rwlock: Fix explicit hand-over (bug 21298)

Without this fix, the rwlock can fail to execute the explicit hand-over
in certain cases (e.g., empty critical sections that switch quickly between
read and write phases).  This can then lead to errors in how __wrphase_futex
is accessed, which in turn can lead to deadlocks.

1 files changed, 8 insertions, 0 deletions

diff --git a/support/xthread.h b/support/xthread.h
index 3552a73e4f..472763ebe8 100644
--- a/support/xthread.h
+++ b/support/xthread.h
@@ -74,6 +74,14 @@ void xpthread_attr_setguardsize (pthread_attr_t *attr,
    PTHREAD_BARRIER_SERIAL_THREAD.  */
 int xpthread_barrier_wait (pthread_barrier_t *barrier);
 
+void xpthread_rwlock_init (pthread_rwlock_t *rwlock,
+			  const pthread_rwlockattr_t *attr);
+void xpthread_rwlockattr_init (pthread_rwlockattr_t *attr);
+void xpthread_rwlockattr_setkind_np (pthread_rwlockattr_t *attr, int pref);
+void xpthread_rwlock_wrlock (pthread_rwlock_t *rwlock);
+void xpthread_rwlock_rdlock (pthread_rwlock_t *rwlock);
+void xpthread_rwlock_unlock (pthread_rwlock_t *rwlock);
+
 __END_DECLS
 
 #endif /* SUPPORT_THREAD_H */