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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
1b375dc3 ML |
2 | /* |
3 | * Wound/Wait Mutexes: blocking mutual exclusion locks with deadlock avoidance | |
4 | * | |
5 | * Original mutex implementation started by Ingo Molnar: | |
6 | * | |
7 | * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> | |
8 | * | |
9 | * Wound/wait implementation: | |
10 | * Copyright (C) 2013 Canonical Ltd. | |
11 | * | |
12 | * This file contains the main data structure and API definitions. | |
13 | */ | |
14 | ||
15 | #ifndef __LINUX_WW_MUTEX_H | |
16 | #define __LINUX_WW_MUTEX_H | |
17 | ||
18 | #include <linux/mutex.h> | |
19 | ||
20 | struct ww_class { | |
21 | atomic_long_t stamp; | |
22 | struct lock_class_key acquire_key; | |
23 | struct lock_class_key mutex_key; | |
24 | const char *acquire_name; | |
25 | const char *mutex_name; | |
26 | }; | |
27 | ||
28 | struct ww_acquire_ctx { | |
29 | struct task_struct *task; | |
30 | unsigned long stamp; | |
31 | unsigned acquired; | |
32 | #ifdef CONFIG_DEBUG_MUTEXES | |
33 | unsigned done_acquire; | |
34 | struct ww_class *ww_class; | |
35 | struct ww_mutex *contending_lock; | |
36 | #endif | |
37 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
38 | struct lockdep_map dep_map; | |
39 | #endif | |
40 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
41 | unsigned deadlock_inject_interval; | |
42 | unsigned deadlock_inject_countdown; | |
43 | #endif | |
44 | }; | |
45 | ||
46 | struct ww_mutex { | |
47 | struct mutex base; | |
48 | struct ww_acquire_ctx *ctx; | |
49 | #ifdef CONFIG_DEBUG_MUTEXES | |
50 | struct ww_class *ww_class; | |
51 | #endif | |
52 | }; | |
53 | ||
54 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
af2e859e CW |
55 | # define __WW_CLASS_MUTEX_INITIALIZER(lockname, class) \ |
56 | , .ww_class = class | |
1b375dc3 | 57 | #else |
af2e859e | 58 | # define __WW_CLASS_MUTEX_INITIALIZER(lockname, class) |
1b375dc3 ML |
59 | #endif |
60 | ||
61 | #define __WW_CLASS_INITIALIZER(ww_class) \ | |
62 | { .stamp = ATOMIC_LONG_INIT(0) \ | |
63 | , .acquire_name = #ww_class "_acquire" \ | |
64 | , .mutex_name = #ww_class "_mutex" } | |
65 | ||
66 | #define __WW_MUTEX_INITIALIZER(lockname, class) \ | |
af2e859e | 67 | { .base = __MUTEX_INITIALIZER(lockname.base) \ |
1b375dc3 ML |
68 | __WW_CLASS_MUTEX_INITIALIZER(lockname, class) } |
69 | ||
70 | #define DEFINE_WW_CLASS(classname) \ | |
71 | struct ww_class classname = __WW_CLASS_INITIALIZER(classname) | |
72 | ||
73 | #define DEFINE_WW_MUTEX(mutexname, ww_class) \ | |
74 | struct ww_mutex mutexname = __WW_MUTEX_INITIALIZER(mutexname, ww_class) | |
75 | ||
76 | /** | |
77 | * ww_mutex_init - initialize the w/w mutex | |
78 | * @lock: the mutex to be initialized | |
79 | * @ww_class: the w/w class the mutex should belong to | |
80 | * | |
81 | * Initialize the w/w mutex to unlocked state and associate it with the given | |
82 | * class. | |
83 | * | |
84 | * It is not allowed to initialize an already locked mutex. | |
85 | */ | |
86 | static inline void ww_mutex_init(struct ww_mutex *lock, | |
87 | struct ww_class *ww_class) | |
88 | { | |
89 | __mutex_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key); | |
90 | lock->ctx = NULL; | |
91 | #ifdef CONFIG_DEBUG_MUTEXES | |
92 | lock->ww_class = ww_class; | |
93 | #endif | |
94 | } | |
95 | ||
96 | /** | |
97 | * ww_acquire_init - initialize a w/w acquire context | |
98 | * @ctx: w/w acquire context to initialize | |
99 | * @ww_class: w/w class of the context | |
100 | * | |
101 | * Initializes an context to acquire multiple mutexes of the given w/w class. | |
102 | * | |
103 | * Context-based w/w mutex acquiring can be done in any order whatsoever within | |
104 | * a given lock class. Deadlocks will be detected and handled with the | |
105 | * wait/wound logic. | |
106 | * | |
107 | * Mixing of context-based w/w mutex acquiring and single w/w mutex locking can | |
108 | * result in undetected deadlocks and is so forbidden. Mixing different contexts | |
109 | * for the same w/w class when acquiring mutexes can also result in undetected | |
110 | * deadlocks, and is hence also forbidden. Both types of abuse will be caught by | |
111 | * enabling CONFIG_PROVE_LOCKING. | |
112 | * | |
113 | * Nesting of acquire contexts for _different_ w/w classes is possible, subject | |
114 | * to the usual locking rules between different lock classes. | |
115 | * | |
116 | * An acquire context must be released with ww_acquire_fini by the same task | |
117 | * before the memory is freed. It is recommended to allocate the context itself | |
118 | * on the stack. | |
119 | */ | |
120 | static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, | |
121 | struct ww_class *ww_class) | |
122 | { | |
123 | ctx->task = current; | |
f4ec57b6 | 124 | ctx->stamp = atomic_long_inc_return_relaxed(&ww_class->stamp); |
1b375dc3 ML |
125 | ctx->acquired = 0; |
126 | #ifdef CONFIG_DEBUG_MUTEXES | |
127 | ctx->ww_class = ww_class; | |
128 | ctx->done_acquire = 0; | |
129 | ctx->contending_lock = NULL; | |
130 | #endif | |
131 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
132 | debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); | |
133 | lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, | |
134 | &ww_class->acquire_key, 0); | |
135 | mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); | |
136 | #endif | |
137 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
138 | ctx->deadlock_inject_interval = 1; | |
139 | ctx->deadlock_inject_countdown = ctx->stamp & 0xf; | |
140 | #endif | |
141 | } | |
142 | ||
143 | /** | |
144 | * ww_acquire_done - marks the end of the acquire phase | |
145 | * @ctx: the acquire context | |
146 | * | |
147 | * Marks the end of the acquire phase, any further w/w mutex lock calls using | |
148 | * this context are forbidden. | |
149 | * | |
150 | * Calling this function is optional, it is just useful to document w/w mutex | |
151 | * code and clearly designated the acquire phase from actually using the locked | |
152 | * data structures. | |
153 | */ | |
154 | static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) | |
155 | { | |
156 | #ifdef CONFIG_DEBUG_MUTEXES | |
157 | lockdep_assert_held(ctx); | |
158 | ||
159 | DEBUG_LOCKS_WARN_ON(ctx->done_acquire); | |
160 | ctx->done_acquire = 1; | |
161 | #endif | |
162 | } | |
163 | ||
164 | /** | |
165 | * ww_acquire_fini - releases a w/w acquire context | |
166 | * @ctx: the acquire context to free | |
167 | * | |
168 | * Releases a w/w acquire context. This must be called _after_ all acquired w/w | |
169 | * mutexes have been released with ww_mutex_unlock. | |
170 | */ | |
171 | static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) | |
172 | { | |
173 | #ifdef CONFIG_DEBUG_MUTEXES | |
174 | mutex_release(&ctx->dep_map, 0, _THIS_IP_); | |
175 | ||
176 | DEBUG_LOCKS_WARN_ON(ctx->acquired); | |
97f2645f | 177 | if (!IS_ENABLED(CONFIG_PROVE_LOCKING)) |
1b375dc3 ML |
178 | /* |
179 | * lockdep will normally handle this, | |
180 | * but fail without anyway | |
181 | */ | |
182 | ctx->done_acquire = 1; | |
183 | ||
97f2645f | 184 | if (!IS_ENABLED(CONFIG_DEBUG_LOCK_ALLOC)) |
1b375dc3 ML |
185 | /* ensure ww_acquire_fini will still fail if called twice */ |
186 | ctx->acquired = ~0U; | |
187 | #endif | |
188 | } | |
189 | ||
1b375dc3 ML |
190 | /** |
191 | * ww_mutex_lock - acquire the w/w mutex | |
192 | * @lock: the mutex to be acquired | |
193 | * @ctx: w/w acquire context, or NULL to acquire only a single lock. | |
194 | * | |
195 | * Lock the w/w mutex exclusively for this task. | |
196 | * | |
197 | * Deadlocks within a given w/w class of locks are detected and handled with the | |
198 | * wait/wound algorithm. If the lock isn't immediately avaiable this function | |
199 | * will either sleep until it is (wait case). Or it selects the current context | |
200 | * for backing off by returning -EDEADLK (wound case). Trying to acquire the | |
201 | * same lock with the same context twice is also detected and signalled by | |
202 | * returning -EALREADY. Returns 0 if the mutex was successfully acquired. | |
203 | * | |
204 | * In the wound case the caller must release all currently held w/w mutexes for | |
205 | * the given context and then wait for this contending lock to be available by | |
206 | * calling ww_mutex_lock_slow. Alternatively callers can opt to not acquire this | |
207 | * lock and proceed with trying to acquire further w/w mutexes (e.g. when | |
208 | * scanning through lru lists trying to free resources). | |
209 | * | |
210 | * The mutex must later on be released by the same task that | |
211 | * acquired it. The task may not exit without first unlocking the mutex. Also, | |
212 | * kernel memory where the mutex resides must not be freed with the mutex still | |
213 | * locked. The mutex must first be initialized (or statically defined) before it | |
214 | * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be | |
215 | * of the same w/w lock class as was used to initialize the acquire context. | |
216 | * | |
217 | * A mutex acquired with this function must be released with ww_mutex_unlock. | |
218 | */ | |
23b19ec3 | 219 | extern int /* __must_check */ ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx); |
1b375dc3 ML |
220 | |
221 | /** | |
222 | * ww_mutex_lock_interruptible - acquire the w/w mutex, interruptible | |
223 | * @lock: the mutex to be acquired | |
224 | * @ctx: w/w acquire context | |
225 | * | |
226 | * Lock the w/w mutex exclusively for this task. | |
227 | * | |
228 | * Deadlocks within a given w/w class of locks are detected and handled with the | |
229 | * wait/wound algorithm. If the lock isn't immediately avaiable this function | |
230 | * will either sleep until it is (wait case). Or it selects the current context | |
231 | * for backing off by returning -EDEADLK (wound case). Trying to acquire the | |
232 | * same lock with the same context twice is also detected and signalled by | |
233 | * returning -EALREADY. Returns 0 if the mutex was successfully acquired. If a | |
234 | * signal arrives while waiting for the lock then this function returns -EINTR. | |
235 | * | |
236 | * In the wound case the caller must release all currently held w/w mutexes for | |
237 | * the given context and then wait for this contending lock to be available by | |
238 | * calling ww_mutex_lock_slow_interruptible. Alternatively callers can opt to | |
239 | * not acquire this lock and proceed with trying to acquire further w/w mutexes | |
240 | * (e.g. when scanning through lru lists trying to free resources). | |
241 | * | |
242 | * The mutex must later on be released by the same task that | |
243 | * acquired it. The task may not exit without first unlocking the mutex. Also, | |
244 | * kernel memory where the mutex resides must not be freed with the mutex still | |
245 | * locked. The mutex must first be initialized (or statically defined) before it | |
246 | * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be | |
247 | * of the same w/w lock class as was used to initialize the acquire context. | |
248 | * | |
249 | * A mutex acquired with this function must be released with ww_mutex_unlock. | |
250 | */ | |
c5470b22 NH |
251 | extern int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock, |
252 | struct ww_acquire_ctx *ctx); | |
1b375dc3 ML |
253 | |
254 | /** | |
255 | * ww_mutex_lock_slow - slowpath acquiring of the w/w mutex | |
256 | * @lock: the mutex to be acquired | |
257 | * @ctx: w/w acquire context | |
258 | * | |
259 | * Acquires a w/w mutex with the given context after a wound case. This function | |
260 | * will sleep until the lock becomes available. | |
261 | * | |
262 | * The caller must have released all w/w mutexes already acquired with the | |
263 | * context and then call this function on the contended lock. | |
264 | * | |
265 | * Afterwards the caller may continue to (re)acquire the other w/w mutexes it | |
266 | * needs with ww_mutex_lock. Note that the -EALREADY return code from | |
267 | * ww_mutex_lock can be used to avoid locking this contended mutex twice. | |
268 | * | |
269 | * It is forbidden to call this function with any other w/w mutexes associated | |
270 | * with the context held. It is forbidden to call this on anything else than the | |
271 | * contending mutex. | |
272 | * | |
273 | * Note that the slowpath lock acquiring can also be done by calling | |
274 | * ww_mutex_lock directly. This function here is simply to help w/w mutex | |
275 | * locking code readability by clearly denoting the slowpath. | |
276 | */ | |
277 | static inline void | |
278 | ww_mutex_lock_slow(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
279 | { | |
280 | int ret; | |
281 | #ifdef CONFIG_DEBUG_MUTEXES | |
282 | DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); | |
283 | #endif | |
284 | ret = ww_mutex_lock(lock, ctx); | |
285 | (void)ret; | |
286 | } | |
287 | ||
288 | /** | |
289 | * ww_mutex_lock_slow_interruptible - slowpath acquiring of the w/w mutex, interruptible | |
290 | * @lock: the mutex to be acquired | |
291 | * @ctx: w/w acquire context | |
292 | * | |
293 | * Acquires a w/w mutex with the given context after a wound case. This function | |
294 | * will sleep until the lock becomes available and returns 0 when the lock has | |
295 | * been acquired. If a signal arrives while waiting for the lock then this | |
296 | * function returns -EINTR. | |
297 | * | |
298 | * The caller must have released all w/w mutexes already acquired with the | |
299 | * context and then call this function on the contended lock. | |
300 | * | |
301 | * Afterwards the caller may continue to (re)acquire the other w/w mutexes it | |
302 | * needs with ww_mutex_lock. Note that the -EALREADY return code from | |
303 | * ww_mutex_lock can be used to avoid locking this contended mutex twice. | |
304 | * | |
305 | * It is forbidden to call this function with any other w/w mutexes associated | |
306 | * with the given context held. It is forbidden to call this on anything else | |
307 | * than the contending mutex. | |
308 | * | |
309 | * Note that the slowpath lock acquiring can also be done by calling | |
310 | * ww_mutex_lock_interruptible directly. This function here is simply to help | |
311 | * w/w mutex locking code readability by clearly denoting the slowpath. | |
312 | */ | |
313 | static inline int __must_check | |
314 | ww_mutex_lock_slow_interruptible(struct ww_mutex *lock, | |
315 | struct ww_acquire_ctx *ctx) | |
316 | { | |
317 | #ifdef CONFIG_DEBUG_MUTEXES | |
318 | DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); | |
319 | #endif | |
320 | return ww_mutex_lock_interruptible(lock, ctx); | |
321 | } | |
322 | ||
323 | extern void ww_mutex_unlock(struct ww_mutex *lock); | |
324 | ||
325 | /** | |
326 | * ww_mutex_trylock - tries to acquire the w/w mutex without acquire context | |
327 | * @lock: mutex to lock | |
328 | * | |
329 | * Trylocks a mutex without acquire context, so no deadlock detection is | |
330 | * possible. Returns 1 if the mutex has been acquired successfully, 0 otherwise. | |
331 | */ | |
332 | static inline int __must_check ww_mutex_trylock(struct ww_mutex *lock) | |
333 | { | |
334 | return mutex_trylock(&lock->base); | |
335 | } | |
336 | ||
337 | /*** | |
338 | * ww_mutex_destroy - mark a w/w mutex unusable | |
339 | * @lock: the mutex to be destroyed | |
340 | * | |
341 | * This function marks the mutex uninitialized, and any subsequent | |
342 | * use of the mutex is forbidden. The mutex must not be locked when | |
343 | * this function is called. | |
344 | */ | |
345 | static inline void ww_mutex_destroy(struct ww_mutex *lock) | |
346 | { | |
347 | mutex_destroy(&lock->base); | |
348 | } | |
349 | ||
350 | /** | |
351 | * ww_mutex_is_locked - is the w/w mutex locked | |
352 | * @lock: the mutex to be queried | |
353 | * | |
354 | * Returns 1 if the mutex is locked, 0 if unlocked. | |
355 | */ | |
356 | static inline bool ww_mutex_is_locked(struct ww_mutex *lock) | |
357 | { | |
358 | return mutex_is_locked(&lock->base); | |
359 | } | |
360 | ||
361 | #endif |