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

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Message-ID: <20070708210729.GC5401@elf.ucw.cz>
Date:	Sun, 8 Jul 2007 23:07:29 +0200
From:	Pavel Machek <pavel@....cz>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	Kyle Moffett <mrmacman_g4@....com>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org
Subject: Re: [PATCH] Remove process freezer from suspend to RAM pathway

Hi!

> > > I just think that the freezer approach, as it is, is backward. We can't
> > > have a 3rd party try to discriminate what to freeze and what not, it
> > > will always get something wrong, and in some cases with the wrong timing
> > > or ordering.
> > 
> > Nice discussion, except for one thing: the freezer doesn't decide what to
> > freeze.  For example, even right now kernel threads decide if they want to be
> > frozen.
> 
> Somewhat... userspace doesn't and workqueues are a gray area.

But userspace must not be neccessary for kernel functioning, so that's
quite okay. And we do need to solve the workqueues.

> Also, I've been thinking this "icebox" idea a bit more and it seems in
> fact a bit racy in some areas, at least for use by things like drivers,
> unless we end up doing something aking to an RCU on suspend, waiting for
> all tasks to reach userland once, but that has the same annoyances as
> the current freezer.
> 
> Thus I'm tempted to go back to saying that driver can handle things
> locally :-)

:-). Or perhaps freezer is not _that_ evil after all?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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