Re: Simple script that locks up my box with recent kernels

From: Jesper Juhl
Date: Wed Nov 22 2006 - 05:55:33 EST


On 22/11/06, Jens Axboe <jens.axboe@xxxxxxxxxx> 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.

--
Jesper Juhl <jesper.juhl@xxxxxxxxx>
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