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

[musl] / src / thread / pthread_mutex_trylock.c

diff --git a/src/thread/pthread_mutex_trylock.c b/src/thread/pthread_mutex_trylock.c
index 25b9e86..6fc604f 100644 (file)
--- a/src/thread/pthread_mutex_trylock.c
+++ b/src/thread/pthread_mutex_trylock.c
@@ -5,19 +5,17 @@ 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;
 
-       if (m->_m_owner == tid) {
-               if (m->_m_type != PTHREAD_MUTEX_RECURSIVE)
-                       return EBUSY;
+       if (m->_m_owner == tid && m->_m_type == PTHREAD_MUTEX_RECURSIVE) {
                if ((unsigned)m->_m_count >= INT_MAX) return EAGAIN;
                m->_m_count++;
                return 0;
        }
 
-       if (a_xchg(&m->_m_lock, 1)) return EBUSY;
+       if (m->_m_owner || a_xchg(&m->_m_lock, 1)) return EBUSY;
        m->_m_owner = tid;
        m->_m_count = 1;
        return 0;