On Tue, 9 Oct 2007 20:26:42 +0900
KAMEZAWA Hiroyuki <[EMAIL PROTECTED]> wrote:
> >
> > > + */
> > > + if (clear_page_cgroup(page, pc) == pc) {
> >
> > OK.. so we've come so far and seen that pc has changed underneath us,
> > what do we do with this pc?
> >
> Hmm... How about this ?
> ==
> if (clear_page_cgroup(page, pc) == pc) {
> /* do usual work */
> } else {
> BUG();
> }
> == or BUG_ON(clear_page_cgroup(page, pc) != pc)
>
> I have no clear idea when this race will occur.
After good sleep, I noticed there is a race with force_reclaim (in patch 6).
force_reclaim doesn't check refcnt before clearing page->pc.
My final view will be
==
if (clear_page_cgroup(page, pc) == pc) {
/* do usual work */
} else {
/* force reclaim clears page->page_cgroup */
}
==
Anyway, I'll add a meaningful comment here.
Thanks,
-Kame
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