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authorQian Cai <cai@lca.pw>2019-05-13 17:16:31 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-05-14 09:47:45 -0700
commit745e10146c31b1c6ed3326286704ae251b17f663 (patch)
treec429770b423b0593b9eaac0850e791957efa3008 /mm/slab.c
parent632b2ef0c72d9ea0f76619ad04ca53aae121f8b9 (diff)
mm/slab.c: fix an infinite loop in leaks_show()
"cat /proc/slab_allocators" could hang forever on SMP machines with kmemleak or object debugging enabled due to other CPUs running do_drain() will keep making kmemleak_object or debug_objects_cache dirty and unable to escape the first loop in leaks_show(), do { set_store_user_clean(cachep); drain_cpu_caches(cachep); ... } while (!is_store_user_clean(cachep)); For example, do_drain slabs_destroy slab_destroy kmem_cache_free __cache_free ___cache_free kmemleak_free_recursive delete_object_full __delete_object put_object free_object_rcu kmem_cache_free cache_free_debugcheck --> dirty kmemleak_object One approach is to check cachep->name and skip both kmemleak_object and debug_objects_cache in leaks_show(). The other is to set store_user_clean after drain_cpu_caches() which leaves a small window between drain_cpu_caches() and set_store_user_clean() where per-CPU caches could be dirty again lead to slightly wrong information has been stored but could also speed up things significantly which sounds like a good compromise. For example, # cat /proc/slab_allocators 0m42.778s # 1st approach 0m0.737s # 2nd approach [akpm@linux-foundation.org: tweak comment] Link: http://lkml.kernel.org/r/20190411032635.10325-1-cai@lca.pw Fixes: d31676dfde25 ("mm/slab: alternative implementation for DEBUG_SLAB_LEAK") Signed-off-by: Qian Cai <cai@lca.pw> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slab.c')
-rw-r--r--mm/slab.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/mm/slab.c b/mm/slab.c
index da4068a95307..2915d912e89a 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4291,8 +4291,12 @@ static int leaks_show(struct seq_file *m, void *p)
* whole processing.
*/
do {
- set_store_user_clean(cachep);
drain_cpu_caches(cachep);
+ /*
+ * drain_cpu_caches() could make kmemleak_object and
+ * debug_objects_cache dirty, so reset afterwards.
+ */
+ set_store_user_clean(cachep);
x[1] = 0;