From: Rich Felker <dalias@aerifal.cx>
Date: Thu, 17 Mar 2011 16:14:40 +0000 (-0400)
Subject: optimize contended normal mutex case; add int compare-and-swap atomic
X-Git-Tag: v0.7.1~8
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=e914f8b7ec79f622fa3b017af434642f61d45ce8;p=oweals%2Fmusl.git

optimize contended normal mutex case; add int compare-and-swap atomic
---

diff --git a/arch/i386/atomic.h b/arch/i386/atomic.h
index e74e4535..bf3c336e 100644
--- a/arch/i386/atomic.h
+++ b/arch/i386/atomic.h
@@ -49,6 +49,13 @@ static inline long a_cas_l(volatile void *p, long t, long s)
 	return t;
 }
 
+static inline int a_cas(volatile int *p, int t, int s)
+{
+	__asm__( "lock ; cmpxchg %3, %1"
+		: "=a"(t), "=m"(*p) : "a"(t), "r"(s) : "memory" );
+	return t;
+}
+
 static inline void *a_swap_p(void *volatile *x, void *v)
 {
 	__asm__( "xchg %0, %1" : "=r"(v), "=m"(*(void **)x) : "0"(v) : "memory" );
diff --git a/arch/x86_64/atomic.h b/arch/x86_64/atomic.h
index 7a665c1b..04f6c28d 100644
--- a/arch/x86_64/atomic.h
+++ b/arch/x86_64/atomic.h
@@ -48,6 +48,13 @@ static inline long a_cas_l(volatile void *p, long t, long s)
 	return t;
 }
 
+static inline int a_cas(volatile int *p, int t, int s)
+{
+	__asm__( "lock ; cmpxchgl %3, %1"
+		: "=a"(t), "=m"(*p) : "a"(t), "r"(s) : "memory" );
+	return t;
+}
+
 static inline void *a_swap_p(void *volatile *x, void *v)
 {
 	__asm__( "xchg %0, %1" : "=r"(v), "=m"(*(void **)x) : "0"(v) : "memory" );
diff --git a/src/thread/pthread_mutex_trylock.c b/src/thread/pthread_mutex_trylock.c
index af421472..6fc604fe 100644
--- a/src/thread/pthread_mutex_trylock.c
+++ b/src/thread/pthread_mutex_trylock.c
@@ -5,7 +5,7 @@ int pthread_mutex_trylock(pthread_mutex_t *m)
 	int tid;
 
 	if (m->_m_type == PTHREAD_MUTEX_NORMAL)
-		return -a_xchg(&m->_m_lock, 1) & EBUSY;
+		return (m->_m_lock || a_swap(&m->_m_lock, 1)) ? EBUSY : 0;
 
 	tid = pthread_self()->tid;