linux-kernel - Re: [Syzkaller & bisect] There is INFO: task hung in __rq_qos

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Message-ID: <66emkxxuzcge3kdd5iwiqexyeqzm3msradf5bhgnxc7zdy3qys@bm5luwh65lgo>
Date: Fri, 25 Oct 2024 06:02:18 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: "Lai, Yi" <yi1.lai@...ux.intel.com>, axboe@...nel.dk, 
	linux-block@...r.kernel.org
Cc: linux-bcachefs@...r.kernel.org, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [Syzkaller & bisect] There is INFO: task hung in
 __rq_qos_throttle

On Fri, Oct 25, 2024 at 05:52:57PM +0800, Lai, Yi wrote:
> On Wed, Oct 23, 2024 at 09:57:53PM -0400, Kent Overstreet wrote:
> > On Mon, Oct 21, 2024 at 06:27:25PM +0800, Lai, Yi wrote:
> > > Hi Kent Overstreet,
> > > 
> > > Greetings!
> > > 
> > > I used Syzkaller and found that there is INFO: task hung in __rq_qos_throttle in v6.12-rc2
> > > 
> > > After bisection and the first bad commit is:
> > > "
> > > 63332394c7e1 bcachefs: Move snapshot table size to struct snapshot_table
> > 
> > You sure...?
> > 
> > Look at the patch, that's a pretty unlikely culprit; we would've seen
> > something from kasan, and anyways there's guards on the new memory
> > accesses/array derefs.
> > 
> > I've been seeing that bug too, but it's very intermittent. How did you
> > get it to trigger reliably enough for a bisect?
> 
> Look into my local bisection log. You are right, that the bug is intermittent
> and takes a very long time to reproduce the issue.
> 
> I didn't observe similar issues during following v6.12-rcx kernel
> fuzzing. I will keep monitoring.

yeah, this is one for Jens...