linux-kernel - Re: Linux 2.6.39-rc3

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Date:	Fri, 15 Apr 2011 00:14:55 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Borislav Petkov <bp@...en8.de>, Jens Axboe <jaxboe@...ionio.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 2.6.39-rc3

On Thu, Apr 14, 2011 at 01:55:02PM -0700, Linus Torvalds wrote:
> On Thu, Apr 14, 2011 at 1:24 PM, Borislav Petkov <bp@...en8.de> wrote:
> >
> > Yep, I had to hit a buglet too. Looks like block layer, ->request_fn
> > (do_ide_request) called in IRQ disabled region. Process is blkid, i.e.
> > some udev helper. Kernel is -rc3 + Joerg's USB quirk fix which should be
> > unrelated.
> 
> I think this particular backtrace should be fixed by commit
> 6631e635c65d ("block: don't flush plugged IO on forced preemtion
> scheduling"), although even without preempt scheduling, I don't think
> it's at all ok to sleep inside __blk_run_queue.
> 
> Jens? Even from a _regular_ schedule, it would not be ok if we end up
> sleeping - we're caching things like the request-queue, and we have
> preempt_disable() inside the scheduler for a very good reason.

Jens already has a fix in his tree to always offload the block I/O
submission to blockd for this case.

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