linux-kernel - Re: [linux-pm] [PATCH] - race-free suspend. Was: Re: [PATCH 0/8] Suspend block api (version 8)

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Date:	Wed, 2 Jun 2010 23:04:44 -0700
From:	mark gross <640e9920@...il.com>
To:	Brian Swetland <swetland@...gle.com>
Cc:	Neil Brown <neilb@...e.de>, Peter Zijlstra <peterz@...radead.org>,
	"Paul@...p1.linux-foundation.org" <Paul@...p1.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Florian Mickler <florian@...kler.org>,
	James Bottomley <James.Bottomley@...e.de>,
	Linux PM <linux-pm@...ts.linux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Felipe Balbi <felipe.balbi@...ia.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [linux-pm] [PATCH] - race-free suspend. Was: Re: [PATCH 0/8]
 Suspend block api (version 8)

On Wed, Jun 02, 2010 at 11:05:18AM -0700, Brian Swetland wrote:
> On Wed, Jun 2, 2010 at 1:06 AM, Neil Brown <neilb@...e.de> wrote:
> > On Wed, 2 Jun 2010 00:05:14 -0700
> > Arve Hjønnevåg <arve@...roid.com> wrote:
> >> > The user-space suspend daemon avoids losing wake-events by using
> >> > fcntl(F_OWNER) to ensure it gets a signal whenever any important wake-event
> >> > is ready to be read by user-space.  This may involve:
> >> >  - the one daemon processing all wake events
> >>
> >> Wake up events are not all processed by one daemon.
> >
> > Not with your current user-space code, no.  Are you saying that you are not
> > open to any significant change in the Android user-space code?  That would
> > make the situation a lot harder to resolve.
> 
> There are many wakeup events possible in a typical system --
> keypresses or other input events, network traffic, telephony events,
> media events (fill audio buffer, fill video decoder buffer, etc), and
> I think requiring that all wakeup event processing bottleneck through
> a single userspace process is non-optimal here.

Um doesn't the android framework bottleneck the user mode lock
processing through the powermanager and any wake up event processing
eventually has to grab a lock through this bottleneck anyway?

> 
> The current suspend-blocker proposal already involves userspace
> changes (it's different than our existing wakelock interface), and
> we're certainly not opposed to any/all userspace changes on principle,
> but on the other hand we're not interested in significant reworks of
> userspace unless they actually improve the situation somehow.  I think
> bottlenecking events through a central daemon would represent a step
> backwards.

I'm not sure its a step in any direction, but I do understand the
avoidance of having to rework a lot of code.

--mgross

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