linux-kernel - Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM pathway

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Date:	Tue, 03 Jul 2007 21:40:26 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	linux-pm@...ts.linux-foundation.org,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to
	RAM pathway

On Tue, 2007-07-03 at 09:44 +0200, Oliver Neukum wrote:
> Am Dienstag, 3. Juli 2007 schrieb Benjamin Herrenschmidt:
> > So to summarize, the plan that makes things work with fuse is:
> > 
> >  - For STR, don't do the freezer thing.
> > 
> >  - For STD, don't sys_sync() after you froze
> > 
> > There might be -other- issues, but that should get you through some of
> 
> At the risk of repeating myself. Character device drivers are written
> with the assumption that normal io and suspend/resume do not race
> with each other due to the freezer.
> What do you intend to do about that?

Ugh ... "character devices" ... that's a pretty wide statement...
there's lots of those and very different one from the other...

Any sane device-driver will have to cope with being suspended in a
"live" system. I've demonstrated multiple times in the past why this is
necessary anyway, for things like dynamic power management, among
others.

The whole freezer thing is a hack job to avoid fixing drivers that need
fixing. Unfortunately, I believe in that area, it's simply not
sustainable. Besides, getting drivers to behave properly isn't very hard
in most cases.

Ben.

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