Re: [PATCH 2/3] swsusp: Do not use page flags

Rafael J. Wysocki
2007-03-15T21:03:14Z

On Thursday, 15 March 2007 20:08, Andrew Morton wrote:
> > On Mon, 12 Mar 2007 22:19:20 +0100 "Rafael J. Wysocki" <rjw@sisk.pl> wrote:
> > +int create_basic_memory_bitmaps(void)
> > +{
> > + struct memory_bitmap *bm1, *bm2;
> > + int error = 0;
> > +
> > + BUG_ON(forbidden_pages_map || free_pages_map);
> > +
> > + bm1 = kzalloc(sizeof(struct memory_bitmap), GFP_ATOMIC);
> > + if (!bm1)
> > + return -ENOMEM;
> > +
> > + error = memory_bm_create(bm1, GFP_ATOMIC | __GFP_COLD, PG_ANY);
> > + if (error)
> > + goto Free_first_object;
> > +
> > + bm2 = kzalloc(sizeof(struct memory_bitmap), GFP_ATOMIC);
> > + if (!bm2)
> > + goto Free_first_bitmap;
> > +
> > + error = memory_bm_create(bm2, GFP_ATOMIC | __GFP_COLD, PG_ANY);
> > + if (error)
>
> What is the risk that we'll go OOM here? GFP_ATOMIC is rather unreliable.

Well, this can be called after processes (including kswapd) has been frozen.
We can't go to sleep at this point.

> And why _does_ suspend use GFP_ATOMIC all over the place?

Generally, because it cannot sleep.