in pthread_mutex_timedlock, avoid repeatedly reading mutex type field

compiler cannot cache immutable fields of the mutex object across
external calls it can't see, much less across atomics.

diff --git a/src/thread/pthread_mutex_timedlock.c b/src/thread/pthread_mutex_timedlock.c
index 0a240e7913418bd86a48c02977c6733e8e49c0f8..f91f4a61b642e02c5cb7dbbb3697f57ffce20989 100644 (file)
--- a/src/thread/pthread_mutex_timedlock.c
+++ b/src/thread/pthread_mutex_timedlock.c
@@ -6,7 +6,8 @@ int __pthread_mutex_timedlock(pthread_mutex_t *restrict m, const struct timespec
            && !a_cas(&m->_m_lock, 0, EBUSY))
                return 0;
 
-       int r, t, priv = (m->_m_type & 128) ^ 128;
+       int type = m->_m_type;
+       int r, t, priv = (type & 128) ^ 128;
 
        r = pthread_mutex_trylock(m);
        if (r != EBUSY) return r;
@@ -15,9 +16,9 @@ int __pthread_mutex_timedlock(pthread_mutex_t *restrict m, const struct timespec
        while (spins-- && m->_m_lock && !m->_m_waiters) a_spin();
 
        while ((r=pthread_mutex_trylock(m)) == EBUSY) {
-               if (!(r=m->_m_lock) || ((r&0x40000000) && (m->_m_type&4)))
+               if (!(r=m->_m_lock) || ((r&0x40000000) && (type&4)))
                        continue;
-               if ((m->_m_type&3) == PTHREAD_MUTEX_ERRORCHECK
+               if ((type&3) == PTHREAD_MUTEX_ERRORCHECK
                 && (r&0x7fffffff) == __pthread_self()->tid)
                        return EDEADLK;