Linux kernel mirror (for testing)
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1/*
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
27#ifndef _LINUX_SRCU_H
28#define _LINUX_SRCU_H
29
30struct srcu_struct_array {
31 int c[2];
32};
33
34struct srcu_struct {
35 int completed;
36 struct srcu_struct_array __percpu *per_cpu_ref;
37 struct mutex mutex;
38#ifdef CONFIG_DEBUG_LOCK_ALLOC
39 struct lockdep_map dep_map;
40#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
41};
42
43#ifndef CONFIG_PREEMPT
44#define srcu_barrier() barrier()
45#else /* #ifndef CONFIG_PREEMPT */
46#define srcu_barrier()
47#endif /* #else #ifndef CONFIG_PREEMPT */
48
49#ifdef CONFIG_DEBUG_LOCK_ALLOC
50
51int __init_srcu_struct(struct srcu_struct *sp, const char *name,
52 struct lock_class_key *key);
53
54#define init_srcu_struct(sp) \
55({ \
56 static struct lock_class_key __srcu_key; \
57 \
58 __init_srcu_struct((sp), #sp, &__srcu_key); \
59})
60
61# define srcu_read_acquire(sp) \
62 lock_acquire(&(sp)->dep_map, 0, 0, 2, 1, NULL, _THIS_IP_)
63# define srcu_read_release(sp) \
64 lock_release(&(sp)->dep_map, 1, _THIS_IP_)
65
66#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
67
68int init_srcu_struct(struct srcu_struct *sp);
69
70# define srcu_read_acquire(sp) do { } while (0)
71# define srcu_read_release(sp) do { } while (0)
72
73#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
74
75void cleanup_srcu_struct(struct srcu_struct *sp);
76int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
77void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
78void synchronize_srcu(struct srcu_struct *sp);
79void synchronize_srcu_expedited(struct srcu_struct *sp);
80long srcu_batches_completed(struct srcu_struct *sp);
81
82#ifdef CONFIG_DEBUG_LOCK_ALLOC
83
84/**
85 * srcu_read_lock_held - might we be in SRCU read-side critical section?
86 *
87 * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in
88 * an SRCU read-side critical section. In absence of CONFIG_PROVE_LOCKING,
89 * this assumes we are in an SRCU read-side critical section unless it can
90 * prove otherwise.
91 */
92static inline int srcu_read_lock_held(struct srcu_struct *sp)
93{
94 if (debug_locks)
95 return lock_is_held(&sp->dep_map);
96 return 1;
97}
98
99#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
100
101static inline int srcu_read_lock_held(struct srcu_struct *sp)
102{
103 return 1;
104}
105
106#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
107
108/**
109 * srcu_dereference - fetch SRCU-protected pointer with checking
110 *
111 * Makes rcu_dereference_check() do the dirty work.
112 */
113#define srcu_dereference(p, sp) \
114 rcu_dereference_check(p, srcu_read_lock_held(sp))
115
116/**
117 * srcu_read_lock - register a new reader for an SRCU-protected structure.
118 * @sp: srcu_struct in which to register the new reader.
119 *
120 * Enter an SRCU read-side critical section. Note that SRCU read-side
121 * critical sections may be nested.
122 */
123static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
124{
125 int retval = __srcu_read_lock(sp);
126
127 srcu_read_acquire(sp);
128 return retval;
129}
130
131/**
132 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
133 * @sp: srcu_struct in which to unregister the old reader.
134 * @idx: return value from corresponding srcu_read_lock().
135 *
136 * Exit an SRCU read-side critical section.
137 */
138static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
139 __releases(sp)
140{
141 srcu_read_release(sp);
142 __srcu_read_unlock(sp, idx);
143}
144
145#endif