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From: Jesper Juhl <jesper.juhl@gmail.com>
To: Jens Axboe <jens.axboe@oracle.com>
Subject: Re: Simple script that locks up my box with recent kernels
Date: Fri, 24 Nov 2006 00:52:13 +0100
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Cc: Linus Torvalds <torvalds@osdl.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>, Jesper Juhl <jesper.juhl@gmail.com>
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On Wednesday 22 November 2006 12:07, Jens Axboe wrote:
> On Wed, Nov 22 2006, Jesper Juhl wrote:
> > On 22/11/06, Jens Axboe <jens.axboe@oracle.com> wrote:
> > >On Wed, Nov 22 2006, Jesper Juhl wrote:
> > >> On 22/11/06, Jens Axboe <jens.axboe@oracle.com> wrote:
> > >> >On Tue, Nov 21 2006, Linus Torvalds wrote:
> > >> >> I don't think we use any irq-disable locking in the VM itself, but I
> > >> >could
> > >> >> imagine some nasty situation with the block device layer getting into 
> > >a
> > >> >> deadlock with interrupts disabled when it runs out of queue entries 
> > >and
> > >> >> cannot allocate more memory..
> > >> >
> > >> >Not likely. Request allocation is done with GFP_NOIO and backed by a
> > >> >memory pool, so as long the vm doesn't go totally nuts because
> > >> >__GFP_WAIT is set, we should be safe there. If it did go crazy, I
> > >> >suspect a sysrq-t would still work.
> > >> >
> > >> >If bouncing is involved for swap, we do have a potential deadlock issue
> > >> >that isn't fixed yet. I just whipped up this completely untested patch,
> > >> >it should shed some light on that issue.
> > >> >
> > >> Thanks Jens, I'll apply that later tonight and force a few lockups and
> > >> see if I get any extra details with that patch.
> > >
> > >Can you post a full dmesg too, as well as clarify which device holds the
> > >swap space?
> > >
> > Sure. I'll post a full dmesg as soon as I get home.
> > 
> > The swap partition is on a IBM Ultrastar U160 10K RPM SCSI disk,
> > hooked up to an Adaptec 29160N controller, using the aic7xxx driver.
> > That disk holds all my filesystems as well and the controller also has
> > a SCSI DVD drive and a SCSI CD writer attached to it.  No SATA/PATA
> > devices in the box, in case that matters.
> 
> Does the box survive io intensive workloads? 

It seems to. It does get sluggish as hell when there is lots of disk I/O but
it seems to be able to survive.  
I'll try some more, with some IO benchmarks + various other stuff to see 
if I can get it to die that way.

> Have you tried using net or 
> serial console to see if it spits out any info before it crashes?

Lacking a second box at the moment, so that's not an option currently :(


> I 
> would not be too surprised if it's the aic7xxx driver taking a dive, I'd
> be a lot more surprised if it's actually the bouncing (I don't think you
> do any, can you post cat /proc/meminfo | grep -i bounce on that box?) or
> a generic vm/block bug causing you problems.
> 
$ cat /proc/meminfo | grep -i bounce
Bounce:              0 kB


-- 
Jesper Juhl <jesper.juhl@gmail.com>


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