linux-kernel - Re: [PATCH 3/6] workqueue: make cancel_rearming_delayed

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Date:	Wed, 7 Feb 2007 18:16:30 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Daniel Drake <dsd@...too.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	David Howells <dhowells@...hat.com>
Subject: Re: [PATCH 3/6] workqueue: make cancel_rearming_delayed_workqueue() work on idle dwork

On 02/07, Daniel Drake wrote:
>
> Oleg Nesterov wrote:
> >cancel_rearming_delayed_workqueue(dwork) will hang forever if dwork was not
> >scheduled, because in that case cancel_delayed_work()->del_timer_sync() 
> >never
> >returns true.
> 
> Thanks! We hit this problem before with the zd1211rw driver and avoided 
> using cancel_rearming_delayed_workqueue() for this reason.

Great. But I am afraid my changelog was incomplete. This patch only fixes
the cancel_rearming_delayed_workqueue(freshly_initialized_dwork) lockup.

The following code

	schedule_delayed_work(dw);
	cancel_rearming_delayed_workqueue(dw);	// OK
	cancel_rearming_delayed_workqueue(dw);	// HANGS!

still doesn't work.

Is it worth fixing? The fix is very simple, and probably makes sense by
itself:

	cancel_delayed_work:

	-	work_release(&work->work);
	+	work->work.data = NULL;

Oleg.

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