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in pthread_mutex_timedlock, avoid repeatedly reading mutex type field

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compiler cannot cache immutable fields of the mutex object across
external calls it can't see, much less across atomics.
This commit is contained in:
Rich Felker 2018-09-04 21:31:47 -04:00
parent 4e4a162d9a
commit d1fa288606
1 changed files with 4 additions and 3 deletions
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7
src/thread/pthread_mutex_timedlock.c
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@ -6,7 +6,8 @@ int __pthread_mutex_timedlock(pthread_mutex_t *restrict m, const struct timespec
&& !a_cas(&m->_m_lock, 0, EBUSY)) && !a_cas(&m->_m_lock, 0, EBUSY))
return 0; 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); r = pthread_mutex_trylock(m);
if (r != EBUSY) return r; 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 (spins-- && m->_m_lock && !m->_m_waiters) a_spin();
while ((r=pthread_mutex_trylock(m)) == EBUSY) { 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; continue;
if ((m->_m_type&3) == PTHREAD_MUTEX_ERRORCHECK if ((type&3) == PTHREAD_MUTEX_ERRORCHECK
&& (r&0x7fffffff) == __pthread_self()->tid) && (r&0x7fffffff) == __pthread_self()->tid)
return EDEADLK; return EDEADLK;