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Date: Tue, 09 Feb 2016 19:02:35 +0100 From: Mike Galbraith <umgwanakikbuti@...il.com> To: Tejun Heo <tj@...nel.org> 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 On Tue, 2016-02-09 at 18:56 +0100, Mike Galbraith wrote: > On Tue, 2016-02-09 at 12:54 -0500, Tejun Heo wrote: > > 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. > > It doesn't do anything unless the user twiddles the mask to exclude > certain (think no_hz_full) CPUs, so there are no clueless victims. (a plus: testers/robots can twiddle mask to help find bugs, _and_ nohz_full people can use it if they so choose)
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