linux-kernel - Re: [RFC PATCH(Experimental) 2/4] Revert changes to workqueue.c

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Message-ID: <20070221062947.GG20820@in.ibm.com>
Date:	Wed, 21 Feb 2007 11:59:47 +0530
From:	Srivatsa Vaddagiri <vatsa@...ibm.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Gautham R Shenoy <ego@...ibm.com>, akpm@...l.org,
	paulmck@...ibm.com, mingo@...e.hu, dipankar@...ibm.com,
	venkatesh.pallipadi@...el.com, linux-kernel@...r.kernel.org,
	rjw@...k.pl
Subject: Re: [RFC PATCH(Experimental) 2/4] Revert changes to workqueue.c

On Tue, Feb 20, 2007 at 11:09:36PM +0300, Oleg Nesterov wrote:
> > Which caller are you referring to here? Maybe we can decide on the
> > option after we see the users of flush_workqueue() in DOWN_PREPARE.
> 
> mm/slab.c:cpuup_callback()

The cancel_rearming_delayed_work, if used as it is in cpuup_callback,
will require that we send DOWN_PREPARE before freeze_processes().

But ..I am wondering if we can avoid doing cancel_rearming_delayed_work
(and thus flush_workqueue) in CPU_DOWN_PREPARE of slab.c. Basically,

mm/slab.c:

	CPU_DOWN_PREPARE:	/* All processes frozen now */
		cancel_delayed_work(&per_cpu(reap_work, cpu).timer);
		del_work(&per_cpu(reap_work, cpu).work);
		break;


At the point of CPU_DOWN_PREPARE, keventd should be frozen and hence
del_work() is a matter of just deleting the work from cwq->worklist.


-- 
Regards,
vatsa
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