diff options
| author | Rich Felker <dalias@aerifal.cx> | 2011-09-25 21:14:40 -0400 |
|---|---|---|
| committer | Rich Felker <dalias@aerifal.cx> | 2011-09-25 21:14:40 -0400 |
| commit | c11d1e696723f41d7873332e51fb6858b417fa5f (patch) | |
| tree | 4109f54cb4bd53b6e21086bf905d53aa19fe7a28 /src/thread/pthread_cond_broadcast.c | |
| parent | cf940165d4caf132405a3fe3df58b57eb735ac04 (diff) | |
| download | musl-c11d1e696723f41d7873332e51fb6858b417fa5f.tar.gz | |
revert previous change in cond var waiter move
using swap has a race condition: the waiters must be added to the
mutex waiter count *before* they are taken off the cond var waiter
count, or wake events can be lost.
Diffstat (limited to 'src/thread/pthread_cond_broadcast.c')
| -rw-r--r-- | src/thread/pthread_cond_broadcast.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/src/thread/pthread_cond_broadcast.c b/src/thread/pthread_cond_broadcast.c index 4fab9994..7e5ea91c 100644 --- a/src/thread/pthread_cond_broadcast.c +++ b/src/thread/pthread_cond_broadcast.c @@ -30,8 +30,12 @@ int pthread_cond_broadcast(pthread_cond_t *c) } /* Move waiter count to the mutex */ - w = a_swap(&c->_c_waiters, 0); - a_fetch_add(&m->_m_waiters, w); + for (;;) { + w = c->_c_waiters; + a_fetch_add(&m->_m_waiters, w); + if (a_cas(&c->_c_waiters, w, 0) == w) break; + a_fetch_add(&m->_m_waiters, -w); + } /* Perform the futex requeue, waking one waiter unless we know * that the calling thread holds the mutex. */ |