On Wed, 3 Feb 2010 23:34:37 +0100
"Rafael J. Wysocki" <rjw@xxxxxxx> wrote:
> On Wednesday 03 February 2010, Andrew Morton wrote:
> > On Wed, 3 Feb 2010 02:44:23 +0100 "Rafael J. Wysocki" <rjw@xxxxxxx> wrote:
> >
> > > +static inline gfp_t clear_gfp_allowed_mask(gfp_t mask)
> > > +{
> > > + gfp_t ret = gfp_allowed_mask;
> > > + gfp_allowed_mask &= ~mask;
> > > + return ret;
> > > +}
> >
> > Fair enuf.
> >
> > Of course, this is all horridly racy/buggy without locking. Would I be
> > correct in hoping that all the callers happen when the system is in
> > everyone-is-frozen mode?
>
> As far as I can tell, gfp_allowed_mask is only touched during init apart from
> this.
Well yes - the new interfaces are the problem - they're racy!
> > Perhaps we should add some documentation (or even an assertion) to
> > prevent someone from using these interfaces from within normal code.
>
> I thought about that, but didn't invent anything smart enough.
>
> Well, maybe except for a comment like "this must be called with pm_mutex held",
> because that's the only case when it would be really safe.
Is that the locking rule? My above guess was incorrect?
Maybe slip a
BUG_ON(!mutex_is_locked(&pm_mutex));
in there?
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