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    SubjectRe: [GIT PULL] tracing/kprobes: Add dynamic tracepoints + instruction decoder
    Frederic Weisbecker wrote:
    > On Thu, Aug 27, 2009 at 11:00:38AM -0400, Masami Hiramatsu wrote:
    >> Frederic Weisbecker wrote:
    >>> Ingo,
    >>>
    >>> This is the kprobes tracing pile of patches. I've tested it
    >>> successfully by setting some kprobes through debugfs by hand.
    >>>
    >>> It brings no known regressions.
    >>>
    >>> However, the stress test provided by Masami have revealed some
    >>> unstable points. Some symbols are unsafe to probe and raise
    >>> probing recursion.
    >>>
    >>> I've added a tiny patch in the series that helps identifying the
    >>> kprobe that has raised such situation.
    >>> For example it has learned me today that it's unsafe to trace
    >>> ret_from_exception() (obviously: it's on the int 3 handler path).
    >>
    >> Thank you, Frederic.
    >>
    >> I'm currently fixing those problems on x86-64 (on kvm).
    >> I'll also check it on x86-32, and fix it.
    >>
    >> Thanks
    >
    >
    >
    > Cool.
    > Don't hesitate to interate through small patches that fix these
    > sites.
    >
    > So that I can continue to test it over time and report you what I find,
    > may be I can try to fix some of them too.
    >
    > I haven't fixed ret_from_exception because I wasn't sure about the
    > right thing to do: putting it in the kprobes section or blacklist its
    > name. It's a bit more delicate to put assembly code into sections so... :)

    It depends on implementation, but I think blacklist is the last resort. :)
    AFAIK, some assembly codes are already pushed into kprobes section.

    Thank you,

    --
    Masami Hiramatsu

    Software Engineer
    Hitachi Computer Products (America), Inc.
    Software Solutions Division

    e-mail: mhiramat@redhat.com



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