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authorRich Felker <dalias@aerifal.cx>2011-03-30 08:58:25 -0400
committerRich Felker <dalias@aerifal.cx>2011-03-30 08:58:25 -0400
commit124b4ebc8a293e616cc0a7eaba3587c9b7ff13ec (patch)
tree80c2bdc3f961b6acb7344d5b8eaf725d219458d0 /src/thread/pthread_mutex_lock.c
parent680630011d38eb9f96f92b2f080cc60f38f6df21 (diff)
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cheap special-case optimization for normal mutexes
cycle-level benchmark on atom cpu showed typical pthread_mutex_lock
call dropping from ~120 cycles to ~90 cycles with this change. benefit
may vary with compiler options and version, but this optimization is
very cheap to make and should always help some.
Diffstat (limited to 'src/thread/pthread_mutex_lock.c')
-rw-r--r--src/thread/pthread_mutex_lock.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/src/thread/pthread_mutex_lock.c b/src/thread/pthread_mutex_lock.c
index 477b3d80..87b19752 100644
--- a/src/thread/pthread_mutex_lock.c
+++ b/src/thread/pthread_mutex_lock.c
@@ -3,6 +3,10 @@
 int pthread_mutex_lock(pthread_mutex_t *m)
 {
 	int r;
+
+	if (m->_m_type == PTHREAD_MUTEX_NORMAL && !a_swap(&m->_m_lock, 1))
+		return 0;
+
 	while ((r=pthread_mutex_trylock(m)) == EBUSY) {
 		if (!(r=m->_m_lock) || (r&0x40000000)) continue;
 		if ((m->_m_type&3) == PTHREAD_MUTEX_ERRORCHECK