[PATCH] signals: dequeue_signal: don't check SIGNAL_GROUP_EXIT when setting SIGNAL_STOP_DEQUEUED - Kernel

This is a discussion on [PATCH] signals: dequeue_signal: don't check SIGNAL_GROUP_EXIT when setting SIGNAL_STOP_DEQUEUED - Kernel ; dequeue_signal() checks SIGNAL_GROUP_EXIT before setting SIGNAL_STOP_DEQUEUED. This was added by 788e05a67c343fa22f2ae1d3ca264e7f15c25eaf a long ago to avoid the coredump/SIGSTOP race. Since then the related code was changed, and now this subtle check is both incomplete and unneeded at the same time. ...

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Thread: [PATCH] signals: dequeue_signal: don't check SIGNAL_GROUP_EXIT when setting SIGNAL_STOP_DEQUEUED

  1. [PATCH] signals: dequeue_signal: don't check SIGNAL_GROUP_EXIT when setting SIGNAL_STOP_DEQUEUED

    dequeue_signal() checks SIGNAL_GROUP_EXIT before setting SIGNAL_STOP_DEQUEUED.
    This was added by 788e05a67c343fa22f2ae1d3ca264e7f15c25eaf a long ago to avoid
    the coredump/SIGSTOP race.

    Since then the related code was changed, and now this subtle check is both
    incomplete and unneeded at the same time. It is incomplete because nowadays
    exec() doesn't set SIGNAL_GROUP_EXIT, so in fact we should check
    signal_group_exit() to avoid a similar race. Fortunately, we doesn't need
    the check at all. The only function which relies on SIGNAL_STOP_DEQUEUED
    is do_signal_stop(), and it ignores this flag if signal_group_exit() == T,
    this covers the SIGNAL_GROUP_EXIT case.

    Signed-off-by: Oleg Nesterov

    --- 26-rc2/kernel/signal.c~1_DS_KILL_EXIT_CHECK 2008-05-31 13:44:08.000000000 +0400
    +++ 26-rc2/kernel/signal.c 2008-05-31 14:54:32.000000000 +0400
    @@ -454,8 +454,7 @@ int dequeue_signal(struct task_struct *t
    * is to alert stop-signal processing code when another
    * processor has come along and cleared the flag.
    */
    - if (!(tsk->signal->flags & SIGNAL_GROUP_EXIT))
    - tsk->signal->flags |= SIGNAL_STOP_DEQUEUED;
    + tsk->signal->flags |= SIGNAL_STOP_DEQUEUED;
    }
    if ((info->si_code & __SI_MASK) == __SI_TIMER && info->si_sys_private) {
    /*

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  2. Re: [PATCH] signals: dequeue_signal: don't check SIGNAL_GROUP_EXIT when setting SIGNAL_STOP_DEQUEUED

    Acked-by: Roland McGrath
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