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621934ee PM |
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 | ||
eabc0694 AS |
27 | #ifndef _LINUX_SRCU_H |
28 | #define _LINUX_SRCU_H | |
29 | ||
d14aada8 | 30 | #include <linux/mutex.h> |
ff195cb6 | 31 | #include <linux/rcupdate.h> |
d14aada8 | 32 | |
621934ee PM |
33 | struct srcu_struct_array { |
34 | int c[2]; | |
35 | }; | |
36 | ||
37 | struct srcu_struct { | |
38 | int completed; | |
43cf38eb | 39 | struct srcu_struct_array __percpu *per_cpu_ref; |
621934ee | 40 | struct mutex mutex; |
632ee200 PM |
41 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
42 | struct lockdep_map dep_map; | |
43 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
621934ee PM |
44 | }; |
45 | ||
46 | #ifndef CONFIG_PREEMPT | |
47 | #define srcu_barrier() barrier() | |
48 | #else /* #ifndef CONFIG_PREEMPT */ | |
49 | #define srcu_barrier() | |
50 | #endif /* #else #ifndef CONFIG_PREEMPT */ | |
51 | ||
632ee200 PM |
52 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
53 | ||
54 | int __init_srcu_struct(struct srcu_struct *sp, const char *name, | |
55 | struct lock_class_key *key); | |
56 | ||
57 | #define init_srcu_struct(sp) \ | |
58 | ({ \ | |
59 | static struct lock_class_key __srcu_key; \ | |
60 | \ | |
61 | __init_srcu_struct((sp), #sp, &__srcu_key); \ | |
62 | }) | |
63 | ||
632ee200 PM |
64 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
65 | ||
e6a92013 | 66 | int init_srcu_struct(struct srcu_struct *sp); |
632ee200 | 67 | |
632ee200 PM |
68 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
69 | ||
621934ee | 70 | void cleanup_srcu_struct(struct srcu_struct *sp); |
632ee200 PM |
71 | int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp); |
72 | void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp); | |
621934ee | 73 | void synchronize_srcu(struct srcu_struct *sp); |
0cd397d3 | 74 | void synchronize_srcu_expedited(struct srcu_struct *sp); |
621934ee | 75 | long srcu_batches_completed(struct srcu_struct *sp); |
eabc0694 | 76 | |
632ee200 PM |
77 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
78 | ||
79 | /** | |
80 | * srcu_read_lock_held - might we be in SRCU read-side critical section? | |
81 | * | |
d20200b5 PM |
82 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU |
83 | * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, | |
632ee200 PM |
84 | * this assumes we are in an SRCU read-side critical section unless it can |
85 | * prove otherwise. | |
ff195cb6 | 86 | * |
867f236b PM |
87 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot |
88 | * and while lockdep is disabled. | |
89 | * | |
ff195cb6 PM |
90 | * Note that if the CPU is in the idle loop from an RCU point of view |
91 | * (ie: that we are in the section between rcu_idle_enter() and | |
92 | * rcu_idle_exit()) then srcu_read_lock_held() returns false even if | |
93 | * the CPU did an srcu_read_lock(). The reason for this is that RCU | |
94 | * ignores CPUs that are in such a section, considering these as in | |
95 | * extended quiescent state, so such a CPU is effectively never in an | |
96 | * RCU read-side critical section regardless of what RCU primitives it | |
97 | * invokes. This state of affairs is required --- we need to keep an | |
98 | * RCU-free window in idle where the CPU may possibly enter into low | |
99 | * power mode. This way we can notice an extended quiescent state to | |
100 | * other CPUs that started a grace period. Otherwise we would delay any | |
101 | * grace period as long as we run in the idle task. | |
632ee200 PM |
102 | */ |
103 | static inline int srcu_read_lock_held(struct srcu_struct *sp) | |
104 | { | |
ff195cb6 PM |
105 | if (rcu_is_cpu_idle()) |
106 | return 0; | |
107 | ||
867f236b | 108 | if (!debug_lockdep_rcu_enabled()) |
ff195cb6 PM |
109 | return 1; |
110 | ||
111 | return lock_is_held(&sp->dep_map); | |
632ee200 PM |
112 | } |
113 | ||
114 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
115 | ||
116 | static inline int srcu_read_lock_held(struct srcu_struct *sp) | |
117 | { | |
118 | return 1; | |
119 | } | |
120 | ||
121 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
122 | ||
c26d34a5 | 123 | /** |
ca5ecddf PM |
124 | * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing |
125 | * @p: the pointer to fetch and protect for later dereferencing | |
126 | * @sp: pointer to the srcu_struct, which is used to check that we | |
127 | * really are in an SRCU read-side critical section. | |
128 | * @c: condition to check for update-side use | |
c26d34a5 | 129 | * |
ca5ecddf PM |
130 | * If PROVE_RCU is enabled, invoking this outside of an RCU read-side |
131 | * critical section will result in an RCU-lockdep splat, unless @c evaluates | |
132 | * to 1. The @c argument will normally be a logical expression containing | |
133 | * lockdep_is_held() calls. | |
c26d34a5 | 134 | */ |
ca5ecddf PM |
135 | #define srcu_dereference_check(p, sp, c) \ |
136 | __rcu_dereference_check((p), srcu_read_lock_held(sp) || (c), __rcu) | |
137 | ||
138 | /** | |
139 | * srcu_dereference - fetch SRCU-protected pointer for later dereferencing | |
140 | * @p: the pointer to fetch and protect for later dereferencing | |
141 | * @sp: pointer to the srcu_struct, which is used to check that we | |
142 | * really are in an SRCU read-side critical section. | |
143 | * | |
144 | * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU | |
145 | * is enabled, invoking this outside of an RCU read-side critical | |
146 | * section will result in an RCU-lockdep splat. | |
147 | */ | |
148 | #define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0) | |
c26d34a5 | 149 | |
632ee200 PM |
150 | /** |
151 | * srcu_read_lock - register a new reader for an SRCU-protected structure. | |
152 | * @sp: srcu_struct in which to register the new reader. | |
153 | * | |
154 | * Enter an SRCU read-side critical section. Note that SRCU read-side | |
73d4da4d PM |
155 | * critical sections may be nested. However, it is illegal to |
156 | * call anything that waits on an SRCU grace period for the same | |
157 | * srcu_struct, whether directly or indirectly. Please note that | |
158 | * one way to indirectly wait on an SRCU grace period is to acquire | |
159 | * a mutex that is held elsewhere while calling synchronize_srcu() or | |
160 | * synchronize_srcu_expedited(). | |
632ee200 PM |
161 | */ |
162 | static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) | |
163 | { | |
164 | int retval = __srcu_read_lock(sp); | |
165 | ||
ff195cb6 | 166 | rcu_lock_acquire(&(sp)->dep_map); |
632ee200 PM |
167 | return retval; |
168 | } | |
169 | ||
170 | /** | |
171 | * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. | |
172 | * @sp: srcu_struct in which to unregister the old reader. | |
173 | * @idx: return value from corresponding srcu_read_lock(). | |
174 | * | |
175 | * Exit an SRCU read-side critical section. | |
176 | */ | |
177 | static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) | |
178 | __releases(sp) | |
179 | { | |
ff195cb6 | 180 | rcu_lock_release(&(sp)->dep_map); |
632ee200 PM |
181 | __srcu_read_unlock(sp, idx); |
182 | } | |
183 | ||
0c53dd8b PM |
184 | /** |
185 | * srcu_read_lock_raw - register a new reader for an SRCU-protected structure. | |
186 | * @sp: srcu_struct in which to register the new reader. | |
187 | * | |
188 | * Enter an SRCU read-side critical section. Similar to srcu_read_lock(), | |
189 | * but avoids the RCU-lockdep checking. This means that it is legal to | |
190 | * use srcu_read_lock_raw() in one context, for example, in an exception | |
191 | * handler, and then have the matching srcu_read_unlock_raw() in another | |
192 | * context, for example in the task that took the exception. | |
193 | * | |
194 | * However, the entire SRCU read-side critical section must reside within a | |
195 | * single task. For example, beware of using srcu_read_lock_raw() in | |
196 | * a device interrupt handler and srcu_read_unlock() in the interrupted | |
197 | * task: This will not work if interrupts are threaded. | |
198 | */ | |
199 | static inline int srcu_read_lock_raw(struct srcu_struct *sp) | |
200 | { | |
201 | unsigned long flags; | |
202 | int ret; | |
203 | ||
204 | local_irq_save(flags); | |
205 | ret = __srcu_read_lock(sp); | |
206 | local_irq_restore(flags); | |
207 | return ret; | |
208 | } | |
209 | ||
210 | /** | |
211 | * srcu_read_unlock_raw - unregister reader from an SRCU-protected structure. | |
212 | * @sp: srcu_struct in which to unregister the old reader. | |
213 | * @idx: return value from corresponding srcu_read_lock_raw(). | |
214 | * | |
215 | * Exit an SRCU read-side critical section without lockdep-RCU checking. | |
216 | * See srcu_read_lock_raw() for more details. | |
217 | */ | |
218 | static inline void srcu_read_unlock_raw(struct srcu_struct *sp, int idx) | |
219 | { | |
220 | unsigned long flags; | |
221 | ||
222 | local_irq_save(flags); | |
223 | __srcu_read_unlock(sp, idx); | |
224 | local_irq_restore(flags); | |
225 | } | |
226 | ||
eabc0694 | 227 | #endif |