diff options
Diffstat (limited to 'nptl/pthread_mutex_lock.c')
| -rw-r--r-- | nptl/pthread_mutex_lock.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c index bdfa529f63..c92bbeea22 100644 --- a/nptl/pthread_mutex_lock.c +++ b/nptl/pthread_mutex_lock.c @@ -182,6 +182,11 @@ __pthread_mutex_lock_full (pthread_mutex_t *mutex) &mutex->__data.__list.__next); oldval = mutex->__data.__lock; + /* This is set to FUTEX_WAITERS iff we might have shared the + FUTEX_WAITERS flag with other threads, and therefore need to keep it + set to avoid lost wake-ups. We have the same requirement in the + simple mutex algorithm. */ + unsigned int assume_other_futex_waiters = 0; do { again: @@ -190,9 +195,11 @@ __pthread_mutex_lock_full (pthread_mutex_t *mutex) /* The previous owner died. Try locking the mutex. */ int newval = id; #ifdef NO_INCR + /* We are not taking assume_other_futex_waiters into accoount + here simply because we'll set FUTEX_WAITERS anyway. */ newval |= FUTEX_WAITERS; #else - newval |= (oldval & FUTEX_WAITERS); + newval |= (oldval & FUTEX_WAITERS) | assume_other_futex_waiters; #endif newval @@ -253,7 +260,11 @@ __pthread_mutex_lock_full (pthread_mutex_t *mutex) } } - oldval = LLL_ROBUST_MUTEX_LOCK (mutex, id); + oldval = LLL_ROBUST_MUTEX_LOCK (mutex, + id | assume_other_futex_waiters); + /* See above. We set FUTEX_WAITERS and might have shared this flag + with other threads; thus, we need to preserve it. */ + assume_other_futex_waiters = FUTEX_WAITERS; if (__builtin_expect (mutex->__data.__owner == PTHREAD_MUTEX_NOTRECOVERABLE, 0)) |