linux-kernel - Re: [PATCH, RFC] reimplement flush

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Message-ID: <20070106152413.GB24274@in.ibm.com>
Date:	Sat, 6 Jan 2007 20:54:14 +0530
From:	Srivatsa Vaddagiri <vatsa@...ibm.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Andrew Morton <akpm@...l.org>, David Howells <dhowells@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...l.org>,
	linux-kernel@...r.kernel.org, Gautham shenoy <ego@...ibm.com>
Subject: Re: [PATCH, RFC] reimplement flush_workqueue()

On Fri, Jan 05, 2007 at 05:07:17PM +0300, Oleg Nesterov wrote:
> How about block_cpu_down() ?

Maybe ..not sure 

If we do introduce such a function, we may need to convert several
preempt_disable() that are there already (with intent of blocking
cpu_down) to block_cpu_down() ..

> These cpu-hotplug races delayed the last workqueue patch I have in my queue.
> flush_workqueue() misses an important optimization: we don't need to insert
> a barrier and have an extra wake_up + wait_for_completion when cwq has no
> pending works. But we need ->current_work (introduced in the next patch) to
> implement this correctly.
> 
> I'll re-send the patch below later, when we finish with the bug you pointed
> out, but it would be nice if you can take a look now.

The patch seems fine to me, though I dont see any cpu hotplug
related problem being exposed/solved in this patch.

-- 
Regards,
vatsa
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