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8c366db0 | 1 | /* SPDX-License-Identifier: GPL-2.0+ */ |
621934ee PM |
2 | /* |
3 | * Sleepable Read-Copy Update mechanism for mutual exclusion | |
4 | * | |
621934ee | 5 | * Copyright (C) IBM Corporation, 2006 |
4e87b2d7 | 6 | * Copyright (C) Fujitsu, 2012 |
621934ee | 7 | * |
8c366db0 | 8 | * Author: Paul McKenney <paulmck@linux.ibm.com> |
4e87b2d7 | 9 | * Lai Jiangshan <laijs@cn.fujitsu.com> |
621934ee PM |
10 | * |
11 | * For detailed explanation of Read-Copy Update mechanism see - | |
8660b7d8 | 12 | * Documentation/RCU/ *.txt |
621934ee PM |
13 | * |
14 | */ | |
15 | ||
eabc0694 AS |
16 | #ifndef _LINUX_SRCU_H |
17 | #define _LINUX_SRCU_H | |
18 | ||
d14aada8 | 19 | #include <linux/mutex.h> |
ff195cb6 | 20 | #include <linux/rcupdate.h> |
931ea9d1 | 21 | #include <linux/workqueue.h> |
8660b7d8 | 22 | #include <linux/rcu_segcblist.h> |
d14aada8 | 23 | |
d8be8173 | 24 | struct srcu_struct; |
c2a8ec07 | 25 | |
632ee200 PM |
26 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
27 | ||
aacb5d91 | 28 | int __init_srcu_struct(struct srcu_struct *ssp, const char *name, |
632ee200 PM |
29 | struct lock_class_key *key); |
30 | ||
aacb5d91 | 31 | #define init_srcu_struct(ssp) \ |
632ee200 PM |
32 | ({ \ |
33 | static struct lock_class_key __srcu_key; \ | |
34 | \ | |
aacb5d91 | 35 | __init_srcu_struct((ssp), #ssp, &__srcu_key); \ |
632ee200 PM |
36 | }) |
37 | ||
55c6659a | 38 | #define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name }, |
632ee200 PM |
39 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
40 | ||
aacb5d91 | 41 | int init_srcu_struct(struct srcu_struct *ssp); |
632ee200 | 42 | |
55c6659a | 43 | #define __SRCU_DEP_MAP_INIT(srcu_name) |
632ee200 PM |
44 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
45 | ||
d8be8173 PM |
46 | #ifdef CONFIG_TINY_SRCU |
47 | #include <linux/srcutiny.h> | |
48 | #elif defined(CONFIG_TREE_SRCU) | |
49 | #include <linux/srcutree.h> | |
07f6e64b | 50 | #else |
0cd7e350 | 51 | #error "Unknown SRCU implementation specified to kernel configuration" |
d8be8173 | 52 | #endif |
55c6659a | 53 | |
aacb5d91 | 54 | void call_srcu(struct srcu_struct *ssp, struct rcu_head *head, |
931ea9d1 | 55 | void (*func)(struct rcu_head *head)); |
f5ad3991 | 56 | void cleanup_srcu_struct(struct srcu_struct *ssp); |
aacb5d91 PM |
57 | int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp); |
58 | void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp); | |
59 | void synchronize_srcu(struct srcu_struct *ssp); | |
8b5bd67c PM |
60 | unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp); |
61 | unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp); | |
62 | bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie); | |
eabc0694 | 63 | |
2e83b879 | 64 | #ifdef CONFIG_NEED_SRCU_NMI_SAFE |
e29a4915 FW |
65 | int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp); |
66 | void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp); | |
2e83b879 | 67 | #else |
e29a4915 | 68 | static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) |
2e83b879 PM |
69 | { |
70 | return __srcu_read_lock(ssp); | |
71 | } | |
e29a4915 | 72 | static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) |
2e83b879 PM |
73 | { |
74 | __srcu_read_unlock(ssp, idx); | |
75 | } | |
76 | #endif /* CONFIG_NEED_SRCU_NMI_SAFE */ | |
77 | ||
8e9c01c7 | 78 | void srcu_init(void); |
8e9c01c7 | 79 | |
632ee200 PM |
80 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
81 | ||
82 | /** | |
83 | * srcu_read_lock_held - might we be in SRCU read-side critical section? | |
aacb5d91 | 84 | * @ssp: The srcu_struct structure to check |
632ee200 | 85 | * |
d20200b5 PM |
86 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU |
87 | * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, | |
632ee200 PM |
88 | * this assumes we are in an SRCU read-side critical section unless it can |
89 | * prove otherwise. | |
ff195cb6 | 90 | * |
867f236b PM |
91 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot |
92 | * and while lockdep is disabled. | |
93 | * | |
511a0868 LJ |
94 | * Note that SRCU is based on its own statemachine and it doesn't |
95 | * relies on normal RCU, it can be called from the CPU which | |
96 | * is in the idle loop from an RCU point of view or offline. | |
632ee200 | 97 | */ |
aacb5d91 | 98 | static inline int srcu_read_lock_held(const struct srcu_struct *ssp) |
632ee200 | 99 | { |
867f236b | 100 | if (!debug_lockdep_rcu_enabled()) |
ff195cb6 | 101 | return 1; |
aacb5d91 | 102 | return lock_is_held(&ssp->dep_map); |
632ee200 PM |
103 | } |
104 | ||
f0f44752 BF |
105 | /* |
106 | * Annotations provide deadlock detection for SRCU. | |
107 | * | |
108 | * Similar to other lockdep annotations, except there is an additional | |
109 | * srcu_lock_sync(), which is basically an empty *write*-side critical section, | |
110 | * see lock_sync() for more information. | |
111 | */ | |
112 | ||
113 | /* Annotates a srcu_read_lock() */ | |
114 | static inline void srcu_lock_acquire(struct lockdep_map *map) | |
115 | { | |
116 | lock_map_acquire_read(map); | |
117 | } | |
118 | ||
119 | /* Annotates a srcu_read_lock() */ | |
120 | static inline void srcu_lock_release(struct lockdep_map *map) | |
121 | { | |
122 | lock_map_release(map); | |
123 | } | |
124 | ||
125 | /* Annotates a synchronize_srcu() */ | |
126 | static inline void srcu_lock_sync(struct lockdep_map *map) | |
127 | { | |
128 | lock_map_sync(map); | |
129 | } | |
130 | ||
632ee200 PM |
131 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
132 | ||
aacb5d91 | 133 | static inline int srcu_read_lock_held(const struct srcu_struct *ssp) |
632ee200 PM |
134 | { |
135 | return 1; | |
136 | } | |
137 | ||
f0f44752 BF |
138 | #define srcu_lock_acquire(m) do { } while (0) |
139 | #define srcu_lock_release(m) do { } while (0) | |
140 | #define srcu_lock_sync(m) do { } while (0) | |
141 | ||
632ee200 PM |
142 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
143 | ||
e29a4915 FW |
144 | #define SRCU_NMI_UNKNOWN 0x0 |
145 | #define SRCU_NMI_UNSAFE 0x1 | |
146 | #define SRCU_NMI_SAFE 0x2 | |
147 | ||
148 | #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU) | |
149 | void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe); | |
150 | #else | |
151 | static inline void srcu_check_nmi_safety(struct srcu_struct *ssp, | |
152 | bool nmi_safe) { } | |
153 | #endif | |
154 | ||
155 | ||
c26d34a5 | 156 | /** |
ca5ecddf PM |
157 | * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing |
158 | * @p: the pointer to fetch and protect for later dereferencing | |
aacb5d91 | 159 | * @ssp: pointer to the srcu_struct, which is used to check that we |
ca5ecddf PM |
160 | * really are in an SRCU read-side critical section. |
161 | * @c: condition to check for update-side use | |
c26d34a5 | 162 | * |
ca5ecddf PM |
163 | * If PROVE_RCU is enabled, invoking this outside of an RCU read-side |
164 | * critical section will result in an RCU-lockdep splat, unless @c evaluates | |
165 | * to 1. The @c argument will normally be a logical expression containing | |
166 | * lockdep_is_held() calls. | |
c26d34a5 | 167 | */ |
aacb5d91 | 168 | #define srcu_dereference_check(p, ssp, c) \ |
24ba5301 CHT |
169 | __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ |
170 | (c) || srcu_read_lock_held(ssp), __rcu) | |
ca5ecddf PM |
171 | |
172 | /** | |
173 | * srcu_dereference - fetch SRCU-protected pointer for later dereferencing | |
174 | * @p: the pointer to fetch and protect for later dereferencing | |
aacb5d91 | 175 | * @ssp: pointer to the srcu_struct, which is used to check that we |
ca5ecddf PM |
176 | * really are in an SRCU read-side critical section. |
177 | * | |
178 | * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU | |
179 | * is enabled, invoking this outside of an RCU read-side critical | |
180 | * section will result in an RCU-lockdep splat. | |
181 | */ | |
aacb5d91 | 182 | #define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0) |
c26d34a5 | 183 | |
0b764a6e JFG |
184 | /** |
185 | * srcu_dereference_notrace - no tracing and no lockdep calls from here | |
f3e763c3 | 186 | * @p: the pointer to fetch and protect for later dereferencing |
aacb5d91 | 187 | * @ssp: pointer to the srcu_struct, which is used to check that we |
f3e763c3 | 188 | * really are in an SRCU read-side critical section. |
0b764a6e | 189 | */ |
aacb5d91 | 190 | #define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1) |
0b764a6e | 191 | |
632ee200 PM |
192 | /** |
193 | * srcu_read_lock - register a new reader for an SRCU-protected structure. | |
aacb5d91 | 194 | * @ssp: srcu_struct in which to register the new reader. |
632ee200 PM |
195 | * |
196 | * Enter an SRCU read-side critical section. Note that SRCU read-side | |
73d4da4d PM |
197 | * critical sections may be nested. However, it is illegal to |
198 | * call anything that waits on an SRCU grace period for the same | |
199 | * srcu_struct, whether directly or indirectly. Please note that | |
200 | * one way to indirectly wait on an SRCU grace period is to acquire | |
201 | * a mutex that is held elsewhere while calling synchronize_srcu() or | |
202 | * synchronize_srcu_expedited(). | |
3842a083 PM |
203 | * |
204 | * Note that srcu_read_lock() and the matching srcu_read_unlock() must | |
205 | * occur in the same context, for example, it is illegal to invoke | |
206 | * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() | |
207 | * was invoked in process context. | |
632ee200 | 208 | */ |
aacb5d91 | 209 | static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) |
632ee200 | 210 | { |
49f5903b | 211 | int retval; |
632ee200 | 212 | |
e29a4915 | 213 | srcu_check_nmi_safety(ssp, false); |
aacb5d91 | 214 | retval = __srcu_read_lock(ssp); |
1da82598 | 215 | srcu_lock_acquire(&ssp->dep_map); |
632ee200 PM |
216 | return retval; |
217 | } | |
218 | ||
2e83b879 PM |
219 | /** |
220 | * srcu_read_lock_nmisafe - register a new reader for an SRCU-protected structure. | |
221 | * @ssp: srcu_struct in which to register the new reader. | |
222 | * | |
223 | * Enter an SRCU read-side critical section, but in an NMI-safe manner. | |
224 | * See srcu_read_lock() for more information. | |
225 | */ | |
226 | static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp) | |
227 | { | |
228 | int retval; | |
229 | ||
e29a4915 FW |
230 | srcu_check_nmi_safety(ssp, true); |
231 | retval = __srcu_read_lock_nmisafe(ssp); | |
3c6b0c1c | 232 | rcu_try_lock_acquire(&ssp->dep_map); |
2e83b879 PM |
233 | return retval; |
234 | } | |
235 | ||
1f45a4db PM |
236 | /* Used by tracing, cannot be traced and cannot invoke lockdep. */ |
237 | static inline notrace int | |
aacb5d91 | 238 | srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) |
1f45a4db PM |
239 | { |
240 | int retval; | |
241 | ||
e29a4915 | 242 | srcu_check_nmi_safety(ssp, false); |
aacb5d91 | 243 | retval = __srcu_read_lock(ssp); |
1f45a4db PM |
244 | return retval; |
245 | } | |
246 | ||
0b1182bd PM |
247 | /** |
248 | * srcu_down_read - register a new reader for an SRCU-protected structure. | |
249 | * @ssp: srcu_struct in which to register the new reader. | |
250 | * | |
251 | * Enter a semaphore-like SRCU read-side critical section. Note that | |
252 | * SRCU read-side critical sections may be nested. However, it is | |
253 | * illegal to call anything that waits on an SRCU grace period for the | |
254 | * same srcu_struct, whether directly or indirectly. Please note that | |
255 | * one way to indirectly wait on an SRCU grace period is to acquire | |
256 | * a mutex that is held elsewhere while calling synchronize_srcu() or | |
257 | * synchronize_srcu_expedited(). But if you want lockdep to help you | |
258 | * keep this stuff straight, you should instead use srcu_read_lock(). | |
259 | * | |
260 | * The semaphore-like nature of srcu_down_read() means that the matching | |
261 | * srcu_up_read() can be invoked from some other context, for example, | |
262 | * from some other task or from an irq handler. However, neither | |
263 | * srcu_down_read() nor srcu_up_read() may be invoked from an NMI handler. | |
264 | * | |
265 | * Calls to srcu_down_read() may be nested, similar to the manner in | |
266 | * which calls to down_read() may be nested. | |
267 | */ | |
268 | static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp) | |
269 | { | |
270 | WARN_ON_ONCE(in_nmi()); | |
271 | srcu_check_nmi_safety(ssp, false); | |
272 | return __srcu_read_lock(ssp); | |
273 | } | |
274 | ||
632ee200 PM |
275 | /** |
276 | * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. | |
aacb5d91 | 277 | * @ssp: srcu_struct in which to unregister the old reader. |
632ee200 PM |
278 | * @idx: return value from corresponding srcu_read_lock(). |
279 | * | |
280 | * Exit an SRCU read-side critical section. | |
281 | */ | |
aacb5d91 PM |
282 | static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) |
283 | __releases(ssp) | |
632ee200 | 284 | { |
c8ca1aa7 | 285 | WARN_ON_ONCE(idx & ~0x1); |
e29a4915 | 286 | srcu_check_nmi_safety(ssp, false); |
1da82598 | 287 | srcu_lock_release(&ssp->dep_map); |
aacb5d91 | 288 | __srcu_read_unlock(ssp, idx); |
632ee200 PM |
289 | } |
290 | ||
2e83b879 PM |
291 | /** |
292 | * srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protected structure. | |
293 | * @ssp: srcu_struct in which to unregister the old reader. | |
294 | * @idx: return value from corresponding srcu_read_lock(). | |
295 | * | |
296 | * Exit an SRCU read-side critical section, but in an NMI-safe manner. | |
297 | */ | |
298 | static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) | |
299 | __releases(ssp) | |
300 | { | |
301 | WARN_ON_ONCE(idx & ~0x1); | |
e29a4915 | 302 | srcu_check_nmi_safety(ssp, true); |
1da82598 | 303 | rcu_lock_release(&ssp->dep_map); |
e29a4915 | 304 | __srcu_read_unlock_nmisafe(ssp, idx); |
2e83b879 PM |
305 | } |
306 | ||
1f45a4db PM |
307 | /* Used by tracing, cannot be traced and cannot call lockdep. */ |
308 | static inline notrace void | |
aacb5d91 | 309 | srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) |
1f45a4db | 310 | { |
e29a4915 | 311 | srcu_check_nmi_safety(ssp, false); |
aacb5d91 | 312 | __srcu_read_unlock(ssp, idx); |
1f45a4db PM |
313 | } |
314 | ||
0b1182bd PM |
315 | /** |
316 | * srcu_up_read - unregister a old reader from an SRCU-protected structure. | |
317 | * @ssp: srcu_struct in which to unregister the old reader. | |
318 | * @idx: return value from corresponding srcu_read_lock(). | |
319 | * | |
320 | * Exit an SRCU read-side critical section, but not necessarily from | |
321 | * the same context as the maching srcu_down_read(). | |
322 | */ | |
323 | static inline void srcu_up_read(struct srcu_struct *ssp, int idx) | |
324 | __releases(ssp) | |
325 | { | |
326 | WARN_ON_ONCE(idx & ~0x1); | |
327 | WARN_ON_ONCE(in_nmi()); | |
328 | srcu_check_nmi_safety(ssp, false); | |
329 | __srcu_read_unlock(ssp, idx); | |
330 | } | |
331 | ||
ce332f66 MT |
332 | /** |
333 | * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock | |
334 | * | |
335 | * Converts the preceding srcu_read_unlock into a two-way memory barrier. | |
336 | * | |
337 | * Call this after srcu_read_unlock, to guarantee that all memory operations | |
338 | * that occur after smp_mb__after_srcu_read_unlock will appear to happen after | |
339 | * the preceding srcu_read_unlock. | |
340 | */ | |
341 | static inline void smp_mb__after_srcu_read_unlock(void) | |
342 | { | |
343 | /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */ | |
344 | } | |
345 | ||
54da6a09 PZ |
346 | DEFINE_LOCK_GUARD_1(srcu, struct srcu_struct, |
347 | _T->idx = srcu_read_lock(_T->lock), | |
348 | srcu_read_unlock(_T->lock, _T->idx), | |
349 | int idx) | |
350 | ||
eabc0694 | 351 | #endif |