Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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, you can access it online at
16 * http://www.gnu.org/licenses/gpl-2.0.html.
17 *
18 * Copyright (C) IBM Corporation, 2006
19 * Copyright (C) Fujitsu, 2012
20 *
21 * Author: Paul McKenney <paulmck@us.ibm.com>
22 * Lai Jiangshan <laijs@cn.fujitsu.com>
23 *
24 * For detailed explanation of Read-Copy Update mechanism see -
25 * Documentation/RCU/ *.txt
26 *
27 */
28
29#ifndef _LINUX_SRCU_H
30#define _LINUX_SRCU_H
31
32#include <linux/mutex.h>
33#include <linux/rcupdate.h>
34#include <linux/workqueue.h>
35#include <linux/rcu_segcblist.h>
36
37struct srcu_struct;
38
39#ifdef CONFIG_DEBUG_LOCK_ALLOC
40
41int __init_srcu_struct(struct srcu_struct *sp, const char *name,
42 struct lock_class_key *key);
43
44#define init_srcu_struct(sp) \
45({ \
46 static struct lock_class_key __srcu_key; \
47 \
48 __init_srcu_struct((sp), #sp, &__srcu_key); \
49})
50
51#define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name },
52#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
53
54int init_srcu_struct(struct srcu_struct *sp);
55
56#define __SRCU_DEP_MAP_INIT(srcu_name)
57#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
58
59#ifdef CONFIG_TINY_SRCU
60#include <linux/srcutiny.h>
61#elif defined(CONFIG_TREE_SRCU)
62#include <linux/srcutree.h>
63#elif defined(CONFIG_CLASSIC_SRCU)
64#include <linux/srcuclassic.h>
65#else
66#error "Unknown SRCU implementation specified to kernel configuration"
67#endif
68
69/**
70 * call_srcu() - Queue a callback for invocation after an SRCU grace period
71 * @sp: srcu_struct in queue the callback
72 * @head: structure to be used for queueing the SRCU callback.
73 * @func: function to be invoked after the SRCU grace period
74 *
75 * The callback function will be invoked some time after a full SRCU
76 * grace period elapses, in other words after all pre-existing SRCU
77 * read-side critical sections have completed. However, the callback
78 * function might well execute concurrently with other SRCU read-side
79 * critical sections that started after call_srcu() was invoked. SRCU
80 * read-side critical sections are delimited by srcu_read_lock() and
81 * srcu_read_unlock(), and may be nested.
82 *
83 * The callback will be invoked from process context, but must nevertheless
84 * be fast and must not block.
85 */
86void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
87 void (*func)(struct rcu_head *head));
88
89void cleanup_srcu_struct(struct srcu_struct *sp);
90int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
91void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
92void synchronize_srcu(struct srcu_struct *sp);
93
94#ifdef CONFIG_DEBUG_LOCK_ALLOC
95
96/**
97 * srcu_read_lock_held - might we be in SRCU read-side critical section?
98 *
99 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
100 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
101 * this assumes we are in an SRCU read-side critical section unless it can
102 * prove otherwise.
103 *
104 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
105 * and while lockdep is disabled.
106 *
107 * Note that SRCU is based on its own statemachine and it doesn't
108 * relies on normal RCU, it can be called from the CPU which
109 * is in the idle loop from an RCU point of view or offline.
110 */
111static inline int srcu_read_lock_held(struct srcu_struct *sp)
112{
113 if (!debug_lockdep_rcu_enabled())
114 return 1;
115 return lock_is_held(&sp->dep_map);
116}
117
118#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
119
120static inline int srcu_read_lock_held(struct srcu_struct *sp)
121{
122 return 1;
123}
124
125#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
126
127/**
128 * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
129 * @p: the pointer to fetch and protect for later dereferencing
130 * @sp: pointer to the srcu_struct, which is used to check that we
131 * really are in an SRCU read-side critical section.
132 * @c: condition to check for update-side use
133 *
134 * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
135 * critical section will result in an RCU-lockdep splat, unless @c evaluates
136 * to 1. The @c argument will normally be a logical expression containing
137 * lockdep_is_held() calls.
138 */
139#define srcu_dereference_check(p, sp, c) \
140 __rcu_dereference_check((p), (c) || srcu_read_lock_held(sp), __rcu)
141
142/**
143 * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
144 * @p: the pointer to fetch and protect for later dereferencing
145 * @sp: pointer to the srcu_struct, which is used to check that we
146 * really are in an SRCU read-side critical section.
147 *
148 * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU
149 * is enabled, invoking this outside of an RCU read-side critical
150 * section will result in an RCU-lockdep splat.
151 */
152#define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
153
154/**
155 * srcu_read_lock - register a new reader for an SRCU-protected structure.
156 * @sp: srcu_struct in which to register the new reader.
157 *
158 * Enter an SRCU read-side critical section. Note that SRCU read-side
159 * critical sections may be nested. However, it is illegal to
160 * call anything that waits on an SRCU grace period for the same
161 * srcu_struct, whether directly or indirectly. Please note that
162 * one way to indirectly wait on an SRCU grace period is to acquire
163 * a mutex that is held elsewhere while calling synchronize_srcu() or
164 * synchronize_srcu_expedited().
165 *
166 * Note that srcu_read_lock() and the matching srcu_read_unlock() must
167 * occur in the same context, for example, it is illegal to invoke
168 * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
169 * was invoked in process context.
170 */
171static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
172{
173 int retval;
174
175 preempt_disable();
176 retval = __srcu_read_lock(sp);
177 preempt_enable();
178 rcu_lock_acquire(&(sp)->dep_map);
179 return retval;
180}
181
182/**
183 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
184 * @sp: srcu_struct in which to unregister the old reader.
185 * @idx: return value from corresponding srcu_read_lock().
186 *
187 * Exit an SRCU read-side critical section.
188 */
189static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
190 __releases(sp)
191{
192 rcu_lock_release(&(sp)->dep_map);
193 __srcu_read_unlock(sp, idx);
194}
195
196/**
197 * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
198 *
199 * Converts the preceding srcu_read_unlock into a two-way memory barrier.
200 *
201 * Call this after srcu_read_unlock, to guarantee that all memory operations
202 * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
203 * the preceding srcu_read_unlock.
204 */
205static inline void smp_mb__after_srcu_read_unlock(void)
206{
207 /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
208}
209
210#endif