linux-kernel - Re: [PATCH] PM / QoS: Fix workqueue deadlock when using pm_qos_update_request

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Message-ID: <4423040.Ds5TZlivfo@vostro.rjw.lan>
Date:	Tue, 13 Aug 2013 22:49:09 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Tejun Heo <tj@...nel.org>
Cc:	Stephen Boyd <sboyd@...eaurora.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM / QoS: Fix workqueue deadlock when using pm_qos_update_request_timeout()

On Tuesday, August 13, 2013 01:01:46 PM Tejun Heo wrote:
> Hello,
> 
> On Tue, Aug 13, 2013 at 09:46:26AM -0700, Stephen Boyd wrote:
> > >> +	if (PM_QOS_DEFAULT_VALUE != req->node.prio)
> > >> +		pm_qos_update_target(
> > >> +				pm_qos_array[req->pm_qos_class]->constraints,
> > >> +				&req->node, PM_QOS_UPDATE_REQ,
> > >> +				PM_QOS_DEFAULT_VALUE);
> > > Maybe it'd be cleaner to add a param or internal variant of
> > > pm_qos_update_request()?
> > 
> > Maybe, but I was trying to make a minimal fix here.
> 
> Hmmm.... it just looks like things can easily get out of sync with the
> complex function call.

Yes, that's just duplicated code.

> I don't think it'll be too invasive if you introduce an internal variant
> which doesn't do the canceling.  Rafael, what do you think?

I'd move the part of pm_qos_update_request() below the
cancel_delayed_work_sync() to a separate static function that'd be
called from two places.

Thanks,
Rafael

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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