linux-kernel - [tip:core/printk] printk: Fix rq-> lock vs logbuf

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Date:	Mon, 18 Feb 2013 06:17:25 -0800
From:	"tip-bot for Bu, Yitian" <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	a.p.zijlstra@...llo.nl, ybu@....qualcomm.com, tglx@...utronix.de
Subject: [tip:core/printk] printk: Fix rq->
 lock vs logbuf_lock unlock lock inversion

Commit-ID:  dbda92d16f8655044e082930e4e9d244b87fde77
Gitweb:     http://git.kernel.org/tip/dbda92d16f8655044e082930e4e9d244b87fde77
Author:     Bu, Yitian <ybu@....qualcomm.com>
AuthorDate: Mon, 18 Feb 2013 12:53:37 +0000
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Mon, 18 Feb 2013 15:05:57 +0100

printk: Fix rq->lock vs logbuf_lock unlock lock inversion

commit 07354eb1a74d1 ("locking printk: Annotate logbuf_lock as raw")
reintroduced a lock inversion problem which was fixed in commit
0b5e1c5255 ("printk: Release console_sem after logbuf_lock"). This
happened probably when fixing up patch rejects.

Restore the ordering and unlock logbuf_lock before releasing
console_sem.

Signed-off-by: ybu <ybu@....qualcomm.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: stable@...r.kernel.org
Link: http://lkml.kernel.org/r/E807E903FE6CBE4D95E420FBFCC273B827413C@nasanexd01h.na.qualcomm.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/printk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/printk.c b/kernel/printk.c
index 267ce78..e698e80 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1358,9 +1358,9 @@ static int console_trylock_for_printk(unsigned int cpu)
 		}
 	}
 	logbuf_cpu = UINT_MAX;
+	raw_spin_unlock(&logbuf_lock);
 	if (wake)
 		up(&console_sem);
-	raw_spin_unlock(&logbuf_lock);
 	return retval;
 }
 
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