Bug in 2b2a1ff64afbadac842bbc58c5166962cf4f7664 ? - Kernel

This is a discussion on Bug in 2b2a1ff64afbadac842bbc58c5166962cf4f7664 ? - Kernel ; From ea5b3ea0dbdb8b9f9ef73e639517cf4805cf2e6f Mon Sep 17 00:00:00 2001 From: Serge E. Hallyn Date: Thu, 31 Jul 2008 07:29:14 -0700 Subject: [PATCH 1/1] notify parent of death Commit 2b2a1ff64afbadac842bbc58c5166962cf4f7664 ("tracehook: death" by ROland McGrath on Jul 25) included a change that apparently ...

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Thread: Bug in 2b2a1ff64afbadac842bbc58c5166962cf4f7664 ?

  1. Bug in 2b2a1ff64afbadac842bbc58c5166962cf4f7664 ?

    From ea5b3ea0dbdb8b9f9ef73e639517cf4805cf2e6f Mon Sep 17 00:00:00 2001
    From: Serge E. Hallyn
    Date: Thu, 31 Jul 2008 07:29:14 -0700
    Subject: [PATCH 1/1] notify parent of death

    Commit 2b2a1ff64afbadac842bbc58c5166962cf4f7664
    ("tracehook: death" by ROland McGrath on Jul 25) included a change
    that apparently causes parents not to be notified of child death
    in normal circumstances. In particular the following testcase
    fails without this patch. (I'm sure this patch is wrong, but
    hopefully it illustrates where a real problem might hide).

    Before commit 2b2a1ff64afbadac842bbc58c5166962cf4f7664, calling
    this program testwait.c and running
    # ./testwait /bin/sh
    # exit
    would succeed. Ever since that commit, exiting the shell makes
    it defunct. With the following patch, it again appears to
    properly exit, and my test machine seems to suffer no ill effects
    from the patch - though I haven't run ltp since as I say I doubt
    the patch is the right solution.

    More likely the last line in tracehook_notify_death() isn't
    quite right.

    thanks,
    -serge

    #include
    #include
    #include
    #include
    #include
    #include
    #include
    #include
    #include
    #include
    #include
    #include

    extern pid_t getpgid(pid_t pid);
    extern pid_t getsid(pid_t pid);

    static const char* procname;

    int do_child(void *vargv)
    {
    char **argv = (char **)vargv;
    execve(argv[0], argv, __environ);
    perror("execve");
    return 1;
    }

    int main(int argc, char *argv[])
    {
    int c;
    int ret, use_clone = 0;
    int pid;
    int status;

    argv = &argv[optind];
    argc = argc - optind;

    int stacksize = 4*getpagesize();
    void *childstack, *stack = malloc(stacksize);

    if (!stack) {
    perror("malloc");
    return -1;
    }
    childstack = stack + stacksize;

    pid = clone(do_child, childstack, 0, (void *)argv);
    if (pid == -1) {
    perror("clone");
    return -1;
    }
    if ((ret = waitpid(pid, &status, __WALL)) < 0)
    printf("waitpid() returns %d, errno %d\n", ret, errno);

    exit(0);
    }

    Signed-off-by: Serge E. Hallyn
    ---
    kernel/exit.c | 2 +-
    1 files changed, 1 insertions(+), 1 deletions(-)

    diff --git a/kernel/exit.c b/kernel/exit.c
    index 6cdf607..847fa12 100644
    --- a/kernel/exit.c
    +++ b/kernel/exit.c
    @@ -924,7 +924,7 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
    tsk->exit_signal = SIGCHLD;

    signal = tracehook_notify_death(tsk, &cookie, group_dead);
    - if (signal > 0)
    + if (signal >= 0)
    signal = do_notify_parent(tsk, signal);

    tsk->exit_state = signal < 0 ? EXIT_DEAD : EXIT_ZOMBIE;
    --
    1.5.3.6

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  2. Re: Bug in 2b2a1ff64afbadac842bbc58c5166962cf4f7664 ?

    Quoting Roland McGrath (roland@redhat.com):
    > Thanks for the report. I just posted the fix for that last night.


    Oh, sorry for the noise. Testing your patch right now.

    thanks,
    -serge
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