Messages in this thread Patch in this message | | | Subject | [PATCH] slab: Fix kmem_cache_destroy() on NUMA | From | Roland Dreier <> | Date | Mon, 15 May 2006 11:41:00 -0700 |
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With CONFIG_NUMA set, kmem_cache_destroy() may fail and say "Can't free all objects." The problem is caused by sequences such as the following (suppose we are on a NUMA machine with two nodes, 0 and 1):
* Allocate an object from cache on node 0. * Free the object on node 1. The object is put into node 1's alien array_cache for node 0. * Call kmem_cache_destroy(), which ultimately ends up in __cache_shrink(). * __cache_shrink() does drain_cpu_caches(), which loops through all nodes. For each node it drains the shared array_cache and then handles the alien array_cache for the other node.
However this means that node 0's shared array_cache will be drained, and then node 1 will move the contents of its alien[0] array_cache into that same shared array_cache. node 0's shared array_cache is never looked at again, so the objects left there will appear to be in use when __cache_shrink() calls __node_shrink() for node 0. So __node_shrink() will return 1 and kmem_cache_destroy() will fail.
This patch fixes this by having drain_cpu_caches() do drain_alien_cache() on every node before it does drain_array() on the nodes' shared array_caches.
The problem was originally reported by Or Gerlitz <ogerlitz@voltaire.com>.
Cc: Christoph Lameter <clameter@sgi.com> Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
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I get a nervous feeling about touching NUMA slab code, because just the topic alone makes it sound hairy. But I think my diagnosis and fix are pretty clear, and this definitely fixes crashes seen when unloading IB modules. It's a regression from 2.6.16, and x86_64 machines with > 1 NUMA node are quite common, so this probably should go into 2.6.17.
diff --git a/mm/slab.c b/mm/slab.c index c32af7e..cb747be 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -2192,11 +2192,14 @@ static void drain_cpu_caches(struct kmem check_irq_on(); for_each_online_node(node) { l3 = cachep->nodelists[node]; - if (l3) { + if (l3 && l3->alien) + drain_alien_cache(cachep, l3->alien); + } + + for_each_online_node(node) { + l3 = cachep->nodelists[node]; + if (l3) drain_array(cachep, l3, l3->shared, 1, node); - if (l3->alien) - drain_alien_cache(cachep, l3->alien); - } } } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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