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

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Message-ID: <20100527175258.GB3543@srcf.ucam.org>
Date:	Thu, 27 May 2010 18:52:58 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arve Hjønnevåg <arve@...roid.com>,
	Florian Mickler <florian@...kler.org>,
	Vitaly Wool <vitalywool@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Paul@...p1.linux-foundation.org, felipe.balbi@...ia.com,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Linux PM <linux-pm@...ts.linux-foundation.org>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

On Thu, May 27, 2010 at 07:46:37PM +0200, Peter Zijlstra wrote:
> On Thu, 2010-05-27 at 18:41 +0100, Matthew Garrett wrote:
> > On Thu, May 27, 2010 at 07:35:50PM +0200, Peter Zijlstra wrote:
> > > Then that's an application bug right there, isn't it?
> > > 
> > > If should have listened to the window server telling its clients it was
> > > going to go away. Drawing after you get that is your own damn fault ;-)
> > 
> > How long do you wait for applications to respond that they've stopped 
> > drawing? What if the application is heavily in swap at the time?
> 
> Since we're talking about a purely idle driven power saving, we wait
> until the cpu is idle.

If that's what you're aiming for then you don't need to block 
applications on hardware access because they should all already have 
idled themselves.

> Note that it doesn't need to broadcast this, it could opt to reply with
> that message on the first drawing attempt after it goes away and block
> on the second.

That's more interesting, but you're changing semantics quite heavily at 
this point.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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