Commit fac26502 authored by Johannes Weiner's avatar Johannes Weiner Committed by Andrew Morton
Browse files

selftests: cgroup: fix test_kmem_basic false positives 

This test fails routinely in our prod testing environment, and I can
reproduce it locally as well.

The test allocates dcache inside a cgroup, then drops the memory limit
and checks that usage drops correspondingly. The reason it fails is
because dentries are freed with an RCU delay - a debugging sleep shows
that usage drops as expected shortly after.

Insert a 1s sleep after dropping the limit. This should be good
enough, assuming that machines running those tests are otherwise not
very busy.

Link: https://lkml.kernel.org/r/20230801135632.1768830-1-hannes@cmpxchg.org


Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 17457784

tools/testing/selftests/cgroup/test_kmem.c

+4 −0
Original line number Diff line number Diff line
@@ -70,6 +70,10 @@ static int test_kmem_basic(const char *root) 
		goto cleanup;



	cg_write(cg, "memory.high", "1M");



	/* wait for RCU freeing */

	sleep(1);



	slab1 = cg_read_key_long(cg, "memory.stat", "slab ");

	if (slab1 <= 0)

		goto cleanup;