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    Subject[PATCH] sysrq: Use SEND_SIG_FORCED instead of force_sig()
    Change send_sig_all() to use do_send_sig_info(SEND_SIG_FORCED)
    instead of force_sig(SIGKILL). With the recent changes we do not
    need force_ to kill the CLONE_NEWPID tasks.

    And this is more correct. force_sig() can race with the exiting
    thread, while do_send_sig_info(group => true) kill the whole

    Some more notes from Oleg Nesterov:

    > Just one note. This change makes no difference for sysrq_handle_kill().
    > But it obviously changes the behaviour sysrq_handle_term(). I think
    > this is fine, if you want to really kill the task which blocks/ignores
    > SIGTERM you can use sysrq_handle_kill().
    > Even ignoring the reasons why force_sig() is simply wrong here,
    > force_sig(SIGTERM) looks strange. The task won't be killed if it has
    > a handler, but SIG_IGN can't help. However if it has the handler
    > but blocks SIGTERM temporary (this is very common) it will be killed.


    > force_sig() can't kill the process if the main thread has already
    > exited. IOW, it is trivial to create the process which can't be
    > killed by sysrq.

    So, this patch fixes the issue.

    Suggested-by: Oleg Nesterov <>
    Acked-by: Greg Kroah-Hartman <>
    Acked-by: Oleg Nesterov <>
    Signed-off-by: Anton Vorontsov <>

    The patch depends on a few Oleg's patches in -mm, so I believe
    this should be -mm material as well.

    drivers/tty/sysrq.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
    index 8db9125..5ab8039 100644
    --- a/drivers/tty/sysrq.c
    +++ b/drivers/tty/sysrq.c
    @@ -329,7 +329,7 @@ static void send_sig_all(int sig)
    if (is_global_init(p))

    - force_sig(sig, p);
    + do_send_sig_info(sig, SEND_SIG_FORCED, p, true);

     \ /
      Last update: 2012-03-24 12:05    [W:0.021 / U:2.532 seconds]
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