diff options
| author | Qian Cai <cai@lca.pw> | 2019-05-13 17:16:31 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-05-14 09:47:45 -0700 |
| commit | 745e10146c31b1c6ed3326286704ae251b17f663 (patch) | |
| tree | c429770b423b0593b9eaac0850e791957efa3008 | |
| parent | 632b2ef0c72d9ea0f76619ad04ca53aae121f8b9 (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>
| -rw-r--r-- | mm/slab.c | 6 |
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; |