linux-kernel - Re: [PATCH 2.6.32-rc6] workqueue: fix race condition in schedule_on_each

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Message-ID: <20091114184910.GA3649@redhat.com>
Date:	Sat, 14 Nov 2009 19:49:11 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2.6.32-rc6] workqueue: fix race condition in
	schedule_on_each_cpu()

On 11/14, Tejun Heo wrote:
>
> 11/14/2009 12:38 AM, Oleg Nesterov wrote:
> > A very minor nit, schedule_on_each_cpu() still checks "orig" twice,
> > perhaps it makes sense to do
> >
> > 	for_each_online_cpu(cpu) {
> > 		struct work_struct *work = per_cpu_ptr(works, cpu);
> >
> > 		INIT_WORK(work, func);
> >
> > 		if (likely(cpu != orig))
> > 			schedule_work_on(cpu, work);
> > 		else
> > 			func(work);
> > 	}
>
> The intention was to schedule works on all other cpus first and then
> execute it on local cpu so that if it takes some time, it doesn't have
> to go through the latency twice.

Ah, indeed, you are right.

Oleg.

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