linux-kernel - Re: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2: hang in atomic copy)

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Message-ID: <20070425224928.GJ17387@elf.ucw.cz>
Date:	Thu, 26 Apr 2007 00:49:28 +0200
From:	Pavel Machek <pavel@....cz>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Kenneth Crudup <kenny@...ix.com>, Nick Piggin <npiggin@...e.de>,
	Mike Galbraith <efault@....de>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Con Kolivas <kernel@...ivas.org>,
	suspend2-devel@...ts.suspend2.net, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2: hang in atomic copy)

Hi!

> > Not the same... but they are still related. "freeze" (for atomic
> > snapshot) is actually subset of "suspend"... freeze needs DMAs off and
> > saved state, and you need DMAs off and saved state for "suspend".
> 
> THEY HAVE ABSOLUTELY NOTHING IN COMMON!
> 
> Nobody in their right mind thinks that "disable DMA" and "suspend" are 
> similar operations. 
> 
> > So it is actually correct to do "suspend" when you want "freeze"; it
> > is just slow. That's why they only differ in parameter these days.
> 
> It is *not* correct to "suspend" when you want "freeze".
> 
> I don't understand how you can even *claim* something like that.

BTW most problems are in thaw/resume functions. Both suspend and
freeze are pretty simple, and they both need to save device state. In
SCSI disk, it would be nice to save options set by sdparm. And both
thaw and resume need to be able to restore the device from both
"powered down" and "some state preserved".
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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