rt-mutex: fix chain walk early wakeup bug

Alexey Kuznetsov found some problems in the pi-futex code. One of the root causes is: When a wakeup happens, we do not to stop the chain walk so we follow a not longer relevant locking chain. Drop out when this happens. Signed-off-by: Thomas Gleixner <[email protected]> Acked-by: Ingo Molnar <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Alexey Kuznetsov <[email protected]> Cc: Ulrich Drepper <[email protected]> Cc: Eric Dumazet <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
csanz · Jun 9, 2007 · 1a539a8 · 1a539a8
1 parent c0d1d2b
commit 1a539a8
Showing 1 changed file with 13 additions and 0 deletions.
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
@@ -189,6 +189,19 @@ int rt_mutex_adjust_prio_chain(struct task_struct *task,
 	if (!waiter || !waiter->task)
 		goto out_unlock_pi;
 
+	/*
+	 * Check the orig_waiter state. After we dropped the locks,
+	 * the previous owner of the lock might have released the lock
+	 * and made us the pending owner:
+	 */
+	if (orig_waiter && !orig_waiter->task)
+		goto out_unlock_pi;
+
+	/*
+	 * Drop out, when the task has no waiters. Note,
+	 * top_waiter can be NULL, when we are in the deboosting
+	 * mode!
+	 */
 	if (top_waiter && (!task_has_pi_waiters(task) ||
 			   top_waiter != task_top_pi_waiter(task)))
 		goto out_unlock_pi;