From: Frank Mayhar <fmayhar@google.com>
To: Tejun Heo <tj@kernel.org>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
Jens Axboe <axboe@kernel.dk>
Subject: Re: Crash in elevator_dispatch_fn() (e.g. deadline_dispatch()) when changing elevators.
Date: Thu, 23 Jan 2014 10:38:33 -0800 [thread overview]
Message-ID: <1390502313.20232.49.camel@bobble.lax.corp.google.com> (raw)
In-Reply-To: <1390405618.20232.42.camel@bobble.lax.corp.google.com>
On Wed, 2014-01-22 at 07:46 -0800, Frank Mayhar wrote:
> On Tue, 2014-01-21 at 07:58 -0800, Frank Mayhar wrote:
> > Replacing? Or adding to? Is BYPASS always set when DYING is set? (My
> > guess is not but I haven't done an exhaustive analysis.) So the
> > relevant code snippet in __elv_next_request() would be:
> > if (unlikely(blk_queue_dying(q)) ||
> > unlikely(blk_queue_bypass(q)) ||
> > !q->elevator->type->ops.elevator_dispatch_fn(q, 0))
> > return NULL;
>
> FYI, I've made this change and tested it. I can't say for certain that
> it fixes the crash (since it's one of those races that's difficult to
> reproduce), but it does seem to pass all the tests I've thrown at it so
> far.
Um, does anyone care about this? Tejun? Jens? Anyone?
This is a real crash; it would be nice if someone would weigh in.
--
Frank Mayhar
310-460-4042
next prev parent reply other threads:[~2014-01-23 18:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1389995976.20232.27.camel@bobble.lax.corp.google.com>
[not found] ` <20140118143145.GD3640@htj.dyndns.org>
2014-01-21 15:58 ` Crash in elevator_dispatch_fn() (e.g. deadline_dispatch()) when changing elevators Frank Mayhar
2014-01-22 15:46 ` Frank Mayhar
2014-01-23 18:38 ` Frank Mayhar [this message]
2014-01-23 18:56 ` Tejun Heo
2014-01-23 21:14 ` Frank Mayhar
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