linux-kernel - Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.

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Date:	Fri, 07 May 2010 11:00:55 -0700
From:	Daniel Walker <dwalker@...o99.com>
To:	Matthew Garrett <mjg@...hat.com>
Cc:	Tony Lindgren <tony@...mide.com>,
	Brian Swetland <swetland@...gle.com>,
	Alan Stern <stern@...land.harvard.edu>,
	mark gross <mgross@...ux.intel.com>, markgross@...gnar.org,
	Len Brown <len.brown@...el.com>, linux-doc@...r.kernel.org,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.

On Fri, 2010-05-07 at 18:51 +0100, Matthew Garrett wrote:
> On Fri, May 07, 2010 at 10:40:43AM -0700, Daniel Walker wrote:
> > On Fri, 2010-05-07 at 18:36 +0100, Matthew Garrett wrote:
> > > If your wakeup latencies are sufficiently low and you have fine-grained 
> > > enough control over your hardware then suspend in idle is a reasonable 
> > > thing to do - but if you have a userspace app that's spinning then 
> > > that doesn't solve the issue.
> > 
> > If there's a userspace app spinning then you don't go idle (or that's my
> > assumption anyway). You mean like repeatedly blocking and unblocking
> > right?
> 
> Right, that's the problem. idle-based suspend works fine if your 
> applications let the system go idle, but if your applications are 
> anything other than absolutely perfect in this respect then you consume 
> significant power even if the device is sitting unused in someone's 
> pocket.

True .. I'd wonder how an OMAP based devices deal with that issue, since
they would have that exact problem. According to what Tony is telling
us. Actually a bogus userspace can do a lot more than just consume power
you could hang the system too.

Daniel


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