linux-kernel - Re: [PATCH] thermal: Use freezable workqueue

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Message-Id: <201102081020.25646.rjw@sisk.pl>
Date:	Tue, 8 Feb 2011 10:20:25 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Len Brown <len.brown@...el.com>,
	ACPI Devel Mailing List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>,
	Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH] thermal: Use freezable workqueue

On Tuesday, February 08, 2011, Dmitry Torokhov wrote:
> On Tue, Feb 08, 2011 at 12:29:57AM +0100, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rjw@...k.pl>
> > 
> > If thermal polling is enabled, which for example is the case for
> > ACPI thermal zones with the _TZP object defined, the thermal driver
> > uses delayed work items for this purpose.  Unfortunately, since
> > they are queued up using schedule_delayed_work(), the work function
> > may be executed during system suspend or resume, which is not
> > desirable.
> > 
> > To prevent that from happening, use a freezable workqueue for
> > queuing up delayed work items in the thermal driver.
> > 
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> > ---
> >  drivers/thermal/thermal_sys.c |   22 ++++++++++++++++++++--
> >  1 file changed, 20 insertions(+), 2 deletions(-)
> > 
> > Index: linux-2.6/drivers/thermal/thermal_sys.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/thermal/thermal_sys.c
> > +++ linux-2.6/drivers/thermal/thermal_sys.c
> > @@ -62,6 +62,20 @@ static DEFINE_MUTEX(thermal_list_lock);
> >  
> >  static unsigned int thermal_event_seqnum;
> >  
> > +static struct workqueue_struct *thermal_wq;
> > +
> > +static int __init thermal_start_workqueue(void)
> > +{
> > +	thermal_wq = alloc_workqueue("thermal", WQ_FREEZEABLE, 0);
> 
> Should probably be unbound as well.

Yup, thanks.

> FWIW, I would not mind if we had a global freezeable workqueue already
> predefined. I could switch input_polldev and vmw_balloon to it and there
> probably could be more users...

Hmm, OK.

Do you think we should add system_freezeable_wq to the set of predefined
workqueues?

Rafael
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