linux-kernel - Re: [RFC][PATCH -mm] PM: Do not sync from within the freezer during suspend to RAM

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Message-Id: <200707050852.15392.nigel@nigel.suspend2.net>
Date:	Thu, 5 Jul 2007 08:52:14 +1000
From:	Nigel Cunningham <nigel@...el.suspend2.net>
To:	Pavel Machek <pavel@....cz>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Oliver Neukum <oliver@...kum.org>,
	Paul Mackerras <paulus@...ba.org>,
	Miklos Szeredi <miklos@...redi.hu>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [RFC][PATCH -mm] PM: Do not sync from within the freezer during suspend to RAM

Hi.

On Thursday 05 July 2007 08:49:42 Pavel Machek wrote:
> On Thu 2007-07-05 08:48:15, Nigel Cunningham wrote:
> > Hi.
> > 
> > On Thursday 05 July 2007 00:58:58 Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rjw@...k.pl>
> > > 
> > > The syncing of filesystems from within the freezer in not needed for 
suspend 
> > to
> > > RAM.  Change freeze_processes() so that it doesn't execute sys_sync() 
and
> > > introduce the "syncing" version of it to be called from the hibernation 
code
> > > paths.
> > > 
> > > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> > > ---
> > >  include/linux/freezer.h |   14 ++++++++++++--
> > >  kernel/power/disk.c     |    2 +-
> > >  kernel/power/main.c     |    6 ++++++
> > >  kernel/power/process.c  |    8 +++++---
> > >  kernel/power/user.c     |    2 +-
> > >  5 files changed, 25 insertions(+), 7 deletions(-)
> > 
> > Looks ok, except that I wonder if you want the following fragment. It 
looks to 
> > me (looking at rc6) like with this code, you'll currently call sys_sync 
twice 
> > when suspending to ram. Maybe I'm misreading it. Also, shouldn't it be 
done 
> > after taking the mutex?
> 
> sys_sync() should be okay to call, mutex or not.

Yeah. That wasn't my point, sorry. Calling sys_sync is pointless if you're 
going to fail to take the mutex. It makes more sense to know you've got it 
before you start doing things related to actually suspending.

Regards,

Nigel
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