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    SubjectRe: [path][rfc] add PR_DETACH prctl command [3/3]
    19.04.2011 21:20, Oleg Nesterov wrote:

    >>> do_signal_parent() must not return DEATH_REAP (this means that
    >>> leader->exit_signal becomes -1), but this can happen and this is bug.
    >>>
    >> Could you please clarify this a bit: according to the comments
    >> in signal.c:
    >> ---
    >> * We are exiting and our parent doesn't care. POSIX.1
    >> * defines special semantics for setting SIGCHLD to SIG_IGN
    >> * or setting the SA_NOCLDWAIT flag: we should be reaped
    >> * automatically and not left for our parent's wait4 call.
    >> ---
    >> That's how I understand it: if DEATH_REAP is returned, the
    >> parent ignores SIGCHILD, and in this case I am not allowing
    >> it to read the detach code with wait(). What is the bug?
    > Indeed. But, once again, that is why do_notify_parent() expects the dead
    > tsk! Please note that if it returns DEATH_REAP it sets ->exit_signal = -1.
    > And this is _only_ allowed if the leader is already dead and we are going
    > to reap it.
    Ah, so, by saying "do_signal_parent() must not return DEATH_REAP (this means that
    leader->exit_signal becomes -1)", you actually meant
    "do_signal_parent(), when returning DEATH_REAP, must not
    set ->exit_signal = -1, because only do_notify_parent()
    can do that"? In other words, do_signal_parent() can return
    DEATH_REAP after all?
    If so - will fix, thanks.



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