8029453: java/util/concurrent/locks/ReentrantLock/TimeoutLockLoops.java failed by timeout

Reviewed-by: bdelsart, ddmitriev, dcubed

src/os/linux/vm/os_linux.cpp

@@ -5922,9 +5922,11 @@ void Parker::unpark() {
         status = pthread_mutex_unlock(_mutex);
         assert (status == 0, "invariant");
       } else {
+        // must capture correct index before unlocking
+        int index = _cur_index;
         status = pthread_mutex_unlock(_mutex);
         assert (status == 0, "invariant");
-        status = pthread_cond_signal (&_cond[_cur_index]);
+        status = pthread_cond_signal (&_cond[index]);
         assert (status == 0, "invariant");
       }
     } else {