From: Roland Dreier Date: Mon, 15 May 2006 18:41:00 +0000 (-0700) Subject: [PATCH] slab: Fix kmem_cache_destroy() on NUMA X-Git-Tag: v2.6.17-rc5~112 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a4523a8b38089478f93bc053c31f678c63f5ee1b;p=linux-2.6 [PATCH] slab: Fix kmem_cache_destroy() on NUMA 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 . Signed-off-by: Roland Dreier Acked-by: Christoph Lameter Acked-by: Pekka Enberg Signed-off-by: Linus Torvalds --- diff --git a/mm/slab.c b/mm/slab.c index b1d643b523..d31a06bfbe 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -2200,11 +2200,14 @@ static void drain_cpu_caches(struct kmem_cache *cachep) 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); - } } }