linux-kernel - [PATCH] futex: fix requeue

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Date:	Wed, 07 Oct 2009 11:46:54 -0700
From:	Darren Hart <dvhltc@...ibm.com>
To:	"lkml, " <linux-kernel@...r.kernel.org>
CC:	Helge Bahmann <hcb@...oticmind.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Dinakar Guniguntala <dino@...ibm.com>,
	John Stultz <johnstul@...ibm.com>
Subject: [PATCH] futex: fix requeue_pi key imbalance

futex: fix requeue_pi key imbalance

From: Darren Hart <dvhltc@...ibm.com>

If futex_wait_requeue_pi() wakes prior to requeue, we drop the reference to the
source futex_key twice, once in handle_early_requeue_pi_wakeup() and once on
our way out. Remove the drop from the handle_early_requeue_pi_wakeup() and keep
the get/drops together in futex_wait_requeue_pi().

Reported-by: Helge Bahmann <hcb@...oticmind.net>
Signed-off-by: Darren Hart <dvhltc@...ibm.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...e.hu>
CC: Eric Dumazet <eric.dumazet@...il.com>
CC: Dinakar Guniguntala <dino@...ibm.com>
CC: John Stultz <johnstul@...ibm.com>
---

 kernel/futex.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)


Index: linux-2.6.git/kernel/futex.c
===================================================================
--- linux-2.6.git.orig/kernel/futex.c
+++ linux-2.6.git/kernel/futex.c
@@ -2117,7 +2117,6 @@ int handle_early_requeue_pi_wakeup(struc
 		 * Unqueue the futex_q and determine which it was.
 		 */
 		plist_del(&q->list, &q->list.plist);
-		drop_futex_key_refs(&q->key);
 
 		if (timeout && !timeout->task)
 			ret = -ETIMEDOUT;
-- 
Darren Hart
IBM Linux Technology Center
Real-Time Linux Team
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