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Merge "Avoid tsan warning about pthread_mutex_destroy."

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Yabin Cui 2015-11-19 01:55:25 +00:00 committed by Gerrit Code Review
commit ea5bb151af
1 changed files with 16 additions and 9 deletions
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21
libc/bionic/pthread_mutex.cpp
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@ -166,10 +166,13 @@ int pthread_mutexattr_getpshared(const pthread_mutexattr_t* attr, int* pshared)
#define MUTEX_STATE_BITS_LOCKED_UNCONTENDED MUTEX_STATE_TO_BITS(MUTEX_STATE_LOCKED_UNCONTENDED)
#define MUTEX_STATE_BITS_LOCKED_CONTENDED MUTEX_STATE_TO_BITS(MUTEX_STATE_LOCKED_CONTENDED)
/* return true iff the mutex if locked with no waiters */
// Return true iff the mutex is unlocked.
#define MUTEX_STATE_BITS_IS_UNLOCKED(v) (((v) & MUTEX_STATE_MASK) == MUTEX_STATE_BITS_UNLOCKED)
// Return true iff the mutex is locked with no waiters.
#define MUTEX_STATE_BITS_IS_LOCKED_UNCONTENDED(v) (((v) & MUTEX_STATE_MASK) == MUTEX_STATE_BITS_LOCKED_UNCONTENDED)
/* return true iff the mutex if locked with maybe waiters */
// return true iff the mutex is locked with maybe waiters.
#define MUTEX_STATE_BITS_IS_LOCKED_CONTENDED(v) (((v) & MUTEX_STATE_MASK) == MUTEX_STATE_BITS_LOCKED_CONTENDED)
/* used to flip from LOCKED_UNCONTENDED to LOCKED_CONTENDED */
@ -637,10 +640,14 @@ int pthread_mutex_timedlock(pthread_mutex_t* mutex_interface, const timespec* ab
}
int pthread_mutex_destroy(pthread_mutex_t* mutex_interface) {
// Use trylock to ensure that the mutex is valid and not already locked.
int error = pthread_mutex_trylock(mutex_interface);
if (error != 0) {
return error;
}
pthread_mutex_internal_t* mutex = __get_internal_mutex(mutex_interface);
uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed);
// Store 0xffff to make the mutex unusable. Although POSIX standard says it is undefined
// behavior to destroy a locked mutex, we prefer not to change mutex->state in that situation.
if (MUTEX_STATE_BITS_IS_UNLOCKED(old_state) &&
atomic_compare_exchange_strong_explicit(&mutex->state, &old_state, 0xffff,
memory_order_relaxed, memory_order_relaxed)) {
return 0;
}
return EBUSY;
}