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Date: Wed, 25 Mar 2009 09:47:24 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Peter Zijlstra <peterz@infradead.org>,
       Christoph Hellwig <hch@infradead.org>, Jason Baron <jbaron@redhat.com>,
       akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
       ltt-dev@lists.casi.polymtl.ca, Frederic Weisbecker <fweisbec@gmail.com>,
       Thomas Gleixner <tglx@linutronix.de>,
       Russell King <rmk+lkml@arm.linux.org.uk>,
       Masami Hiramatsu <mhiramat@redhat.com>,
       "Frank Ch. Eigler" <fche@redhat.com>, Hideo AOKI <haoki@redhat.com>,
       Takashi Nishiie <t-nishiie@np.css.fujitsu.com>,
       Steven Rostedt <rostedt@goodmis.org>,
       Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Subject: Re: [patch 2/9] LTTng instrumentation - irq
Message-ID: <20090325084724.GA28171@elte.hu>
References: <20090324155625.420966314@polymtl.ca> <20090324160148.080628193@polymtl.ca> <20090324173354.GC3129@redhat.com> <20090324175049.GC31117@elte.hu> <20090324175750.GE3129@redhat.com> <20090324191252.GA11665@elte.hu> <20090324201146.GA4350@Krystal> <20090324205120.GB24320@elte.hu>
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* Ingo Molnar <mingo@elte.hu> wrote:

> 
> * Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
> 
> > If we want to do this logically, without thinking about tracer 
> > performance impact, we could/should do :
> > 
> > trace_irq_entry(irqno, pt_regs)
> >   for_each_handler() {
> >     trace_irq_handler_entry(action)
> >     action->handler()
> >     trace_irq_handler_exit(ret)
> >   }
> > trace_irq_exit(retval)
> 
> Not really.

Put differently: we seem to agree on handler invocation entry/exit 
events (and those are handled by Jason's patch already), and that's 
good.

I dont think we need two events for physical IRQ events though. One 
is enough: entry event. What meaning does 'retval' have in your 
pseudo-code above? None typically.

	Ingo