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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) | |
653a5b0b | 31 | #define ww_mutex_base_is_locked(b) mutex_is_locked((b)) |
2408f7a3 PZ |
32 | #else |
33 | #define WW_MUTEX_BASE rt_mutex | |
34 | #define ww_mutex_base_init(l,n,k) __rt_mutex_init(l,n,k) | |
2408f7a3 PZ |
35 | #define ww_mutex_base_is_locked(b) rt_mutex_base_is_locked(&(b)->rtmutex) |
36 | #endif | |
653a5b0b | 37 | |
1b375dc3 ML |
38 | struct ww_class { |
39 | atomic_long_t stamp; | |
40 | struct lock_class_key acquire_key; | |
41 | struct lock_class_key mutex_key; | |
42 | const char *acquire_name; | |
43 | const char *mutex_name; | |
08295b3b | 44 | unsigned int is_wait_die; |
1b375dc3 ML |
45 | }; |
46 | ||
4f1893ec | 47 | struct ww_mutex { |
653a5b0b | 48 | struct WW_MUTEX_BASE base; |
4f1893ec | 49 | struct ww_acquire_ctx *ctx; |
2408f7a3 | 50 | #ifdef DEBUG_WW_MUTEXES |
4f1893ec TG |
51 | struct ww_class *ww_class; |
52 | #endif | |
53 | }; | |
54 | ||
1b375dc3 ML |
55 | struct ww_acquire_ctx { |
56 | struct task_struct *task; | |
57 | unsigned long stamp; | |
55f036ca | 58 | unsigned int acquired; |
08295b3b TH |
59 | unsigned short wounded; |
60 | unsigned short is_wait_die; | |
2408f7a3 | 61 | #ifdef DEBUG_WW_MUTEXES |
55f036ca | 62 | unsigned int done_acquire; |
1b375dc3 | 63 | struct ww_class *ww_class; |
2408f7a3 | 64 | void *contending_lock; |
1b375dc3 ML |
65 | #endif |
66 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
67 | struct lockdep_map dep_map; | |
68 | #endif | |
69 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
55f036ca PZ |
70 | unsigned int deadlock_inject_interval; |
71 | unsigned int deadlock_inject_countdown; | |
1b375dc3 ML |
72 | #endif |
73 | }; | |
74 | ||
08295b3b | 75 | #define __WW_CLASS_INITIALIZER(ww_class, _is_wait_die) \ |
1b375dc3 ML |
76 | { .stamp = ATOMIC_LONG_INIT(0) \ |
77 | , .acquire_name = #ww_class "_acquire" \ | |
08295b3b TH |
78 | , .mutex_name = #ww_class "_mutex" \ |
79 | , .is_wait_die = _is_wait_die } | |
1b375dc3 | 80 | |
08295b3b TH |
81 | #define DEFINE_WD_CLASS(classname) \ |
82 | struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 1) | |
83 | ||
1b375dc3 | 84 | #define DEFINE_WW_CLASS(classname) \ |
08295b3b | 85 | struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 0) |
1b375dc3 | 86 | |
1b375dc3 ML |
87 | /** |
88 | * ww_mutex_init - initialize the w/w mutex | |
89 | * @lock: the mutex to be initialized | |
90 | * @ww_class: the w/w class the mutex should belong to | |
91 | * | |
92 | * Initialize the w/w mutex to unlocked state and associate it with the given | |
5261ced4 WL |
93 | * class. Static define macro for w/w mutex is not provided and this function |
94 | * is the only way to properly initialize the w/w mutex. | |
1b375dc3 ML |
95 | * |
96 | * It is not allowed to initialize an already locked mutex. | |
97 | */ | |
98 | static inline void ww_mutex_init(struct ww_mutex *lock, | |
99 | struct ww_class *ww_class) | |
100 | { | |
653a5b0b | 101 | ww_mutex_base_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key); |
1b375dc3 | 102 | lock->ctx = NULL; |
2408f7a3 | 103 | #ifdef DEBUG_WW_MUTEXES |
1b375dc3 ML |
104 | lock->ww_class = ww_class; |
105 | #endif | |
106 | } | |
107 | ||
108 | /** | |
109 | * ww_acquire_init - initialize a w/w acquire context | |
110 | * @ctx: w/w acquire context to initialize | |
111 | * @ww_class: w/w class of the context | |
112 | * | |
113 | * Initializes an context to acquire multiple mutexes of the given w/w class. | |
114 | * | |
115 | * Context-based w/w mutex acquiring can be done in any order whatsoever within | |
116 | * a given lock class. Deadlocks will be detected and handled with the | |
55f036ca | 117 | * wait/die logic. |
1b375dc3 ML |
118 | * |
119 | * Mixing of context-based w/w mutex acquiring and single w/w mutex locking can | |
120 | * result in undetected deadlocks and is so forbidden. Mixing different contexts | |
121 | * for the same w/w class when acquiring mutexes can also result in undetected | |
122 | * deadlocks, and is hence also forbidden. Both types of abuse will be caught by | |
123 | * enabling CONFIG_PROVE_LOCKING. | |
124 | * | |
125 | * Nesting of acquire contexts for _different_ w/w classes is possible, subject | |
126 | * to the usual locking rules between different lock classes. | |
127 | * | |
128 | * An acquire context must be released with ww_acquire_fini by the same task | |
129 | * before the memory is freed. It is recommended to allocate the context itself | |
130 | * on the stack. | |
131 | */ | |
132 | static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, | |
133 | struct ww_class *ww_class) | |
134 | { | |
135 | ctx->task = current; | |
f4ec57b6 | 136 | ctx->stamp = atomic_long_inc_return_relaxed(&ww_class->stamp); |
1b375dc3 | 137 | ctx->acquired = 0; |
08295b3b TH |
138 | ctx->wounded = false; |
139 | ctx->is_wait_die = ww_class->is_wait_die; | |
2408f7a3 | 140 | #ifdef DEBUG_WW_MUTEXES |
1b375dc3 ML |
141 | ctx->ww_class = ww_class; |
142 | ctx->done_acquire = 0; | |
143 | ctx->contending_lock = NULL; | |
144 | #endif | |
145 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
146 | debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); | |
147 | lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, | |
148 | &ww_class->acquire_key, 0); | |
149 | mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); | |
150 | #endif | |
151 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH | |
152 | ctx->deadlock_inject_interval = 1; | |
153 | ctx->deadlock_inject_countdown = ctx->stamp & 0xf; | |
154 | #endif | |
155 | } | |
156 | ||
157 | /** | |
158 | * ww_acquire_done - marks the end of the acquire phase | |
159 | * @ctx: the acquire context | |
160 | * | |
161 | * Marks the end of the acquire phase, any further w/w mutex lock calls using | |
162 | * this context are forbidden. | |
163 | * | |
164 | * Calling this function is optional, it is just useful to document w/w mutex | |
165 | * code and clearly designated the acquire phase from actually using the locked | |
166 | * data structures. | |
167 | */ | |
168 | static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) | |
169 | { | |
2408f7a3 | 170 | #ifdef DEBUG_WW_MUTEXES |
1b375dc3 ML |
171 | lockdep_assert_held(ctx); |
172 | ||
173 | DEBUG_LOCKS_WARN_ON(ctx->done_acquire); | |
174 | ctx->done_acquire = 1; | |
175 | #endif | |
176 | } | |
177 | ||
178 | /** | |
179 | * ww_acquire_fini - releases a w/w acquire context | |
180 | * @ctx: the acquire context to free | |
181 | * | |
182 | * Releases a w/w acquire context. This must be called _after_ all acquired w/w | |
183 | * mutexes have been released with ww_mutex_unlock. | |
184 | */ | |
185 | static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) | |
186 | { | |
bee64578 | 187 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
5facae4f | 188 | mutex_release(&ctx->dep_map, _THIS_IP_); |
bee64578 | 189 | #endif |
2408f7a3 | 190 | #ifdef DEBUG_WW_MUTEXES |
1b375dc3 | 191 | DEBUG_LOCKS_WARN_ON(ctx->acquired); |
97f2645f | 192 | if (!IS_ENABLED(CONFIG_PROVE_LOCKING)) |
1b375dc3 ML |
193 | /* |
194 | * lockdep will normally handle this, | |
195 | * but fail without anyway | |
196 | */ | |
197 | ctx->done_acquire = 1; | |
198 | ||
97f2645f | 199 | if (!IS_ENABLED(CONFIG_DEBUG_LOCK_ALLOC)) |
1b375dc3 ML |
200 | /* ensure ww_acquire_fini will still fail if called twice */ |
201 | ctx->acquired = ~0U; | |
202 | #endif | |
203 | } | |
204 | ||
1b375dc3 ML |
205 | /** |
206 | * ww_mutex_lock - acquire the w/w mutex | |
207 | * @lock: the mutex to be acquired | |
208 | * @ctx: w/w acquire context, or NULL to acquire only a single lock. | |
209 | * | |
210 | * Lock the w/w mutex exclusively for this task. | |
211 | * | |
212 | * Deadlocks within a given w/w class of locks are detected and handled with the | |
55f036ca | 213 | * wait/die algorithm. If the lock isn't immediately available this function |
1b375dc3 | 214 | * will either sleep until it is (wait case). Or it selects the current context |
55f036ca | 215 | * for backing off by returning -EDEADLK (die case). Trying to acquire the |
1b375dc3 ML |
216 | * same lock with the same context twice is also detected and signalled by |
217 | * returning -EALREADY. Returns 0 if the mutex was successfully acquired. | |
218 | * | |
55f036ca | 219 | * In the die case the caller must release all currently held w/w mutexes for |
1b375dc3 ML |
220 | * the given context and then wait for this contending lock to be available by |
221 | * calling ww_mutex_lock_slow. Alternatively callers can opt to not acquire this | |
222 | * lock and proceed with trying to acquire further w/w mutexes (e.g. when | |
223 | * scanning through lru lists trying to free resources). | |
224 | * | |
225 | * The mutex must later on be released by the same task that | |
226 | * acquired it. The task may not exit without first unlocking the mutex. Also, | |
227 | * kernel memory where the mutex resides must not be freed with the mutex still | |
228 | * locked. The mutex must first be initialized (or statically defined) before it | |
229 | * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be | |
230 | * of the same w/w lock class as was used to initialize the acquire context. | |
231 | * | |
232 | * A mutex acquired with this function must be released with ww_mutex_unlock. | |
233 | */ | |
23b19ec3 | 234 | extern int /* __must_check */ ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx); |
1b375dc3 ML |
235 | |
236 | /** | |
237 | * ww_mutex_lock_interruptible - acquire the w/w mutex, interruptible | |
238 | * @lock: the mutex to be acquired | |
239 | * @ctx: w/w acquire context | |
240 | * | |
241 | * Lock the w/w mutex exclusively for this task. | |
242 | * | |
243 | * Deadlocks within a given w/w class of locks are detected and handled with the | |
55f036ca | 244 | * wait/die algorithm. If the lock isn't immediately available this function |
1b375dc3 | 245 | * will either sleep until it is (wait case). Or it selects the current context |
55f036ca | 246 | * for backing off by returning -EDEADLK (die case). Trying to acquire the |
1b375dc3 ML |
247 | * same lock with the same context twice is also detected and signalled by |
248 | * returning -EALREADY. Returns 0 if the mutex was successfully acquired. If a | |
249 | * signal arrives while waiting for the lock then this function returns -EINTR. | |
250 | * | |
55f036ca | 251 | * In the die case the caller must release all currently held w/w mutexes for |
1b375dc3 ML |
252 | * the given context and then wait for this contending lock to be available by |
253 | * calling ww_mutex_lock_slow_interruptible. Alternatively callers can opt to | |
254 | * not acquire this lock and proceed with trying to acquire further w/w mutexes | |
255 | * (e.g. when scanning through lru lists trying to free resources). | |
256 | * | |
257 | * The mutex must later on be released by the same task that | |
258 | * acquired it. The task may not exit without first unlocking the mutex. Also, | |
259 | * kernel memory where the mutex resides must not be freed with the mutex still | |
260 | * locked. The mutex must first be initialized (or statically defined) before it | |
261 | * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be | |
262 | * of the same w/w lock class as was used to initialize the acquire context. | |
263 | * | |
264 | * A mutex acquired with this function must be released with ww_mutex_unlock. | |
265 | */ | |
c5470b22 NH |
266 | extern int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock, |
267 | struct ww_acquire_ctx *ctx); | |
1b375dc3 ML |
268 | |
269 | /** | |
270 | * ww_mutex_lock_slow - slowpath acquiring of the w/w mutex | |
271 | * @lock: the mutex to be acquired | |
272 | * @ctx: w/w acquire context | |
273 | * | |
55f036ca | 274 | * Acquires a w/w mutex with the given context after a die case. This function |
1b375dc3 ML |
275 | * will sleep until the lock becomes available. |
276 | * | |
277 | * The caller must have released all w/w mutexes already acquired with the | |
278 | * context and then call this function on the contended lock. | |
279 | * | |
280 | * Afterwards the caller may continue to (re)acquire the other w/w mutexes it | |
281 | * needs with ww_mutex_lock. Note that the -EALREADY return code from | |
282 | * ww_mutex_lock can be used to avoid locking this contended mutex twice. | |
283 | * | |
284 | * It is forbidden to call this function with any other w/w mutexes associated | |
285 | * with the context held. It is forbidden to call this on anything else than the | |
286 | * contending mutex. | |
287 | * | |
288 | * Note that the slowpath lock acquiring can also be done by calling | |
289 | * ww_mutex_lock directly. This function here is simply to help w/w mutex | |
290 | * locking code readability by clearly denoting the slowpath. | |
291 | */ | |
292 | static inline void | |
293 | ww_mutex_lock_slow(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) | |
294 | { | |
295 | int ret; | |
2408f7a3 | 296 | #ifdef DEBUG_WW_MUTEXES |
1b375dc3 ML |
297 | DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); |
298 | #endif | |
299 | ret = ww_mutex_lock(lock, ctx); | |
300 | (void)ret; | |
301 | } | |
302 | ||
303 | /** | |
304 | * ww_mutex_lock_slow_interruptible - slowpath acquiring of the w/w mutex, interruptible | |
305 | * @lock: the mutex to be acquired | |
306 | * @ctx: w/w acquire context | |
307 | * | |
55f036ca | 308 | * Acquires a w/w mutex with the given context after a die case. This function |
1b375dc3 ML |
309 | * will sleep until the lock becomes available and returns 0 when the lock has |
310 | * been acquired. If a signal arrives while waiting for the lock then this | |
311 | * function returns -EINTR. | |
312 | * | |
313 | * The caller must have released all w/w mutexes already acquired with the | |
314 | * context and then call this function on the contended lock. | |
315 | * | |
316 | * Afterwards the caller may continue to (re)acquire the other w/w mutexes it | |
317 | * needs with ww_mutex_lock. Note that the -EALREADY return code from | |
318 | * ww_mutex_lock can be used to avoid locking this contended mutex twice. | |
319 | * | |
320 | * It is forbidden to call this function with any other w/w mutexes associated | |
321 | * with the given context held. It is forbidden to call this on anything else | |
322 | * than the contending mutex. | |
323 | * | |
324 | * Note that the slowpath lock acquiring can also be done by calling | |
325 | * ww_mutex_lock_interruptible directly. This function here is simply to help | |
326 | * w/w mutex locking code readability by clearly denoting the slowpath. | |
327 | */ | |
328 | static inline int __must_check | |
329 | ww_mutex_lock_slow_interruptible(struct ww_mutex *lock, | |
330 | struct ww_acquire_ctx *ctx) | |
331 | { | |
2408f7a3 | 332 | #ifdef DEBUG_WW_MUTEXES |
1b375dc3 ML |
333 | DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); |
334 | #endif | |
335 | return ww_mutex_lock_interruptible(lock, ctx); | |
336 | } | |
337 | ||
338 | extern void ww_mutex_unlock(struct ww_mutex *lock); | |
339 | ||
12235da8 ML |
340 | extern int __must_check ww_mutex_trylock(struct ww_mutex *lock, |
341 | struct ww_acquire_ctx *ctx); | |
1b375dc3 ML |
342 | |
343 | /*** | |
344 | * ww_mutex_destroy - mark a w/w mutex unusable | |
345 | * @lock: the mutex to be destroyed | |
346 | * | |
347 | * This function marks the mutex uninitialized, and any subsequent | |
348 | * use of the mutex is forbidden. The mutex must not be locked when | |
349 | * this function is called. | |
350 | */ | |
351 | static inline void ww_mutex_destroy(struct ww_mutex *lock) | |
352 | { | |
2408f7a3 | 353 | #ifndef CONFIG_PREEMPT_RT |
1b375dc3 | 354 | mutex_destroy(&lock->base); |
2408f7a3 | 355 | #endif |
1b375dc3 ML |
356 | } |
357 | ||
358 | /** | |
359 | * ww_mutex_is_locked - is the w/w mutex locked | |
360 | * @lock: the mutex to be queried | |
361 | * | |
362 | * Returns 1 if the mutex is locked, 0 if unlocked. | |
363 | */ | |
364 | static inline bool ww_mutex_is_locked(struct ww_mutex *lock) | |
365 | { | |
653a5b0b | 366 | return ww_mutex_base_is_locked(&lock->base); |
1b375dc3 ML |
367 | } |
368 | ||
369 | #endif |