Re: [PATCH] hugetlb: fix lockdep splat caused by pmd sharing

From: Dave Jones
Date: Tue Jul 30 2013 - 19:39:14 EST

On Wed, Jul 31, 2013 at 08:35:30AM +0900, Minchan Kim wrote:
> > which is a false positive caused by hugetlb pmd sharing code which
> > allocates a new pmd from withing mappint->i_mmap_mutex. If this
> > allocation causes reclaim then the lockdep detector complains that we
> > might self-deadlock.
> >
> > This is not correct though, because hugetlb pages are not reclaimable so
> > their mapping will be never touched from the reclaim path.
> >
> > The patch tells lockup detector that hugetlb i_mmap_mutex is special
> > by assigning it a separate lockdep class so it won't report possible
> > deadlocks on unrelated mappings.
> >
> > [peterz@xxxxxxxxxxxxx: comment for annotation]
> > Reported-by: Dave Jones <davej@xxxxxxxxxx>
> > Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
> Reviewed-by: Minchan Kim <minchan@xxxxxxxxxx>
> Thanks, Michal!
> Only remained thing is Dave's testing.

I've added it to my builds, all is quiet so far..


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