From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: Tejun Heo <tj@kernel.org>, 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: Fri, 05 Feb 2016 06:44:29 +0100 [thread overview]
Message-ID: <1454651069.3545.41.camel@gmail.com> (raw)
In-Reply-To: <20160203162441.GE14091@mtj.duckdns.org>
On Wed, 2016-02-03 at 11:24 -0500, Tejun Heo wrote:
> 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.
If the intent of the below is to fulfill a guarantee...
+ /* timer isn't guaranteed to run in this cpu, record earlier */
+ if (cpu == WORK_CPU_UNBOUND)
+ cpu = raw_smp_processor_id();
dwork->cpu = cpu;
timer->expires = jiffies + delay;
- if (unlikely(cpu != WORK_CPU_UNBOUND))
- add_timer_on(timer, cpu);
- else
- add_timer(timer);
+ add_timer_on(timer, cpu);
...it appears to be incomplete. Hotplug aside, when adding a timer
with the expectation that it stay put, should it not also be pinned?
-Mike
prev parent reply other threads:[~2016-02-05 5:44 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
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 [this message]
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