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    SubjectRe: [PATCH] new irq tracer
    * Masami Hiramatsu (mhiramat@redhat.com) wrote:
    >
    >
    > KOSAKI Motohiro wrote:
    > >> /**
    > >> * handle_IRQ_event - irq action chain handler
    > >> * @irq: the interrupt number
    > >> @@ -354,7 +358,9 @@ irqreturn_t handle_IRQ_event(unsigned int irq, struct irqaction *action)
    > >> local_irq_enable_in_hardirq();
    > >>
    > >> do {
    > >> + trace_irq_entry(irq);
    > >> ret = action->handler(irq, action->dev_id);
    > >> + trace_irq_exit(irq, ret);
    > >> if (ret == IRQ_HANDLED)
    > >> status |= action->flags;
    > >> retval |= ret;
    > >
    > > Nobdy want unnecessary redundant tracepoint.
    > > Please discuss with mathieu, and merge his tracepoint.
    >
    > Hmm, from the viewpoint of trouble shooting, the place of LTTng's tracepoint
    > is enough. However, from the same viewpoint, it should pass irq-number
    > to irq-exit event too, because we may lost some previous events by buffer-overflow
    > etc.
    >
    > trace_irq_entry(irq, NULL);
    > ret = _handle_IRQ_event(irq, action);
    > trace_irq_exit(irq, ret);
    > ^^^^
    >

    I seriously doubt we should consider a trace with missing events as
    "reliable". If your only argument is that when the buffers are not large
    enough we could lose events, then I think we should just hint people at
    doing the right thing, which is to tweak the tracer parameters (e.g.
    larger buffers) so they stop losing events.

    A trace with events lost is really a scenario close to a corrupted
    trace because we don't know which event has been lost, nor where. I
    don't think we should increase the event size to support that kind of
    broken scenario.

    Mathieu

    > Thank you,
    >
    > --
    > Masami Hiramatsu
    >
    > Software Engineer
    > Hitachi Computer Products (America) Inc.
    > Software Solutions Division
    >
    > e-mail: mhiramat@redhat.com
    >

    --
    Mathieu Desnoyers
    OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


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