linux-kernel - Re: [PATCH] workqueues: insert_work: use "list

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Message-ID: <20080613101312.GA4319@ff.dom.local>
Date:	Fri, 13 Jun 2008 10:13:12 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Max Krasnyansky <maxk@...lcomm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] workqueues: insert_work: use "list_head *" instead of
	"int tail"

On 13-06-2008 00:24, Jarek Poplawski wrote:
> On Thu, Jun 12, 2008 at 08:55:50PM +0400, Oleg Nesterov wrote:
>> On 06/12, Oleg Nesterov wrote:
>>> insert_work() inserts the new work_struct before or after cwq->worklist,
>>> depending on the "int tail" parameter. Change it to accept "list_head *"
>>> instead, this shrinks .text a bit and allows us to insert the barrier
>>> after specific work_struct.
>> This allows us to implement
>>
>> 	int flush_work(struct work_struct *work)
>> 	{
> ...
>> 	}
>>
>> suggested by Peter. It only waits for selected work_struct.
>>
>> I doubt it will have a lot of users though. In most cases we need
>> cancel_work_sync() and nothing more.
> 
> I guess it could've had enough users if it were done a bit sooner...
> 
> I didn't check this implementation yet, but if it's "rtnl_lock in
> other works" safe then it could've been used in David Miller's fresh
> patch replacing last uses of flush_scheduled_work() in net drivers'
> ->stop() etc (thread: "Re: 2.6.25rc7 lockdep trace") - there would
> be far less doubts about possible change of functionality.

Hmm... I see it's definitely not for this. I should forget about my
crazy idea. Yes, cancel_work_sync() is mostly enough, and flush_
remains dangerous. (Maybe it's better not to get new users for this?)

Regards,
Jarek P.
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