[ 3.8.y.z extended stable ] Patch "printk: Fix rq->lock vs logbuf_lock unlock lock inversion" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.5.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 462d89335237e46adbeba5ecc14f34e8d894a495 Mon Sep 17 00:00:00 2001
From: "Bu, Yitian" <ybu at qti.qualcomm.com>
Date: Mon, 18 Feb 2013 12:53:37 +0000
Subject: printk: Fix rq->lock vs logbuf_lock unlock lock inversion

commit dbda92d16f8655044e082930e4e9d244b87fde77 upstream.

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 at qti.qualcomm.com>
Cc: Peter Zijlstra <a.p.zijlstra at chello.nl>
Link: http://lkml.kernel.org/r/E807E903FE6CBE4D95E420FBFCC273B827413C@nasanexd01h.na.qualcomm.com
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 kernel/printk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/printk.c b/kernel/printk.c
index 0f0ac58..37425c3 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1367,9 +1367,9 @@ 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;
 }

--
1.8.1.2