int __pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock) { int result = EBUSY; if (ELIDE_TRYLOCK (rwlock->__data.__rwelision, rwlock->__data.__lock == 0 && rwlock->__data.__nr_readers == 0 && rwlock->__data.__writer, 0)) return 0; lll_lock (rwlock->__data.__lock, rwlock->__data.__shared); if (rwlock->__data.__writer == 0 && (rwlock->__data.__nr_writers_queued == 0 || PTHREAD_RWLOCK_PREFER_READER_P (rwlock))) { if (__glibc_unlikely (++rwlock->__data.__nr_readers == 0)) { --rwlock->__data.__nr_readers; result = EAGAIN; } else result = 0; } lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared); return result; }
int __pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock) { int result = EBUSY; bool wake = false; int futex_shared = rwlock->__data.__shared == LLL_PRIVATE ? FUTEX_PRIVATE : FUTEX_SHARED; if (ELIDE_TRYLOCK (rwlock->__data.__rwelision, rwlock->__data.__lock == 0 && rwlock->__data.__nr_readers == 0 && rwlock->__data.__writer, 0)) return 0; lll_lock (rwlock->__data.__lock, rwlock->__data.__shared); if (rwlock->__data.__writer == 0 && (rwlock->__data.__nr_writers_queued == 0 || PTHREAD_RWLOCK_PREFER_READER_P (rwlock))) { if (__glibc_unlikely (++rwlock->__data.__nr_readers == 0)) { --rwlock->__data.__nr_readers; result = EAGAIN; } else { result = 0; /* See pthread_rwlock_rdlock. */ if (rwlock->__data.__nr_readers == 1 && rwlock->__data.__nr_readers_queued > 0 && rwlock->__data.__nr_writers_queued > 0) { ++rwlock->__data.__readers_wakeup; wake = true; } } } lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared); if (wake) futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX, futex_shared); return result; }