spin before waiting on futex in mutex and rwlock lock operations

[musl] / src / thread / pthread_rwlock_timedrdlock.c

diff --git a/src/thread/pthread_rwlock_timedrdlock.c b/src/thread/pthread_rwlock_timedrdlock.c
index a2b4d44..884b7a1 100644 (file)
--- a/src/thread/pthread_rwlock_timedrdlock.c
+++ b/src/thread/pthread_rwlock_timedrdlock.c
@@ -3,6 +3,13 @@
 int pthread_rwlock_timedrdlock(pthread_rwlock_t *restrict rw, const struct timespec *restrict at)
 {
        int r, t;
+
+       r = pthread_rwlock_tryrdlock(rw);
+       if (r != EBUSY) return r;
+       
+       int spins = 100;
+       while (spins-- && rw->_rw_lock) a_spin();
+
        while ((r=pthread_rwlock_tryrdlock(rw))==EBUSY) {
                if (!(r=rw->_rw_lock) || (r&0x7fffffff)!=0x7fffffff) continue;
                t = r | 0x80000000;