Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: 2.6.35.5: hibernation broken... AGAIN | Date | Thu, 2 Dec 2010 01:00:39 +0100 |
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On Thursday, December 02, 2010, KAMEZAWA Hiroyuki wrote: > On Wed, 1 Dec 2010 23:23:31 +0100 > "Rafael J. Wysocki" <rjw@sisk.pl> wrote: > > > On Wednesday, December 01, 2010, Rafael J. Wysocki wrote: > > > On Wednesday, December 01, 2010, KAMEZAWA Hiroyuki wrote: > > > > On Wed, 1 Dec 2010 01:38:53 +0100 > > > > "Rafael J. Wysocki" <rjw@sisk.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? > > > > Please note that pm_restore_gfp_mask() can be legitimately called before > > pm_restrict_gfp_mask() via the SNAPSHOT_CREATE_IMAGE hibernate ioctl, so the > > test you're suggesting wouldn't really work. > > > > Hm, I just wonder some tests not for breaking gfp_allowed_mask by > - double call
That's easy. It's sufficient to do WARN_ON(saved_gfp_mask) at the beginning of pm_restrict_gfp_mask(). This also takes care of the "forget to restore" case to some extent, because pm_restrict_gfp_mask() will generally be only called twice in a row if there's a missing pm_restore_gfp_mask() in between.
> - forget to restore
This is kind of difficult in general. You can't detect a missing pm_restore_gfp_mask() other than by checking if pm_restrict_gfp_mask() is not called twice in a row IMHO.
> That will be fatal.
Yes, it will.
> I'm not very interested in implementation detail
Well ...
Thanks, Rafael
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