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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 5/5] futex: Cleanup the goto confusion in requeue_pi()
Date: Sat, 19 Dec 2015 20:07:41 -0000	[thread overview]
Message-ID: <20151219200607.526665141@linutronix.de> (raw)
In-Reply-To: <20151219200501.563704646@linutronix.de>

[-- Attachment #1: futex--Cleanup-goto-mess-in-requeue-pi --]
[-- Type: text/plain, Size: 935 bytes --]

out_unlock: does not only drop the locks, it also drops the refcount
on the pi_state. Really intuitive.

Move the label after the put_pi_state() call and use 'break' in the
error handling path of the requeue loop.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/futex.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1842,20 +1842,21 @@ static int futex_requeue(u32 __user *uad
 				 */
 				this->pi_state = NULL;
 				put_pi_state(pi_state);
-				goto out_unlock;
+				break;
 			}
 		}
 		requeue_futex(this, hb1, hb2, &key2);
 		drop_count++;
 	}
 
-out_unlock:
 	/*
 	 * We took an extra initial reference to the pi_state either
 	 * in futex_proxy_trylock_atomic() or in lookup_pi_state(). We
 	 * need to drop it here again.
 	 */
 	put_pi_state(pi_state);
+
+out_unlock:
 	double_unlock_hb(hb1, hb2);
 	wake_up_q(&wake_q);
 	hb_waiters_dec(hb2);



  parent reply	other threads:[~2015-12-19 20:09 UTC|newest]

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 ` [patch 1/5] futex: Drop refcount if requeue_pi() acquired the rtmutex Thomas Gleixner
2015-12-20 13:18   ` [tip:locking/core] " 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 ` Thomas Gleixner [this message]
2015-12-20  5:15   ` [patch 5/5] futex: Cleanup the goto confusion in requeue_pi() 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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