optimize spin lock not to dirty cache line while spinning

diff --git a/src/thread/pthread_spin_lock.c b/src/thread/pthread_spin_lock.c
index df575f0858681b76afb8895478778b67e8ca2a7b..0462e0f3a4004ca469cf6f99f7c24566f383a423 100644 (file)
--- a/src/thread/pthread_spin_lock.c
+++ b/src/thread/pthread_spin_lock.c
@@ -2,6 +2,6 @@
 
 int pthread_spin_lock(pthread_spinlock_t *s)
 {
-       while (a_swap(s, 1)) a_spin();
+       while (*(volatile int *)s || a_cas(s, 0, 1)) a_spin();
        return 0;
 }