linux-kernel - Re: [PATCH 3/3] PM / Sleep: Make __pm_stay

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Date:	Thu, 16 Feb 2012 23:09:15 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Arve Hjønnevåg <arve@...roid.com>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] PM / Sleep: Make __pm_stay_awake() delete wakeup source timers

On Thursday, February 16, 2012, Arve Hjønnevåg wrote:
> 2012/2/15 Rafael J. Wysocki <rjw@...k.pl>:
> > From: Rafael J. Wysocki <rjw@...k.pl>
> >
> > If __pm_stay_awake() is called after __pm_wakeup_event() for the same
> > wakep source object before its timer expires, it won't cancel the
> > timer, so the wakeup source will be deactivated from the timer
> > function as scheduled by __pm_wakeup_event().  In that case
> > __pm_stay_awake() doesn't have any effect beyond incrementing
> > the wakeup source's event_count field, although it should cancel
> > the timer and make the wakeup source stay active until __pm_relax()
> > is called for it.
> >
> > Conversely, if __pm_wakeup_event() is called for a wakeup source
> > that has been activated by __pm_stay_awake() before, it will set up
> > the timer to deactivate the wakeup source, although it should leave
> > it active until __pm_relax() is called for it.
> 
> We have many drivers that call wake_lock_timeout instead of
> wake_unlock to cancel a previous wake_lock call. These drivers will
> need to use two wakeup sources if __pm_wakeup_event does not always
> set the timeout. I think it is better to have the state of the wakeup
> source only depend on the last function you called, instead of that
> last function being a noop in some cases.

OK

Rafael
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