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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Arve =?iso-8859-1?q?Hj=F8nnev=E5g?= <arve@android.com>
Subject: Re: [RFD] Automatic suspend
Date: Fri, 27 Feb 2009 23:55:10 +0100
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Cc: Matthew Garrett <mjg59@srcf.ucam.org>, Pavel Machek <pavel@ucw.cz>,
       Alan Stern <stern@rowland.harvard.edu>,
       "Woodruff, Richard" <r-woodruff2@ti.com>,
       Arjan van de Ven <arjan@infradead.org>,
       Kyle Moffett <kyle@moffetthome.net>, Oliver Neukum <oliver@neukum.org>,
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       pm list <linux-pm@lists.linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>,
       Nigel Cunningham <nigel@nigel.suspend2.net>,
       mark gross <mgross@linux.intel.com>, Uli Luckas <u.luckas@road.de>,
       Igor Stoppa <igor.stoppa@nokia.com>,
       Brian Swetland <swetland@google.com>, Len Brown <lenb@kernel.org>
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On Friday 27 February 2009, Arve Hjønnevåg wrote:
> On Fri, Feb 27, 2009 at 12:54 PM, Rafael J. Wysocki <rjw@sisk.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.

Sorry, I overlooked and/or didn't remember that.  My bad.

Rafael