linux-kernel - [PATCH 1/1] ptrace: task_clear_jobctl_trapping()->wake_up

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Message-ID: <20140516135137.GB19210@redhat.com>
Date:	Fri, 16 May 2014 15:51:37 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	David Howells <dhowells@...hat.com>
Cc:	Mel Gorman <mgorman@...e.de>, Johannes Weiner <hannes@...xchg.org>,
	Vlastimil Babka <vbabka@...e.cz>, Jan Kara <jack@...e.cz>,
	Michal Hocko <mhocko@...e.cz>, Hugh Dickins <hughd@...gle.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>,
	Linux-FSDevel <linux-fsdevel@...r.kernel.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 1/1] ptrace: task_clear_jobctl_trapping()->wake_up_bit()
	needs mb()

__wake_up_bit() checks waitqueue_active() and thus the caller needs
mb() as wake_up_bit() documents, fix task_clear_jobctl_trapping().

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 kernel/signal.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index c2a8542..f4c4119 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -277,6 +277,7 @@ void task_clear_jobctl_trapping(struct task_struct *task)
 {
 	if (unlikely(task->jobctl & JOBCTL_TRAPPING)) {
 		task->jobctl &= ~JOBCTL_TRAPPING;
+		smp_mb();	/* advised by wake_up_bit() */
 		wake_up_bit(&task->jobctl, JOBCTL_TRAPPING_BIT);
 	}
 }
-- 
1.5.5.1


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