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    SubjectRe: Why I want PTRACE_O_TRACESTOP option
    On Fri, September 9, 2011 18:26, Oleg Nesterov wrote:
    > On 09/09, Indan Zupancic wrote:
    >> It is very useful to set options atomically at SEIZE time.
    > Nobody argues with this.
    >> Another important reason to make PTRACE_O_TRACESTOP an option is
    >> because not everyone uses SEIZE: Users using PTRACE_TRACEME can't
    >> set this option at all.
    > Yes. This was already discussed, PTRACE_TRACEME obviously doesn't
    > work if you need the new features. So far it was decided TRACEME
    > should be avoided,

    How do you want to attach/seize a just forked child without races
    in a less ugly way than with TRACEME?

    > but perhaps we can add SEIZE_ME. And, unlike
    > TRACEME it should probably stop immediately to simplify the
    > synchronization with parent. Afaik, any user of TRACEME does
    > something like kill(getpid(), SIGSTOP), this doesn't look very
    > good.

    I let the child send a SIGTERM to itself, so if anything goes wrong
    it terminates. It's only needed because you have to set options.

    > But personally I'd prefer to avoid SEIZE_ME.

    Me too. There is no need for it if PTRACE_O_TRACESTOP exists.

    Alternatively, if you do want to add it, just allow PTRACE_SEIZE
    with zero/own PID to achieve the same.



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