linux-kernel - Re: [PATCH 2/3] workqueue: Add an API to create a singlethread workqueue attached to the current task's cgroup

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Message-ID: <4BFEA434.6080405@kernel.org>
Date:	Thu, 27 May 2010 18:56:20 +0200
From:	Tejun Heo <tj@...nel.org>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	Oleg Nesterov <oleg@...hat.com>,
	Sridhar Samudrala <sri@...ibm.com>,
	netdev <netdev@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitri Vorobiev <dmitri.vorobiev@...ial.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 2/3] workqueue: Add an API to create a singlethread	workqueue
 attached to the current task's cgroup

Hello,

On 05/27/2010 06:39 PM, Michael S. Tsirkin wrote:
>> Unless you're gonna convert every driver to use this
>> special kind of workqueue (and what happens when multiple tasks from
>> different cgroups share the driver?),
> 
> We'll then create a workqueue per task. Each workqueue will have the
> right cgroup. But we are not trying to selve the problem for
> every driver.

Ah... I see.  You're gonna use multiple workqueues.  Once concern that
I have is that this is abuse of workqueue interface to certain level
and depends on the implementation detail of workqueue rather than its
intended usage model.  stop_machine() was a similar case and in the
end it was better served by a different mechanism built on kthread
directly (cpu_stop).  Wouldn't it be cleaner to use kthread directly
for your case too?  You're basically trying to use workqueue as a
frontend to kthread, so...

Thanks.

-- 
tejun
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