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

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Date:	Thu, 5 Jul 2007 21:37:57 +1000
From:	Nigel Cunningham <nigel@...el.suspend2.net>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	nigel@...pend2.net, Pavel Machek <pavel@....cz>,
	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 21:28:49 Rafael J. Wysocki wrote:
> On Thursday, 5 July 2007 00:52, Nigel Cunningham wrote:
> > On Thursday 05 July 2007 08:49:42 Pavel Machek wrote:
> > > On Thu 2007-07-05 08:48:15, Nigel Cunningham wrote:
> > > > On Thursday 05 July 2007 00:58:58 Rafael J. Wysocki wrote:
> > > > > 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.
> 
> Well, that's a valid point, I'll move it under the mutex.

Okee doke.
 
> And why do you think it will be called twice?

Hmm. Looking again now, I can't see why I thought that. Maybe I just hadn't 
had enough caffeine today at that stage :)

Nigel
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