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    SubjectRe: [PATCH 1/1] ptrace: make sure do_wait() won't hang after PTRACE_ATTACH
    Hello Tejun,

    On 02/15, Tejun Heo wrote:
    >
    > Hello, Oleg, Denys.
    >
    > On Mon, Feb 14, 2011 at 09:01:30PM +0100, Oleg Nesterov wrote:
    > > > Or we can avoid entering TASK_TRACED on ptrace(PTRACE_GETSIGINFO) et al.
    > > > Can we remain in TASK_STOPPED?
    > >
    > > Oh, unlikely, I think.
    >
    > Actually I was thinking along this line. We can allow
    > PTRACE_GETSIGINFO to proceed without forcing the tracee into TRACED
    > state, the rationale being the operation is required to tell between
    > group stop and ptrace trap. Am I missing something?

    I do not think this is really wrong (except this means another user
    visible change and I never know if it is fine).

    But I think it doesn't really help. Yes, this is probably enough for
    strace (I don't know for sure) , but a more "sophisticated" debugger
    may want to do something else with the stopped tracee.


    And. Denys suggested this assuming PTRACE_CONT-doesnt-resume-until-SIGCONT,
    and in this case this is not really needed. The debugger can safely do
    PTRACE_GETSIGINFO even if this changes the state to TASK_TRACED.
    Once it does PTRACE_CONT the tracee becomes "visible" to SIGCONT. Or,
    if SIGCONT comes in between, the tracee runs.

    Oleg.



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