diff options
| author | Rich Felker <dalias@aerifal.cx> | 2011-08-02 20:31:15 -0400 |
|---|---|---|
| committer | Rich Felker <dalias@aerifal.cx> | 2011-08-02 20:31:15 -0400 |
| commit | c68de0be2fb649f91b31080224fb6e48084eaaee (patch) | |
| tree | d9495283490f37833ca6e32f4b6876ca10ac06eb /src/thread/pthread_mutex_trylock.c | |
| parent | 344ea148852ed02f280cb92f8fc1611529d60448 (diff) | |
| download | musl-c68de0be2fb649f91b31080224fb6e48084eaaee.tar.gz | |
avoid accessing mutex memory after atomic unlock
this change is needed to fix a race condition and ensure that it's
possible to unlock and destroy or unmap the mutex as soon as
pthread_mutex_lock succeeds. POSIX explicitly gives such an example in
the rationale and requires an implementation to allow such usage.
Diffstat (limited to 'src/thread/pthread_mutex_trylock.c')
| -rw-r--r-- | src/thread/pthread_mutex_trylock.c | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/src/thread/pthread_mutex_trylock.c b/src/thread/pthread_mutex_trylock.c index 1fb6d0f2..4a424bc9 100644 --- a/src/thread/pthread_mutex_trylock.c +++ b/src/thread/pthread_mutex_trylock.c @@ -2,15 +2,14 @@ int pthread_mutex_trylock(pthread_mutex_t *m) { - int tid; - int own; + int tid, old, own; pthread_t self; if (m->_m_type == PTHREAD_MUTEX_NORMAL) - return a_swap(&m->_m_lock, EBUSY); + return a_cas(&m->_m_lock, 0, EBUSY) & EBUSY; self = pthread_self(); - tid = self->tid | 0x80000000; + tid = self->tid; if (m->_m_type >= 4) { if (!self->robust_list.off) @@ -20,14 +19,15 @@ int pthread_mutex_trylock(pthread_mutex_t *m) self->robust_list.pending = &m->_m_next; } - if (m->_m_lock == tid && (m->_m_type&3) == PTHREAD_MUTEX_RECURSIVE) { + old = m->_m_lock; + own = old & 0x7fffffff; + if (own == tid && (m->_m_type&3) == PTHREAD_MUTEX_RECURSIVE) { if ((unsigned)m->_m_count >= INT_MAX) return EAGAIN; m->_m_count++; return 0; } - own = m->_m_lock; - if ((own && !(own & 0x40000000)) || a_cas(&m->_m_lock, own, tid)!=own) + if ((own && !(own & 0x40000000)) || a_cas(&m->_m_lock, old, tid)!=old) return EBUSY; m->_m_count = 1; |