linux-kernel - [tip:locking/core] futex: Cleanup the goto confusion in requeue

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Date:	Sun, 20 Dec 2015 05:20:01 -0800
From:	tip-bot for Thomas Gleixner <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	hpa@...or.com, peterz@...radead.org, tglx@...utronix.de,
	dave@...olabs.net, Andy_Lowe@...tor.com, darren@...art.com,
	mingo@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip:locking/core] futex:
  Cleanup the goto confusion in requeue_pi()

Commit-ID:  885c2cb770b5ac2507c41bc9f91a5d1c98337bee
Gitweb:     http://git.kernel.org/tip/885c2cb770b5ac2507c41bc9f91a5d1c98337bee
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Sat, 19 Dec 2015 20:07:41 +0000
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Sun, 20 Dec 2015 12:43:25 +0100

futex: Cleanup the goto confusion in requeue_pi()

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@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Darren Hart <darren@...art.com>
Cc: Davidlohr Bueso <dave@...olabs.net>
Cc: Bhuvanesh_Surachari@...tor.com
Cc: Andy Lowe <Andy_Lowe@...tor.com>
Link: http://lkml.kernel.org/r/20151219200607.526665141@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/futex.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index dcec018..461d438 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1839,20 +1839,25 @@ retry_private:
 				 */
 				this->pi_state = NULL;
 				put_pi_state(pi_state);
-				goto out_unlock;
+				/*
+				 * We stop queueing more waiters and let user
+				 * space deal with the mess.
+				 */
+				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);
--
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