linux-kernel - Re: [linux-pm] [RFC][PATCH 1/5] PM/Freezer: Disable OOM killer whentasks are frozen

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Message-Id: <200905071409.45362.rjw@sisk.pl>
Date:	Thu, 7 May 2009 14:09:44 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Matt Helsley <matthltc@...ibm.com>
Cc:	pm list <linux-pm@...ts.linux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [linux-pm] [RFC][PATCH 1/5] PM/Freezer: Disable OOM killer whentasks are frozen

On Thursday 07 May 2009, Matt Helsley wrote:
> On Thu, May 07, 2009 at 12:41:04AM +0200, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rjw@...k.pl>
> > 
> > The OOM killer is not really going to work while tasks are frozen, so
> > we can just give up calling it in that case.
> > 
> > This will allow us to safely use memory allocations for decreasing
> > the number of saveable pages in the hibernation core code instead of
> > using any artificial memory shriking mechanisms for this purpose.
> > 
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> 
> 
> > ---
> >  include/linux/freezer.h |    2 ++
> >  kernel/power/process.c  |   12 ++++++++++++
> >  mm/page_alloc.c         |    5 +++++
> >  3 files changed, 19 insertions(+)
> > 
> > Index: linux-2.6/kernel/power/process.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/power/process.c
> > +++ linux-2.6/kernel/power/process.c
> > @@ -19,6 +19,8 @@
> >   */
> >  #define TIMEOUT	(20 * HZ)
> > 
> > +static bool tasks_frozen;
> > +
> >  static inline int freezeable(struct task_struct * p)
> >  {
> >  	if ((p == current) ||
> > @@ -120,6 +122,10 @@ int freeze_processes(void)
> >   Exit:
> >  	BUG_ON(in_atomic());
> >  	printk("\n");
> > +
> > +	if (!error)
> > +		tasks_frozen = true;
> > +
> 
> It's not really about whether some tasks are frozen -- that can 
> happen using the cgroup freezer too. The flag really indicates if
> all killable tasks are frozen. That can't happen using the cgroup
> freezer since the root cgroup can't be frozen. So I think some name changes 
> are in order but otherwise the patch looks fine.

Well, as I said in the [0/5] message, I'm not sure if the patch is really
necessary.  I'll change the names if it turns out to be.

Thanks,
Rafael
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