1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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 | * |
9 | * Wait/Die implementation: |
10 | * Copyright (C) 2013 Canonical Ltd. |
11 | * Choice of algorithm: |
12 | * Copyright (C) 2018 WMWare Inc. |
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 | #include <linux/rtmutex.h> |
22 | |
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 |
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_is_locked(b) mutex_is_locked((b)) |
32 | #else |
33 | #define WW_MUTEX_BASE rt_mutex |
34 | #define ww_mutex_base_init(l,n,k) __rt_mutex_init(l,n,k) |
35 | #define ww_mutex_base_is_locked(b) rt_mutex_base_is_locked(&(b)->rtmutex) |
36 | #endif |
37 | |
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; |
44 | unsigned int is_wait_die; |
45 | }; |
46 | |
47 | struct ww_mutex { |
48 | struct WW_MUTEX_BASE base; |
49 | struct ww_acquire_ctx *ctx; |
50 | #ifdef DEBUG_WW_MUTEXES |
51 | struct ww_class *ww_class; |
52 | #endif |
53 | }; |
54 | |
55 | struct ww_acquire_ctx { |
56 | struct task_struct *task; |
57 | unsigned long stamp; |
58 | unsigned int acquired; |
59 | unsigned short wounded; |
60 | unsigned short is_wait_die; |
61 | #ifdef DEBUG_WW_MUTEXES |
62 | unsigned int done_acquire; |
63 | struct ww_class *ww_class; |
64 | void *contending_lock; |
65 | #endif |
66 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
67 | struct lockdep_map dep_map; |
68 | #endif |
69 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH |
70 | unsigned int deadlock_inject_interval; |
71 | unsigned int deadlock_inject_countdown; |
72 | #endif |
73 | }; |
74 | |
75 | #define __WW_CLASS_INITIALIZER(ww_class, _is_wait_die) \ |
76 | { .stamp = ATOMIC_LONG_INIT(0) \ |
77 | , .acquire_name = #ww_class "_acquire" \ |
78 | , .mutex_name = #ww_class "_mutex" \ |
79 | , .is_wait_die = _is_wait_die } |
80 | |
81 | #define DEFINE_WD_CLASS(classname) \ |
82 | struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 1) |
83 | |
84 | #define DEFINE_WW_CLASS(classname) \ |
85 | struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 0) |
86 | |
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 |
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. |
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 | { |
101 | ww_mutex_base_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key); |
102 | lock->ctx = NULL; |
103 | #ifdef DEBUG_WW_MUTEXES |
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 |
117 | * wait/die logic. |
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; |
136 | ctx->stamp = atomic_long_inc_return_relaxed(v: &ww_class->stamp); |
137 | ctx->acquired = 0; |
138 | ctx->wounded = false; |
139 | ctx->is_wait_die = ww_class->is_wait_die; |
140 | #ifdef DEBUG_WW_MUTEXES |
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(from: (void *)ctx, len: sizeof(*ctx)); |
147 | lockdep_init_map(lock: &ctx->dep_map, name: ww_class->acquire_name, |
148 | key: &ww_class->acquire_key, subclass: 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 | { |
170 | #ifdef DEBUG_WW_MUTEXES |
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 | { |
187 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
188 | mutex_release(&ctx->dep_map, _THIS_IP_); |
189 | #endif |
190 | #ifdef DEBUG_WW_MUTEXES |
191 | DEBUG_LOCKS_WARN_ON(ctx->acquired); |
192 | if (!IS_ENABLED(CONFIG_PROVE_LOCKING)) |
193 | /* |
194 | * lockdep will normally handle this, |
195 | * but fail without anyway |
196 | */ |
197 | ctx->done_acquire = 1; |
198 | |
199 | if (!IS_ENABLED(CONFIG_DEBUG_LOCK_ALLOC)) |
200 | /* ensure ww_acquire_fini will still fail if called twice */ |
201 | ctx->acquired = ~0U; |
202 | #endif |
203 | } |
204 | |
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 |
213 | * wait/die algorithm. If the lock isn't immediately available this function |
214 | * will either sleep until it is (wait case). Or it selects the current context |
215 | * for backing off by returning -EDEADLK (die case). Trying to acquire the |
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 | * |
219 | * In the die case the caller must release all currently held w/w mutexes for |
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 | */ |
234 | extern int /* __must_check */ ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx); |
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 |
244 | * wait/die algorithm. If the lock isn't immediately available this function |
245 | * will either sleep until it is (wait case). Or it selects the current context |
246 | * for backing off by returning -EDEADLK (die case). Trying to acquire the |
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 | * |
251 | * In the die case the caller must release all currently held w/w mutexes for |
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 | */ |
266 | extern int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock, |
267 | struct ww_acquire_ctx *ctx); |
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 | * |
274 | * Acquires a w/w mutex with the given context after a die case. This function |
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; |
296 | #ifdef DEBUG_WW_MUTEXES |
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 | * |
308 | * Acquires a w/w mutex with the given context after a die case. This function |
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 | { |
332 | #ifdef DEBUG_WW_MUTEXES |
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 | |
340 | extern int __must_check ww_mutex_trylock(struct ww_mutex *lock, |
341 | struct ww_acquire_ctx *ctx); |
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 | { |
353 | #ifndef CONFIG_PREEMPT_RT |
354 | mutex_destroy(lock: &lock->base); |
355 | #endif |
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 | { |
366 | return ww_mutex_base_is_locked(&lock->base); |
367 | } |
368 | |
369 | #endif |
370 | |