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

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Message-ID: <CAMP5XgenQF11AUSkn2iWT679bWHe8XeQ1mbrKcSzbDNQLctp5w@mail.gmail.com>
Date:	Wed, 15 Feb 2012 20:39:02 -0800
From:	Arve Hjønnevåg <arve@...roid.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
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

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.

-- 
Arve Hjønnevåg
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