diff options
Diffstat (limited to 'nptl/pthread_rwlock_trywrlock.c')
| -rw-r--r-- | nptl/pthread_rwlock_trywrlock.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/nptl/pthread_rwlock_trywrlock.c b/nptl/pthread_rwlock_trywrlock.c index fd37a71ce4..fae475cc70 100644 --- a/nptl/pthread_rwlock_trywrlock.c +++ b/nptl/pthread_rwlock_trywrlock.c @@ -46,8 +46,15 @@ __pthread_rwlock_trywrlock (pthread_rwlock_t *rwlock) &rwlock->__data.__readers, &r, r | PTHREAD_RWLOCK_WRPHASE | PTHREAD_RWLOCK_WRLOCKED)) { + /* We have become the primary writer and we cannot have shared + the PTHREAD_RWLOCK_FUTEX_USED flag with someone else, so we + can simply enable blocking (see full wrlock code). */ atomic_store_relaxed (&rwlock->__data.__writers_futex, 1); - atomic_store_relaxed (&rwlock->__data.__wrphase_futex, 1); + /* If we started a write phase, we need to enable readers to + wait. If we did not, we must not change it because other threads + may have set the PTHREAD_RWLOCK_FUTEX_USED in the meantime. */ + if ((r & PTHREAD_RWLOCK_WRPHASE) == 0) + atomic_store_relaxed (&rwlock->__data.__wrphase_futex, 1); atomic_store_relaxed (&rwlock->__data.__cur_writer, THREAD_GETMEM (THREAD_SELF, tid)); return 0; |