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    SubjectRe: [RFC] Proposal for ptrace improvements
    On 03/03, Oleg Nesterov wrote:
    > I'll ask the questions later.

    Right now I do not see any holes (but I'll try more ;)

    One question, to ensure I really understand you. To simplify,
    consider this particular example.


    int main(void)
    kill(SIGSTOP, getpid());

    printf("I am running\n");

    for (;;)

    To simplify again, suppose that the debugger attaches when it is
    already stopped, then it does PTRACE_CONT(0).

    In this case the tracee remains SIGNAL_STOP_STOPPED but prints
    "I am running" and enters the endless loop.

    (the new debugger can do PTRACE_SEIZE after that and "return"
    it to the stopped state without affecting jctl state).

    Now, if SIGCONT comes (from anywhere) it clears SIGNAL_STOP_STOPPED,
    the tracee traps and reports this event to debugger.


    And, once again. In the mt case, I assume that SIGCONT makes
    every traced thread to report this event individually, right?

    (I am talking about the case when the group-stop was finished,
    iow "every" probably means the threads which participated and
    reported CLD_STOPPED to the debugger).

    In both cases, later then this SIGCONT will be reported again
    as any "normal" signal when some thread dequeues it.

    Is my understanding correct?



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