linux-kernel - Re: [RFD] Automatic suspend

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Message-ID: <d6200be20902271409y395822c9ic8f1223f6551631c@mail.gmail.com>
Date:	Fri, 27 Feb 2009 14:09:12 -0800
From:	Arve Hjønnevåg <arve@...roid.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Matthew Garrett <mjg59@...f.ucam.org>, Pavel Machek <pavel@....cz>,
	Alan Stern <stern@...land.harvard.edu>,
	"Woodruff, Richard" <r-woodruff2@...com>,
	Arjan van de Ven <arjan@...radead.org>,
	Kyle Moffett <kyle@...fetthome.net>,
	Oliver Neukum <oliver@...kum.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	mark gross <mgross@...ux.intel.com>,
	Uli Luckas <u.luckas@...d.de>,
	Igor Stoppa <igor.stoppa@...ia.com>,
	Brian Swetland <swetland@...gle.com>,
	Len Brown <lenb@...nel.org>
Subject: Re: [RFD] Automatic suspend

On Fri, Feb 27, 2009 at 12:54 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> On Friday 27 February 2009, Matthew Garrett wrote:
>> On Fri, Feb 27, 2009 at 03:22:39PM +0100, Rafael J. Wysocki wrote:
>> > On Friday 27 February 2009, Pavel Machek wrote:
>> > > Wakelocks done right are single atomic_t... and if you set it to 0,
>> > > you just unblock "sleeper" thread or something. Zero polling and very
>> > > simple...
>> >
>> > Except that you have to check all of the wakelocks periodically in a loop =>
>> > polling.  So?
>>
>> Why do you need to check them? If you're taking this approach you just
>> have something like:
>>
>> suspend_unblock() {
>>       if (atomc_dec_and_test(&suspend_lock))
>>               suspend();
>> }
>>
>> and then check that the lock count is still 0 after device_suspend().
>> There's no need to poll.
>
> I was talking about wakelocks as originally proposed.

Can you be more specific? My wakelock implementation triggers suspend
when the active list becomes empty. No polling required.

-- 
Arve Hjønnevåg
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