Commit | Line | Data |
---|---|---|
1b375dc3 ML |
1 | /* |
2 | * Wound/Wait Mutexes: blocking mutual exclusion locks with deadlock avoidance | |
3 | * | |
4 | * Original mutex implementation started by Ingo Molnar: | |
5 | * | |
6 | * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> | |
7 | * | |
8 | * Wound/wait implementation: | |
9 | * Copyright (C) 2013 Canonical Ltd. | |
10 | * | |
11 | * This file contains the main data structure and API definitions. | |
12 | */ | |
13 | ||
14 | #ifndef __LINUX_WW_MUTEX_H | |
15 | #define __LINUX_WW_MUTEX_H | |
16 | ||
17 | #include <linux/mutex.h> | |
18 | ||
19 | struct ww_class { | |
20 | atomic_long_t stamp; | |
21 | struct lock_class_key acquire_key; | |
22 | struct lock_class_key mutex_key; | |
23 | const char *acquire_name; | |
24 | const char *mutex_name; | |
25 | }; | |
26 | ||
27 | struct ww_acquire_ctx { | |
28 | struct task_struct *task; | |
29 | unsigned long stamp; | |
30 | unsigned acquired; | |
31 | #ifdef CONFIG_DEBUG_MUTEXES | |
32 | unsigned done_acquire; | |
33 | struct ww_class *ww_class; | |
34 | struct ww_mutex *contending_lock; | |
35 | #endif | |
36 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
37 | struct lockdep_map dep_map; | |
38 | #endif | |
39 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
40 | unsigned deadlock_inject_interval; | |
41 | unsigned deadlock_inject_countdown; | |
42 | #endif | |
43 | }; | |
44 | ||
45 | struct ww_mutex { | |
46 | struct mutex base; | |
47 | struct ww_acquire_ctx *ctx; | |
48 | #ifdef CONFIG_DEBUG_MUTEXES | |
49 | struct ww_class *ww_class; | |
50 | #endif | |
51 | }; | |
52 | ||
53 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
54 | # define __WW_CLASS_MUTEX_INITIALIZER(lockname, ww_class) \ | |
55 | , .ww_class = &ww_class | |
56 | #else | |
57 | # define __WW_CLASS_MUTEX_INITIALIZER(lockname, ww_class) | |
58 | #endif | |
59 | ||
60 | #define __WW_CLASS_INITIALIZER(ww_class) \ | |
61 | { .stamp = ATOMIC_LONG_INIT(0) \ | |
62 | , .acquire_name = #ww_class "_acquire" \ | |
63 | , .mutex_name = #ww_class "_mutex" } | |
64 | ||
65 | #define __WW_MUTEX_INITIALIZER(lockname, class) \ | |
66 | { .base = { \__MUTEX_INITIALIZER(lockname) } \ | |
67 | __WW_CLASS_MUTEX_INITIALIZER(lockname, class) } | |
68 | ||
69 | #define DEFINE_WW_CLASS(classname) \ | |
70 | struct ww_class classname = __WW_CLASS_INITIALIZER(classname) | |
71 | ||
72 | #define DEFINE_WW_MUTEX(mutexname, ww_class) \ | |
73 | struct ww_mutex mutexname = __WW_MUTEX_INITIALIZER(mutexname, ww_class) | |
74 | ||
75 | /** | |
76 | * ww_mutex_init - initialize the w/w mutex | |
77 | * @lock: the mutex to be initialized | |
78 | * @ww_class: the w/w class the mutex should belong to | |
79 | * | |
80 | * Initialize the w/w mutex to unlocked state and associate it with the given | |
81 | * class. | |
82 | * | |
83 | * It is not allowed to initialize an already locked mutex. | |
84 | */ | |
85 | static inline void ww_mutex_init(struct ww_mutex *lock, | |
86 | struct ww_class *ww_class) | |
87 | { | |
88 | __mutex_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key); | |
89 | lock->ctx = NULL; | |
90 | #ifdef CONFIG_DEBUG_MUTEXES | |
91 | lock->ww_class = ww_class; | |
92 | #endif | |
93 | } | |
94 | ||
95 | /** | |
96 | * ww_acquire_init - initialize a w/w acquire context | |
97 | * @ctx: w/w acquire context to initialize | |
98 | * @ww_class: w/w class of the context | |
99 | * | |
100 | * Initializes an context to acquire multiple mutexes of the given w/w class. | |
101 | * | |
102 | * Context-based w/w mutex acquiring can be done in any order whatsoever within | |
103 | * a given lock class. Deadlocks will be detected and handled with the | |
104 | * wait/wound logic. | |
105 | * | |
106 | * Mixing of context-based w/w mutex acquiring and single w/w mutex locking can | |
107 | * result in undetected deadlocks and is so forbidden. Mixing different contexts | |
108 | * for the same w/w class when acquiring mutexes can also result in undetected | |
109 | * deadlocks, and is hence also forbidden. Both types of abuse will be caught by | |
110 | * enabling CONFIG_PROVE_LOCKING. | |
111 | * | |
112 | * Nesting of acquire contexts for _different_ w/w classes is possible, subject | |
113 | * to the usual locking rules between different lock classes. | |
114 | * | |
115 | * An acquire context must be released with ww_acquire_fini by the same task | |
116 | * before the memory is freed. It is recommended to allocate the context itself | |
117 | * on the stack. | |
118 | */ | |
119 | static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, | |
120 | struct ww_class *ww_class) | |
121 | { | |
122 | ctx->task = current; | |
123 | ctx->stamp = atomic_long_inc_return(&ww_class->stamp); | |
124 | ctx->acquired = 0; | |
125 | #ifdef CONFIG_DEBUG_MUTEXES | |
126 | ctx->ww_class = ww_class; | |
127 | ctx->done_acquire = 0; | |
128 | ctx->contending_lock = NULL; | |
129 | #endif | |
130 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
131 | debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); | |
132 | lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, | |
133 | &ww_class->acquire_key, 0); | |
134 | mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); | |
135 | #endif | |
136 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
137 | ctx->deadlock_inject_interval = 1; | |
138 | ctx->deadlock_inject_countdown = ctx->stamp & 0xf; | |
139 | #endif | |
140 | } | |
141 | ||
142 | /** | |
143 | * ww_acquire_done - marks the end of the acquire phase | |
144 | * @ctx: the acquire context | |
145 | * | |
146 | * Marks the end of the acquire phase, any further w/w mutex lock calls using | |
147 | * this context are forbidden. | |
148 | * | |
149 | * Calling this function is optional, it is just useful to document w/w mutex | |
150 | * code and clearly designated the acquire phase from actually using the locked | |
151 | * data structures. | |
152 | */ | |
153 | static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) | |
154 | { | |
155 | #ifdef CONFIG_DEBUG_MUTEXES | |
156 | lockdep_assert_held(ctx); | |
157 | ||
158 | DEBUG_LOCKS_WARN_ON(ctx->done_acquire); | |
159 | ctx->done_acquire = 1; | |
160 | #endif | |
161 | } | |
162 | ||
163 | /** | |
164 | * ww_acquire_fini - releases a w/w acquire context | |
165 | * @ctx: the acquire context to free | |
166 | * | |
167 | * Releases a w/w acquire context. This must be called _after_ all acquired w/w | |
168 | * mutexes have been released with ww_mutex_unlock. | |
169 | */ | |
170 | static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) | |
171 | { | |
172 | #ifdef CONFIG_DEBUG_MUTEXES | |
173 | mutex_release(&ctx->dep_map, 0, _THIS_IP_); | |
174 | ||
175 | DEBUG_LOCKS_WARN_ON(ctx->acquired); | |
176 | if (!config_enabled(CONFIG_PROVE_LOCKING)) | |
177 | /* | |
178 | * lockdep will normally handle this, | |
179 | * but fail without anyway | |
180 | */ | |
181 | ctx->done_acquire = 1; | |
182 | ||
183 | if (!config_enabled(CONFIG_DEBUG_LOCK_ALLOC)) | |
184 | /* ensure ww_acquire_fini will still fail if called twice */ | |
185 | ctx->acquired = ~0U; | |
186 | #endif | |
187 | } | |
188 | ||
189 | extern int __must_check __ww_mutex_lock(struct ww_mutex *lock, | |
190 | struct ww_acquire_ctx *ctx); | |
191 | extern int __must_check __ww_mutex_lock_interruptible(struct ww_mutex *lock, | |
192 | struct ww_acquire_ctx *ctx); | |
193 | ||
194 | /** | |
195 | * ww_mutex_lock - acquire the w/w mutex | |
196 | * @lock: the mutex to be acquired | |
197 | * @ctx: w/w acquire context, or NULL to acquire only a single lock. | |
198 | * | |
199 | * Lock the w/w mutex exclusively for this task. | |
200 | * | |
201 | * Deadlocks within a given w/w class of locks are detected and handled with the | |
202 | * wait/wound algorithm. If the lock isn't immediately avaiable this function | |
203 | * will either sleep until it is (wait case). Or it selects the current context | |
204 | * for backing off by returning -EDEADLK (wound case). Trying to acquire the | |
205 | * same lock with the same context twice is also detected and signalled by | |
206 | * returning -EALREADY. Returns 0 if the mutex was successfully acquired. | |
207 | * | |
208 | * In the wound case the caller must release all currently held w/w mutexes for | |
209 | * the given context and then wait for this contending lock to be available by | |
210 | * calling ww_mutex_lock_slow. Alternatively callers can opt to not acquire this | |
211 | * lock and proceed with trying to acquire further w/w mutexes (e.g. when | |
212 | * scanning through lru lists trying to free resources). | |
213 | * | |
214 | * The mutex must later on be released by the same task that | |
215 | * acquired it. The task may not exit without first unlocking the mutex. Also, | |
216 | * kernel memory where the mutex resides must not be freed with the mutex still | |
217 | * locked. The mutex must first be initialized (or statically defined) before it | |
218 | * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be | |
219 | * of the same w/w lock class as was used to initialize the acquire context. | |
220 | * | |
221 | * A mutex acquired with this function must be released with ww_mutex_unlock. | |
222 | */ | |
223 | static inline int ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
224 | { | |
225 | if (ctx) | |
226 | return __ww_mutex_lock(lock, ctx); | |
227 | ||
228 | mutex_lock(&lock->base); | |
229 | return 0; | |
230 | } | |
231 | ||
232 | /** | |
233 | * ww_mutex_lock_interruptible - acquire the w/w mutex, interruptible | |
234 | * @lock: the mutex to be acquired | |
235 | * @ctx: w/w acquire context | |
236 | * | |
237 | * Lock the w/w mutex exclusively for this task. | |
238 | * | |
239 | * Deadlocks within a given w/w class of locks are detected and handled with the | |
240 | * wait/wound algorithm. If the lock isn't immediately avaiable this function | |
241 | * will either sleep until it is (wait case). Or it selects the current context | |
242 | * for backing off by returning -EDEADLK (wound case). Trying to acquire the | |
243 | * same lock with the same context twice is also detected and signalled by | |
244 | * returning -EALREADY. Returns 0 if the mutex was successfully acquired. If a | |
245 | * signal arrives while waiting for the lock then this function returns -EINTR. | |
246 | * | |
247 | * In the wound case the caller must release all currently held w/w mutexes for | |
248 | * the given context and then wait for this contending lock to be available by | |
249 | * calling ww_mutex_lock_slow_interruptible. Alternatively callers can opt to | |
250 | * not acquire this lock and proceed with trying to acquire further w/w mutexes | |
251 | * (e.g. when scanning through lru lists trying to free resources). | |
252 | * | |
253 | * The mutex must later on be released by the same task that | |
254 | * acquired it. The task may not exit without first unlocking the mutex. Also, | |
255 | * kernel memory where the mutex resides must not be freed with the mutex still | |
256 | * locked. The mutex must first be initialized (or statically defined) before it | |
257 | * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be | |
258 | * of the same w/w lock class as was used to initialize the acquire context. | |
259 | * | |
260 | * A mutex acquired with this function must be released with ww_mutex_unlock. | |
261 | */ | |
262 | static inline int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock, | |
263 | struct ww_acquire_ctx *ctx) | |
264 | { | |
265 | if (ctx) | |
266 | return __ww_mutex_lock_interruptible(lock, ctx); | |
267 | else | |
268 | return mutex_lock_interruptible(&lock->base); | |
269 | } | |
270 | ||
271 | /** | |
272 | * ww_mutex_lock_slow - slowpath acquiring of the w/w mutex | |
273 | * @lock: the mutex to be acquired | |
274 | * @ctx: w/w acquire context | |
275 | * | |
276 | * Acquires a w/w mutex with the given context after a wound case. This function | |
277 | * will sleep until the lock becomes available. | |
278 | * | |
279 | * The caller must have released all w/w mutexes already acquired with the | |
280 | * context and then call this function on the contended lock. | |
281 | * | |
282 | * Afterwards the caller may continue to (re)acquire the other w/w mutexes it | |
283 | * needs with ww_mutex_lock. Note that the -EALREADY return code from | |
284 | * ww_mutex_lock can be used to avoid locking this contended mutex twice. | |
285 | * | |
286 | * It is forbidden to call this function with any other w/w mutexes associated | |
287 | * with the context held. It is forbidden to call this on anything else than the | |
288 | * contending mutex. | |
289 | * | |
290 | * Note that the slowpath lock acquiring can also be done by calling | |
291 | * ww_mutex_lock directly. This function here is simply to help w/w mutex | |
292 | * locking code readability by clearly denoting the slowpath. | |
293 | */ | |
294 | static inline void | |
295 | ww_mutex_lock_slow(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
296 | { | |
297 | int ret; | |
298 | #ifdef CONFIG_DEBUG_MUTEXES | |
299 | DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); | |
300 | #endif | |
301 | ret = ww_mutex_lock(lock, ctx); | |
302 | (void)ret; | |
303 | } | |
304 | ||
305 | /** | |
306 | * ww_mutex_lock_slow_interruptible - slowpath acquiring of the w/w mutex, interruptible | |
307 | * @lock: the mutex to be acquired | |
308 | * @ctx: w/w acquire context | |
309 | * | |
310 | * Acquires a w/w mutex with the given context after a wound case. This function | |
311 | * will sleep until the lock becomes available and returns 0 when the lock has | |
312 | * been acquired. If a signal arrives while waiting for the lock then this | |
313 | * function returns -EINTR. | |
314 | * | |
315 | * The caller must have released all w/w mutexes already acquired with the | |
316 | * context and then call this function on the contended lock. | |
317 | * | |
318 | * Afterwards the caller may continue to (re)acquire the other w/w mutexes it | |
319 | * needs with ww_mutex_lock. Note that the -EALREADY return code from | |
320 | * ww_mutex_lock can be used to avoid locking this contended mutex twice. | |
321 | * | |
322 | * It is forbidden to call this function with any other w/w mutexes associated | |
323 | * with the given context held. It is forbidden to call this on anything else | |
324 | * than the contending mutex. | |
325 | * | |
326 | * Note that the slowpath lock acquiring can also be done by calling | |
327 | * ww_mutex_lock_interruptible directly. This function here is simply to help | |
328 | * w/w mutex locking code readability by clearly denoting the slowpath. | |
329 | */ | |
330 | static inline int __must_check | |
331 | ww_mutex_lock_slow_interruptible(struct ww_mutex *lock, | |
332 | struct ww_acquire_ctx *ctx) | |
333 | { | |
334 | #ifdef CONFIG_DEBUG_MUTEXES | |
335 | DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); | |
336 | #endif | |
337 | return ww_mutex_lock_interruptible(lock, ctx); | |
338 | } | |
339 | ||
340 | extern void ww_mutex_unlock(struct ww_mutex *lock); | |
341 | ||
342 | /** | |
343 | * ww_mutex_trylock - tries to acquire the w/w mutex without acquire context | |
344 | * @lock: mutex to lock | |
345 | * | |
346 | * Trylocks a mutex without acquire context, so no deadlock detection is | |
347 | * possible. Returns 1 if the mutex has been acquired successfully, 0 otherwise. | |
348 | */ | |
349 | static inline int __must_check ww_mutex_trylock(struct ww_mutex *lock) | |
350 | { | |
351 | return mutex_trylock(&lock->base); | |
352 | } | |
353 | ||
354 | /*** | |
355 | * ww_mutex_destroy - mark a w/w mutex unusable | |
356 | * @lock: the mutex to be destroyed | |
357 | * | |
358 | * This function marks the mutex uninitialized, and any subsequent | |
359 | * use of the mutex is forbidden. The mutex must not be locked when | |
360 | * this function is called. | |
361 | */ | |
362 | static inline void ww_mutex_destroy(struct ww_mutex *lock) | |
363 | { | |
364 | mutex_destroy(&lock->base); | |
365 | } | |
366 | ||
367 | /** | |
368 | * ww_mutex_is_locked - is the w/w mutex locked | |
369 | * @lock: the mutex to be queried | |
370 | * | |
371 | * Returns 1 if the mutex is locked, 0 if unlocked. | |
372 | */ | |
373 | static inline bool ww_mutex_is_locked(struct ww_mutex *lock) | |
374 | { | |
375 | return mutex_is_locked(&lock->base); | |
376 | } | |
377 | ||
378 | #endif |