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Subject[patch 2/4] 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 <tglx@linutronix.de>

---
kernel/rtmutex.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

Index: linux-2.6.22-rc4/kernel/rtmutex.c
===================================================================
--- linux-2.6.22-rc4.orig/kernel/rtmutex.c 2007-06-08 01:39:38.000000000 +0200
+++ linux-2.6.22-rc4/kernel/rtmutex.c 2007-06-08 01:39:38.000000000 +0200
@@ -189,6 +189,19 @@ int rt_mutex_adjust_prio_chain(struct ta
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;
--

-
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