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

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Message-ID: <20160209175400.GC3741@mtj.duckdns.org>
Date:	Tue, 9 Feb 2016 12:54:00 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Michal Hocko <mhocko@...nel.org>, Jiri Slaby <jslaby@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Petr Mladek <pmladek@...e.com>, Jan Kara <jack@...e.cz>,
	Ben Hutchings <ben@...adent.org.uk>,
	Sasha Levin <sasha.levin@...cle.com>, Shaohua Li <shli@...com>,
	LKML <linux-kernel@...r.kernel.org>,
	stable <stable@...r.kernel.org>,
	Daniel Bilik <daniel.bilik@...system.cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: Crashes with 874bbfe600a6 in 3.18.25

Hello, Mike.

On Tue, Feb 09, 2016 at 06:04:04PM +0100, Mike Galbraith wrote:
> workqueue: schedule WORK_CPU_UNBOUND work on wq_unbound_cpumask CPUs
> 
> WORK_CPU_UNBOUND work items queued to a bound workqueue always run
> locally.  This is a good thing normally, but not when the user has
> asked us to keep unbound work away from certain CPUs.  Round robin
> these to wq_unbound_cpumask CPUs instead, as perturbation avoidance
> trumps performance.

I don't think doing this by default for everyone is a good idea.  A
lot of workqueue usages tend to touch whatever the scheduler was
touching after all.  Doing things per-cpu is generally a pretty good
thing.

Thanks.

-- 
tejun