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

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Date:	Tue, 3 Jul 2007 19:20:59 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	Pavel Machek <pavel@....cz>,
	Nigel Cunningham <nigel@...el.suspend2.net>
Subject: Re: [PATCH] Remove process freezer from suspend to RAM pathway

Am Dienstag, 3. Juli 2007 schrieb Rafael J. Wysocki:
> On Tuesday, 3 July 2007 15:08, Rafael J. Wysocki wrote:
> > On Tuesday, 3 July 2007 07:51, Benjamin Herrenschmidt wrote:
> > > On Tue, 2007-07-03 at 05:29 +0100, Matthew Garrett wrote:
> > > > Suspend to RAM on a machine with / on a fuse filesystem turns out to be 
> > > > a screaming nightmare - either the suspend fails because syslog (for 
> > > > instance) can't be frozen, or the machine deadlocks for some other 
> > > > reason I haven't tracked down. We could "fix" fuse, or alternatively we 
> > > > could do what we do for suspend to RAM on other platforms (PPC and APM) 
> > > > and just not use the freezer.
> > > 
> > > The main reason for deadlocks is because we do a sys_sync() after the
> > > freeze, which we shouldn't do.
> > 
> > So why don't we remove the sys_sync() from freeze_processes() instead?
> 
> The patch follows (untested).
> 
> Greetings,
> Rafael
> 
> 
> ---
> From: Rafael J. Wysocki <rjw@...k.pl>
> 
> We shouldn't sync filesystems from within the freezer, because it's not needed
> for suspend to RAM and leads to problems with FUSE.

This seems fishy. Swsusp needs enough clean memory to make enough
room for the image. If you sync before you freeze, the running tasks can
redirty memory.
What makes you sure that you don't die as shrink_all_memory() writes out
pages?

	Regards
		Oliver

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