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From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Darren Hart <darren@dvhart.com>,
	Davidlohr Bueso <dave@stgolabs.net>,
	Bhuvanesh_Surachari@mentor.com, Andy Lowe <Andy_Lowe@mentor.com>
Subject: [patch 1/5] futex: Drop refcount if requeue_pi() acquired the rtmutex
Date: Sat, 19 Dec 2015 20:07:38 -0000
Message-ID: <20151219200607.178132067@linutronix.de> (raw)
In-Reply-To: <20151219200501.563704646@linutronix.de>


[-- Attachment #0: futex--Drop-refcount-if-requeue_pi-acquired-the-rtmutex --]
[-- Type: text/plain, Size: 810 bytes --]

If the proxy lock in the requeue loop acquires the rtmutex for a
waiter then it acquired also refcount on the pi_state related to the
futex, but the waiter side does not drop the reference count.

Add the missing free_pi_state() call.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
---
 kernel/futex.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2755,6 +2755,11 @@ static int futex_wait_requeue_pi(u32 __u
 		if (q.pi_state && (q.pi_state->owner != current)) {
 			spin_lock(q.lock_ptr);
 			ret = fixup_pi_state_owner(uaddr2, &q, current);
+			/*
+			 * Drop the reference to the pi state which
+			 * the requeue_pi() code acquired for us.
+			 */
+			free_pi_state(q.pi_state);
 			spin_unlock(q.lock_ptr);
 		}
 	} else {



  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-19 20:07 [patch 0/5] futex: Plug a pi_state leak and clarify the refcounting Thomas Gleixner
2015-12-19 20:07 ` Thomas Gleixner [this message]
2015-12-20 13:18   ` [tip:locking/core] futex: Drop refcount if requeue_pi() acquired the rtmutex tip-bot for Thomas Gleixner
2015-12-19 20:07 ` [patch 2/5] futex: Rename free_pi_state() to put_pi_state() Thomas Gleixner
2015-12-20 13:19   ` [tip:locking/core] futex: Rename free_pi_state() to put_pi_state( ) tip-bot for Thomas Gleixner
2015-12-19 20:07 ` [patch 3/5] futex: Document pi_state refcounting in requeue code Thomas Gleixner
2015-12-20  7:41   ` Darren Hart
2015-12-20 13:19   ` [tip:locking/core] " tip-bot for Thomas Gleixner
2015-12-19 20:07 ` [patch 4/5] futex: Remove pointless put_pi_state calls in requeue() Thomas Gleixner
2015-12-20 13:19   ` [tip:locking/core] " tip-bot for Thomas Gleixner
2015-12-19 20:07 ` [patch 5/5] futex: Cleanup the goto confusion in requeue_pi() Thomas Gleixner
2015-12-20  5:15   ` Darren Hart
2015-12-20  5:40     ` Mike Galbraith
2015-12-20  7:37       ` Darren Hart
2015-12-20  5:46     ` Darren Hart
2015-12-20 13:20   ` [tip:locking/core] " tip-bot for Thomas Gleixner

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