lkml.org 
[lkml]   [2011]   [Apr]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [path][rfc] add PR_DETACH prctl command [3/3]
    On 04/19, Stas Sergeev wrote:
    >
    > 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,

    Yes.

    > because only do_notify_parent()
    > can do that"?

    because we can only do this if we are going to reap the task

    > If so - will fix, thanks.

    Stas, please do not trim CC. I am very glad Alan looked at this patch,
    I hope he will participate. Better yet, add Linus too as I already asked ;)

    Oleg.



    \
     
     \ /
      Last update: 2011-04-19 20:21    [W:0.024 / U:157.888 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site