Re: 2.6.35.5: hibernation broken... AGAIN

From: Rafael J. Wysocki
Date: Wed Dec 01 2010 - 16:26:41 EST


On Wednesday, December 01, 2010, KAMEZAWA Hiroyuki wrote:
> On Wed, 1 Dec 2010 01:38:53 +0100
> "Rafael J. Wysocki" <rjw@xxxxxxx> 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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