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    SubjectRe: [PATCHSET] ptrace,signal: group stop / ptrace updates
    * Anca Emanuel (anca.emanuel@gmail.com) wrote:
    > On Fri, Jan 28, 2011 at 7:41 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
    > > On Fri, 28 Jan 2011, Ingo Molnar wrote:
    > >> See that '^C^C' line? That is where i had to do Ctrl-C twice.
    > >>
    > >> It only fails here about once every 10 times, so it's very rare. I have a stock F14
    > >> system running on that box, with the very latest .38 based kernel.
    > >
    > > Tripped over the refuse ^C thing today twice. Had to kill a kernel
    > > build from another shell. It just happily displayed ^C and never
    > > stopped. That happens once in a while and I have no idea either how to
    > > debug that.
    >
    > cc: Mathieu
    >
    > Use lttng ?

    Heh :) I'm sure Ingo and Thomas have their own tools for that ;) There is
    one extra thing in the LTTng instrumentation that can help solve this problem:
    the "input subsystem" instrumentation (enabled with ltt-armall -i). You can then
    get a dump of:

    - Your keystrokes (you can then grep for your ctrl-c input)
    - Read/poll/select system calls (so you know when your terminal receives the
    input).
    - Signals sent/delivered

    Some of these are already instrumented in the mainline kernel, so you might get
    away without the input subsystem instrumentation.

    If I had to take a wild guess, my bet would be to take a look in the area of
    signal delivery, but you never know, maybe it's a userspace bug in the X
    terminal emulator code that is causing this weirdness.

    Hope this helps,

    Mathieu

    --
    Mathieu Desnoyers
    Operating System Efficiency R&D Consultant
    EfficiOS Inc.
    http://www.efficios.com


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