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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 | ||
1b375dc3 | 51 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
af2e859e CW |
52 | # define __WW_CLASS_MUTEX_INITIALIZER(lockname, class) \ |
53 | , .ww_class = class | |
1b375dc3 | 54 | #else |
af2e859e | 55 | # define __WW_CLASS_MUTEX_INITIALIZER(lockname, class) |
1b375dc3 ML |
56 | #endif |
57 | ||
08295b3b | 58 | #define __WW_CLASS_INITIALIZER(ww_class, _is_wait_die) \ |
1b375dc3 ML |
59 | { .stamp = ATOMIC_LONG_INIT(0) \ |
60 | , .acquire_name = #ww_class "_acquire" \ | |
08295b3b TH |
61 | , .mutex_name = #ww_class "_mutex" \ |
62 | , .is_wait_die = _is_wait_die } | |
1b375dc3 ML |
63 | |
64 | #define __WW_MUTEX_INITIALIZER(lockname, class) \ | |
af2e859e | 65 | { .base = __MUTEX_INITIALIZER(lockname.base) \ |
1b375dc3 ML |
66 | __WW_CLASS_MUTEX_INITIALIZER(lockname, class) } |
67 | ||
08295b3b TH |
68 | #define DEFINE_WD_CLASS(classname) \ |
69 | struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 1) | |
70 | ||
1b375dc3 | 71 | #define DEFINE_WW_CLASS(classname) \ |
08295b3b | 72 | struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 0) |
1b375dc3 ML |
73 | |
74 | #define DEFINE_WW_MUTEX(mutexname, ww_class) \ | |
75 | struct ww_mutex mutexname = __WW_MUTEX_INITIALIZER(mutexname, ww_class) | |
76 | ||
77 | /** | |
78 | * ww_mutex_init - initialize the w/w mutex | |
79 | * @lock: the mutex to be initialized | |
80 | * @ww_class: the w/w class the mutex should belong to | |
81 | * | |
82 | * Initialize the w/w mutex to unlocked state and associate it with the given | |
83 | * class. | |
84 | * | |
85 | * It is not allowed to initialize an already locked mutex. | |
86 | */ | |
87 | static inline void ww_mutex_init(struct ww_mutex *lock, | |
88 | struct ww_class *ww_class) | |
89 | { | |
90 | __mutex_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key); | |
91 | lock->ctx = NULL; | |
92 | #ifdef CONFIG_DEBUG_MUTEXES | |
93 | lock->ww_class = ww_class; | |
94 | #endif | |
95 | } | |
96 | ||
97 | /** | |
98 | * ww_acquire_init - initialize a w/w acquire context | |
99 | * @ctx: w/w acquire context to initialize | |
100 | * @ww_class: w/w class of the context | |
101 | * | |
102 | * Initializes an context to acquire multiple mutexes of the given w/w class. | |
103 | * | |
104 | * Context-based w/w mutex acquiring can be done in any order whatsoever within | |
105 | * a given lock class. Deadlocks will be detected and handled with the | |
55f036ca | 106 | * wait/die logic. |
1b375dc3 ML |
107 | * |
108 | * Mixing of context-based w/w mutex acquiring and single w/w mutex locking can | |
109 | * result in undetected deadlocks and is so forbidden. Mixing different contexts | |
110 | * for the same w/w class when acquiring mutexes can also result in undetected | |
111 | * deadlocks, and is hence also forbidden. Both types of abuse will be caught by | |
112 | * enabling CONFIG_PROVE_LOCKING. | |
113 | * | |
114 | * Nesting of acquire contexts for _different_ w/w classes is possible, subject | |
115 | * to the usual locking rules between different lock classes. | |
116 | * | |
117 | * An acquire context must be released with ww_acquire_fini by the same task | |
118 | * before the memory is freed. It is recommended to allocate the context itself | |
119 | * on the stack. | |
120 | */ | |
121 | static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, | |
122 | struct ww_class *ww_class) | |
123 | { | |
124 | ctx->task = current; | |
f4ec57b6 | 125 | ctx->stamp = atomic_long_inc_return_relaxed(&ww_class->stamp); |
1b375dc3 | 126 | ctx->acquired = 0; |
08295b3b TH |
127 | ctx->wounded = false; |
128 | ctx->is_wait_die = ww_class->is_wait_die; | |
1b375dc3 ML |
129 | #ifdef CONFIG_DEBUG_MUTEXES |
130 | ctx->ww_class = ww_class; | |
131 | ctx->done_acquire = 0; | |
132 | ctx->contending_lock = NULL; | |
133 | #endif | |
134 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
135 | debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); | |
136 | lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, | |
137 | &ww_class->acquire_key, 0); | |
138 | mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); | |
139 | #endif | |
140 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
141 | ctx->deadlock_inject_interval = 1; | |
142 | ctx->deadlock_inject_countdown = ctx->stamp & 0xf; | |
143 | #endif | |
144 | } | |
145 | ||
146 | /** | |
147 | * ww_acquire_done - marks the end of the acquire phase | |
148 | * @ctx: the acquire context | |
149 | * | |
150 | * Marks the end of the acquire phase, any further w/w mutex lock calls using | |
151 | * this context are forbidden. | |
152 | * | |
153 | * Calling this function is optional, it is just useful to document w/w mutex | |
154 | * code and clearly designated the acquire phase from actually using the locked | |
155 | * data structures. | |
156 | */ | |
157 | static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) | |
158 | { | |
159 | #ifdef CONFIG_DEBUG_MUTEXES | |
160 | lockdep_assert_held(ctx); | |
161 | ||
162 | DEBUG_LOCKS_WARN_ON(ctx->done_acquire); | |
163 | ctx->done_acquire = 1; | |
164 | #endif | |
165 | } | |
166 | ||
167 | /** | |
168 | * ww_acquire_fini - releases a w/w acquire context | |
169 | * @ctx: the acquire context to free | |
170 | * | |
171 | * Releases a w/w acquire context. This must be called _after_ all acquired w/w | |
172 | * mutexes have been released with ww_mutex_unlock. | |
173 | */ | |
174 | static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) | |
175 | { | |
176 | #ifdef CONFIG_DEBUG_MUTEXES | |
5facae4f | 177 | mutex_release(&ctx->dep_map, _THIS_IP_); |
1b375dc3 ML |
178 | |
179 | DEBUG_LOCKS_WARN_ON(ctx->acquired); | |
97f2645f | 180 | if (!IS_ENABLED(CONFIG_PROVE_LOCKING)) |
1b375dc3 ML |
181 | /* |
182 | * lockdep will normally handle this, | |
183 | * but fail without anyway | |
184 | */ | |
185 | ctx->done_acquire = 1; | |
186 | ||
97f2645f | 187 | if (!IS_ENABLED(CONFIG_DEBUG_LOCK_ALLOC)) |
1b375dc3 ML |
188 | /* ensure ww_acquire_fini will still fail if called twice */ |
189 | ctx->acquired = ~0U; | |
190 | #endif | |
191 | } | |
192 | ||
1b375dc3 ML |
193 | /** |
194 | * ww_mutex_lock - acquire the w/w mutex | |
195 | * @lock: the mutex to be acquired | |
196 | * @ctx: w/w acquire context, or NULL to acquire only a single lock. | |
197 | * | |
198 | * Lock the w/w mutex exclusively for this task. | |
199 | * | |
200 | * Deadlocks within a given w/w class of locks are detected and handled with the | |
55f036ca | 201 | * wait/die algorithm. If the lock isn't immediately available this function |
1b375dc3 | 202 | * will either sleep until it is (wait case). Or it selects the current context |
55f036ca | 203 | * for backing off by returning -EDEADLK (die case). Trying to acquire the |
1b375dc3 ML |
204 | * same lock with the same context twice is also detected and signalled by |
205 | * returning -EALREADY. Returns 0 if the mutex was successfully acquired. | |
206 | * | |
55f036ca | 207 | * In the die case the caller must release all currently held w/w mutexes for |
1b375dc3 ML |
208 | * the given context and then wait for this contending lock to be available by |
209 | * calling ww_mutex_lock_slow. Alternatively callers can opt to not acquire this | |
210 | * lock and proceed with trying to acquire further w/w mutexes (e.g. when | |
211 | * scanning through lru lists trying to free resources). | |
212 | * | |
213 | * The mutex must later on be released by the same task that | |
214 | * acquired it. The task may not exit without first unlocking the mutex. Also, | |
215 | * kernel memory where the mutex resides must not be freed with the mutex still | |
216 | * locked. The mutex must first be initialized (or statically defined) before it | |
217 | * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be | |
218 | * of the same w/w lock class as was used to initialize the acquire context. | |
219 | * | |
220 | * A mutex acquired with this function must be released with ww_mutex_unlock. | |
221 | */ | |
23b19ec3 | 222 | extern int /* __must_check */ ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx); |
1b375dc3 ML |
223 | |
224 | /** | |
225 | * ww_mutex_lock_interruptible - acquire the w/w mutex, interruptible | |
226 | * @lock: the mutex to be acquired | |
227 | * @ctx: w/w acquire context | |
228 | * | |
229 | * Lock the w/w mutex exclusively for this task. | |
230 | * | |
231 | * Deadlocks within a given w/w class of locks are detected and handled with the | |
55f036ca | 232 | * wait/die algorithm. If the lock isn't immediately available this function |
1b375dc3 | 233 | * will either sleep until it is (wait case). Or it selects the current context |
55f036ca | 234 | * for backing off by returning -EDEADLK (die case). Trying to acquire the |
1b375dc3 ML |
235 | * same lock with the same context twice is also detected and signalled by |
236 | * returning -EALREADY. Returns 0 if the mutex was successfully acquired. If a | |
237 | * signal arrives while waiting for the lock then this function returns -EINTR. | |
238 | * | |
55f036ca | 239 | * In the die case the caller must release all currently held w/w mutexes for |
1b375dc3 ML |
240 | * the given context and then wait for this contending lock to be available by |
241 | * calling ww_mutex_lock_slow_interruptible. Alternatively callers can opt to | |
242 | * not acquire this lock and proceed with trying to acquire further w/w mutexes | |
243 | * (e.g. when scanning through lru lists trying to free resources). | |
244 | * | |
245 | * The mutex must later on be released by the same task that | |
246 | * acquired it. The task may not exit without first unlocking the mutex. Also, | |
247 | * kernel memory where the mutex resides must not be freed with the mutex still | |
248 | * locked. The mutex must first be initialized (or statically defined) before it | |
249 | * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be | |
250 | * of the same w/w lock class as was used to initialize the acquire context. | |
251 | * | |
252 | * A mutex acquired with this function must be released with ww_mutex_unlock. | |
253 | */ | |
c5470b22 NH |
254 | extern int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock, |
255 | struct ww_acquire_ctx *ctx); | |
1b375dc3 ML |
256 | |
257 | /** | |
258 | * ww_mutex_lock_slow - slowpath acquiring of the w/w mutex | |
259 | * @lock: the mutex to be acquired | |
260 | * @ctx: w/w acquire context | |
261 | * | |
55f036ca | 262 | * Acquires a w/w mutex with the given context after a die case. This function |
1b375dc3 ML |
263 | * will sleep until the lock becomes available. |
264 | * | |
265 | * The caller must have released all w/w mutexes already acquired with the | |
266 | * context and then call this function on the contended lock. | |
267 | * | |
268 | * Afterwards the caller may continue to (re)acquire the other w/w mutexes it | |
269 | * needs with ww_mutex_lock. Note that the -EALREADY return code from | |
270 | * ww_mutex_lock can be used to avoid locking this contended mutex twice. | |
271 | * | |
272 | * It is forbidden to call this function with any other w/w mutexes associated | |
273 | * with the context held. It is forbidden to call this on anything else than the | |
274 | * contending mutex. | |
275 | * | |
276 | * Note that the slowpath lock acquiring can also be done by calling | |
277 | * ww_mutex_lock directly. This function here is simply to help w/w mutex | |
278 | * locking code readability by clearly denoting the slowpath. | |
279 | */ | |
280 | static inline void | |
281 | ww_mutex_lock_slow(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
282 | { | |
283 | int ret; | |
284 | #ifdef CONFIG_DEBUG_MUTEXES | |
285 | DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); | |
286 | #endif | |
287 | ret = ww_mutex_lock(lock, ctx); | |
288 | (void)ret; | |
289 | } | |
290 | ||
291 | /** | |
292 | * ww_mutex_lock_slow_interruptible - slowpath acquiring of the w/w mutex, interruptible | |
293 | * @lock: the mutex to be acquired | |
294 | * @ctx: w/w acquire context | |
295 | * | |
55f036ca | 296 | * Acquires a w/w mutex with the given context after a die case. This function |
1b375dc3 ML |
297 | * will sleep until the lock becomes available and returns 0 when the lock has |
298 | * been acquired. If a signal arrives while waiting for the lock then this | |
299 | * function returns -EINTR. | |
300 | * | |
301 | * The caller must have released all w/w mutexes already acquired with the | |
302 | * context and then call this function on the contended lock. | |
303 | * | |
304 | * Afterwards the caller may continue to (re)acquire the other w/w mutexes it | |
305 | * needs with ww_mutex_lock. Note that the -EALREADY return code from | |
306 | * ww_mutex_lock can be used to avoid locking this contended mutex twice. | |
307 | * | |
308 | * It is forbidden to call this function with any other w/w mutexes associated | |
309 | * with the given context held. It is forbidden to call this on anything else | |
310 | * than the contending mutex. | |
311 | * | |
312 | * Note that the slowpath lock acquiring can also be done by calling | |
313 | * ww_mutex_lock_interruptible directly. This function here is simply to help | |
314 | * w/w mutex locking code readability by clearly denoting the slowpath. | |
315 | */ | |
316 | static inline int __must_check | |
317 | ww_mutex_lock_slow_interruptible(struct ww_mutex *lock, | |
318 | struct ww_acquire_ctx *ctx) | |
319 | { | |
320 | #ifdef CONFIG_DEBUG_MUTEXES | |
321 | DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); | |
322 | #endif | |
323 | return ww_mutex_lock_interruptible(lock, ctx); | |
324 | } | |
325 | ||
326 | extern void ww_mutex_unlock(struct ww_mutex *lock); | |
327 | ||
328 | /** | |
329 | * ww_mutex_trylock - tries to acquire the w/w mutex without acquire context | |
330 | * @lock: mutex to lock | |
331 | * | |
332 | * Trylocks a mutex without acquire context, so no deadlock detection is | |
333 | * possible. Returns 1 if the mutex has been acquired successfully, 0 otherwise. | |
334 | */ | |
335 | static inline int __must_check ww_mutex_trylock(struct ww_mutex *lock) | |
336 | { | |
337 | return mutex_trylock(&lock->base); | |
338 | } | |
339 | ||
340 | /*** | |
341 | * ww_mutex_destroy - mark a w/w mutex unusable | |
342 | * @lock: the mutex to be destroyed | |
343 | * | |
344 | * This function marks the mutex uninitialized, and any subsequent | |
345 | * use of the mutex is forbidden. The mutex must not be locked when | |
346 | * this function is called. | |
347 | */ | |
348 | static inline void ww_mutex_destroy(struct ww_mutex *lock) | |
349 | { | |
350 | mutex_destroy(&lock->base); | |
351 | } | |
352 | ||
353 | /** | |
354 | * ww_mutex_is_locked - is the w/w mutex locked | |
355 | * @lock: the mutex to be queried | |
356 | * | |
357 | * Returns 1 if the mutex is locked, 0 if unlocked. | |
358 | */ | |
359 | static inline bool ww_mutex_is_locked(struct ww_mutex *lock) | |
360 | { | |
361 | return mutex_is_locked(&lock->base); | |
362 | } | |
363 | ||
364 | #endif |