Note that this function does not implicitly check for RCU read-side
817 * critical sections. If this function gains lots of uses, it might
818 * make sense to provide versions for each flavor of RCU, but it does
819 * not make sense as of early 2010.
820 */
821#define rcu_dereference_index_check(p, c) \
822 __rcu_dereference_index_check((p), (c))
823
824/**
825 * rcu_dereference_protected() - fetch RCU pointer when updates prevented
826 * @p: The pointer to read, prior to dereferencing
827 * @c: The conditions under which the dereference will take place
Paul E. McKenneyb62730b2010-04-09 15:39:10 -0700828 *
829 * Return the value of the specified RCU-protected pointer, but omit
830 * both the smp_read_barrier_depends() and the ACCESS_ONCE(). This
831 * is useful in cases where update-side locks prevent the value of the
832 * pointer from changing. Please note that this primitive does -not-
833 * prevent the compiler from repeating this reference or combining it
834 * with other references, so it should not be used without protection
835 * of appropriate locks.
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700836 *
837 * This function is only for update-side use. Using this function
838 * when protected only by rcu_read_lock() will result in infrequent
839 * but very ugly failures.
Paul E. McKenneyb62730b2010-04-09 15:39:10 -0700840 */
841#define rcu_dereference_protected(p, c) \
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700842 __rcu_dereference_protected((p), (c), __rcu)
Paul E. McKenneybc33f242009-08-22 13:56:47 -0700843
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700844
845/**
846 * rcu_dereference() - fetch RCU-protected pointer for dereferencing
847 * @p: The pointer to read, prior to dereferencing
848 *
849 * This is a simple wrapper around rcu_dereference_check().
850 */
851#define rcu_dereference(p) rcu_dereference_check(p, 0)
852
853/**
854 * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing
855 * @p: The pointer to read, prior to dereferencing
856 *
857 * Makes rcu_dereference_check() do the dirty work.
858 */
859#define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0)
860
861/**
862 * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing
863 * @p: The pointer to read, prior to dereferencing
864 *
865 * Makes rcu_dereference_check() do the dirty work.
866 */
867#define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0)
868
869/**
870 * rcu_read_lock() - mark the beginning of an RCU read-side critical section
Linus Torvalds1da177e2005-04-16 15:20:36 -0700871 *
Paul E. McKenney9b06e812005-05-01 08:59:04 -0700872 * When synchronize_rcu() is invoked on one CPU while other CPUs
Linus Torvalds1da177e2005-04-16 15:20:36 -0700873 * are within RCU read-side critical sections, then the
Paul E. McKenney9b06e812005-05-01 08:59:04 -0700874 * synchronize_rcu() is guaranteed to block until after all the other
Linus Torvalds1da177e2005-04-16 15:20:36 -0700875 * CPUs exit their critical sections. Similarly, if call_rcu() is invoked
876 * on one CPU while other CPUs are within RCU read-side critical
877 * sections, invocation of the corresponding RCU callback is deferred
878 * until after the all the other CPUs exit their critical sections.
879 *
880 * Note, however, that RCU callbacks are permitted to run concurrently
Paul E. McKenney77d84852010-07-08 17:38:59 -0700881 * with new RCU read-side critical sections. One way that this can happen
Linus Torvalds1da177e2005-04-16 15:20:36 -0700882 * is via the following sequence of events: (1) CPU 0 enters an RCU
883 * read-side critical section, (2) CPU 1 invokes call_rcu() to register
884 * an RCU callback, (3) CPU 0 exits the RCU read-side critical section,
885 * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU
886 * callback is invoked. This is legal, because the RCU read-side critical
887 * section that was running concurrently with the call_rcu() (and which
888 * therefore might be referencing something that the corresponding RCU
889 * callback would free up) has completed before the corresponding
890 * RCU callback is invoked.
891 *
892 * RCU read-side critical sections may be nested. Any deferred actions
893 * will be deferred until the outermost RCU read-side critical section
894 * completes.
895 *
Paul E. McKenney9079fd72010-08-07 21:59:54 -0700896 * You can avoid reading and understanding the next paragraph by
897 * following this rule: don't put anything in an rcu_read_lock() RCU
898 * read-side critical section that would block in a !PREEMPT kernel.
899 * But if you want the full story, read on!
900 *
Paul E. McKenneyab74fdf2014-05-04 15:41:21 -0700901 * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU),
902 * it is illegal to block while in an RCU read-side critical section.
Pranith Kumar28f65692014-09-22 14:00:48 -0400903 * In preemptible RCU implementations (PREEMPT_RCU) in CONFIG_PREEMPT
Paul E. McKenneyab74fdf2014-05-04 15:41:21 -0700904 * kernel builds, RCU read-side critical sections may be preempted,
905 * but explicit blocking is illegal. Finally, in preemptible RCU
906 * implementations in real-time (with -rt patchset) kernel builds, RCU
907 * read-side critical sections may be preempted and they may also block, but
908 * only when acquiring spinlocks that are subject to priority inheritance.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700909 */
Paul E. McKenneybc33f242009-08-22 13:56:47 -0700910static inline void rcu_read_lock(void)
911{
912 __rcu_read_lock();
913 __acquire(RCU);
Paul E. McKenneyd8ab29f2011-10-07 18:22:03 +0200914 rcu_lock_acquire(&rcu_lock_map);
Paul E. McKenney5c173eb2013-09-13 17:20:11 -0700915 rcu_lockdep_assert(rcu_is_watching(),
Heiko Carstensbde23c62012-02-01 10:30:46 -0800916 "rcu_read_lock() used illegally while idle");
Paul E. McKenneybc33f242009-08-22 13:56:47 -0700917}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700918
Linus Torvalds1da177e2005-04-16 15:20:36 -0700919/*
920 * So where is rcu_write_lock()? It does not exist, as there is no
921 * way for writers to lock out RCU readers. This is a feature, not
922 * a bug -- this property is what provides RCU's performance benefits.
923 * Of course, writers must coordinate with each other. The normal
924 * spinlock primitives work well for this, but any other technique may be
925 * used as well. RCU does not care how the writers keep out of each
926 * others' way, as long as they do so.
927 */
Paul E. McKenney3d76c082009-09-28 07:46:32 -0700928
929/**
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700930 * rcu_read_unlock() - marks the end of an RCU read-side critical section.
Paul E. McKenney3d76c082009-09-28 07:46:32 -0700931 *
Paul E. McKenneyf27bc482014-05-04 15:38:38 -0700932 * In most situations, rcu_read_unlock() is immune from deadlock.
933 * However, in kernels built with CONFIG_RCU_BOOST, rcu_read_unlock()
934 * is responsible for deboosting, which it does via rt_mutex_unlock().
935 * Unfortunately, this function acquires the scheduler's runqueue and
936 * priority-inheritance spinlocks. This means that deadlock could result
937 * if the caller of rcu_read_unlock() already holds one of these locks or
Oleg Nesterovce36f2f2014-09-28 23:44:21 +0200938 * any lock that is ever acquired while holding them; or any lock which
939 * can be taken from interrupt context because rcu_boost()->rt_mutex_lock()
940 * does not disable irqs while taking ->wait_lock.
Paul E. McKenneyf27bc482014-05-04 15:38:38 -0700941 *
942 * That said, RCU readers are never priority boosted unless they were
943 * preempted. Therefore, one way to avoid deadlock is to make sure
944 * that preemption never happens within any RCU read-side critical
945 * section whose outermost rcu_read_unlock() is called with one of
946 * rt_mutex_unlock()'s locks held. Such preemption can be avoided in
947 * a number of ways, for example, by invoking preempt_disable() before
948 * critical section's outermost rcu_read_lock().
949 *
950 * Given that the set of locks acquired by rt_mutex_unlock() might change
951 * at any time, a somewhat more future-proofed approach is to make sure
952 * that that preemption never happens within any RCU read-side critical
953 * section whose outermost rcu_read_unlock() is called with irqs disabled.
954 * This approach relies on the fact that rt_mutex_unlock() currently only
955 * acquires irq-disabled locks.
956 *
957 * The second of these two approaches is best in most situations,
958 * however, the first approach can also be useful, at least to those
959 * developers willing to keep abreast of the set of locks acquired by
960 * rt_mutex_unlock().
961 *
Paul E. McKenney3d76c082009-09-28 07:46:32 -0700962 * See rcu_read_lock() for more information.
963 */
Paul E. McKenneybc33f242009-08-22 13:56:47 -0700964static inline void rcu_read_unlock(void)
965{
Paul E. McKenney5c173eb2013-09-13 17:20:11 -0700966 rcu_lockdep_assert(rcu_is_watching(),
Heiko Carstensbde23c62012-02-01 10:30:46 -0800967 "rcu_read_unlock() used illegally while idle");
Paul E. McKenneybc33f242009-08-22 13:56:47 -0700968 __release(RCU);
969 __rcu_read_unlock();
Paul E. McKenneyd24209bb2015-01-21 15:26:03 -0800970 rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */
Paul E. McKenneybc33f242009-08-22 13:56:47 -0700971}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700972
973/**
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700974 * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section
Linus Torvalds1da177e2005-04-16 15:20:36 -0700975 *
976 * This is equivalent of rcu_read_lock(), but to be used when updates
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700977 * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since
978 * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a
979 * softirq handler to be a quiescent state, a process in RCU read-side
980 * critical section must be protected by disabling softirqs. Read-side
981 * critical sections in interrupt context can use just rcu_read_lock(),
982 * though this should at least be commented to avoid confusing people
983 * reading the code.
Paul E. McKenney3842a082011-11-28 10:42:42 -0800984 *
985 * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh()
986 * must occur in the same context, for example, it is illegal to invoke
987 * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh()
988 * was invoked from some other task.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700989 */
Paul E. McKenneybc33f242009-08-22 13:56:47 -0700990static inline void rcu_read_lock_bh(void)
991{
Paul E. McKenney6206ab92011-08-01 06:22:11 -0700992 local_bh_disable();
Paul E. McKenneybc33f242009-08-22 13:56:47 -0700993 __acquire(RCU_BH);
Paul E. McKenneyd8ab29f2011-10-07 18:22:03 +0200994 rcu_lock_acquire(&rcu_bh_lock_map);
Paul E. McKenney5c173eb2013-09-13 17:20:11 -0700995 rcu_lockdep_assert(rcu_is_watching(),
Heiko Carstensbde23c62012-02-01 10:30:46 -0800996 "rcu_read_lock_bh() used illegally while idle");
Paul E. McKenneybc33f242009-08-22 13:56:47 -0700997}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700998
999/*
1000 * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section
1001 *
1002 * See rcu_read_lock_bh() for more information.
1003 */
Paul E. McKenneybc33f242009-08-22 13:56:47 -07001004static inline void rcu_read_unlock_bh(void)
1005{
Paul E. McKenney5c173eb2013-09-13 17:20:11 -07001006 rcu_lockdep_assert(rcu_is_watching(),
Heiko Carstensbde23c62012-02-01 10:30:46 -08001007 "rcu_read_unlock_bh() used illegally while idle");
Paul E. McKenneyd8ab29f2011-10-07 18:22:03 +02001008 rcu_lock_release(&rcu_bh_lock_map);
Paul E. McKenneybc33f242009-08-22 13:56:47 -07001009 __release(RCU_BH);
Paul E. McKenney6206ab92011-08-01 06:22:11 -07001010 local_bh_enable();
Paul E. McKenneybc33f242009-08-22 13:56:47 -07001011}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001012
1013/**
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -07001014 * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section
Mathieu Desnoyers1c50b722008-09-29 11:06:46 -04001015 *
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -07001016 * This is equivalent of rcu_read_lock(), but to be used when updates
1017 * are being done using call_rcu_sched() or synchronize_rcu_sched().
1018 * Read-side critical sections can also be introduced by anything that
1019 * disables preemption, including local_irq_disable() and friends.
Paul E. McKenney3842a082011-11-28 10:42:42 -08001020 *
1021 * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched()
1022 * must occur in the same context, for example, it is illegal to invoke
1023 * rcu_read_unlock_sched() from process context if the matching
1024 * rcu_read_lock_sched() was invoked from an NMI handler.
Mathieu Desnoyers1c50b722008-09-29 11:06:46 -04001025 */
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001026static inline void rcu_read_lock_sched(void)
1027{
1028 preempt_disable();
Paul E. McKenneybc33f242009-08-22 13:56:47 -07001029 __acquire(RCU_SCHED);
Paul E. McKenneyd8ab29f2011-10-07 18:22:03 +02001030 rcu_lock_acquire(&rcu_sched_lock_map);
Paul E. McKenney5c173eb2013-09-13 17:20:11 -07001031 rcu_lockdep_assert(rcu_is_watching(),
Heiko Carstensbde23c62012-02-01 10:30:46 -08001032 "rcu_read_lock_sched() used illegally while idle");
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001033}
Paul E. McKenney1eba8f82009-09-23 09:50:42 -07001034
1035/* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */
Paul E. McKenney7c614d62009-08-24 09:42:00 -07001036static inline notrace void rcu_read_lock_sched_notrace(void)
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001037{
1038 preempt_disable_notrace();
Paul E. McKenneybc33f242009-08-22 13:56:47 -07001039 __acquire(RCU_SCHED);
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001040}
Mathieu Desnoyers1c50b722008-09-29 11:06:46 -04001041
1042/*
1043 * rcu_read_unlock_sched - marks the end of a RCU-classic critical section
1044 *
1045 * See rcu_read_lock_sched for more information.
1046 */
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001047static inline void rcu_read_unlock_sched(void)
1048{
Paul E. McKenney5c173eb2013-09-13 17:20:11 -07001049 rcu_lockdep_assert(rcu_is_watching(),
Heiko Carstensbde23c62012-02-01 10:30:46 -08001050 "rcu_read_unlock_sched() used illegally while idle");
Paul E. McKenneyd8ab29f2011-10-07 18:22:03 +02001051 rcu_lock_release(&rcu_sched_lock_map);
Paul E. McKenneybc33f242009-08-22 13:56:47 -07001052 __release(RCU_SCHED);
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001053 preempt_enable();
1054}
Paul E. McKenney1eba8f82009-09-23 09:50:42 -07001055
1056/* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */
Paul E. McKenney7c614d62009-08-24 09:42:00 -07001057static inline notrace void rcu_read_unlock_sched_notrace(void)
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001058{
Paul E. McKenneybc33f242009-08-22 13:56:47 -07001059 __release(RCU_SCHED);
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001060 preempt_enable_notrace();
1061}
Mathieu Desnoyers1c50b722008-09-29 11:06:46 -04001062
Mathieu Desnoyers1c50b722008-09-29 11:06:46 -04001063/**
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -07001064 * RCU_INIT_POINTER() - initialize an RCU protected pointer
1065 *
Paul E. McKenney6846c0c2011-07-31 22:33:02 -07001066 * Initialize an RCU-protected pointer in special cases where readers
1067 * do not need ordering constraints on the CPU or the compiler. These
1068 * special cases are:
1069 *
1070 * 1. This use of RCU_INIT_POINTER() is NULLing out the pointer -or-
1071 * 2. The caller has taken whatever steps are required to prevent
1072 * RCU readers from concurrently accessing this pointer -or-
1073 * 3. The referenced data structure has already been exposed to
1074 * readers either at compile time or via rcu_assign_pointer() -and-
1075 * a. You have not made -any- reader-visible changes to
1076 * this structure since then -or-
1077 * b. It is OK for readers accessing this structure from its
1078 * new location to see the old state of the structure. (For
1079 * example, the changes were to statistical counters or to
1080 * other state where exact synchronization is not required.)
1081 *
1082 * Failure to follow these rules governing use of RCU_INIT_POINTER() will
1083 * result in impossible-to-diagnose memory corruption. As in the structures
1084 * will look OK in crash dumps, but any concurrent RCU readers might
1085 * see pre-initialized values of the referenced data structure. So
1086 * please be very careful how you use RCU_INIT_POINTER()!!!
1087 *
1088 * If you are creating an RCU-protected linked structure that is accessed
1089 * by a single external-to-structure RCU-protected pointer, then you may
1090 * use RCU_INIT_POINTER() to initialize the internal RCU-protected
1091 * pointers, but you must use rcu_assign_pointer() to initialize the
1092 * external-to-structure pointer -after- you have completely initialized
1093 * the reader-accessible portions of the linked structure.
Paul E. McKenney71a9b262014-03-31 13:13:02 -07001094 *
1095 * Note that unlike rcu_assign_pointer(), RCU_INIT_POINTER() provides no
1096 * ordering guarantees for either the CPU or the compiler.
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -07001097 */
1098#define RCU_INIT_POINTER(p, v) \
Paul E. McKenneyd1b88eb2012-05-16 15:42:30 -07001099 do { \
Pranith Kumar1a6c9b22014-09-25 14:03:34 -04001100 rcu_dereference_sparse(p, __rcu); \
Paul E. McKenney462225ae2013-11-11 09:59:34 -08001101 p = RCU_INITIALIZER(v); \
Paul E. McKenneyd1b88eb2012-05-16 15:42:30 -07001102 } while (0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001103
Paul E. McKenney172708d2012-05-16 15:23:45 -07001104/**
1105 * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer
1106 *
1107 * GCC-style initialization for an RCU-protected pointer in a structure field.
1108 */
1109#define RCU_POINTER_INITIALIZER(p, v) \
Paul E. McKenney462225ae2013-11-11 09:59:34 -08001110 .p = RCU_INITIALIZER(v)
Lai Jiangshan9ab15442011-03-18 11:15:47 +08001111
Jan Engelhardtd8169d42012-04-19 11:44:39 -07001112/*
1113 * Does the specified offset indicate that the corresponding rcu_head
1114 * structure can be handled by kfree_rcu()?
1115 */
1116#define __is_kfree_rcu_offset(offset) ((offset) < 4096)
1117
1118/*
1119 * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain.
1120 */
1121#define __kfree_rcu(head, offset) \
1122 do { \
1123 BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \
Paul E. McKenney4fa3b6c2012-06-05 15:53:53 -07001124 kfree_call_rcu(head, (void (*)(struct rcu_head *))(unsigned long)(offset)); \
Jan Engelhardtd8169d42012-04-19 11:44:39 -07001125 } while (0)
1126
Lai Jiangshan9ab15442011-03-18 11:15:47 +08001127/**
1128 * kfree_rcu() - kfree an object after a grace period.
1129 * @ptr: pointer to kfree
1130 * @rcu_head: the name of the struct rcu_head within the type of @ptr.
1131 *
1132 * Many rcu callbacks functions just call kfree() on the base structure.
1133 * These functions are trivial, but their size adds up, and furthermore
1134 * when they are used in a kernel module, that module must invoke the
1135 * high-latency rcu_barrier() function at module-unload time.
1136 *
1137 * The kfree_rcu() function handles this issue. Rather than encoding a
1138 * function address in the embedded rcu_head structure, kfree_rcu() instead
1139 * encodes the offset of the rcu_head structure within the base structure.
1140 * Because the functions are not allowed in the low-order 4096 bytes of
1141 * kernel virtual memory, offsets up to 4095 bytes can be accommodated.
1142 * If the offset is larger than 4095 bytes, a compile-time error will
1143 * be generated in __kfree_rcu(). If this error is triggered, you can
1144 * either fall back to use of call_rcu() or rearrange the structure to
1145 * position the rcu_head structure into the first 4096 bytes.
1146 *
1147 * Note that the allowable offset might decrease in the future, for example,
1148 * to allow something like kmem_cache_free_rcu().
Jan Engelhardtd8169d42012-04-19 11:44:39 -07001149 *
1150 * The BUILD_BUG_ON check must not involve any function calls, hence the
1151 * checks are done in macros here.
Lai Jiangshan9ab15442011-03-18 11:15:47 +08001152 */
1153#define kfree_rcu(ptr, rcu_head) \
1154 __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
1155
Paul E. McKenneyffa83fb2013-11-17 19:27:16 -08001156#if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL)
Paul E. McKenneyaa6da512014-10-21 13:23:08 -07001157static inline int rcu_needs_cpu(unsigned long *delta_jiffies)
Paul E. McKenneyffa83fb2013-11-17 19:27:16 -08001158{
1159 *delta_jiffies = ULONG_MAX;
1160 return 0;
1161}
1162#endif /* #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL) */
1163
Paul E. McKenney2f33b512013-11-17 18:25:48 -08001164#if defined(CONFIG_RCU_NOCB_CPU_ALL)
1165static inline bool rcu_is_nocb_cpu(int cpu) { return true; }
1166#elif defined(CONFIG_RCU_NOCB_CPU)
Teodora Baluta584dc4c2013-11-11 17:11:23 +02001167bool rcu_is_nocb_cpu(int cpu);
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01001168#else
1169static inline bool rcu_is_nocb_cpu(int cpu) { return false; }
Paul E. McKenney2f33b512013-11-17 18:25:48 -08001170#endif
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01001171
1172
Paul E. McKenney0edd1b12013-06-21 16:37:22 -07001173/* Only for use by adaptive-ticks code. */
1174#ifdef CONFIG_NO_HZ_FULL_SYSIDLE
Teodora Baluta584dc4c2013-11-11 17:11:23 +02001175bool rcu_sys_is_idle(void);
1176void rcu_sysidle_force_exit(void);
Paul E. McKenney0edd1b12013-06-21 16:37:22 -07001177#else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
1178
1179static inline bool rcu_sys_is_idle(void)
1180{
1181 return false;
1182}
1183
1184static inline void rcu_sysidle_force_exit(void)
1185{
1186}
1187
1188#endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
1189
1190
Linus Torvalds1da177e2005-04-16 15:20:36 -07001191#endif /* __LINUX_RCUPDATE_H */