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

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Date:	Mon, 24 May 2010 23:24:51 +0200
From:	Pavel Machek <pavel@....cz>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Paul Walmsley <paul@...an.com>, Arve Hj?nnev?g <arve@...roid.com>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	Tony Lindgren <tony@...mide.com>,
	Kevin Hilman <khilman@...prootsystems.com>,
	magnus.damm@...il.com, Theodore Ts'o <tytso@....edu>,
	mark gross <mgross@...ux.intel.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Geoff Smith <geoffx.smith@...el.com>,
	Brian Swetland <swetland@...gle.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Matthew Garrett <mjg@...hat.com>,
	Beno?t Cousson <b-cousson@...com>, linux-omap@...r.kernel.org,
	Vitaly Wool <vitalywool@...il.com>,
	Linus Walleij <linus.walleij@...csson.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Liam Girdwood <lrg@...mlogic.co.uk>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

Hi!

> > There are several general problems with the design of opportunistic
> > suspend and suspend-blocks.
> > 
> > 1. The opportunistic suspend code bypasses existing Linux kernel code,
> >    such as timers and the scheduler, that indicates when code
> >    needs to run, and when the system is idle.
> 
> Whoa!  That's not my understanding at all.
> 
> As I see it, opportunistic suspend doesn't bypass any code that isn't 
> already bypassed by the existing suspend code.  Users can do
> 
> 	echo mem >/sys/power/state
> 
> whenever they want, without regard to kernel timers and the scheduler 
> (other than the fact that the user's thread must be running in order to 
> carry out the write, of course).

Yep. And while I'm co-responsible for that interface, I would not
call it exactly nice. Yes, it does the job.

But imagine horrors atd/cron would have to do to work properly with
that interface... setting rtc wakeups etc.

So yes, mem > state already breaks promises, but lets not extend that.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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