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ksefltests: pidfd: Fix wait_states: Test terminated by timeout
[ Upstream commit 88e1f16ba5
]
0Day/LKP observed that the kselftest blocks forever since one of the
pidfd_wait doesn't terminate in 1 of 30 runs. 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 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 <philip.li@intel.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
parent
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1 changed files with 10 additions and 0 deletions
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@ -95,20 +95,28 @@ TEST(wait_states)
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.flags = CLONE_PIDFD | CLONE_PARENT_SETTID,
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.exit_signal = SIGCHLD,
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};
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int pfd[2];
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pid_t pid;
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siginfo_t info = {
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.si_signo = 0,
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};
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ASSERT_EQ(pipe(pfd), 0);
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pid = sys_clone3(&args);
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ASSERT_GE(pid, 0);
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if (pid == 0) {
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char buf[2];
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close(pfd[1]);
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kill(getpid(), SIGSTOP);
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ASSERT_EQ(read(pfd[0], buf, 1), 1);
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close(pfd[0]);
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kill(getpid(), SIGSTOP);
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exit(EXIT_SUCCESS);
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}
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close(pfd[0]);
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ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WSTOPPED, NULL), 0);
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ASSERT_EQ(info.si_signo, SIGCHLD);
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ASSERT_EQ(info.si_code, CLD_STOPPED);
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@ -117,6 +125,8 @@ TEST(wait_states)
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ASSERT_EQ(sys_pidfd_send_signal(pidfd, SIGCONT, NULL, 0), 0);
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ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WCONTINUED, NULL), 0);
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ASSERT_EQ(write(pfd[1], "C", 1), 1);
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close(pfd[1]);
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ASSERT_EQ(info.si_signo, SIGCHLD);
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ASSERT_EQ(info.si_code, CLD_CONTINUED);
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ASSERT_EQ(info.si_pid, parent_tid);
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