overhaul rwlocks to address several issues

[musl] / src / thread / pthread_rwlock_unlock.c

diff --git a/src/thread/pthread_rwlock_unlock.c b/src/thread/pthread_rwlock_unlock.c
index 060e3fe..5edca63 100644 (file)
--- a/src/thread/pthread_rwlock_unlock.c
+++ b/src/thread/pthread_rwlock_unlock.c
@@ -2,16 +2,17 @@
 
 int pthread_rwlock_unlock(pthread_rwlock_t *rw)
 {
-       struct pthread *self = pthread_self();
-       if (rw->_rw_owner == self->tid) {
-               rw->_rw_owner = 0;
-               a_store(&rw->_rw_wrlock, 0);
-               if (rw->_rw_waiters)
-                       __wake(&rw->_rw_wrlock, -1, 0);
-               return 0;
-       }
-       a_dec(&rw->_rw_readers);
-       if (rw->_rw_waiters && !rw->_rw_readers)
-               __wake(&rw->_rw_readers, 1, 0);
+       int val, cnt, waiters, new;
+
+       do {
+               val = rw->_rw_lock;
+               cnt = val & 0x7fffffff;
+               waiters = rw->_rw_waiters;
+               new = (cnt == 0x7fffffff || cnt == 1) ? 0 : val-1;
+       } while (a_cas(&rw->_rw_lock, val, new) != val);
+
+       if (!new && (waiters || val<0))
+               __wake(&rw->_rw_lock, 1, 0);
+
        return 0;
 }