From: Johannes Weiner Date: Tue, 1 Aug 2023 13:56:32 +0000 (-0400) Subject: selftests: cgroup: fix test_kmem_basic false positives X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=fac2650276eced3c94bcdbc21d0e5be637c1e582;p=linux.git 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: Johannes Weiner Acked-by: Paul E. McKenney Cc: Michal Hocko Cc: Roman Gushchin Signed-off-by: Andrew Morton --- diff --git a/tools/testing/selftests/cgroup/test_kmem.c b/tools/testing/selftests/cgroup/test_kmem.c index 258ddc565deba..1b2cec9d18a42 100644 --- a/tools/testing/selftests/cgroup/test_kmem.c +++ b/tools/testing/selftests/cgroup/test_kmem.c @@ -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;