Blame view
kernel/mutex.c
13.1 KB
6053ee3b3 [PATCH] mutex sub... |
1 2 3 4 5 6 7 8 9 10 11 12 |
/* * kernel/mutex.c * * Mutexes: blocking mutual exclusion locks * * Started by Ingo Molnar: * * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> * * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and * David Howells for suggestions and improvements. * |
0d66bf6d3 mutex: implement ... |
13 14 15 16 17 |
* - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline * from the -rt tree, where it was originally implemented for rtmutexes * by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale * and Sven Dietrich. * |
6053ee3b3 [PATCH] mutex sub... |
18 19 20 21 22 23 24 |
* Also see Documentation/mutex-design.txt. */ #include <linux/mutex.h> #include <linux/sched.h> #include <linux/module.h> #include <linux/spinlock.h> #include <linux/interrupt.h> |
9a11b49a8 [PATCH] lockdep: ... |
25 |
#include <linux/debug_locks.h> |
6053ee3b3 [PATCH] mutex sub... |
26 27 28 29 30 31 32 33 34 35 36 37 |
/* * In the DEBUG case we are using the "NULL fastpath" for mutexes, * which forces all calls into the slowpath: */ #ifdef CONFIG_DEBUG_MUTEXES # include "mutex-debug.h" # include <asm-generic/mutex-null.h> #else # include "mutex.h" # include <asm/mutex.h> #endif |
ef5d4707b [PATCH] lockdep: ... |
38 39 |
void __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) |
6053ee3b3 [PATCH] mutex sub... |
40 41 42 43 |
{ atomic_set(&lock->count, 1); spin_lock_init(&lock->wait_lock); INIT_LIST_HEAD(&lock->wait_list); |
0d66bf6d3 mutex: implement ... |
44 |
mutex_clear_owner(lock); |
6053ee3b3 [PATCH] mutex sub... |
45 |
|
ef5d4707b [PATCH] lockdep: ... |
46 |
debug_mutex_init(lock, name, key); |
6053ee3b3 [PATCH] mutex sub... |
47 48 49 |
} EXPORT_SYMBOL(__mutex_init); |
e4564f79d lockdep: fixup mu... |
50 |
#ifndef CONFIG_DEBUG_LOCK_ALLOC |
6053ee3b3 [PATCH] mutex sub... |
51 52 53 54 55 56 |
/* * We split the mutex lock/unlock logic into separate fastpath and * slowpath functions, to reduce the register pressure on the fastpath. * We also put the fastpath first in the kernel image, to make sure the * branch is predicted by the CPU as default-untaken. */ |
7918baa55 mutex: __used is ... |
57 |
static __used noinline void __sched |
9a11b49a8 [PATCH] lockdep: ... |
58 |
__mutex_lock_slowpath(atomic_t *lock_count); |
6053ee3b3 [PATCH] mutex sub... |
59 |
|
ef5dc121d mutex: Fix annota... |
60 |
/** |
6053ee3b3 [PATCH] mutex sub... |
61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 |
* mutex_lock - acquire the mutex * @lock: the mutex to be acquired * * Lock the mutex exclusively for this task. If the mutex is not * available right now, it will sleep until it can get it. * * The mutex must later on be released by the same task that * acquired it. Recursive locking is not allowed. The task * may not exit without first unlocking the mutex. Also, kernel * memory where the mutex resides mutex must not be freed with * the mutex still locked. The mutex must first be initialized * (or statically defined) before it can be locked. memset()-ing * the mutex to 0 is not allowed. * * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging * checks that will enforce the restrictions and will also do * deadlock debugging. ) * * This function is similar to (but not equivalent to) down(). */ |
b09d2501e mutex: drop "inli... |
81 |
void __sched mutex_lock(struct mutex *lock) |
6053ee3b3 [PATCH] mutex sub... |
82 |
{ |
c544bdb19 [PATCH] mark mute... |
83 |
might_sleep(); |
6053ee3b3 [PATCH] mutex sub... |
84 85 86 |
/* * The locking fastpath is the 1->0 transition from * 'unlocked' into 'locked' state. |
6053ee3b3 [PATCH] mutex sub... |
87 88 |
*/ __mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath); |
0d66bf6d3 mutex: implement ... |
89 |
mutex_set_owner(lock); |
6053ee3b3 [PATCH] mutex sub... |
90 91 92 |
} EXPORT_SYMBOL(mutex_lock); |
e4564f79d lockdep: fixup mu... |
93 |
#endif |
6053ee3b3 [PATCH] mutex sub... |
94 |
|
7918baa55 mutex: __used is ... |
95 |
static __used noinline void __sched __mutex_unlock_slowpath(atomic_t *lock_count); |
6053ee3b3 [PATCH] mutex sub... |
96 |
|
ef5dc121d mutex: Fix annota... |
97 |
/** |
6053ee3b3 [PATCH] mutex sub... |
98 99 100 101 102 103 104 105 106 107 |
* mutex_unlock - release the mutex * @lock: the mutex to be released * * Unlock a mutex that has been locked by this task previously. * * This function must not be used in interrupt context. Unlocking * of a not locked mutex is not allowed. * * This function is similar to (but not equivalent to) up(). */ |
7ad5b3a50 kernel: remove fa... |
108 |
void __sched mutex_unlock(struct mutex *lock) |
6053ee3b3 [PATCH] mutex sub... |
109 110 111 112 |
{ /* * The unlocking fastpath is the 0->1 transition from 'locked' * into 'unlocked' state: |
6053ee3b3 [PATCH] mutex sub... |
113 |
*/ |
0d66bf6d3 mutex: implement ... |
114 115 116 117 118 119 120 121 |
#ifndef CONFIG_DEBUG_MUTEXES /* * When debugging is enabled we must not clear the owner before time, * the slow path will always be taken, and that clears the owner field * after verifying that it was indeed current. */ mutex_clear_owner(lock); #endif |
6053ee3b3 [PATCH] mutex sub... |
122 123 124 125 126 127 128 129 130 |
__mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath); } EXPORT_SYMBOL(mutex_unlock); /* * Lock a mutex (possibly interruptible), slowpath: */ static inline int __sched |
e4564f79d lockdep: fixup mu... |
131 132 |
__mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, unsigned long ip) |
6053ee3b3 [PATCH] mutex sub... |
133 134 135 |
{ struct task_struct *task = current; struct mutex_waiter waiter; |
1fb00c6cb [PATCH] work arou... |
136 |
unsigned long flags; |
6053ee3b3 [PATCH] mutex sub... |
137 |
|
41719b030 mutex: preemption... |
138 |
preempt_disable(); |
0d66bf6d3 mutex: implement ... |
139 |
mutex_acquire(&lock->dep_map, subclass, 0, ip); |
c02260277 mutex: Better con... |
140 141 |
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER |
0d66bf6d3 mutex: implement ... |
142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 |
/* * Optimistic spinning. * * We try to spin for acquisition when we find that there are no * pending waiters and the lock owner is currently running on a * (different) CPU. * * The rationale is that if the lock owner is running, it is likely to * release the lock soon. * * Since this needs the lock owner, and this mutex implementation * doesn't track the owner atomically in the lock field, we need to * track it non-atomically. * * We can't do this for DEBUG_MUTEXES because that relies on wait_lock * to serialize everything. */ for (;;) { struct thread_info *owner; /* |
fd6be105b mutex: Fix optimi... |
164 165 166 167 168 169 170 |
* If we own the BKL, then don't spin. The owner of * the mutex might be waiting on us to release the BKL. */ if (unlikely(current->lock_depth >= 0)) break; /* |
0d66bf6d3 mutex: implement ... |
171 172 173 174 175 176 |
* If there's an owner, wait for it to either * release the lock or go to sleep. */ owner = ACCESS_ONCE(lock->owner); if (owner && !mutex_spin_on_owner(lock, owner)) break; |
ac6e60ee4 mutex: adaptive s... |
177 178 179 180 181 182 |
if (atomic_cmpxchg(&lock->count, 1, 0) == 1) { lock_acquired(&lock->dep_map, ip); mutex_set_owner(lock); preempt_enable(); return 0; } |
0d66bf6d3 mutex: implement ... |
183 184 185 186 187 188 189 190 |
/* * When there's no owner, we might have preempted between the * owner acquiring the lock and setting the owner field. If * we're an RT task that will live-lock because we won't let * the owner complete. */ if (!owner && (need_resched() || rt_task(task))) break; |
0d66bf6d3 mutex: implement ... |
191 192 193 194 195 196 197 198 199 |
/* * The cpu_relax() call is a compiler barrier which forces * everything in this loop to be re-loaded. We don't need * memory barriers as we'll eventually observe the right * values at the cost of a few extra spins. */ cpu_relax(); } #endif |
1fb00c6cb [PATCH] work arou... |
200 |
spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b3 [PATCH] mutex sub... |
201 |
|
9a11b49a8 [PATCH] lockdep: ... |
202 |
debug_mutex_lock_common(lock, &waiter); |
c9f4f06d3 wrap access to th... |
203 |
debug_mutex_add_waiter(lock, &waiter, task_thread_info(task)); |
6053ee3b3 [PATCH] mutex sub... |
204 205 206 207 |
/* add waiting tasks to the end of the waitqueue (FIFO): */ list_add_tail(&waiter.list, &lock->wait_list); waiter.task = task; |
93d81d1ac mutex: small cleanup |
208 |
if (atomic_xchg(&lock->count, -1) == 1) |
4fe87745a lockstat: hook in... |
209 |
goto done; |
e4564f79d lockdep: fixup mu... |
210 |
lock_contended(&lock->dep_map, ip); |
4fe87745a lockstat: hook in... |
211 |
|
6053ee3b3 [PATCH] mutex sub... |
212 213 214 215 216 217 218 219 220 221 |
for (;;) { /* * Lets try to take the lock again - this is needed even if * we get here for the first time (shortly after failing to * acquire the lock), to make sure that we get a wakeup once * it's unlocked. Later on, if we sleep, this is the * operation that gives us the lock. We xchg it to -1, so * that when we release the lock, we properly wake up the * other waiters: */ |
93d81d1ac mutex: small cleanup |
222 |
if (atomic_xchg(&lock->count, -1) == 1) |
6053ee3b3 [PATCH] mutex sub... |
223 224 225 226 227 228 |
break; /* * got a signal? (This code gets eliminated in the * TASK_UNINTERRUPTIBLE case.) */ |
6ad36762d __mutex_lock_comm... |
229 |
if (unlikely(signal_pending_state(state, task))) { |
ad776537c Add mutex_lock_ki... |
230 231 |
mutex_remove_waiter(lock, &waiter, task_thread_info(task)); |
e4564f79d lockdep: fixup mu... |
232 |
mutex_release(&lock->dep_map, 1, ip); |
1fb00c6cb [PATCH] work arou... |
233 |
spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b3 [PATCH] mutex sub... |
234 235 |
debug_mutex_free_waiter(&waiter); |
41719b030 mutex: preemption... |
236 |
preempt_enable(); |
6053ee3b3 [PATCH] mutex sub... |
237 238 239 240 241 |
return -EINTR; } __set_task_state(task, state); /* didnt get the lock, go to sleep: */ |
1fb00c6cb [PATCH] work arou... |
242 |
spin_unlock_mutex(&lock->wait_lock, flags); |
ff743345b sched: remove ext... |
243 244 245 |
preempt_enable_no_resched(); schedule(); preempt_disable(); |
1fb00c6cb [PATCH] work arou... |
246 |
spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b3 [PATCH] mutex sub... |
247 |
} |
4fe87745a lockstat: hook in... |
248 |
done: |
c7e78cff6 lockstat: contend... |
249 |
lock_acquired(&lock->dep_map, ip); |
6053ee3b3 [PATCH] mutex sub... |
250 |
/* got the lock - rejoice! */ |
0d66bf6d3 mutex: implement ... |
251 252 |
mutex_remove_waiter(lock, &waiter, current_thread_info()); mutex_set_owner(lock); |
6053ee3b3 [PATCH] mutex sub... |
253 254 255 256 |
/* set it to 0 if there are no waiters left: */ if (likely(list_empty(&lock->wait_list))) atomic_set(&lock->count, 0); |
1fb00c6cb [PATCH] work arou... |
257 |
spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b3 [PATCH] mutex sub... |
258 259 |
debug_mutex_free_waiter(&waiter); |
41719b030 mutex: preemption... |
260 |
preempt_enable(); |
6053ee3b3 [PATCH] mutex sub... |
261 |
|
6053ee3b3 [PATCH] mutex sub... |
262 263 |
return 0; } |
ef5d4707b [PATCH] lockdep: ... |
264 265 266 267 268 |
#ifdef CONFIG_DEBUG_LOCK_ALLOC void __sched mutex_lock_nested(struct mutex *lock, unsigned int subclass) { might_sleep(); |
e4564f79d lockdep: fixup mu... |
269 |
__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, _RET_IP_); |
ef5d4707b [PATCH] lockdep: ... |
270 271 272 |
} EXPORT_SYMBOL_GPL(mutex_lock_nested); |
d63a5a74d [PATCH] lockdep: ... |
273 274 |
int __sched |
ad776537c Add mutex_lock_ki... |
275 276 277 278 279 280 281 282 |
mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass) { might_sleep(); return __mutex_lock_common(lock, TASK_KILLABLE, subclass, _RET_IP_); } EXPORT_SYMBOL_GPL(mutex_lock_killable_nested); int __sched |
d63a5a74d [PATCH] lockdep: ... |
283 284 285 |
mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass) { might_sleep(); |
0d66bf6d3 mutex: implement ... |
286 287 |
return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, subclass, _RET_IP_); |
d63a5a74d [PATCH] lockdep: ... |
288 289 290 |
} EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested); |
ef5d4707b [PATCH] lockdep: ... |
291 |
#endif |
6053ee3b3 [PATCH] mutex sub... |
292 293 294 |
/* * Release the lock, slowpath: */ |
7ad5b3a50 kernel: remove fa... |
295 |
static inline void |
ef5d4707b [PATCH] lockdep: ... |
296 |
__mutex_unlock_common_slowpath(atomic_t *lock_count, int nested) |
6053ee3b3 [PATCH] mutex sub... |
297 |
{ |
02706647a [PATCH] mutex: tr... |
298 |
struct mutex *lock = container_of(lock_count, struct mutex, count); |
1fb00c6cb [PATCH] work arou... |
299 |
unsigned long flags; |
6053ee3b3 [PATCH] mutex sub... |
300 |
|
1fb00c6cb [PATCH] work arou... |
301 |
spin_lock_mutex(&lock->wait_lock, flags); |
ef5d4707b [PATCH] lockdep: ... |
302 |
mutex_release(&lock->dep_map, nested, _RET_IP_); |
9a11b49a8 [PATCH] lockdep: ... |
303 |
debug_mutex_unlock(lock); |
6053ee3b3 [PATCH] mutex sub... |
304 305 306 307 308 309 310 311 |
/* * some architectures leave the lock unlocked in the fastpath failure * case, others need to leave it locked. In the later case we have to * unlock it here */ if (__mutex_slowpath_needs_to_unlock()) atomic_set(&lock->count, 1); |
6053ee3b3 [PATCH] mutex sub... |
312 313 314 315 316 317 318 319 320 321 |
if (!list_empty(&lock->wait_list)) { /* get the first entry from the wait-list: */ struct mutex_waiter *waiter = list_entry(lock->wait_list.next, struct mutex_waiter, list); debug_mutex_wake_waiter(lock, waiter); wake_up_process(waiter->task); } |
1fb00c6cb [PATCH] work arou... |
322 |
spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b3 [PATCH] mutex sub... |
323 324 325 |
} /* |
9a11b49a8 [PATCH] lockdep: ... |
326 327 |
* Release the lock, slowpath: */ |
7918baa55 mutex: __used is ... |
328 |
static __used noinline void |
9a11b49a8 [PATCH] lockdep: ... |
329 330 |
__mutex_unlock_slowpath(atomic_t *lock_count) { |
ef5d4707b [PATCH] lockdep: ... |
331 |
__mutex_unlock_common_slowpath(lock_count, 1); |
9a11b49a8 [PATCH] lockdep: ... |
332 |
} |
e4564f79d lockdep: fixup mu... |
333 |
#ifndef CONFIG_DEBUG_LOCK_ALLOC |
9a11b49a8 [PATCH] lockdep: ... |
334 |
/* |
6053ee3b3 [PATCH] mutex sub... |
335 336 337 |
* Here come the less common (and hence less performance-critical) APIs: * mutex_lock_interruptible() and mutex_trylock(). */ |
7ad5b3a50 kernel: remove fa... |
338 |
static noinline int __sched |
ad776537c Add mutex_lock_ki... |
339 |
__mutex_lock_killable_slowpath(atomic_t *lock_count); |
7ad5b3a50 kernel: remove fa... |
340 |
static noinline int __sched |
9a11b49a8 [PATCH] lockdep: ... |
341 |
__mutex_lock_interruptible_slowpath(atomic_t *lock_count); |
6053ee3b3 [PATCH] mutex sub... |
342 |
|
ef5dc121d mutex: Fix annota... |
343 344 |
/** * mutex_lock_interruptible - acquire the mutex, interruptible |
6053ee3b3 [PATCH] mutex sub... |
345 346 347 348 349 350 351 352 353 |
* @lock: the mutex to be acquired * * Lock the mutex like mutex_lock(), and return 0 if the mutex has * been acquired or sleep until the mutex becomes available. If a * signal arrives while waiting for the lock then this function * returns -EINTR. * * This function is similar to (but not equivalent to) down_interruptible(). */ |
7ad5b3a50 kernel: remove fa... |
354 |
int __sched mutex_lock_interruptible(struct mutex *lock) |
6053ee3b3 [PATCH] mutex sub... |
355 |
{ |
0d66bf6d3 mutex: implement ... |
356 |
int ret; |
c544bdb19 [PATCH] mark mute... |
357 |
might_sleep(); |
0d66bf6d3 mutex: implement ... |
358 |
ret = __mutex_fastpath_lock_retval |
6053ee3b3 [PATCH] mutex sub... |
359 |
(&lock->count, __mutex_lock_interruptible_slowpath); |
0d66bf6d3 mutex: implement ... |
360 361 362 363 |
if (!ret) mutex_set_owner(lock); return ret; |
6053ee3b3 [PATCH] mutex sub... |
364 365 366 |
} EXPORT_SYMBOL(mutex_lock_interruptible); |
7ad5b3a50 kernel: remove fa... |
367 |
int __sched mutex_lock_killable(struct mutex *lock) |
ad776537c Add mutex_lock_ki... |
368 |
{ |
0d66bf6d3 mutex: implement ... |
369 |
int ret; |
ad776537c Add mutex_lock_ki... |
370 |
might_sleep(); |
0d66bf6d3 mutex: implement ... |
371 |
ret = __mutex_fastpath_lock_retval |
ad776537c Add mutex_lock_ki... |
372 |
(&lock->count, __mutex_lock_killable_slowpath); |
0d66bf6d3 mutex: implement ... |
373 374 375 376 |
if (!ret) mutex_set_owner(lock); return ret; |
ad776537c Add mutex_lock_ki... |
377 378 |
} EXPORT_SYMBOL(mutex_lock_killable); |
7918baa55 mutex: __used is ... |
379 |
static __used noinline void __sched |
e4564f79d lockdep: fixup mu... |
380 381 382 383 384 385 |
__mutex_lock_slowpath(atomic_t *lock_count) { struct mutex *lock = container_of(lock_count, struct mutex, count); __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0, _RET_IP_); } |
7ad5b3a50 kernel: remove fa... |
386 |
static noinline int __sched |
ad776537c Add mutex_lock_ki... |
387 388 389 390 391 392 |
__mutex_lock_killable_slowpath(atomic_t *lock_count) { struct mutex *lock = container_of(lock_count, struct mutex, count); return __mutex_lock_common(lock, TASK_KILLABLE, 0, _RET_IP_); } |
7ad5b3a50 kernel: remove fa... |
393 |
static noinline int __sched |
9a11b49a8 [PATCH] lockdep: ... |
394 |
__mutex_lock_interruptible_slowpath(atomic_t *lock_count) |
6053ee3b3 [PATCH] mutex sub... |
395 396 |
{ struct mutex *lock = container_of(lock_count, struct mutex, count); |
e4564f79d lockdep: fixup mu... |
397 |
return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, _RET_IP_); |
6053ee3b3 [PATCH] mutex sub... |
398 |
} |
e4564f79d lockdep: fixup mu... |
399 |
#endif |
6053ee3b3 [PATCH] mutex sub... |
400 401 402 403 404 405 406 407 |
/* * Spinlock based trylock, we take the spinlock and check whether we * can get the lock: */ static inline int __mutex_trylock_slowpath(atomic_t *lock_count) { struct mutex *lock = container_of(lock_count, struct mutex, count); |
1fb00c6cb [PATCH] work arou... |
408 |
unsigned long flags; |
6053ee3b3 [PATCH] mutex sub... |
409 |
int prev; |
1fb00c6cb [PATCH] work arou... |
410 |
spin_lock_mutex(&lock->wait_lock, flags); |
6053ee3b3 [PATCH] mutex sub... |
411 412 |
prev = atomic_xchg(&lock->count, -1); |
ef5d4707b [PATCH] lockdep: ... |
413 |
if (likely(prev == 1)) { |
0d66bf6d3 mutex: implement ... |
414 |
mutex_set_owner(lock); |
ef5d4707b [PATCH] lockdep: ... |
415 416 |
mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_); } |
0d66bf6d3 mutex: implement ... |
417 |
|
6053ee3b3 [PATCH] mutex sub... |
418 419 420 |
/* Set it back to 0 if there are no waiters: */ if (likely(list_empty(&lock->wait_list))) atomic_set(&lock->count, 0); |
1fb00c6cb [PATCH] work arou... |
421 |
spin_unlock_mutex(&lock->wait_lock, flags); |
6053ee3b3 [PATCH] mutex sub... |
422 423 424 |
return prev == 1; } |
ef5dc121d mutex: Fix annota... |
425 426 |
/** * mutex_trylock - try to acquire the mutex, without waiting |
6053ee3b3 [PATCH] mutex sub... |
427 428 429 430 431 432 |
* @lock: the mutex to be acquired * * Try to acquire the mutex atomically. Returns 1 if the mutex * has been acquired successfully, and 0 on contention. * * NOTE: this function follows the spin_trylock() convention, so |
ef5dc121d mutex: Fix annota... |
433 |
* it is negated from the down_trylock() return values! Be careful |
6053ee3b3 [PATCH] mutex sub... |
434 435 436 437 438 |
* about this when converting semaphore users to mutexes. * * This function must not be used in interrupt context. The * mutex must be released by the same task that acquired it. */ |
7ad5b3a50 kernel: remove fa... |
439 |
int __sched mutex_trylock(struct mutex *lock) |
6053ee3b3 [PATCH] mutex sub... |
440 |
{ |
0d66bf6d3 mutex: implement ... |
441 442 443 444 445 446 447 |
int ret; ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath); if (ret) mutex_set_owner(lock); return ret; |
6053ee3b3 [PATCH] mutex sub... |
448 |
} |
6053ee3b3 [PATCH] mutex sub... |
449 |
EXPORT_SYMBOL(mutex_trylock); |
a511e3f96 mutex: add atomic... |
450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 |
/** * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0 * @cnt: the atomic which we are to dec * @lock: the mutex to return holding if we dec to 0 * * return true and hold lock if we dec to 0, return false otherwise */ int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) { /* dec if we can't possibly hit 0 */ if (atomic_add_unless(cnt, -1, 1)) return 0; /* we might hit 0, so take the lock */ mutex_lock(lock); if (!atomic_dec_and_test(cnt)) { /* when we actually did the dec, we didn't hit 0 */ mutex_unlock(lock); return 0; } /* we hit 0, and we hold the lock */ return 1; } EXPORT_SYMBOL(atomic_dec_and_mutex_lock); |