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    SubjectRe: [PATCH 01/13] jump label v9: notifier atomic call chain notrace
    On Wed, Jun 09, 2010 at 11:58:13PM +0200, Frederic Weisbecker wrote:
    > On Wed, Jun 09, 2010 at 05:38:52PM -0400, Jason Baron wrote:
    > > From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
    > >
    > > In LTTng, being able to use the atomic notifier from cpu idle entry to
    > > ensure the tracer flush the last events in the current subbuffer
    > > requires the rcu read-side to be marked "notrace", otherwise it can end
    > > up calling back into lockdep and the tracer.
    > >
    > > Also apply to the the die notifier.
    > >
    > > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
    > > Signed-off-by: Jason Baron <jbaron@redhat.com>
    > > Reviewed-by: Masami Hiramatsu <mhiramat@redhat.com>
    > > ---
    >
    >
    >
    > I don't understand the purpose of this patch. The only notifier
    > I see that is used by jmp label is the module notifier, and I
    > don't see how it can do bad things if we don't use the notrace
    > version.
    >

    hmmm...yeah, this patch was introduced b/c of the use of the 'int3'
    notifier when updating the kernel text. We got into a recursive loop
    without it. However, since the current implementation is using
    stop_machine() to do text updates, I don't think this patch is necessary
    until we have the more optimal text updating mechanism in place. I'll
    re-test without this patch.

    thanks,

    -Jason


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