On Wed, Jan 23, 2013 at 11:45 PM, Christoph Lameter <cl@xxxxxxxxx> wrote:
> The variables accessed in slab_alloc are volatile and therefore
> the page pointer passed to node_match can be NULL. The processing
> of data in slab_alloc is tentative until either the cmpxhchg
> succeeds or the __slab_alloc slowpath is invoked. Both are
> able to perform the same allocation from the freelist.
>
> Check for the NULL pointer in node_match.
>
> A false positive will lead to a retry of the loop in __slab_alloc.
>
> Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
Steven, how did you trigger the problem - i.e. is this -rt only
problem? Does the patch work for you?
> Index: linux/mm/slub.c
> ===================================================================
> --- linux.orig/mm/slub.c 2013-01-18 08:47:29.198954250 -0600
> +++ linux/mm/slub.c 2013-01-18 08:47:40.579126371 -0600
> @@ -2041,7 +2041,7 @@ static void flush_all(struct kmem_cache
> static inline int node_match(struct page *page, int node)
> {
> #ifdef CONFIG_NUMA
> - if (node != NUMA_NO_NODE && page_to_nid(page) != node)
> + if (!page || (node != NUMA_NO_NODE && page_to_nid(page) != node))
> return 0;
> #endif
> return 1;
>
> --
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