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    SubjectRe: [Patch] Tracing/ftrace: Adds a marker to allow user comments
    On Thu, 28 Aug 2008 11:04:36 +0100
    "Frédéric Weisbecker" <fweisbec@gmail.com> wrote:

    > 2008/8/27 Pekka Paalanen <pq@iki.fi>:
    > >
    > > tracers. I would also like to be able to have e.g. mmiotrace_marker(),
    > > which would have the same signature as ftrace_printk(), but is a no-op if
    > > mmiotrace is not active. So, we could have an __ftrace_vprintk() to make
    > > writing such wrappers easy. And the wrappers could be #ifdef'd away, if
    > > the corresponding tracer is not built.
    >
    > I like your idea of a ftrace_vprintk wrapper.
    > But actually I'm questioning about the fact that the tracing api
    > itself is not generic enough.

    I think making it more modular would be nice, but I'm not really working
    on the generic parts.

    > And (always IMHO) I think that functions like __trace_mmiotrace_rw()
    > shouldn't be located on trace.c but implemented on the appropriate
    > tracer (in this example: trace_mmiotrace.c).

    I feel the same.

    > > I recall somewhere mentioning, that one shouldn't leave ftrace_printk's
    > > lying around in "final" code, so I'm not sure how people feel about this
    > > wrapping idea, especially when e.g. mmiotrace is hoped to be built-in by
    > > default. OTOH, I don't think in-tree drivers and stuff want to use them,
    > > so they would be mostly offered for out-of-tree modules
    > > (reverse-engineering) and developers (debugging). That makes me wonder
    > > if they would be accepted (as exported symbols).
    >
    > Yes I think such a function should really be exported. For example
    > using mmiotrace on a module and beeing able to signal the fact that we
    > are entering the "foo" function seems to me very useful. It's
    > important to know where we are in all these IO for debugging....

    Yes, but the atmosphere is that if there are no users in-tree, the feature
    gets kicked, out-of-tree users or no. That's the reason mmiotrace went
    in-tree in the first place. So, to get that stuff exported, we might need
    in-tree users, I believe.


    Thanks.

    --
    Pekka Paalanen
    http://www.iki.fi/pq/
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