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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 | 33 | struct srcu_struct_array { |
cef50120 | 34 | unsigned long c[2]; |
b52ce066 | 35 | unsigned long seq[2]; |
621934ee PM |
36 | }; |
37 | ||
38 | struct srcu_struct { | |
cef50120 | 39 | unsigned completed; |
43cf38eb | 40 | struct srcu_struct_array __percpu *per_cpu_ref; |
621934ee | 41 | struct mutex mutex; |
632ee200 PM |
42 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
43 | struct lockdep_map dep_map; | |
44 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
621934ee PM |
45 | }; |
46 | ||
632ee200 PM |
47 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
48 | ||
49 | int __init_srcu_struct(struct srcu_struct *sp, const char *name, | |
50 | struct lock_class_key *key); | |
51 | ||
52 | #define init_srcu_struct(sp) \ | |
53 | ({ \ | |
54 | static struct lock_class_key __srcu_key; \ | |
55 | \ | |
56 | __init_srcu_struct((sp), #sp, &__srcu_key); \ | |
57 | }) | |
58 | ||
632ee200 PM |
59 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
60 | ||
e6a92013 | 61 | int init_srcu_struct(struct srcu_struct *sp); |
632ee200 | 62 | |
632ee200 PM |
63 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
64 | ||
621934ee | 65 | void cleanup_srcu_struct(struct srcu_struct *sp); |
632ee200 PM |
66 | int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp); |
67 | void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp); | |
621934ee | 68 | void synchronize_srcu(struct srcu_struct *sp); |
0cd397d3 | 69 | void synchronize_srcu_expedited(struct srcu_struct *sp); |
621934ee | 70 | long srcu_batches_completed(struct srcu_struct *sp); |
eabc0694 | 71 | |
632ee200 PM |
72 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
73 | ||
74 | /** | |
75 | * srcu_read_lock_held - might we be in SRCU read-side critical section? | |
76 | * | |
d20200b5 PM |
77 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU |
78 | * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, | |
632ee200 PM |
79 | * this assumes we are in an SRCU read-side critical section unless it can |
80 | * prove otherwise. | |
ff195cb6 | 81 | * |
867f236b PM |
82 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot |
83 | * and while lockdep is disabled. | |
84 | * | |
ff195cb6 PM |
85 | * Note that if the CPU is in the idle loop from an RCU point of view |
86 | * (ie: that we are in the section between rcu_idle_enter() and | |
87 | * rcu_idle_exit()) then srcu_read_lock_held() returns false even if | |
88 | * the CPU did an srcu_read_lock(). The reason for this is that RCU | |
89 | * ignores CPUs that are in such a section, considering these as in | |
90 | * extended quiescent state, so such a CPU is effectively never in an | |
91 | * RCU read-side critical section regardless of what RCU primitives it | |
92 | * invokes. This state of affairs is required --- we need to keep an | |
93 | * RCU-free window in idle where the CPU may possibly enter into low | |
94 | * power mode. This way we can notice an extended quiescent state to | |
95 | * other CPUs that started a grace period. Otherwise we would delay any | |
96 | * grace period as long as we run in the idle task. | |
c0d6d01b PM |
97 | * |
98 | * Similarly, we avoid claiming an SRCU read lock held if the current | |
99 | * CPU is offline. | |
632ee200 PM |
100 | */ |
101 | static inline int srcu_read_lock_held(struct srcu_struct *sp) | |
102 | { | |
867f236b | 103 | if (!debug_lockdep_rcu_enabled()) |
ff195cb6 | 104 | return 1; |
c0d6d01b PM |
105 | if (rcu_is_cpu_idle()) |
106 | return 0; | |
107 | if (!rcu_lockdep_current_cpu_online()) | |
108 | return 0; | |
ff195cb6 | 109 | return lock_is_held(&sp->dep_map); |
632ee200 PM |
110 | } |
111 | ||
112 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
113 | ||
114 | static inline int srcu_read_lock_held(struct srcu_struct *sp) | |
115 | { | |
116 | return 1; | |
117 | } | |
118 | ||
119 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
120 | ||
c26d34a5 | 121 | /** |
ca5ecddf PM |
122 | * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing |
123 | * @p: the pointer to fetch and protect for later dereferencing | |
124 | * @sp: pointer to the srcu_struct, which is used to check that we | |
125 | * really are in an SRCU read-side critical section. | |
126 | * @c: condition to check for update-side use | |
c26d34a5 | 127 | * |
ca5ecddf PM |
128 | * If PROVE_RCU is enabled, invoking this outside of an RCU read-side |
129 | * critical section will result in an RCU-lockdep splat, unless @c evaluates | |
130 | * to 1. The @c argument will normally be a logical expression containing | |
131 | * lockdep_is_held() calls. | |
c26d34a5 | 132 | */ |
ca5ecddf PM |
133 | #define srcu_dereference_check(p, sp, c) \ |
134 | __rcu_dereference_check((p), srcu_read_lock_held(sp) || (c), __rcu) | |
135 | ||
136 | /** | |
137 | * srcu_dereference - fetch SRCU-protected pointer for later dereferencing | |
138 | * @p: the pointer to fetch and protect for later dereferencing | |
139 | * @sp: pointer to the srcu_struct, which is used to check that we | |
140 | * really are in an SRCU read-side critical section. | |
141 | * | |
142 | * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU | |
143 | * is enabled, invoking this outside of an RCU read-side critical | |
144 | * section will result in an RCU-lockdep splat. | |
145 | */ | |
146 | #define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0) | |
c26d34a5 | 147 | |
632ee200 PM |
148 | /** |
149 | * srcu_read_lock - register a new reader for an SRCU-protected structure. | |
150 | * @sp: srcu_struct in which to register the new reader. | |
151 | * | |
152 | * Enter an SRCU read-side critical section. Note that SRCU read-side | |
73d4da4d PM |
153 | * critical sections may be nested. However, it is illegal to |
154 | * call anything that waits on an SRCU grace period for the same | |
155 | * srcu_struct, whether directly or indirectly. Please note that | |
156 | * one way to indirectly wait on an SRCU grace period is to acquire | |
157 | * a mutex that is held elsewhere while calling synchronize_srcu() or | |
158 | * synchronize_srcu_expedited(). | |
3842a083 PM |
159 | * |
160 | * Note that srcu_read_lock() and the matching srcu_read_unlock() must | |
161 | * occur in the same context, for example, it is illegal to invoke | |
162 | * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() | |
163 | * was invoked in process context. | |
632ee200 PM |
164 | */ |
165 | static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) | |
166 | { | |
167 | int retval = __srcu_read_lock(sp); | |
168 | ||
ff195cb6 | 169 | rcu_lock_acquire(&(sp)->dep_map); |
bde23c68 HC |
170 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
171 | "srcu_read_lock() used illegally while idle"); | |
632ee200 PM |
172 | return retval; |
173 | } | |
174 | ||
175 | /** | |
176 | * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. | |
177 | * @sp: srcu_struct in which to unregister the old reader. | |
178 | * @idx: return value from corresponding srcu_read_lock(). | |
179 | * | |
180 | * Exit an SRCU read-side critical section. | |
181 | */ | |
182 | static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) | |
183 | __releases(sp) | |
184 | { | |
bde23c68 HC |
185 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
186 | "srcu_read_unlock() used illegally while idle"); | |
ff195cb6 | 187 | rcu_lock_release(&(sp)->dep_map); |
632ee200 PM |
188 | __srcu_read_unlock(sp, idx); |
189 | } | |
190 | ||
0c53dd8b PM |
191 | /** |
192 | * srcu_read_lock_raw - register a new reader for an SRCU-protected structure. | |
193 | * @sp: srcu_struct in which to register the new reader. | |
194 | * | |
195 | * Enter an SRCU read-side critical section. Similar to srcu_read_lock(), | |
196 | * but avoids the RCU-lockdep checking. This means that it is legal to | |
197 | * use srcu_read_lock_raw() in one context, for example, in an exception | |
198 | * handler, and then have the matching srcu_read_unlock_raw() in another | |
199 | * context, for example in the task that took the exception. | |
200 | * | |
201 | * However, the entire SRCU read-side critical section must reside within a | |
202 | * single task. For example, beware of using srcu_read_lock_raw() in | |
203 | * a device interrupt handler and srcu_read_unlock() in the interrupted | |
204 | * task: This will not work if interrupts are threaded. | |
205 | */ | |
206 | static inline int srcu_read_lock_raw(struct srcu_struct *sp) | |
207 | { | |
208 | unsigned long flags; | |
209 | int ret; | |
210 | ||
211 | local_irq_save(flags); | |
212 | ret = __srcu_read_lock(sp); | |
213 | local_irq_restore(flags); | |
214 | return ret; | |
215 | } | |
216 | ||
217 | /** | |
218 | * srcu_read_unlock_raw - unregister reader from an SRCU-protected structure. | |
219 | * @sp: srcu_struct in which to unregister the old reader. | |
220 | * @idx: return value from corresponding srcu_read_lock_raw(). | |
221 | * | |
222 | * Exit an SRCU read-side critical section without lockdep-RCU checking. | |
223 | * See srcu_read_lock_raw() for more details. | |
224 | */ | |
225 | static inline void srcu_read_unlock_raw(struct srcu_struct *sp, int idx) | |
226 | { | |
227 | unsigned long flags; | |
228 | ||
229 | local_irq_save(flags); | |
230 | __srcu_read_unlock(sp, idx); | |
231 | local_irq_restore(flags); | |
232 | } | |
233 | ||
eabc0694 | 234 | #endif |