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Paul E. McKenney621934e2006-10-04 02:17:02 -07001/*
2 * Sleepable Read-Copy Update mechanism for mutual exclusion
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
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.
Paul E. McKenney621934e2006-10-04 02:17:02 -070017 *
18 * Copyright (C) IBM Corporation, 2006
Lai Jiangshan4e87b2d2012-10-13 01:14:14 +080019 * Copyright (C) Fujitsu, 2012
Paul E. McKenney621934e2006-10-04 02:17:02 -070020 *
21 * Author: Paul McKenney <paulmck@us.ibm.com>
Lai Jiangshan4e87b2d2012-10-13 01:14:14 +080022 * Lai Jiangshan <laijs@cn.fujitsu.com>
Paul E. McKenney621934e2006-10-04 02:17:02 -070023 *
24 * For detailed explanation of Read-Copy Update mechanism see -
25 * Documentation/RCU/ *.txt
26 *
27 */
28
Alan Sterneabc0692006-10-04 02:17:04 -070029#ifndef _LINUX_SRCU_H
30#define _LINUX_SRCU_H
31
Paul E. McKenneyd14aada2010-04-19 22:24:22 -070032#include <linux/mutex.h>
Paul E. McKenneyff195cb2011-10-07 18:22:04 +020033#include <linux/rcupdate.h>
Lai Jiangshan931ea9d2012-03-19 16:12:13 +080034#include <linux/workqueue.h>
Paul E. McKenneyd14aada2010-04-19 22:24:22 -070035
Paul E. McKenney621934e2006-10-04 02:17:02 -070036struct srcu_struct_array {
Paul E. McKenneycef50122012-02-05 07:42:44 -080037 unsigned long c[2];
Lai Jiangshanb52ce062012-02-27 09:29:09 -080038 unsigned long seq[2];
Paul E. McKenney621934e2006-10-04 02:17:02 -070039};
40
Lai Jiangshan931ea9d2012-03-19 16:12:13 +080041struct rcu_batch {
42 struct rcu_head *head, **tail;
43};
44
Lai Jiangshan55c6659a2012-10-13 01:14:16 +080045#define RCU_BATCH_INIT(name) { NULL, &(name.head) }
46
Paul E. McKenney621934e2006-10-04 02:17:02 -070047struct srcu_struct {
Paul E. McKenneya5c198f2014-11-23 20:30:06 -080048 unsigned long completed;
Tejun Heo43cf38e2010-02-02 14:38:57 +090049 struct srcu_struct_array __percpu *per_cpu_ref;
Lai Jiangshan931ea9d2012-03-19 16:12:13 +080050 spinlock_t queue_lock; /* protect ->batch_queue, ->running */
51 bool running;
52 /* callbacks just queued */
53 struct rcu_batch batch_queue;
54 /* callbacks try to do the first check_zero */
55 struct rcu_batch batch_check0;
56 /* callbacks done with the first check_zero and the flip */
57 struct rcu_batch batch_check1;
58 struct rcu_batch batch_done;
59 struct delayed_work work;
Paul E. McKenney632ee202010-02-22 17:04:45 -080060#ifdef CONFIG_DEBUG_LOCK_ALLOC
61 struct lockdep_map dep_map;
62#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
Paul E. McKenney621934e2006-10-04 02:17:02 -070063};
64
Paul E. McKenney632ee202010-02-22 17:04:45 -080065#ifdef CONFIG_DEBUG_LOCK_ALLOC
66
67int __init_srcu_struct(struct srcu_struct *sp, const char *name,
68 struct lock_class_key *key);
69
70#define init_srcu_struct(sp) \
71({ \
72 static struct lock_class_key __srcu_key; \
73 \
74 __init_srcu_struct((sp), #sp, &__srcu_key); \
75})
76
Lai Jiangshan55c6659a2012-10-13 01:14:16 +080077#define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name },
Paul E. McKenney632ee202010-02-22 17:04:45 -080078#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
79
Alan Sterne6a92012006-10-04 02:17:05 -070080int init_srcu_struct(struct srcu_struct *sp);
Paul E. McKenney632ee202010-02-22 17:04:45 -080081
Lai Jiangshan55c6659a2012-10-13 01:14:16 +080082#define __SRCU_DEP_MAP_INIT(srcu_name)
Paul E. McKenney632ee202010-02-22 17:04:45 -080083#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
84
Lai Jiangshanf2ebfbc2012-10-13 01:14:15 +080085void process_srcu(struct work_struct *work);
86
Lai Jiangshan55c6659a2012-10-13 01:14:16 +080087#define __SRCU_STRUCT_INIT(name) \
88 { \
89 .completed = -300, \
90 .per_cpu_ref = &name##_srcu_array, \
91 .queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock), \
92 .running = false, \
93 .batch_queue = RCU_BATCH_INIT(name.batch_queue), \
94 .batch_check0 = RCU_BATCH_INIT(name.batch_check0), \
95 .batch_check1 = RCU_BATCH_INIT(name.batch_check1), \
96 .batch_done = RCU_BATCH_INIT(name.batch_done), \
97 .work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\
98 __SRCU_DEP_MAP_INIT(name) \
99 }
100
101/*
102 * define and init a srcu struct at build time.
103 * dont't call init_srcu_struct() nor cleanup_srcu_struct() on it.
104 */
Paul E. McKenney9735af52014-11-26 10:42:50 -0800105#define __DEFINE_SRCU(name, is_static) \
Lai Jiangshan55c6659a2012-10-13 01:14:16 +0800106 static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
Paul E. McKenney9735af52014-11-26 10:42:50 -0800107 is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
108#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
109#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
Lai Jiangshan55c6659a2012-10-13 01:14:16 +0800110
Lai Jiangshan931ea9d2012-03-19 16:12:13 +0800111/**
112 * call_srcu() - Queue a callback for invocation after an SRCU grace period
113 * @sp: srcu_struct in queue the callback
114 * @head: structure to be used for queueing the SRCU callback.
115 * @func: function to be invoked after the SRCU grace period
116 *
117 * The callback function will be invoked some time after a full SRCU
118 * grace period elapses, in other words after all pre-existing SRCU
119 * read-side critical sections have completed. However, the callback
120 * function might well execute concurrently with other SRCU read-side
121 * critical sections that started after call_srcu() was invoked. SRCU
122 * read-side critical sections are delimited by srcu_read_lock() and
123 * srcu_read_unlock(), and may be nested.
124 *
125 * The callback will be invoked from process context, but must nevertheless
126 * be fast and must not block.
127 */
128void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
129 void (*func)(struct rcu_head *head));
130
Paul E. McKenney621934e2006-10-04 02:17:02 -0700131void cleanup_srcu_struct(struct srcu_struct *sp);
Paul E. McKenney632ee202010-02-22 17:04:45 -0800132int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
133void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
Paul E. McKenney621934e2006-10-04 02:17:02 -0700134void synchronize_srcu(struct srcu_struct *sp);
Paul E. McKenney0cd397d2009-10-25 19:03:51 -0700135void synchronize_srcu_expedited(struct srcu_struct *sp);
Paul E. McKenneya5c198f2014-11-23 20:30:06 -0800136unsigned long srcu_batches_completed(struct srcu_struct *sp);
Lai Jiangshan931ea9d2012-03-19 16:12:13 +0800137void srcu_barrier(struct srcu_struct *sp);
Alan Sterneabc0692006-10-04 02:17:04 -0700138
Paul E. McKenney632ee202010-02-22 17:04:45 -0800139#ifdef CONFIG_DEBUG_LOCK_ALLOC
140
141/**
142 * srcu_read_lock_held - might we be in SRCU read-side critical section?
143 *
Paul E. McKenneyd20200b2010-03-30 10:52:21 -0700144 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
145 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
Paul E. McKenney632ee202010-02-22 17:04:45 -0800146 * this assumes we are in an SRCU read-side critical section unless it can
147 * prove otherwise.
Paul E. McKenneyff195cb2011-10-07 18:22:04 +0200148 *
Paul E. McKenney867f2362011-10-07 18:22:05 +0200149 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
150 * and while lockdep is disabled.
151 *
Lai Jiangshan511a0862012-11-29 16:46:06 +0800152 * Note that SRCU is based on its own statemachine and it doesn't
153 * relies on normal RCU, it can be called from the CPU which
154 * is in the idle loop from an RCU point of view or offline.
Paul E. McKenney632ee202010-02-22 17:04:45 -0800155 */
156static inline int srcu_read_lock_held(struct srcu_struct *sp)
157{
Paul E. McKenney867f2362011-10-07 18:22:05 +0200158 if (!debug_lockdep_rcu_enabled())
Paul E. McKenneyff195cb2011-10-07 18:22:04 +0200159 return 1;
Paul E. McKenneyff195cb2011-10-07 18:22:04 +0200160 return lock_is_held(&sp->dep_map);
Paul E. McKenney632ee202010-02-22 17:04:45 -0800161}
162
163#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
164
165static inline int srcu_read_lock_held(struct srcu_struct *sp)
166{
167 return 1;
168}
169
170#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
171
172/**
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700173 * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
174 * @p: the pointer to fetch and protect for later dereferencing
175 * @sp: pointer to the srcu_struct, which is used to check that we
176 * really are in an SRCU read-side critical section.
177 * @c: condition to check for update-side use
Paul E. McKenneyc26d34a2010-02-22 17:04:46 -0800178 *
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700179 * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
180 * critical section will result in an RCU-lockdep splat, unless @c evaluates
181 * to 1. The @c argument will normally be a logical expression containing
182 * lockdep_is_held() calls.
Paul E. McKenneyc26d34a2010-02-22 17:04:46 -0800183 */
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700184#define srcu_dereference_check(p, sp, c) \
Paul E. McKenneyb826565a2015-02-02 11:46:33 -0800185 __rcu_dereference_check((p), (c) || srcu_read_lock_held(sp), __rcu)
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700186
187/**
188 * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
189 * @p: the pointer to fetch and protect for later dereferencing
190 * @sp: pointer to the srcu_struct, which is used to check that we
191 * really are in an SRCU read-side critical section.
192 *
193 * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU
194 * is enabled, invoking this outside of an RCU read-side critical
195 * section will result in an RCU-lockdep splat.
196 */
197#define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
Paul E. McKenneyc26d34a2010-02-22 17:04:46 -0800198
199/**
Paul E. McKenney632ee202010-02-22 17:04:45 -0800200 * srcu_read_lock - register a new reader for an SRCU-protected structure.
201 * @sp: srcu_struct in which to register the new reader.
202 *
203 * Enter an SRCU read-side critical section. Note that SRCU read-side
Paul E. McKenney73d4da42010-08-16 10:50:54 -0700204 * critical sections may be nested. However, it is illegal to
205 * call anything that waits on an SRCU grace period for the same
206 * srcu_struct, whether directly or indirectly. Please note that
207 * one way to indirectly wait on an SRCU grace period is to acquire
208 * a mutex that is held elsewhere while calling synchronize_srcu() or
209 * synchronize_srcu_expedited().
Paul E. McKenney3842a082011-11-28 10:42:42 -0800210 *
211 * Note that srcu_read_lock() and the matching srcu_read_unlock() must
212 * occur in the same context, for example, it is illegal to invoke
213 * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
214 * was invoked in process context.
Paul E. McKenney632ee202010-02-22 17:04:45 -0800215 */
216static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
217{
Paul E. McKenney49f59032015-09-01 00:42:57 -0700218 int retval;
Paul E. McKenney632ee202010-02-22 17:04:45 -0800219
Paul E. McKenney49f59032015-09-01 00:42:57 -0700220 preempt_disable();
221 retval = __srcu_read_lock(sp);
222 preempt_enable();
Paul E. McKenneyff195cb2011-10-07 18:22:04 +0200223 rcu_lock_acquire(&(sp)->dep_map);
Paul E. McKenney632ee202010-02-22 17:04:45 -0800224 return retval;
225}
226
227/**
228 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
229 * @sp: srcu_struct in which to unregister the old reader.
230 * @idx: return value from corresponding srcu_read_lock().
231 *
232 * Exit an SRCU read-side critical section.
233 */
234static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
235 __releases(sp)
236{
Paul E. McKenneyff195cb2011-10-07 18:22:04 +0200237 rcu_lock_release(&(sp)->dep_map);
Paul E. McKenney632ee202010-02-22 17:04:45 -0800238 __srcu_read_unlock(sp, idx);
239}
240
Michael S. Tsirkince332f62013-11-04 22:36:17 +0200241/**
242 * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
243 *
244 * Converts the preceding srcu_read_unlock into a two-way memory barrier.
245 *
246 * Call this after srcu_read_unlock, to guarantee that all memory operations
247 * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
248 * the preceding srcu_read_unlock.
249 */
250static inline void smp_mb__after_srcu_read_unlock(void)
251{
252 /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
253}
254
Alan Sterneabc0692006-10-04 02:17:04 -0700255#endif