Re: [PATCH] mm: page_alloc: place zone id check before VM_BUG_ON_PAGE check

[Mel Gorman]

On Tue, Dec 09, 2014 at 03:40:35PM +0800, Weijie Yang wrote:
> If the free page and its buddy has different zone id, the current
> zone->lock cann't prevent buddy page getting allocated, this could
> trigger VM_BUG_ON_PAGE in a very tiny chance:
> 

Under what circumstances can a buddy page be allocated without the
zone->lock? Any parallel allocation from that zone that takes place will
be from the per-cpu allocator and should not be affected by this. Have
you actually hit this race?

-- 
Mel Gorman
SUSE Labs
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