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    SubjectRe: [PATCH] ptrace: make former thread ID available via PTRACE_GETEVENTMSG after PTRACE_EVENT_EXEC stop (v.2)
    On 06/27, Tejun Heo wrote:
    > Hello, Oleg, Denys.
    > On Sun, Jun 26, 2011 at 10:04:42PM +0200, Oleg Nesterov wrote:
    > > May be PT_TRACE_EXEC makes more sense. Note that
    > > ptrace_event_enabled() was recently added.
    > Do we want to enable this silently? Wouldn't it be better to make it
    > dependent on PT_SEIZED?

    Hmm. Not sure I understand. Why can't PTRACE_SEIZE add PT_TRACE_EXEC
    (and PT_TRACESYSGOOD) along with PT_SEIZED during attach?

    I think this makes more sense, this way the tracer can disable this
    later via PTRACE_SETOPTIONS if it wants. Not that I think this is really
    useful but still. Otherwise we are going to silently disable
    PTRACE_O_TRACEEXEC, this may be confusing.

    But. If we want the PT_TRACE_EXEC behaviour for PT_SEIZED task (personally
    I think we do), then we should probably record the old pid unconditionally,
    the tracer can attach later.

    Even in this case ptrace_event(PTRACE_EVENT_EXEC) can race with detach +
    attach in theory, but I think in this case we do not care.


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