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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 | * | |
55f036ca | 9 | * Wait/Die implementation: |
1b375dc3 | 10 | * Copyright (C) 2013 Canonical Ltd. |
08295b3b TH |
11 | * Choice of algorithm: |
12 | * Copyright (C) 2018 WMWare Inc. | |
1b375dc3 ML |
13 | * |
14 | * This file contains the main data structure and API definitions. | |
15 | */ | |
16 | ||
17 | #ifndef __LINUX_WW_MUTEX_H | |
18 | #define __LINUX_WW_MUTEX_H | |
19 | ||
20 | #include <linux/mutex.h> | |
21 | ||
22 | struct ww_class { | |
23 | atomic_long_t stamp; | |
24 | struct lock_class_key acquire_key; | |
25 | struct lock_class_key mutex_key; | |
26 | const char *acquire_name; | |
27 | const char *mutex_name; | |
08295b3b | 28 | unsigned int is_wait_die; |
1b375dc3 ML |
29 | }; |
30 | ||
31 | struct ww_acquire_ctx { | |
32 | struct task_struct *task; | |
33 | unsigned long stamp; | |
55f036ca | 34 | unsigned int acquired; |
08295b3b TH |
35 | unsigned short wounded; |
36 | unsigned short is_wait_die; | |
1b375dc3 | 37 | #ifdef CONFIG_DEBUG_MUTEXES |
55f036ca | 38 | unsigned int done_acquire; |
1b375dc3 ML |
39 | struct ww_class *ww_class; |
40 | struct ww_mutex *contending_lock; | |
41 | #endif | |
42 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
43 | struct lockdep_map dep_map; | |
44 | #endif | |
45 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
55f036ca PZ |
46 | unsigned int deadlock_inject_interval; |
47 | unsigned int deadlock_inject_countdown; | |
1b375dc3 ML |
48 | #endif |
49 | }; | |
50 | ||
51 | struct ww_mutex { | |
52 | struct mutex base; | |
53 | struct ww_acquire_ctx *ctx; | |
54 | #ifdef CONFIG_DEBUG_MUTEXES | |
55 | struct ww_class *ww_class; | |
56 | #endif | |
57 | }; | |
58 | ||
59 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
af2e859e CW |
60 | # define __WW_CLASS_MUTEX_INITIALIZER(lockname, class) \ |
61 | , .ww_class = class | |
1b375dc3 | 62 | #else |
af2e859e | 63 | # define __WW_CLASS_MUTEX_INITIALIZER(lockname, class) |
1b375dc3 ML |
64 | #endif |
65 | ||
08295b3b | 66 | #define __WW_CLASS_INITIALIZER(ww_class, _is_wait_die) \ |
1b375dc3 ML |
67 | { .stamp = ATOMIC_LONG_INIT(0) \ |
68 | , .acquire_name = #ww_class "_acquire" \ | |
08295b3b TH |
69 | , .mutex_name = #ww_class "_mutex" \ |
70 | , .is_wait_die = _is_wait_die } | |
1b375dc3 ML |
71 | |
72 | #define __WW_MUTEX_INITIALIZER(lockname, class) \ | |
af2e859e | 73 | { .base = __MUTEX_INITIALIZER(lockname.base) \ |
1b375dc3 ML |
74 | __WW_CLASS_MUTEX_INITIALIZER(lockname, class) } |
75 | ||
08295b3b TH |
76 | #define DEFINE_WD_CLASS(classname) \ |
77 | struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 1) | |
78 | ||
1b375dc3 | 79 | #define DEFINE_WW_CLASS(classname) \ |
08295b3b | 80 | struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 0) |
1b375dc3 ML |
81 | |
82 | #define DEFINE_WW_MUTEX(mutexname, ww_class) \ | |
83 | struct ww_mutex mutexname = __WW_MUTEX_INITIALIZER(mutexname, ww_class) | |
84 | ||
85 | /** | |
86 | * ww_mutex_init - initialize the w/w mutex | |
87 | * @lock: the mutex to be initialized | |
88 | * @ww_class: the w/w class the mutex should belong to | |
89 | * | |
90 | * Initialize the w/w mutex to unlocked state and associate it with the given | |
91 | * class. | |
92 | * | |
93 | * It is not allowed to initialize an already locked mutex. | |
94 | */ | |
95 | static inline void ww_mutex_init(struct ww_mutex *lock, | |
96 | struct ww_class *ww_class) | |
97 | { | |
98 | __mutex_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key); | |
99 | lock->ctx = NULL; | |
100 | #ifdef CONFIG_DEBUG_MUTEXES | |
101 | lock->ww_class = ww_class; | |
102 | #endif | |
103 | } | |
104 | ||
105 | /** | |
106 | * ww_acquire_init - initialize a w/w acquire context | |
107 | * @ctx: w/w acquire context to initialize | |
108 | * @ww_class: w/w class of the context | |
109 | * | |
110 | * Initializes an context to acquire multiple mutexes of the given w/w class. | |
111 | * | |
112 | * Context-based w/w mutex acquiring can be done in any order whatsoever within | |
113 | * a given lock class. Deadlocks will be detected and handled with the | |
55f036ca | 114 | * wait/die logic. |
1b375dc3 ML |
115 | * |
116 | * Mixing of context-based w/w mutex acquiring and single w/w mutex locking can | |
117 | * result in undetected deadlocks and is so forbidden. Mixing different contexts | |
118 | * for the same w/w class when acquiring mutexes can also result in undetected | |
119 | * deadlocks, and is hence also forbidden. Both types of abuse will be caught by | |
120 | * enabling CONFIG_PROVE_LOCKING. | |
121 | * | |
122 | * Nesting of acquire contexts for _different_ w/w classes is possible, subject | |
123 | * to the usual locking rules between different lock classes. | |
124 | * | |
125 | * An acquire context must be released with ww_acquire_fini by the same task | |
126 | * before the memory is freed. It is recommended to allocate the context itself | |
127 | * on the stack. | |
128 | */ | |
129 | static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, | |
130 | struct ww_class *ww_class) | |
131 | { | |
132 | ctx->task = current; | |
f4ec57b6 | 133 | ctx->stamp = atomic_long_inc_return_relaxed(&ww_class->stamp); |
1b375dc3 | 134 | ctx->acquired = 0; |
08295b3b TH |
135 | ctx->wounded = false; |
136 | ctx->is_wait_die = ww_class->is_wait_die; | |
1b375dc3 ML |
137 | #ifdef CONFIG_DEBUG_MUTEXES |
138 | ctx->ww_class = ww_class; | |
139 | ctx->done_acquire = 0; | |
140 | ctx->contending_lock = NULL; | |
141 | #endif | |
142 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
143 | debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); | |
144 | lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, | |
145 | &ww_class->acquire_key, 0); | |
146 | mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); | |
147 | #endif | |
148 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
149 | ctx->deadlock_inject_interval = 1; | |
150 | ctx->deadlock_inject_countdown = ctx->stamp & 0xf; | |
151 | #endif | |
152 | } | |
153 | ||
154 | /** | |
155 | * ww_acquire_done - marks the end of the acquire phase | |
156 | * @ctx: the acquire context | |
157 | * | |
158 | * Marks the end of the acquire phase, any further w/w mutex lock calls using | |
159 | * this context are forbidden. | |
160 | * | |
161 | * Calling this function is optional, it is just useful to document w/w mutex | |
162 | * code and clearly designated the acquire phase from actually using the locked | |
163 | * data structures. | |
164 | */ | |
165 | static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) | |
166 | { | |
167 | #ifdef CONFIG_DEBUG_MUTEXES | |
168 | lockdep_assert_held(ctx); | |
169 | ||
170 | DEBUG_LOCKS_WARN_ON(ctx->done_acquire); | |
171 | ctx->done_acquire = 1; | |
172 | #endif | |
173 | } | |
174 | ||
175 | /** | |
176 | * ww_acquire_fini - releases a w/w acquire context | |
177 | * @ctx: the acquire context to free | |
178 | * | |
179 | * Releases a w/w acquire context. This must be called _after_ all acquired w/w | |
180 | * mutexes have been released with ww_mutex_unlock. | |
181 | */ | |
182 | static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) | |
183 | { | |
184 | #ifdef CONFIG_DEBUG_MUTEXES | |
185 | mutex_release(&ctx->dep_map, 0, _THIS_IP_); | |
186 | ||
187 | DEBUG_LOCKS_WARN_ON(ctx->acquired); | |
97f2645f | 188 | if (!IS_ENABLED(CONFIG_PROVE_LOCKING)) |
1b375dc3 ML |
189 | /* |
190 | * lockdep will normally handle this, | |
191 | * but fail without anyway | |
192 | */ | |
193 | ctx->done_acquire = 1; | |
194 | ||
97f2645f | 195 | if (!IS_ENABLED(CONFIG_DEBUG_LOCK_ALLOC)) |
1b375dc3 ML |
196 | /* ensure ww_acquire_fini will still fail if called twice */ |
197 | ctx->acquired = ~0U; | |
198 | #endif | |
199 | } | |
200 | ||
1b375dc3 ML |
201 | /** |
202 | * ww_mutex_lock - acquire the w/w mutex | |
203 | * @lock: the mutex to be acquired | |
204 | * @ctx: w/w acquire context, or NULL to acquire only a single lock. | |
205 | * | |
206 | * Lock the w/w mutex exclusively for this task. | |
207 | * | |
208 | * Deadlocks within a given w/w class of locks are detected and handled with the | |
55f036ca | 209 | * wait/die algorithm. If the lock isn't immediately available this function |
1b375dc3 | 210 | * will either sleep until it is (wait case). Or it selects the current context |
55f036ca | 211 | * for backing off by returning -EDEADLK (die case). Trying to acquire the |
1b375dc3 ML |
212 | * same lock with the same context twice is also detected and signalled by |
213 | * returning -EALREADY. Returns 0 if the mutex was successfully acquired. | |
214 | * | |
55f036ca | 215 | * In the die case the caller must release all currently held w/w mutexes for |
1b375dc3 ML |
216 | * the given context and then wait for this contending lock to be available by |
217 | * calling ww_mutex_lock_slow. Alternatively callers can opt to not acquire this | |
218 | * lock and proceed with trying to acquire further w/w mutexes (e.g. when | |
219 | * scanning through lru lists trying to free resources). | |
220 | * | |
221 | * The mutex must later on be released by the same task that | |
222 | * acquired it. The task may not exit without first unlocking the mutex. Also, | |
223 | * kernel memory where the mutex resides must not be freed with the mutex still | |
224 | * locked. The mutex must first be initialized (or statically defined) before it | |
225 | * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be | |
226 | * of the same w/w lock class as was used to initialize the acquire context. | |
227 | * | |
228 | * A mutex acquired with this function must be released with ww_mutex_unlock. | |
229 | */ | |
23b19ec3 | 230 | extern int /* __must_check */ ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx); |
1b375dc3 ML |
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 | |
55f036ca | 240 | * wait/die algorithm. If the lock isn't immediately available this function |
1b375dc3 | 241 | * will either sleep until it is (wait case). Or it selects the current context |
55f036ca | 242 | * for backing off by returning -EDEADLK (die case). Trying to acquire the |
1b375dc3 ML |
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 | * | |
55f036ca | 247 | * In the die case the caller must release all currently held w/w mutexes for |
1b375dc3 ML |
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 | */ | |
c5470b22 NH |
262 | extern int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock, |
263 | struct ww_acquire_ctx *ctx); | |
1b375dc3 ML |
264 | |
265 | /** | |
266 | * ww_mutex_lock_slow - slowpath acquiring of the w/w mutex | |
267 | * @lock: the mutex to be acquired | |
268 | * @ctx: w/w acquire context | |
269 | * | |
55f036ca | 270 | * Acquires a w/w mutex with the given context after a die case. This function |
1b375dc3 ML |
271 | * will sleep until the lock becomes available. |
272 | * | |
273 | * The caller must have released all w/w mutexes already acquired with the | |
274 | * context and then call this function on the contended lock. | |
275 | * | |
276 | * Afterwards the caller may continue to (re)acquire the other w/w mutexes it | |
277 | * needs with ww_mutex_lock. Note that the -EALREADY return code from | |
278 | * ww_mutex_lock can be used to avoid locking this contended mutex twice. | |
279 | * | |
280 | * It is forbidden to call this function with any other w/w mutexes associated | |
281 | * with the context held. It is forbidden to call this on anything else than the | |
282 | * contending mutex. | |
283 | * | |
284 | * Note that the slowpath lock acquiring can also be done by calling | |
285 | * ww_mutex_lock directly. This function here is simply to help w/w mutex | |
286 | * locking code readability by clearly denoting the slowpath. | |
287 | */ | |
288 | static inline void | |
289 | ww_mutex_lock_slow(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
290 | { | |
291 | int ret; | |
292 | #ifdef CONFIG_DEBUG_MUTEXES | |
293 | DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); | |
294 | #endif | |
295 | ret = ww_mutex_lock(lock, ctx); | |
296 | (void)ret; | |
297 | } | |
298 | ||
299 | /** | |
300 | * ww_mutex_lock_slow_interruptible - slowpath acquiring of the w/w mutex, interruptible | |
301 | * @lock: the mutex to be acquired | |
302 | * @ctx: w/w acquire context | |
303 | * | |
55f036ca | 304 | * Acquires a w/w mutex with the given context after a die case. This function |
1b375dc3 ML |
305 | * will sleep until the lock becomes available and returns 0 when the lock has |
306 | * been acquired. If a signal arrives while waiting for the lock then this | |
307 | * function returns -EINTR. | |
308 | * | |
309 | * The caller must have released all w/w mutexes already acquired with the | |
310 | * context and then call this function on the contended lock. | |
311 | * | |
312 | * Afterwards the caller may continue to (re)acquire the other w/w mutexes it | |
313 | * needs with ww_mutex_lock. Note that the -EALREADY return code from | |
314 | * ww_mutex_lock can be used to avoid locking this contended mutex twice. | |
315 | * | |
316 | * It is forbidden to call this function with any other w/w mutexes associated | |
317 | * with the given context held. It is forbidden to call this on anything else | |
318 | * than the contending mutex. | |
319 | * | |
320 | * Note that the slowpath lock acquiring can also be done by calling | |
321 | * ww_mutex_lock_interruptible directly. This function here is simply to help | |
322 | * w/w mutex locking code readability by clearly denoting the slowpath. | |
323 | */ | |
324 | static inline int __must_check | |
325 | ww_mutex_lock_slow_interruptible(struct ww_mutex *lock, | |
326 | struct ww_acquire_ctx *ctx) | |
327 | { | |
328 | #ifdef CONFIG_DEBUG_MUTEXES | |
329 | DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); | |
330 | #endif | |
331 | return ww_mutex_lock_interruptible(lock, ctx); | |
332 | } | |
333 | ||
334 | extern void ww_mutex_unlock(struct ww_mutex *lock); | |
335 | ||
336 | /** | |
337 | * ww_mutex_trylock - tries to acquire the w/w mutex without acquire context | |
338 | * @lock: mutex to lock | |
339 | * | |
340 | * Trylocks a mutex without acquire context, so no deadlock detection is | |
341 | * possible. Returns 1 if the mutex has been acquired successfully, 0 otherwise. | |
342 | */ | |
343 | static inline int __must_check ww_mutex_trylock(struct ww_mutex *lock) | |
344 | { | |
345 | return mutex_trylock(&lock->base); | |
346 | } | |
347 | ||
348 | /*** | |
349 | * ww_mutex_destroy - mark a w/w mutex unusable | |
350 | * @lock: the mutex to be destroyed | |
351 | * | |
352 | * This function marks the mutex uninitialized, and any subsequent | |
353 | * use of the mutex is forbidden. The mutex must not be locked when | |
354 | * this function is called. | |
355 | */ | |
356 | static inline void ww_mutex_destroy(struct ww_mutex *lock) | |
357 | { | |
358 | mutex_destroy(&lock->base); | |
359 | } | |
360 | ||
361 | /** | |
362 | * ww_mutex_is_locked - is the w/w mutex locked | |
363 | * @lock: the mutex to be queried | |
364 | * | |
365 | * Returns 1 if the mutex is locked, 0 if unlocked. | |
366 | */ | |
367 | static inline bool ww_mutex_is_locked(struct ww_mutex *lock) | |
368 | { | |
369 | return mutex_is_locked(&lock->base); | |
370 | } | |
371 | ||
372 | #endif |