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    SubjectRe: [RFC] [PATCH 7/7] Ftrace plugin for Uprobes
    Masami Hiramatsu wrote:
    > Steven Rostedt wrote:
    >> On Tue, 2010-01-12 at 05:54 +0100, Frederic Weisbecker wrote:
    >>> Now what if I want to launch ls and want to profile a function
    >>> inside. What can I do with a trace event. I can't create the
    >>> probe event based on a pid as I don't know it in advance.
    >>> I could give it the ls cmdline and it manages to activate
    >>> on the next ls launched. This is racy as another ls can
    >>> be launched concurrently.
    >> You make a wrapper script:
    >> #!/bin/sh
    >> <add probe to ls with pid> $$
    >> exec $*
    >> I do this all the time to limit the function tracer to a specific app.
    >> #!/bin/sh
    >> echo $$ > /debug/tracing/set_ftrace_pid
    >> echo function > /debug/tracing/current_tracer
    >> exec $*
    > I recommend you to add below line at the end of the script,
    > from my experience. :)
    > echo nop > /debug/tracing/current_tracer

    Oops, my bad, it doesn't work after exec...
    But, it is very important to disable function tracer after
    tracing target process.

    So, perhaps, below script may work.

    (echo $BASHPID > /debug/tracing/set_ftrace_pid
    echo function > /debug/tracing/current_tracer
    exec $*)
    echo nop > /debug/tracing/current_tracer


    Masami Hiramatsu

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


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