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    SubjectRe: [PATCH 1/1] ptrace: make sure do_wait() won't hang after PTRACE_ATTACH
    On 02/14, Tejun Heo wrote:
    >
    > On Mon, Feb 14, 2011 at 05:15:15PM +0100, Oleg Nesterov wrote:
    > > > > PTRACE_CONT in this situation would do the same.
    > > >
    > > > This can be fixed by updating strace, right? strace can look at the
    > > > wait(2) exit code and if the tracee stopped for group stop, wait for
    > > > the tracee to be continued instead of issuing PTRACE_SYSCALL.
    > >
    > > Yes, in this particular case strace could be more clever.
    > >
    > > But. The tracee should react to SIGCONT after that, this means we
    > > shouldn't "delay" this stop or force the TASK_TRACED state.
    >
    > Yeap, which is achievable by treating group stop differently from
    > ptrace traps and make it proceed to TASK_TRACED only if ptrace wants
    > to issue commands.

    Yes, agreed. And this is exactly what we currently do. Except, as you
    pointed out, the simple s/STOPPED/TRACED/ change is buggy. But the fix
    you suggested should be almost invisible to the userland.

    > (reiterating just to make sure there's no
    > misunderstanding)

    The same from my side ;)

    Oleg.



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