Greg Kroah-Hartman | b244131 | 2017-11-01 15:07:57 +0100 | [diff] [blame] | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
Maarten Lankhorst | 1b375dc | 2013-07-05 09:29:32 +0200 | [diff] [blame] | 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 | * Wound/wait implementation: |
| 10 | * Copyright (C) 2013 Canonical Ltd. |
| 11 | * |
| 12 | * This file contains the main data structure and API definitions. |
| 13 | */ |
| 14 | |
| 15 | #ifndef __LINUX_WW_MUTEX_H |
| 16 | #define __LINUX_WW_MUTEX_H |
| 17 | |
| 18 | #include <linux/mutex.h> |
| 19 | |
| 20 | struct ww_class { |
| 21 | atomic_long_t stamp; |
| 22 | struct lock_class_key acquire_key; |
| 23 | struct lock_class_key mutex_key; |
| 24 | const char *acquire_name; |
| 25 | const char *mutex_name; |
| 26 | }; |
| 27 | |
| 28 | struct ww_acquire_ctx { |
| 29 | struct task_struct *task; |
| 30 | unsigned long stamp; |
| 31 | unsigned acquired; |
| 32 | #ifdef CONFIG_DEBUG_MUTEXES |
| 33 | unsigned done_acquire; |
| 34 | struct ww_class *ww_class; |
| 35 | struct ww_mutex *contending_lock; |
| 36 | #endif |
| 37 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 38 | struct lockdep_map dep_map; |
| 39 | #endif |
| 40 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH |
| 41 | unsigned deadlock_inject_interval; |
| 42 | unsigned deadlock_inject_countdown; |
| 43 | #endif |
| 44 | }; |
| 45 | |
| 46 | struct ww_mutex { |
| 47 | struct mutex base; |
| 48 | struct ww_acquire_ctx *ctx; |
| 49 | #ifdef CONFIG_DEBUG_MUTEXES |
| 50 | struct ww_class *ww_class; |
| 51 | #endif |
| 52 | }; |
| 53 | |
| 54 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
Chris Wilson | af2e859e | 2016-12-01 11:47:04 +0000 | [diff] [blame] | 55 | # define __WW_CLASS_MUTEX_INITIALIZER(lockname, class) \ |
| 56 | , .ww_class = class |
Maarten Lankhorst | 1b375dc | 2013-07-05 09:29:32 +0200 | [diff] [blame] | 57 | #else |
Chris Wilson | af2e859e | 2016-12-01 11:47:04 +0000 | [diff] [blame] | 58 | # define __WW_CLASS_MUTEX_INITIALIZER(lockname, class) |
Maarten Lankhorst | 1b375dc | 2013-07-05 09:29:32 +0200 | [diff] [blame] | 59 | #endif |
| 60 | |
| 61 | #define __WW_CLASS_INITIALIZER(ww_class) \ |
| 62 | { .stamp = ATOMIC_LONG_INIT(0) \ |
| 63 | , .acquire_name = #ww_class "_acquire" \ |
| 64 | , .mutex_name = #ww_class "_mutex" } |
| 65 | |
| 66 | #define __WW_MUTEX_INITIALIZER(lockname, class) \ |
Chris Wilson | af2e859e | 2016-12-01 11:47:04 +0000 | [diff] [blame] | 67 | { .base = __MUTEX_INITIALIZER(lockname.base) \ |
Maarten Lankhorst | 1b375dc | 2013-07-05 09:29:32 +0200 | [diff] [blame] | 68 | __WW_CLASS_MUTEX_INITIALIZER(lockname, class) } |
| 69 | |
| 70 | #define DEFINE_WW_CLASS(classname) \ |
| 71 | struct ww_class classname = __WW_CLASS_INITIALIZER(classname) |
| 72 | |
| 73 | #define DEFINE_WW_MUTEX(mutexname, ww_class) \ |
| 74 | struct ww_mutex mutexname = __WW_MUTEX_INITIALIZER(mutexname, ww_class) |
| 75 | |
| 76 | /** |
| 77 | * ww_mutex_init - initialize the w/w mutex |
| 78 | * @lock: the mutex to be initialized |
| 79 | * @ww_class: the w/w class the mutex should belong to |
| 80 | * |
| 81 | * Initialize the w/w mutex to unlocked state and associate it with the given |
| 82 | * class. |
| 83 | * |
| 84 | * It is not allowed to initialize an already locked mutex. |
| 85 | */ |
| 86 | static inline void ww_mutex_init(struct ww_mutex *lock, |
| 87 | struct ww_class *ww_class) |
| 88 | { |
| 89 | __mutex_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key); |
| 90 | lock->ctx = NULL; |
| 91 | #ifdef CONFIG_DEBUG_MUTEXES |
| 92 | lock->ww_class = ww_class; |
| 93 | #endif |
| 94 | } |
| 95 | |
| 96 | /** |
| 97 | * ww_acquire_init - initialize a w/w acquire context |
| 98 | * @ctx: w/w acquire context to initialize |
| 99 | * @ww_class: w/w class of the context |
| 100 | * |
| 101 | * Initializes an context to acquire multiple mutexes of the given w/w class. |
| 102 | * |
| 103 | * Context-based w/w mutex acquiring can be done in any order whatsoever within |
| 104 | * a given lock class. Deadlocks will be detected and handled with the |
| 105 | * wait/wound logic. |
| 106 | * |
| 107 | * Mixing of context-based w/w mutex acquiring and single w/w mutex locking can |
| 108 | * result in undetected deadlocks and is so forbidden. Mixing different contexts |
| 109 | * for the same w/w class when acquiring mutexes can also result in undetected |
| 110 | * deadlocks, and is hence also forbidden. Both types of abuse will be caught by |
| 111 | * enabling CONFIG_PROVE_LOCKING. |
| 112 | * |
| 113 | * Nesting of acquire contexts for _different_ w/w classes is possible, subject |
| 114 | * to the usual locking rules between different lock classes. |
| 115 | * |
| 116 | * An acquire context must be released with ww_acquire_fini by the same task |
| 117 | * before the memory is freed. It is recommended to allocate the context itself |
| 118 | * on the stack. |
| 119 | */ |
| 120 | static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, |
| 121 | struct ww_class *ww_class) |
| 122 | { |
| 123 | ctx->task = current; |
Peter Zijlstra | f4ec57b | 2016-11-24 12:46:26 +0100 | [diff] [blame] | 124 | ctx->stamp = atomic_long_inc_return_relaxed(&ww_class->stamp); |
Maarten Lankhorst | 1b375dc | 2013-07-05 09:29:32 +0200 | [diff] [blame] | 125 | ctx->acquired = 0; |
| 126 | #ifdef CONFIG_DEBUG_MUTEXES |
| 127 | ctx->ww_class = ww_class; |
| 128 | ctx->done_acquire = 0; |
| 129 | ctx->contending_lock = NULL; |
| 130 | #endif |
| 131 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 132 | debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); |
| 133 | lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, |
| 134 | &ww_class->acquire_key, 0); |
| 135 | mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); |
| 136 | #endif |
| 137 | #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH |
| 138 | ctx->deadlock_inject_interval = 1; |
| 139 | ctx->deadlock_inject_countdown = ctx->stamp & 0xf; |
| 140 | #endif |
| 141 | } |
| 142 | |
| 143 | /** |
| 144 | * ww_acquire_done - marks the end of the acquire phase |
| 145 | * @ctx: the acquire context |
| 146 | * |
| 147 | * Marks the end of the acquire phase, any further w/w mutex lock calls using |
| 148 | * this context are forbidden. |
| 149 | * |
| 150 | * Calling this function is optional, it is just useful to document w/w mutex |
| 151 | * code and clearly designated the acquire phase from actually using the locked |
| 152 | * data structures. |
| 153 | */ |
| 154 | static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) |
| 155 | { |
| 156 | #ifdef CONFIG_DEBUG_MUTEXES |
| 157 | lockdep_assert_held(ctx); |
| 158 | |
| 159 | DEBUG_LOCKS_WARN_ON(ctx->done_acquire); |
| 160 | ctx->done_acquire = 1; |
| 161 | #endif |
| 162 | } |
| 163 | |
| 164 | /** |
| 165 | * ww_acquire_fini - releases a w/w acquire context |
| 166 | * @ctx: the acquire context to free |
| 167 | * |
| 168 | * Releases a w/w acquire context. This must be called _after_ all acquired w/w |
| 169 | * mutexes have been released with ww_mutex_unlock. |
| 170 | */ |
| 171 | static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) |
| 172 | { |
| 173 | #ifdef CONFIG_DEBUG_MUTEXES |
| 174 | mutex_release(&ctx->dep_map, 0, _THIS_IP_); |
| 175 | |
| 176 | DEBUG_LOCKS_WARN_ON(ctx->acquired); |
Masahiro Yamada | 97f2645 | 2016-08-03 13:45:50 -0700 | [diff] [blame] | 177 | if (!IS_ENABLED(CONFIG_PROVE_LOCKING)) |
Maarten Lankhorst | 1b375dc | 2013-07-05 09:29:32 +0200 | [diff] [blame] | 178 | /* |
| 179 | * lockdep will normally handle this, |
| 180 | * but fail without anyway |
| 181 | */ |
| 182 | ctx->done_acquire = 1; |
| 183 | |
Masahiro Yamada | 97f2645 | 2016-08-03 13:45:50 -0700 | [diff] [blame] | 184 | if (!IS_ENABLED(CONFIG_DEBUG_LOCK_ALLOC)) |
Maarten Lankhorst | 1b375dc | 2013-07-05 09:29:32 +0200 | [diff] [blame] | 185 | /* ensure ww_acquire_fini will still fail if called twice */ |
| 186 | ctx->acquired = ~0U; |
| 187 | #endif |
| 188 | } |
| 189 | |
Maarten Lankhorst | 1b375dc | 2013-07-05 09:29:32 +0200 | [diff] [blame] | 190 | /** |
| 191 | * ww_mutex_lock - acquire the w/w mutex |
| 192 | * @lock: the mutex to be acquired |
| 193 | * @ctx: w/w acquire context, or NULL to acquire only a single lock. |
| 194 | * |
| 195 | * Lock the w/w mutex exclusively for this task. |
| 196 | * |
| 197 | * Deadlocks within a given w/w class of locks are detected and handled with the |
| 198 | * wait/wound algorithm. If the lock isn't immediately avaiable this function |
| 199 | * will either sleep until it is (wait case). Or it selects the current context |
| 200 | * for backing off by returning -EDEADLK (wound case). Trying to acquire the |
| 201 | * same lock with the same context twice is also detected and signalled by |
| 202 | * returning -EALREADY. Returns 0 if the mutex was successfully acquired. |
| 203 | * |
| 204 | * In the wound case the caller must release all currently held w/w mutexes for |
| 205 | * the given context and then wait for this contending lock to be available by |
| 206 | * calling ww_mutex_lock_slow. Alternatively callers can opt to not acquire this |
| 207 | * lock and proceed with trying to acquire further w/w mutexes (e.g. when |
| 208 | * scanning through lru lists trying to free resources). |
| 209 | * |
| 210 | * The mutex must later on be released by the same task that |
| 211 | * acquired it. The task may not exit without first unlocking the mutex. Also, |
| 212 | * kernel memory where the mutex resides must not be freed with the mutex still |
| 213 | * locked. The mutex must first be initialized (or statically defined) before it |
| 214 | * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be |
| 215 | * of the same w/w lock class as was used to initialize the acquire context. |
| 216 | * |
| 217 | * A mutex acquired with this function must be released with ww_mutex_unlock. |
| 218 | */ |
Ingo Molnar | 23b19ec | 2017-01-14 12:11:59 +0100 | [diff] [blame] | 219 | extern int /* __must_check */ ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx); |
Maarten Lankhorst | 1b375dc | 2013-07-05 09:29:32 +0200 | [diff] [blame] | 220 | |
| 221 | /** |
| 222 | * ww_mutex_lock_interruptible - acquire the w/w mutex, interruptible |
| 223 | * @lock: the mutex to be acquired |
| 224 | * @ctx: w/w acquire context |
| 225 | * |
| 226 | * Lock the w/w mutex exclusively for this task. |
| 227 | * |
| 228 | * Deadlocks within a given w/w class of locks are detected and handled with the |
| 229 | * wait/wound algorithm. If the lock isn't immediately avaiable this function |
| 230 | * will either sleep until it is (wait case). Or it selects the current context |
| 231 | * for backing off by returning -EDEADLK (wound case). Trying to acquire the |
| 232 | * same lock with the same context twice is also detected and signalled by |
| 233 | * returning -EALREADY. Returns 0 if the mutex was successfully acquired. If a |
| 234 | * signal arrives while waiting for the lock then this function returns -EINTR. |
| 235 | * |
| 236 | * In the wound case the caller must release all currently held w/w mutexes for |
| 237 | * the given context and then wait for this contending lock to be available by |
| 238 | * calling ww_mutex_lock_slow_interruptible. Alternatively callers can opt to |
| 239 | * not acquire this lock and proceed with trying to acquire further w/w mutexes |
| 240 | * (e.g. when scanning through lru lists trying to free resources). |
| 241 | * |
| 242 | * The mutex must later on be released by the same task that |
| 243 | * acquired it. The task may not exit without first unlocking the mutex. Also, |
| 244 | * kernel memory where the mutex resides must not be freed with the mutex still |
| 245 | * locked. The mutex must first be initialized (or statically defined) before it |
| 246 | * can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be |
| 247 | * of the same w/w lock class as was used to initialize the acquire context. |
| 248 | * |
| 249 | * A mutex acquired with this function must be released with ww_mutex_unlock. |
| 250 | */ |
Nicolai Hähnle | c5470b2 | 2016-12-21 19:46:33 +0100 | [diff] [blame] | 251 | extern int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock, |
| 252 | struct ww_acquire_ctx *ctx); |
Maarten Lankhorst | 1b375dc | 2013-07-05 09:29:32 +0200 | [diff] [blame] | 253 | |
| 254 | /** |
| 255 | * ww_mutex_lock_slow - slowpath acquiring of the w/w mutex |
| 256 | * @lock: the mutex to be acquired |
| 257 | * @ctx: w/w acquire context |
| 258 | * |
| 259 | * Acquires a w/w mutex with the given context after a wound case. This function |
| 260 | * will sleep until the lock becomes available. |
| 261 | * |
| 262 | * The caller must have released all w/w mutexes already acquired with the |
| 263 | * context and then call this function on the contended lock. |
| 264 | * |
| 265 | * Afterwards the caller may continue to (re)acquire the other w/w mutexes it |
| 266 | * needs with ww_mutex_lock. Note that the -EALREADY return code from |
| 267 | * ww_mutex_lock can be used to avoid locking this contended mutex twice. |
| 268 | * |
| 269 | * It is forbidden to call this function with any other w/w mutexes associated |
| 270 | * with the context held. It is forbidden to call this on anything else than the |
| 271 | * contending mutex. |
| 272 | * |
| 273 | * Note that the slowpath lock acquiring can also be done by calling |
| 274 | * ww_mutex_lock directly. This function here is simply to help w/w mutex |
| 275 | * locking code readability by clearly denoting the slowpath. |
| 276 | */ |
| 277 | static inline void |
| 278 | ww_mutex_lock_slow(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
| 279 | { |
| 280 | int ret; |
| 281 | #ifdef CONFIG_DEBUG_MUTEXES |
| 282 | DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); |
| 283 | #endif |
| 284 | ret = ww_mutex_lock(lock, ctx); |
| 285 | (void)ret; |
| 286 | } |
| 287 | |
| 288 | /** |
| 289 | * ww_mutex_lock_slow_interruptible - slowpath acquiring of the w/w mutex, interruptible |
| 290 | * @lock: the mutex to be acquired |
| 291 | * @ctx: w/w acquire context |
| 292 | * |
| 293 | * Acquires a w/w mutex with the given context after a wound case. This function |
| 294 | * will sleep until the lock becomes available and returns 0 when the lock has |
| 295 | * been acquired. If a signal arrives while waiting for the lock then this |
| 296 | * function returns -EINTR. |
| 297 | * |
| 298 | * The caller must have released all w/w mutexes already acquired with the |
| 299 | * context and then call this function on the contended lock. |
| 300 | * |
| 301 | * Afterwards the caller may continue to (re)acquire the other w/w mutexes it |
| 302 | * needs with ww_mutex_lock. Note that the -EALREADY return code from |
| 303 | * ww_mutex_lock can be used to avoid locking this contended mutex twice. |
| 304 | * |
| 305 | * It is forbidden to call this function with any other w/w mutexes associated |
| 306 | * with the given context held. It is forbidden to call this on anything else |
| 307 | * than the contending mutex. |
| 308 | * |
| 309 | * Note that the slowpath lock acquiring can also be done by calling |
| 310 | * ww_mutex_lock_interruptible directly. This function here is simply to help |
| 311 | * w/w mutex locking code readability by clearly denoting the slowpath. |
| 312 | */ |
| 313 | static inline int __must_check |
| 314 | ww_mutex_lock_slow_interruptible(struct ww_mutex *lock, |
| 315 | struct ww_acquire_ctx *ctx) |
| 316 | { |
| 317 | #ifdef CONFIG_DEBUG_MUTEXES |
| 318 | DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); |
| 319 | #endif |
| 320 | return ww_mutex_lock_interruptible(lock, ctx); |
| 321 | } |
| 322 | |
| 323 | extern void ww_mutex_unlock(struct ww_mutex *lock); |
| 324 | |
| 325 | /** |
| 326 | * ww_mutex_trylock - tries to acquire the w/w mutex without acquire context |
| 327 | * @lock: mutex to lock |
| 328 | * |
| 329 | * Trylocks a mutex without acquire context, so no deadlock detection is |
| 330 | * possible. Returns 1 if the mutex has been acquired successfully, 0 otherwise. |
| 331 | */ |
| 332 | static inline int __must_check ww_mutex_trylock(struct ww_mutex *lock) |
| 333 | { |
| 334 | return mutex_trylock(&lock->base); |
| 335 | } |
| 336 | |
| 337 | /*** |
| 338 | * ww_mutex_destroy - mark a w/w mutex unusable |
| 339 | * @lock: the mutex to be destroyed |
| 340 | * |
| 341 | * This function marks the mutex uninitialized, and any subsequent |
| 342 | * use of the mutex is forbidden. The mutex must not be locked when |
| 343 | * this function is called. |
| 344 | */ |
| 345 | static inline void ww_mutex_destroy(struct ww_mutex *lock) |
| 346 | { |
| 347 | mutex_destroy(&lock->base); |
| 348 | } |
| 349 | |
| 350 | /** |
| 351 | * ww_mutex_is_locked - is the w/w mutex locked |
| 352 | * @lock: the mutex to be queried |
| 353 | * |
| 354 | * Returns 1 if the mutex is locked, 0 if unlocked. |
| 355 | */ |
| 356 | static inline bool ww_mutex_is_locked(struct ww_mutex *lock) |
| 357 | { |
| 358 | return mutex_is_locked(&lock->base); |
| 359 | } |
| 360 | |
| 361 | #endif |