linux-kernel - Re: SLUB regression in current Linus

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Message-ID: <alpine.DEB.2.00.1105250945240.23309@router.home>
Date:	Wed, 25 May 2011 09:47:43 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	James Morris <jmorris@...ei.org>
cc:	Pekka Enberg <penberg@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: SLUB regression in current Linus

On Wed, 25 May 2011, James Morris wrote:

> It turned out the system was still unstable with the attached config
> (e.g. spontaneous reboot).

Ahh. Thank you.

Here is the fix:

Subject: slub: Fix double bit unlock in debug mode

Commit 442b06bcea23a01934d3da7ec5898fa154a6cafb added a deactivate_slab()
in the debug case in __slab_alloc(). deactivate_slab() unlocks the current
slab used for allocation. Going to the label unlock_out: does it again.

So simply return the object. In the debug case we do not need all the other
processing that unlock_out: does.

Signed-off-by: Christoph Lameter <cl@...ux.com>

---
 mm/slub.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2011-05-25 09:41:27.000000000 -0500
+++ linux-2.6/mm/slub.c	2011-05-25 09:41:39.000000000 -0500
@@ -1884,7 +1884,8 @@ debug:
 	deactivate_slab(s, c);
 	c->page = NULL;
 	c->node = NUMA_NO_NODE;
-	goto unlock_out;
+	local_irq_restore(flags);
+	return object;
 }

 /*
View attachment "conf-test" of type "TEXT/PLAIN" (52548 bytes)