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    SubjectRe: Some FTRACE related question


    On Sat, 22 Nov 2008, Peter Teoh wrote:

    > Q1: how to use ftrace to ftrace itself? (i would like to see some
    > ftrace-triggered flow) In view of the following patch:

    ftrace can be very dangerous, (the function tracer part of ftrace).
    It would be very difficult for ftrace to ftrace itself.
    When I need to debug ftrace, I use my old tracer logdev:

    http://rostedt.homelinux.com/logdev

    >
    > http://linux.derkeiler.com/Mailing-Lists/Kernel/2008-11/msg03745.html
    >
    > Is it to prevent this from being possible?
    >
    > Q2: how to ftrace s2ram and resume? I attempted to do it, but the
    > trace output is always filled with "resume" related functions when it
    > started up, which is only logical.

    s2ram does a lot of nasty tricks. On startup, it calls functions before
    smp_prossor_id() is defined. We use that to disable ftrace recursion (see
    Q1 ;-). But if you use that in s2ram resume, it will blow up.

    Now, you can try to hack ftrace for your own tracing to handle the above
    problems.

    -- Steve



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