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[2603:7000:c01:2716:8f57:5681:ccd3:4a2e]) by smtp.gmail.com with ESMTPSA id c27-20020ac8009b000000b004054b435f8csm4446390qtg.65.2023.08.01.06.56.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Aug 2023 06:56:32 -0700 (PDT) From: Johannes Weiner To: Andrew Morton Cc: Roman Gushchin , Michal Hocko , "Paul E. McKenney" , linux-kselftest@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] selftests: cgroup: fix test_kmem_basic false positives Date: Tue, 1 Aug 2023 09:56:32 -0400 Message-ID: <20230801135632.1768830-1-hannes@cmpxchg.org> X-Mailer: git-send-email 2.41.0 MIME-Version: 1.0 X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1773043991097982677 X-GMAIL-MSGID: 1773043991097982677 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. Signed-off-by: Johannes Weiner Acked-by: Paul E. McKenney --- tools/testing/selftests/cgroup/test_kmem.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/tools/testing/selftests/cgroup/test_kmem.c b/tools/testing/selftests/cgroup/test_kmem.c index 258ddc565deb..1b2cec9d18a4 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;