lkml.org 
[lkml]   [2022]   [Jul]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH] ksefltest: pidfd: Fix wait_states: Test terminated by timeout
    Date
    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'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 <philip.li@intel.com>
    Reported-by: kernel test robot <lkp@intel.com>
    Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
    ---
    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);
    --
    2.36.0
    \
     
     \ /
      Last update: 2022-07-18 04:59    [W:3.197 / U:0.528 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site