linux-kernel - Re: 2.6.35.5: hibernation broken... AGAIN

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Message-Id: <201012012225.40329.rjw@sisk.pl>
Date:	Wed, 1 Dec 2010 22:25:40 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Ondrej Zary <linux@...nbow-software.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Balbir Singh <balbir@...ibm.com>
Subject: Re: 2.6.35.5: hibernation broken... AGAIN

On Wednesday, December 01, 2010, KAMEZAWA Hiroyuki wrote:
> On Wed, 1 Dec 2010 01:38:53 +0100
> "Rafael J. Wysocki" <rjw@...k.pl> wrote:
> 
> > On Wednesday, December 01, 2010, Rafael J. Wysocki wrote:
> > > On Tuesday, November 30, 2010, Hugh Dickins wrote:
> > > > On Sat, 27 Nov 2010, Rafael J. Wysocki wrote:
> > > > > On Saturday, November 27, 2010, Ondrej Zary wrote:
> > ...
> > > > 
> > > > Trivial point, I suppose, but it bothers me that PM is accumulating
> > > > wrappers around wrappers around gfp_allowed_mask.  Looks like
> > > > clear_gfp_allowed_mask and set_gfp_allowed_mask (oddly asymmetrical)
> > > > were not really what we need.  How about scrapping them, and putting
> > > > pm_restrict_gfp_mask() and pm_restore_gfp_mask() into page_alloc.c?
> > > 
> > > Sure, that sounds like a good idea indeed.
> > 
> > Below is an updated patch in which I tried to address your comments.
> > 
> > I didn't find it very useful to couple pm_restore_gfp_mask() with the thawing
> > of tasks, but nevertheless I think all of the spots where it's needed are
> > covered now.
> > 
> > The patch has only been compile-tested for now, so caveat emptor.
> > 
> 
> Hmm, can't we have some error check as 
> 
> > +static gfp_t saved_gfp_mask;
> 
> atomic_t gfp_mask_save_mode_counter;
> 
> > +
> > +void pm_restore_gfp_mask(void)
> >  {
> >  	WARN_ON(!mutex_is_locked(&pm_mutex));
> > -	gfp_allowed_mask = mask;
> 
> 	if (atomic_dec_return(&gfp_mask_save_mode_counter))
> 		WARN_ONCE()
> 
> > +	if (saved_gfp_mask) {
> > +		gfp_allowed_mask = saved_gfp_mask;
> > +		saved_gfp_mask = 0;
> > +	}
> >  }
> 
> > +void pm_restrict_gfp_mask(void)
> >  {
> > -	gfp_t ret = gfp_allowed_mask;
> > -
> >  	WARN_ON(!mutex_is_locked(&pm_mutex));
> > -	gfp_allowed_mask &= ~mask;
> > -	return ret;
> > +	saved_gfp_mask = gfp_allowed_mask;
> > +	gfp_allowed_mask &= ~GFP_IOFS;
> 
> 	if (atomic_inc_return(&gfp_mask_save_mode_counter) > 1)
> 		WARN_ONCE()
> 
> or some ?

What exactly would that be useful for?

Rafael
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