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From d1fa28860634af4f0efd70d533a756b51a45f83e Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Tue, 4 Sep 2018 21:31:47 -0400
Subject: [PATCH 2/3] 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.
---
src/thread/pthread_mutex_timedlock.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/src/thread/pthread_mutex_timedlock.c b/src/thread/pthread_mutex_timedlock.c
index 0a240e79..f91f4a61 100644
--- 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;
--
2.19.0
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