From: Tejun Heo <tj@kernel.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>, Thomas Gleixner <tglx@linutronix.de>,
Petr Mladek <pmladek@suse.com>, Jan Kara <jack@suse.cz>,
Ben Hutchings <ben@decadent.org.uk>,
Sasha Levin <sasha.levin@oracle.com>, Shaohua Li <shli@fb.com>,
LKML <linux-kernel@vger.kernel.org>,
stable@vger.kernel.org, Daniel Bilik <daniel.bilik@neosystem.cz>
Subject: Re: Crashes with 874bbfe600a6 in 3.18.25
Date: Wed, 3 Feb 2016 11:24:41 -0500 [thread overview]
Message-ID: <20160203162441.GE14091@mtj.duckdns.org> (raw)
In-Reply-To: <20160203122855.GB6762@dhcp22.suse.cz>
On Wed, Feb 03, 2016 at 01:28:56PM +0100, Michal Hocko wrote:
> > The CPU was 168, and that one was offlined in the meantime. So
> > __queue_work fails at:
> > if (!(wq->flags & WQ_UNBOUND))
> > pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
> > else
> > pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
> > ^^^ ^^^^ NODE is -1
> > \ pwq is NULL
> >
> > if (last_pool && last_pool != pwq->pool) { <--- BOOM
So, the proper fix here is keeping cpu <-> node mapping stable across
cpu on/offlining which has been being worked on for a long time now.
The patchst is pending and it fixes other issues too.
> So I think 874bbfe600a6 is really bogus. It should be reverted. We
> already have a proper fix for vmstat 176bed1de5bf ("vmstat: explicitly
> schedule per-cpu work on the CPU we need it to run on"). This which
> should be used for the stable trees as a replacement.
It's not bogus. We can't flip a property that has been guaranteed
without any provision for verification. Why do you think vmstat blow
up in the first place? vmstat would be the canary case as it runs
frequently on all systems. It's exactly the sign that we can't break
this guarantee willy-nilly.
Thanks.
--
tejun
next prev parent reply other threads:[~2016-02-03 16:24 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-20 21:19 Crashes with 874bbfe600a6 in 3.18.25 Jan Kara
2016-01-20 21:39 ` Shaohua Li
2016-01-21 9:52 ` Jan Kara
2016-01-21 13:29 ` Sasha Levin
2016-01-22 1:10 ` Sasha Levin
2016-01-22 16:09 ` Tejun Heo
2016-01-23 2:20 ` Ben Hutchings
2016-01-23 16:11 ` Thomas Gleixner
2016-01-26 9:34 ` Jan Kara
2016-01-26 9:49 ` Thomas Gleixner
2016-01-26 11:14 ` Petr Mladek
2016-01-26 13:09 ` Thomas Gleixner
2016-02-03 9:35 ` Jiri Slaby
2016-02-03 10:41 ` Thomas Gleixner
2016-02-03 12:28 ` Michal Hocko
2016-02-03 16:24 ` Tejun Heo [this message]
2016-02-03 16:48 ` Michal Hocko
2016-02-03 16:59 ` Tejun Heo
2016-02-04 6:37 ` Michal Hocko
2016-02-04 7:40 ` Michal Hocko
2016-02-03 17:01 ` Mike Galbraith
2016-02-03 17:06 ` Tejun Heo
2016-02-03 17:13 ` Mike Galbraith
2016-02-03 17:15 ` Tejun Heo
2016-02-04 2:00 ` Mike Galbraith
2016-02-05 16:49 ` Tejun Heo
2016-02-05 20:47 ` Mike Galbraith
2016-02-05 20:54 ` Tejun Heo
2016-02-05 20:59 ` Mike Galbraith
2016-02-05 21:06 ` Tejun Heo
2016-02-06 13:07 ` Henrique de Moraes Holschuh
2016-02-07 5:19 ` Mike Galbraith
2016-02-07 5:59 ` Mike Galbraith
2016-02-09 15:31 ` Mike Galbraith
2016-02-09 16:39 ` Linus Torvalds
2016-02-09 16:50 ` Tejun Heo
2016-02-09 17:04 ` Mike Galbraith
2016-02-09 17:54 ` Tejun Heo
2016-02-09 17:56 ` Mike Galbraith
2016-02-09 18:02 ` Mike Galbraith
2016-02-09 18:27 ` Tejun Heo
2016-02-09 17:04 ` Linus Torvalds
2016-02-09 17:51 ` Tejun Heo
2016-02-09 18:06 ` Linus Torvalds
2016-02-04 10:04 ` Mike Galbraith
2016-02-04 10:46 ` Thomas Gleixner
2016-02-04 11:07 ` Mike Galbraith
2016-02-04 11:20 ` Jan Kara
2016-02-04 16:39 ` Daniel Bilik
2016-02-05 2:40 ` Mike Galbraith
2016-02-05 8:11 ` Daniel Bilik
2016-02-05 8:33 ` Mike Galbraith
2016-02-03 18:46 ` Thomas Gleixner
2016-02-03 19:01 ` Tejun Heo
2016-02-03 19:05 ` Thomas Gleixner
2016-02-03 19:15 ` Tejun Heo
2016-02-05 5:44 ` Mike Galbraith
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