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    SubjectRe: [PATCH 2/8] kill tracehook_notify_death()

    On Thu, Jun 23, 2011 at 07:06:50PM +0200, Oleg Nesterov wrote:
    > [PATCH v2 2/8] kill tracehook_notify_death()
    > Kill tracehook_notify_death(), reimplement the logic in its caller,
    > exit_notify().
    > Also, change the exec_id's check to use thread_group_leader() instead
    > of task_detached(), this is more clear. This logic only applies to
    > the exiting leader, a sub-thread must never change its exit_signal.
    > Note: when the traced group leader exits the exit_signal-or-SIGCHLD
    > logic looks really strange:
    > - we notify the tracer even if !thread_group_empty() but
    > do_wait(WEXITED) can't work until all threads exit

    Yeap, we've discussed this before and this indeed is odd. However, is
    there something ptracer can't do with PTRACE_EVENT_EXIT instead? If
    PTRACE_EVENT_EXIT can be used instead for most practical purposes, I
    think we're better off just documenting the fact and advise use of
    PTRACE_EVENT_EXIT rather than trying to change the behavior.

    > - if the tracer is real_parent, it is not clear why can't
    > we use ->exit_signal event if !thread_group_empty()

    I've been thinking a bit more about this and it doesn't seem that
    changing this is necessarily a good idea. The current behavior does
    make certain sense (overridden exit_signal is used only for the real
    parent when the process is being reaped) and doesn't cause any actual
    problem, so I don't think we need to change this behavior.

    > + if (unlikely(tsk->ptrace)) {
    > + int sig = thread_group_leader(tsk) &&
    > + thread_group_empty(tsk) &&
    > + !ptrace_reparented(tsk) ?
    > + tsk->exit_signal : SIGCHLD;

    Heh, I think this needs to be prettier even at the cost of an inline



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