linux-kernel - Re: Crashes with 874bbfe600a6 in 3.18.25

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Message-ID: <20160122160903.GH32380@htj.duckdns.org>
Date:	Fri, 22 Jan 2016 11:09:03 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Jan Kara <jack@...e.cz>, Shaohua Li <shli@...com>,
	LKML <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
	Daniel Bilik <daniel.bilik@...system.cz>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Crashes with 874bbfe600a6 in 3.18.25

(cc'ing Thomas)

On Thu, Jan 21, 2016 at 08:10:20PM -0500, Sasha Levin wrote:
> On 01/21/2016 04:52 AM, Jan Kara wrote:
> > On Wed 20-01-16 13:39:01, Shaohua Li wrote:
> >> On Wed, Jan 20, 2016 at 10:19:26PM +0100, Jan Kara wrote:
> >>> Hello,
> >>>
> >>> a friend of mine started seeing crashes with 3.18.25 kernel - once
> >>> appropriate load is put on the machine it crashes within minutes. He
> >>> tracked down that reverting commit 874bbfe600a6 (this is the commit ID from
> >>> Linus' tree, in stable tree the commit ID is 1e7af294dd03) "workqueue: make
> >>> sure delayed work run in local cpu" makes the kernel stable again. I'm
> >>> attaching screenshot of the crash - sadly the initial part is missing but
> >>> it seems that we crashed when processing timers on otherwise idle CPU. This
> >>> is a production machine so experimentation is not easy but if we really
> >>> need more information it may be possible to reproduce the issue again and
> >>> gather it.
> >>>
> >>> Anyone has idea what is going on? I was looking into the code for a while
> >>> but so far I have no good explanation.  It would be good to understand the
> >>> cause instead of just blindly reverting the commit from stable tree...
> >>
> >> Tejun fixed a bug in timer: 22b886dd10180939. is it included in 3.18.25?
> > 
> > That doesn't seem to be included in 3.18-stable although it was CCed to stable.
> > Sasha?
> 
> Looks like it requires more than trivial backport (I think). Tejun?

The timer migration has changed quite a bit.  Given that we've never
seen vmstat work crashing in 3.18 era, I wonder whether the right
thing to do here is reverting 874bbfe600a6 from 3.18 stable?

Thanks.

-- 
tejun