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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> | |
2408f7a3 | 21 | #include <linux/rtmutex.h> |
1b375dc3 | 22 | |
2408f7a3 PZ |
23 | #if defined(CONFIG_DEBUG_MUTEXES) || \ |
24 | (defined(CONFIG_PREEMPT_RT) && defined(CONFIG_DEBUG_RT_MUTEXES)) | |
25 | #define DEBUG_WW_MUTEXES | |
26 | #endif | |
27 | ||
28 | #ifndef CONFIG_PREEMPT_RT | |
653a5b0b TG |
29 | #define WW_MUTEX_BASE mutex |
30 | #define ww_mutex_base_init(l,n,k) __mutex_init(l,n,k) | |
31 | #define ww_mutex_base_trylock(l) mutex_trylock(l) | |
32 | #define ww_mutex_base_is_locked(b) mutex_is_locked((b)) | |
2408f7a3 PZ |
33 | #else |
34 | #define WW_MUTEX_BASE rt_mutex | |
35 | #define ww_mutex_base_init(l,n,k) __rt_mutex_init(l,n,k) | |
36 | #define ww_mutex_base_trylock(l) rt_mutex_trylock(l) | |
37 | #define ww_mutex_base_is_locked(b) rt_mutex_base_is_locked(&(b)->rtmutex) | |
38 | #endif | |
653a5b0b | 39 | |
1b375dc3 ML |
40 | struct ww_class { |
41 | atomic_long_t stamp; | |
42 | struct lock_class_key acquire_key; | |
43 | struct lock_class_key mutex_key; | |
44 | const char *acquire_name; | |
45 | const char *mutex_name; | |
08295b3b | 46 | unsigned int is_wait_die; |
1b375dc3 ML |
47 | }; |
48 | ||
4f1893ec | 49 | struct ww_mutex { |
653a5b0b | 50 | struct WW_MUTEX_BASE base; |
4f1893ec | 51 | struct ww_acquire_ctx *ctx; |
2408f7a3 | 52 | #ifdef DEBUG_WW_MUTEXES |
4f1893ec TG |
53 | struct ww_class *ww_class; |
54 | #endif | |
55 | }; | |
56 | ||
1b375dc3 ML |
57 | struct ww_acquire_ctx { |
58 | struct task_struct *task; | |
59 | unsigned long stamp; | |
55f036ca | 60 | unsigned int acquired; |
08295b3b TH |
61 | unsigned short wounded; |
62 | unsigned short is_wait_die; | |
2408f7a3 | 63 | #ifdef DEBUG_WW_MUTEXES |
55f036ca | 64 | unsigned int done_acquire; |
1b375dc3 | 65 | struct ww_class *ww_class; |
2408f7a3 | 66 | void *contending_lock; |
1b375dc3 ML |
67 | #endif |
68 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
69 | struct lockdep_map dep_map; | |
70 | #endif | |
71 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
55f036ca PZ |
72 | unsigned int deadlock_inject_interval; |
73 | unsigned int deadlock_inject_countdown; | |
1b375dc3 ML |
74 | #endif |
75 | }; | |
76 | ||
08295b3b | 77 | #define __WW_CLASS_INITIALIZER(ww_class, _is_wait_die) \ |
1b375dc3 ML |
78 | { .stamp = ATOMIC_LONG_INIT(0) \ |
79 | , .acquire_name = #ww_class "_acquire" \ | |
08295b3b TH |
80 | , .mutex_name = #ww_class "_mutex" \ |
81 | , .is_wait_die = _is_wait_die } | |
1b375dc3 | 82 | |
08295b3b TH |
83 | #define DEFINE_WD_CLASS(classname) \ |
84 | struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 1) | |
85 | ||
1b375dc3 | 86 | #define DEFINE_WW_CLASS(classname) \ |
08295b3b | 87 | struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 0) |
1b375dc3 | 88 | |
1b375dc3 ML |
89 | /** |
90 | * ww_mutex_init - initialize the w/w mutex | |
91 | * @lock: the mutex to be initialized | |
92 | * @ww_class: the w/w class the mutex should belong to | |
93 | * | |
94 | * Initialize the w/w mutex to unlocked state and associate it with the given | |
5261ced4 WL |
95 | * class. Static define macro for w/w mutex is not provided and this function |
96 | * is the only way to properly initialize the w/w mutex. | |
1b375dc3 ML |
97 | * |
98 | * It is not allowed to initialize an already locked mutex. | |
99 | */ | |
100 | static inline void ww_mutex_init(struct ww_mutex *lock, | |
101 | struct ww_class *ww_class) | |
102 | { | |
653a5b0b | 103 | ww_mutex_base_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key); |
1b375dc3 | 104 | lock->ctx = NULL; |
2408f7a3 | 105 | #ifdef DEBUG_WW_MUTEXES |
1b375dc3 ML |
106 | lock->ww_class = ww_class; |
107 | #endif | |
108 | } | |
109 | ||
110 | /** | |
111 | * ww_acquire_init - initialize a w/w acquire context | |
112 | * @ctx: w/w acquire context to initialize | |
113 | * @ww_class: w/w class of the context | |
114 | * | |
115 | * Initializes an context to acquire multiple mutexes of the given w/w class. | |
116 | * | |
117 | * Context-based w/w mutex acquiring can be done in any order whatsoever within | |
118 | * a given lock class. Deadlocks will be detected and handled with the | |
55f036ca | 119 | * wait/die logic. |
1b375dc3 ML |
120 | * |
121 | * Mixing of context-based w/w mutex acquiring and single w/w mutex locking can | |
122 | * result in undetected deadlocks and is so forbidden. Mixing different contexts | |
123 | * for the same w/w class when acquiring mutexes can also result in undetected | |
124 | * deadlocks, and is hence also forbidden. Both types of abuse will be caught by | |
125 | * enabling CONFIG_PROVE_LOCKING. | |
126 | * | |
127 | * Nesting of acquire contexts for _different_ w/w classes is possible, subject | |
128 | * to the usual locking rules between different lock classes. | |
129 | * | |
130 | * An acquire context must be released with ww_acquire_fini by the same task | |
131 | * before the memory is freed. It is recommended to allocate the context itself | |
132 | * on the stack. | |
133 | */ | |
134 | static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, | |
135 | struct ww_class *ww_class) | |
136 | { | |
137 | ctx->task = current; | |
f4ec57b6 | 138 | ctx->stamp = atomic_long_inc_return_relaxed(&ww_class->stamp); |
1b375dc3 | 139 | ctx->acquired = 0; |
08295b3b TH |
140 | ctx->wounded = false; |
141 | ctx->is_wait_die = ww_class->is_wait_die; | |
2408f7a3 | 142 | #ifdef DEBUG_WW_MUTEXES |
1b375dc3 ML |
143 | ctx->ww_class = ww_class; |
144 | ctx->done_acquire = 0; | |
145 | ctx->contending_lock = NULL; | |
146 | #endif | |
147 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
148 | debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); | |
149 | lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, | |
150 | &ww_class->acquire_key, 0); | |
151 | mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); | |
152 | #endif | |
153 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
154 | ctx->deadlock_inject_interval = 1; | |
155 | ctx->deadlock_inject_countdown = ctx->stamp & 0xf; | |
156 | #endif | |
157 | } | |
158 | ||
159 | /** | |
160 | * ww_acquire_done - marks the end of the acquire phase | |
161 | * @ctx: the acquire context | |
162 | * | |
163 | * Marks the end of the acquire phase, any further w/w mutex lock calls using | |
164 | * this context are forbidden. | |
165 | * | |
166 | * Calling this function is optional, it is just useful to document w/w mutex | |
167 | * code and clearly designated the acquire phase from actually using the locked | |
168 | * data structures. | |
169 | */ | |
170 | static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) | |
171 | { | |
2408f7a3 | 172 | #ifdef DEBUG_WW_MUTEXES |
1b375dc3 ML |
173 | lockdep_assert_held(ctx); |
174 | ||
175 | DEBUG_LOCKS_WARN_ON(ctx->done_acquire); | |
176 | ctx->done_acquire = 1; | |
177 | #endif | |
178 | } | |
179 | ||
180 | /** | |
181 | * ww_acquire_fini - releases a w/w acquire context | |
182 | * @ctx: the acquire context to free | |
183 | * | |
184 | * Releases a w/w acquire context. This must be called _after_ all acquired w/w | |
185 | * mutexes have been released with ww_mutex_unlock. | |
186 | */ | |
187 | static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) | |
188 | { | |
bee64578 | 189 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
5facae4f | 190 | mutex_release(&ctx->dep_map, _THIS_IP_); |
bee64578 | 191 | #endif |
2408f7a3 | 192 | #ifdef DEBUG_WW_MUTEXES |
1b375dc3 | 193 | DEBUG_LOCKS_WARN_ON(ctx->acquired); |
97f2645f | 194 | if (!IS_ENABLED(CONFIG_PROVE_LOCKING)) |
1b375dc3 ML |
195 | /* |
196 | * lockdep will normally handle this, | |
197 | * but fail without anyway | |
198 | */ | |
199 | ctx->done_acquire = 1; | |
200 | ||
97f2645f | 201 | if (!IS_ENABLED(CONFIG_DEBUG_LOCK_ALLOC)) |
1b375dc3 ML |
202 | /* ensure ww_acquire_fini will still fail if called twice */ |
203 | ctx->acquired = ~0U; | |
204 | #endif | |
205 | } | |
206 | ||
1b375dc3 ML |
207 | /** |
208 | * ww_mutex_lock - acquire the w/w mutex | |
209 | * @lock: the mutex to be acquired | |
210 | * @ctx: w/w acquire context, or NULL to acquire only a single lock. | |
211 | * | |
212 | * Lock the w/w mutex exclusively for this task. | |
213 | * | |
214 | * Deadlocks within a given w/w class of locks are detected and handled with the | |
55f036ca | 215 | * wait/die algorithm. If the lock isn't immediately available this function |
1b375dc3 | 216 | * will either sleep until it is (wait case). Or it selects the current context |
55f036ca | 217 | * for backing off by returning -EDEADLK (die case). Trying to acquire the |
1b375dc3 ML |
218 | * same lock with the same context twice is also detected and signalled by |
219 | * returning -EALREADY. Returns 0 if the mutex was successfully acquired. | |
220 | * | |
55f036ca | 221 | * In the die case the caller must release all currently held w/w mutexes for |
1b375dc3 ML |
222 | * the given context and then wait for this contending lock to be available by |
223 | * calling ww_mutex_lock_slow. Alternatively callers can opt to not acquire this | |
224 | * lock and proceed with trying to acquire further w/w mutexes (e.g. when | |
225 | * scanning through lru lists trying to free resources). | |
226 | * | |
227 | * The mutex must later on be released by the same task that | |
228 | * acquired it. The task may not exit without first unlocking the mutex. Also, | |
229 | * kernel memory where the mutex resides must not be freed with the mutex still | |
230 | * locked. The mutex must first be initialized (or statically defined) before it | |
231 | * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be | |
232 | * of the same w/w lock class as was used to initialize the acquire context. | |
233 | * | |
234 | * A mutex acquired with this function must be released with ww_mutex_unlock. | |
235 | */ | |
23b19ec3 | 236 | extern int /* __must_check */ ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx); |
1b375dc3 ML |
237 | |
238 | /** | |
239 | * ww_mutex_lock_interruptible - acquire the w/w mutex, interruptible | |
240 | * @lock: the mutex to be acquired | |
241 | * @ctx: w/w acquire context | |
242 | * | |
243 | * Lock the w/w mutex exclusively for this task. | |
244 | * | |
245 | * Deadlocks within a given w/w class of locks are detected and handled with the | |
55f036ca | 246 | * wait/die algorithm. If the lock isn't immediately available this function |
1b375dc3 | 247 | * will either sleep until it is (wait case). Or it selects the current context |
55f036ca | 248 | * for backing off by returning -EDEADLK (die case). Trying to acquire the |
1b375dc3 ML |
249 | * same lock with the same context twice is also detected and signalled by |
250 | * returning -EALREADY. Returns 0 if the mutex was successfully acquired. If a | |
251 | * signal arrives while waiting for the lock then this function returns -EINTR. | |
252 | * | |
55f036ca | 253 | * In the die case the caller must release all currently held w/w mutexes for |
1b375dc3 ML |
254 | * the given context and then wait for this contending lock to be available by |
255 | * calling ww_mutex_lock_slow_interruptible. Alternatively callers can opt to | |
256 | * not acquire this lock and proceed with trying to acquire further w/w mutexes | |
257 | * (e.g. when scanning through lru lists trying to free resources). | |
258 | * | |
259 | * The mutex must later on be released by the same task that | |
260 | * acquired it. The task may not exit without first unlocking the mutex. Also, | |
261 | * kernel memory where the mutex resides must not be freed with the mutex still | |
262 | * locked. The mutex must first be initialized (or statically defined) before it | |
263 | * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be | |
264 | * of the same w/w lock class as was used to initialize the acquire context. | |
265 | * | |
266 | * A mutex acquired with this function must be released with ww_mutex_unlock. | |
267 | */ | |
c5470b22 NH |
268 | extern int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock, |
269 | struct ww_acquire_ctx *ctx); | |
1b375dc3 ML |
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 | * | |
55f036ca | 276 | * Acquires a w/w mutex with the given context after a die case. This function |
1b375dc3 ML |
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; | |
2408f7a3 | 298 | #ifdef DEBUG_WW_MUTEXES |
1b375dc3 ML |
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 | * | |
55f036ca | 310 | * Acquires a w/w mutex with the given context after a die case. This function |
1b375dc3 ML |
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 | { | |
2408f7a3 | 334 | #ifdef DEBUG_WW_MUTEXES |
1b375dc3 ML |
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 | { | |
653a5b0b | 351 | return ww_mutex_base_trylock(&lock->base); |
1b375dc3 ML |
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 | { | |
2408f7a3 | 364 | #ifndef CONFIG_PREEMPT_RT |
1b375dc3 | 365 | mutex_destroy(&lock->base); |
2408f7a3 | 366 | #endif |
1b375dc3 ML |
367 | } |
368 | ||
369 | /** | |
370 | * ww_mutex_is_locked - is the w/w mutex locked | |
371 | * @lock: the mutex to be queried | |
372 | * | |
373 | * Returns 1 if the mutex is locked, 0 if unlocked. | |
374 | */ | |
375 | static inline bool ww_mutex_is_locked(struct ww_mutex *lock) | |
376 | { | |
653a5b0b | 377 | return ww_mutex_base_is_locked(&lock->base); |
1b375dc3 ML |
378 | } |
379 | ||
380 | #endif |