linux-kernel - Re: [PATCH 0/8] Suspend block api (version 6)

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Date:	Tue, 11 May 2010 09:58:21 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Matthew Garrett <mjg@...hat.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Kevin Hilman <khilman@...prootsystems.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Alan Stern <stern@...land.harvard.edu>,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	Paul Walmsley <paul@...an.com>, magnus.damm@...il.com,
	mark gross <mgross@...ux.intel.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Geoff Smith <geoffx.smith@...el.com>,
	Brian Swetland <swetland@...gle.com>
Subject: Re: [PATCH 0/8] Suspend block api (version 6)

* Matthew Garrett <mjg@...hat.com> [100511 09:41]:
> On Tue, May 11, 2010 at 09:36:33AM -0700, Tony Lindgren wrote:
> > OK, so can the suspend blocker then become just:
> > 
> > # Block suspend while idle, system stays running
> > # echo default > /sys/power/policy
> > 
> > and the when it's OK to suspend:
> > 
> > # Allow suspend while idle, system suspends when it hits kernel idle loop
> > # echo opportunistic > /sys/power/policy
> > 
> > or do you still need something more to ensure the data gets into your
> > app and be handled?
> 
> Yes. You still need suspend blocks.

Maybe not if echo opportunistic > /sys/power/policy gets cleared by
the kernel if the kernel idle loop can't make it. That means something
has blocked the suspend attempt in a driver for example. The system
keeps running, and the userspace can deal with the situation.
 
> > The part I really don't like is the idea of patching all over the drivers
> > and userspace for the wakelocks/suspendblocks.
> 
> I don't like the idea either, but given that nobody has actually 
> provided any other ideas that would actually work then I don't think 
> we've got a great deal of choice.

If the opportunistic kernel flag is one time attempt only, then you
could take care of the wakelock/suspendblock handling in the userspace
completely. And once the userspace wakelock/suspendblock is cleared,
the userspace can again echo opportunistic > /sys/power/policy.

Regards,

Tony
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