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[2a03:2880:20ff:e::face:b00c]) by smtp.gmail.com with ESMTPSA id i68-20020a375447000000b006809e0adfffsm2529753qkb.25.2022.04.23.08.57.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 23 Apr 2022 08:57:12 -0700 (PDT) From: David Vernet To: akpm@linux-foundation.org Cc: tj@kernel.org, roman.gushchin@linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, hannes@cmpxchg.org, mhocko@kernel.org, shakeelb@google.com, kernel-team@fb.com, void@manifault.com Subject: [PATCH v2 4/5] cgroup: Removing racy check in test_memcg_sock() Date: Sat, 23 Apr 2022 08:56:21 -0700 Message-Id: <20220423155619.3669555-5-void@manifault.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220423155619.3669555-1-void@manifault.com> References: <20220423155619.3669555-1-void@manifault.com> MIME-Version: 1.0 X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 128E81C0038 X-Stat-Signature: ea36g4hcketgxs6jigtz1uxgsenzir4h X-Rspam-User: Authentication-Results: imf21.hostedemail.com; dkim=none; spf=pass (imf21.hostedemail.com: domain of dcvernet@gmail.com designates 209.85.160.181 as permitted sender) smtp.mailfrom=dcvernet@gmail.com; dmarc=none X-HE-Tag: 1650729430-886628 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: test_memcg_sock() in the cgroup memcg tests, verifies expected memory accounting for sockets. The test forks a process which functions as a TCP server, and sends large buffers back and forth between itself (as the TCP client) and the forked TCP server. While doing so, it verifies that memory.current and memory.stat.sock look correct. There is currently a check in tcp_client() which asserts memory.current >= memory.stat.sock. This check is racy, as between memory.current and memory.stat.sock being queried, a packet could come in which causes mem_cgroup_charge_skmem() to be invoked. This could cause memory.stat.sock to exceed memory.current. Reversing the order of querying doesn't address the problem either, as memory may be reclaimed between the two calls. Instead, this patch just removes that assertion altogether, and instead relies on the values_close() check that follows to validate the expected accounting. Signed-off-by: David Vernet Acked-by: Roman Gushchin --- tools/testing/selftests/cgroup/test_memcontrol.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c index e899b3f28c22..38d2054eefe6 100644 --- a/tools/testing/selftests/cgroup/test_memcontrol.c +++ b/tools/testing/selftests/cgroup/test_memcontrol.c @@ -993,9 +993,6 @@ static int tcp_client(const char *cgroup, unsigned short port) if (current < 0 || sock < 0) goto close_sk; - if (current < sock) - goto close_sk; - if (values_close(current, sock, 10)) { ret = KSFT_PASS; break;