1 | /* SPDX-License-Identifier: GPL-2.0+ */ |
2 | /* |
3 | * Sleepable Read-Copy Update mechanism for mutual exclusion |
4 | * |
5 | * Copyright (C) IBM Corporation, 2006 |
6 | * Copyright (C) Fujitsu, 2012 |
7 | * |
8 | * Author: Paul McKenney <paulmck@linux.ibm.com> |
9 | * Lai Jiangshan <laijs@cn.fujitsu.com> |
10 | * |
11 | * For detailed explanation of Read-Copy Update mechanism see - |
12 | * Documentation/RCU/ *.txt |
13 | * |
14 | */ |
15 | |
16 | #ifndef _LINUX_SRCU_H |
17 | #define _LINUX_SRCU_H |
18 | |
19 | #include <linux/mutex.h> |
20 | #include <linux/rcupdate.h> |
21 | #include <linux/workqueue.h> |
22 | #include <linux/rcu_segcblist.h> |
23 | |
24 | struct srcu_struct; |
25 | |
26 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
27 | |
28 | int __init_srcu_struct(struct srcu_struct *ssp, const char *name, |
29 | struct lock_class_key *key); |
30 | |
31 | #define init_srcu_struct(ssp) \ |
32 | ({ \ |
33 | static struct lock_class_key __srcu_key; \ |
34 | \ |
35 | __init_srcu_struct((ssp), #ssp, &__srcu_key); \ |
36 | }) |
37 | |
38 | #define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name }, |
39 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
40 | |
41 | int init_srcu_struct(struct srcu_struct *ssp); |
42 | |
43 | #define __SRCU_DEP_MAP_INIT(srcu_name) |
44 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
45 | |
46 | #ifdef CONFIG_TINY_SRCU |
47 | #include <linux/srcutiny.h> |
48 | #elif defined(CONFIG_TREE_SRCU) |
49 | #include <linux/srcutree.h> |
50 | #else |
51 | #error "Unknown SRCU implementation specified to kernel configuration" |
52 | #endif |
53 | |
54 | void call_srcu(struct srcu_struct *ssp, struct rcu_head *head, |
55 | void (*func)(struct rcu_head *head)); |
56 | void cleanup_srcu_struct(struct srcu_struct *ssp); |
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); |
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); |
63 | |
64 | #ifdef CONFIG_NEED_SRCU_NMI_SAFE |
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); |
67 | #else |
68 | static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) |
69 | { |
70 | return __srcu_read_lock(ssp); |
71 | } |
72 | static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) |
73 | { |
74 | __srcu_read_unlock(ssp, idx); |
75 | } |
76 | #endif /* CONFIG_NEED_SRCU_NMI_SAFE */ |
77 | |
78 | void srcu_init(void); |
79 | |
80 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
81 | |
82 | /** |
83 | * srcu_read_lock_held - might we be in SRCU read-side critical section? |
84 | * @ssp: The srcu_struct structure to check |
85 | * |
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, |
88 | * this assumes we are in an SRCU read-side critical section unless it can |
89 | * prove otherwise. |
90 | * |
91 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot |
92 | * and while lockdep is disabled. |
93 | * |
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. |
97 | */ |
98 | static inline int srcu_read_lock_held(const struct srcu_struct *ssp) |
99 | { |
100 | if (!debug_lockdep_rcu_enabled()) |
101 | return 1; |
102 | return lock_is_held(lock: &ssp->dep_map); |
103 | } |
104 | |
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 | |
131 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
132 | |
133 | static inline int srcu_read_lock_held(const struct srcu_struct *ssp) |
134 | { |
135 | return 1; |
136 | } |
137 | |
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 | |
142 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
143 | |
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 | |
156 | /** |
157 | * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing |
158 | * @p: the pointer to fetch and protect for later dereferencing |
159 | * @ssp: pointer to the srcu_struct, which is used to check that we |
160 | * really are in an SRCU read-side critical section. |
161 | * @c: condition to check for update-side use |
162 | * |
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. |
167 | */ |
168 | #define srcu_dereference_check(p, ssp, c) \ |
169 | __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ |
170 | (c) || srcu_read_lock_held(ssp), __rcu) |
171 | |
172 | /** |
173 | * srcu_dereference - fetch SRCU-protected pointer for later dereferencing |
174 | * @p: the pointer to fetch and protect for later dereferencing |
175 | * @ssp: pointer to the srcu_struct, which is used to check that we |
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 | */ |
182 | #define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0) |
183 | |
184 | /** |
185 | * srcu_dereference_notrace - no tracing and no lockdep calls from here |
186 | * @p: the pointer to fetch and protect for later dereferencing |
187 | * @ssp: pointer to the srcu_struct, which is used to check that we |
188 | * really are in an SRCU read-side critical section. |
189 | */ |
190 | #define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1) |
191 | |
192 | /** |
193 | * srcu_read_lock - register a new reader for an SRCU-protected structure. |
194 | * @ssp: srcu_struct in which to register the new reader. |
195 | * |
196 | * Enter an SRCU read-side critical section. Note that SRCU read-side |
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(). |
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. |
208 | */ |
209 | static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) |
210 | { |
211 | int retval; |
212 | |
213 | srcu_check_nmi_safety(ssp, nmi_safe: false); |
214 | retval = __srcu_read_lock(ssp); |
215 | srcu_lock_acquire(map: &ssp->dep_map); |
216 | return retval; |
217 | } |
218 | |
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 | |
230 | srcu_check_nmi_safety(ssp, nmi_safe: true); |
231 | retval = __srcu_read_lock_nmisafe(ssp); |
232 | rcu_try_lock_acquire(map: &ssp->dep_map); |
233 | return retval; |
234 | } |
235 | |
236 | /* Used by tracing, cannot be traced and cannot invoke lockdep. */ |
237 | static inline notrace int |
238 | srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) |
239 | { |
240 | int retval; |
241 | |
242 | srcu_check_nmi_safety(ssp, nmi_safe: false); |
243 | retval = __srcu_read_lock(ssp); |
244 | return retval; |
245 | } |
246 | |
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, nmi_safe: false); |
272 | return __srcu_read_lock(ssp); |
273 | } |
274 | |
275 | /** |
276 | * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. |
277 | * @ssp: srcu_struct in which to unregister the old reader. |
278 | * @idx: return value from corresponding srcu_read_lock(). |
279 | * |
280 | * Exit an SRCU read-side critical section. |
281 | */ |
282 | static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) |
283 | __releases(ssp) |
284 | { |
285 | WARN_ON_ONCE(idx & ~0x1); |
286 | srcu_check_nmi_safety(ssp, nmi_safe: false); |
287 | srcu_lock_release(map: &ssp->dep_map); |
288 | __srcu_read_unlock(ssp, idx); |
289 | } |
290 | |
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); |
302 | srcu_check_nmi_safety(ssp, nmi_safe: true); |
303 | rcu_lock_release(map: &ssp->dep_map); |
304 | __srcu_read_unlock_nmisafe(ssp, idx); |
305 | } |
306 | |
307 | /* Used by tracing, cannot be traced and cannot call lockdep. */ |
308 | static inline notrace void |
309 | srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) |
310 | { |
311 | srcu_check_nmi_safety(ssp, nmi_safe: false); |
312 | __srcu_read_unlock(ssp, idx); |
313 | } |
314 | |
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, nmi_safe: false); |
329 | __srcu_read_unlock(ssp, idx); |
330 | } |
331 | |
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 | |
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 | |
351 | #endif |
352 | |