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Mon, 18 Jul 2022 02:58:39 +0000 From: "lizhijian@fujitsu.com" To: Christian Brauner , Shuah Khan CC: "linux-kernel@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "lizhijian@fujitsu.com" , Philip Li , kernel test robot Subject: [PATCH] ksefltest: pidfd: Fix wait_states: Test terminated by timeout Thread-Topic: [PATCH] ksefltest: pidfd: Fix wait_states: Test terminated by timeout Thread-Index: AQHYmlJIC25sNz3jw0SpQWU1Pz6Prw== Date: Mon, 18 Jul 2022 02:58:39 +0000 Message-ID: <20220718025826.29148-1-lizhijian@fujitsu.com> Accept-Language: en-US, zh-CN Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: git-send-email 2.36.0 authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=fujitsu.com; x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 9d928727-0198-4516-8fd4-08da68696a83 x-ms-traffictypediagnostic: OSBPR01MB2901:EE_ x-ms-exchange-senderadcheck: 1 x-ms-exchange-antispam-relay: 0 x-microsoft-antispam: BCL:0; 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After digging into the source, we found that it blocks at: ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WCONTINUED, NULL), 0); wait_states has below testing flow: CHILD PARENT ---------------+-------------- 1 STOP itself 2 WAIT for CHILD STOPPED 3 SIGNAL CHILD to CONT 4 CONT 5 STOP itself 5' WAIT for CHILD CONT 6 WAIT for CHILD STOPPED The problem is that the kernel cannot ensure the order of 5 and 5', once 5's goes first, the test will fail. we can reproduce it by: $ while true; do make run_tests -C pidfd; done Introduce a blocking read in child process to make sure the parent can check its WCONTINUED. CC: Philip Li Reported-by: kernel test robot Signed-off-by: Li Zhijian --- I have almost forgotten this patch since the former version post over 6 months ago. This time I just do a rebase and update the comments. V2: rewrite with pipe to avoid usleep --- tools/testing/selftests/pidfd/pidfd_wait.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/tools/testing/selftests/pidfd/pidfd_wait.c b/tools/testing/selftests/pidfd/pidfd_wait.c index 070c1c876df1..3f7bc6517dea 100644 --- a/tools/testing/selftests/pidfd/pidfd_wait.c +++ b/tools/testing/selftests/pidfd/pidfd_wait.c @@ -95,20 +95,27 @@ TEST(wait_states) .flags = CLONE_PIDFD | CLONE_PARENT_SETTID, .exit_signal = SIGCHLD, }; + int ret, pfd[2]; pid_t pid; siginfo_t info = { .si_signo = 0, }; + ASSERT_EQ(pipe(pfd), 0); pid = sys_clone3(&args); ASSERT_GE(pid, 0); if (pid == 0) { + char buf[2]; + close(pfd[1]); kill(getpid(), SIGSTOP); + ASSERT_EQ(read(pfd[0], buf, 1), 1); + close(pfd[0]); kill(getpid(), SIGSTOP); exit(EXIT_SUCCESS); } + close(pfd[0]); ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WSTOPPED, NULL), 0); ASSERT_EQ(info.si_signo, SIGCHLD); ASSERT_EQ(info.si_code, CLD_STOPPED); @@ -117,6 +124,8 @@ TEST(wait_states) ASSERT_EQ(sys_pidfd_send_signal(pidfd, SIGCONT, NULL, 0), 0); ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WCONTINUED, NULL), 0); + ASSERT_EQ(write(pfd[1], "C", 1), 1); + close(pfd[1]); ASSERT_EQ(info.si_signo, SIGCHLD); ASSERT_EQ(info.si_code, CLD_CONTINUED); ASSERT_EQ(info.si_pid, parent_tid);