linux-kernel - Re: [PATCH 4/8] kernel/workqueue.c: unbound work queue rescuer runs on first cpu in cpumask_online

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Message-ID: <20111005200030.GA373@dhcp-172-17-108-109.mtv.corp.google.com>
Date:	Wed, 5 Oct 2011 13:00:30 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Fenghua Yu <fenghua.yu@...el.com>, Ingo Molnar <mingo@...e.hu>,
	H Peter Anvin <hpa@...or.com>,
	Zwane Mwaikambo <zwane@....linux.org.uk>,
	Tony Luck <tony.luck@...el.com>,
	Asit K Mallick <asit.k.mallick@...el.com>,
	Suresh B Siddha <suresh.b.siddha@...el.com>,
	Len Brown <lenb@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/8] kernel/workqueue.c: unbound work queue rescuer
 runs on first cpu in cpumask_online_cpu

On Wed, Oct 05, 2011 at 09:19:22PM +0200, Peter Zijlstra wrote:
> On Wed, 2011-10-05 at 20:52 +0200, Thomas Gleixner wrote:
> > On Wed, 5 Oct 2011, Fenghua Yu wrote:
> > 
> > > From: Fenghua Yu <fenghua.yu@...el.com>
> > > 
> > > If work queue is unbound to a specific cpu, run rescuer on first cpu in
> > > cpumask_online_cpu instead BSP which could be offlined.
> > 
> > This patch needs to be applied separate from that series as it fixes a
> > bug which affects all architectures which can offline the boot cpu.
> 
> AFAIKT it really doesn't matter in this case, all the rescuer_thread()
> needs is some bit set in that mask, since its UNBOUND it won't actually
> try and migrate to any cpu and just run wherever it woke up.

Yeah, for unbound, it's just a random fixed ID.  Changing it
dynamically wouldn't break anything but is pointless.  So, NACK.

Thanks.

-- 
tejun
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