linux-kernel - Re: next-20081119: general protection fault: get_next_timer

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Message-Id: <20081125115710.6c249f32.sfr@canb.auug.org.au>
Date:	Tue, 25 Nov 2008 11:57:10 +1100
From:	Stephen Rothwell <sfr@...b.auug.org.au>
To:	malahal@...ibm.com
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Mike Anderson <andmike@...ux.vnet.ibm.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Alexander Beregalov <a.beregalov@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-next@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>, linux-scsi@...r.kernel.org,
	David Miller <davem@...emloft.net>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: next-20081119: general protection fault:
 get_next_timer_interrupt()

On Mon, 24 Nov 2008 16:09:02 -0800 malahal@...ibm.com wrote:
>
> Thomas Gleixner [tglx@...utronix.de] wrote:
> > On Mon, 24 Nov 2008, Mike Anderson wrote:
> > > Thomas Gleixner <tglx@...utronix.de> wrote:
> > > > Yeah, block could it be as well. Jens, Mike ?
> > > 
> > > I added a comment to bug 12020 on Thursday about a few other systems that
> > > where seeing the signature shown in bug 12020. It appeared from debug that
> > > there where a few paths that where adding timers for requests that where
> > > not expected.
> > > 
> > > http://bugzilla.kernel.org/show_bug.cgi?id=12020
> > > 
> > > It would be good to know if the debug patch below effects your problem as while.
> > > 
> > > If it does we need to investigated a solution to resolve not adding a
> > > timer for these requests.
> 
> The block timer code calls del_timer(), should it call del_timer_sync()?
> It is possible although unlikely that you are hitting del_timer_sync vs
> del_timer problem in the block timeout code. Can only be seen on SMP
> systems though!

Is this still a problem in next-20081121? In that tree, the block commit
"block: leave the request timeout timer running even on an empty list"
was changed to add this:

diff --git a/block/blk-core.c b/block/blk-core.c
index 04267d6..44f547c 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -391,6 +391,7 @@ EXPORT_SYMBOL(blk_stop_queue);
 void blk_sync_queue(struct request_queue *q)
 {
 	del_timer_sync(&q->unplug_timer);
+	del_timer_sync(&q->timeout);
 	kblockd_flush_work(&q->unplug_work);
 }
 EXPORT_SYMBOL(blk_sync_queue);

After I spent some time bisecting a boot failure in PowerPC.
-- 
Cheers,
Stephen Rothwell                    sfr@...b.auug.org.au
http://www.canb.auug.org.au/~sfr/

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