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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
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright (C) IBM Corporation, 2006
19 *
20 * Author: Paul McKenney <paulmck@us.ibm.com>
21 *
22 * For detailed explanation of Read-Copy Update mechanism see -
23 * Documentation/RCU/ *.txt
24 *
25 */
26
Alan Sterneabc0692006-10-04 02:17:04 -070027#ifndef _LINUX_SRCU_H
28#define _LINUX_SRCU_H
29
Paul E. McKenneyd14aada2010-04-19 22:24:22 -070030#include <linux/mutex.h>
31
Paul E. McKenney621934e2006-10-04 02:17:02 -070032struct srcu_struct_array {
33 int c[2];
34};
35
36struct srcu_struct {
37 int completed;
Tejun Heo43cf38e2010-02-02 14:38:57 +090038 struct srcu_struct_array __percpu *per_cpu_ref;
Paul E. McKenney621934e2006-10-04 02:17:02 -070039 struct mutex mutex;
Paul E. McKenney632ee202010-02-22 17:04:45 -080040#ifdef CONFIG_DEBUG_LOCK_ALLOC
41 struct lockdep_map dep_map;
42#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
Paul E. McKenney621934e2006-10-04 02:17:02 -070043};
44
45#ifndef CONFIG_PREEMPT
46#define srcu_barrier() barrier()
47#else /* #ifndef CONFIG_PREEMPT */
48#define srcu_barrier()
49#endif /* #else #ifndef CONFIG_PREEMPT */
50
Paul E. McKenney632ee202010-02-22 17:04:45 -080051#ifdef CONFIG_DEBUG_LOCK_ALLOC
52
53int __init_srcu_struct(struct srcu_struct *sp, const char *name,
54 struct lock_class_key *key);
55
56#define init_srcu_struct(sp) \
57({ \
58 static struct lock_class_key __srcu_key; \
59 \
60 __init_srcu_struct((sp), #sp, &__srcu_key); \
61})
62
63# define srcu_read_acquire(sp) \
64 lock_acquire(&(sp)->dep_map, 0, 0, 2, 1, NULL, _THIS_IP_)
65# define srcu_read_release(sp) \
66 lock_release(&(sp)->dep_map, 1, _THIS_IP_)
67
68#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
69
Alan Sterne6a92012006-10-04 02:17:05 -070070int init_srcu_struct(struct srcu_struct *sp);
Paul E. McKenney632ee202010-02-22 17:04:45 -080071
72# define srcu_read_acquire(sp) do { } while (0)
73# define srcu_read_release(sp) do { } while (0)
74
75#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
76
Paul E. McKenney621934e2006-10-04 02:17:02 -070077void cleanup_srcu_struct(struct srcu_struct *sp);
Paul E. McKenney632ee202010-02-22 17:04:45 -080078int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
79void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
Paul E. McKenney621934e2006-10-04 02:17:02 -070080void synchronize_srcu(struct srcu_struct *sp);
Paul E. McKenney0cd397d2009-10-25 19:03:51 -070081void synchronize_srcu_expedited(struct srcu_struct *sp);
Paul E. McKenney621934e2006-10-04 02:17:02 -070082long srcu_batches_completed(struct srcu_struct *sp);
Alan Sterneabc0692006-10-04 02:17:04 -070083
Paul E. McKenney632ee202010-02-22 17:04:45 -080084#ifdef CONFIG_DEBUG_LOCK_ALLOC
85
86/**
87 * srcu_read_lock_held - might we be in SRCU read-side critical section?
88 *
Paul E. McKenneyd20200b2010-03-30 10:52:21 -070089 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
90 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
Paul E. McKenney632ee202010-02-22 17:04:45 -080091 * this assumes we are in an SRCU read-side critical section unless it can
92 * prove otherwise.
93 */
94static inline int srcu_read_lock_held(struct srcu_struct *sp)
95{
96 if (debug_locks)
97 return lock_is_held(&sp->dep_map);
98 return 1;
99}
100
101#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
102
103static inline int srcu_read_lock_held(struct srcu_struct *sp)
104{
105 return 1;
106}
107
108#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
109
110/**
Paul E. McKenneyc26d34a2010-02-22 17:04:46 -0800111 * srcu_dereference - fetch SRCU-protected pointer with checking
112 *
113 * Makes rcu_dereference_check() do the dirty work.
114 */
115#define srcu_dereference(p, sp) \
116 rcu_dereference_check(p, srcu_read_lock_held(sp))
117
118/**
Paul E. McKenney632ee202010-02-22 17:04:45 -0800119 * srcu_read_lock - register a new reader for an SRCU-protected structure.
120 * @sp: srcu_struct in which to register the new reader.
121 *
122 * Enter an SRCU read-side critical section. Note that SRCU read-side
123 * critical sections may be nested.
124 */
125static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
126{
127 int retval = __srcu_read_lock(sp);
128
129 srcu_read_acquire(sp);
130 return retval;
131}
132
133/**
134 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
135 * @sp: srcu_struct in which to unregister the old reader.
136 * @idx: return value from corresponding srcu_read_lock().
137 *
138 * Exit an SRCU read-side critical section.
139 */
140static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
141 __releases(sp)
142{
143 srcu_read_release(sp);
144 __srcu_read_unlock(sp, idx);
145}
146
Alan Sterneabc0692006-10-04 02:17:04 -0700147#endif