linux-kernel - Re: [patch 2/9] LTTng instrumentation

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Message-ID: <20090324191449.GB11665@elte.hu>
Date:	Tue, 24 Mar 2009 20:14:49 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	ltt-dev@...ts.casi.polymtl.ca,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jason Baron <jbaron@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Russell King <rmk+lkml@....linux.org.uk>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Hideo AOKI <haoki@...hat.com>,
	Takashi Nishiie <t-nishiie@...css.fujitsu.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
Subject: Re: [patch 2/9] LTTng instrumentation - irq


* Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> wrote:

> +static irqreturn_t __handle_irq_next_handler(unsigned int irq,
> +	struct irqaction **action, irqreturn_t *retval, unsigned int *status)
> +{
> +	irqreturn_t ret;
> +
> +	ret = (*action)->handler(irq, (*action)->dev_id);
> +	if (ret == IRQ_HANDLED)
> +		*status |= (*action)->flags;
> +	*retval |= ret;
> +	*action = (*action)->next;
> +	return ret;
> +}
> +
>  static irqreturn_t _handle_IRQ_event(unsigned int irq, struct irqaction *action)
>  {
>  	irqreturn_t ret, retval = IRQ_NONE;
> @@ -324,13 +345,12 @@ static irqreturn_t _handle_IRQ_event(uns
>  	if (!(action->flags & IRQF_DISABLED))
>  		local_irq_enable_in_hardirq();
>  
> -	do {
> -		ret = action->handler(irq, action->dev_id);
> -		if (ret == IRQ_HANDLED)
> -			status |= action->flags;
> -		retval |= ret;
> -		action = action->next;
> -	} while (action);
> +	ret = __handle_irq_next_handler(irq, &action, &retval, &status);
> +
> +	while (action) {
> +		trace_irq_next_handler(irq, action, ret);
> +		ret = __handle_irq_next_handler(irq, &action, &retval, &status);
> +	}

Hm, this is rather unclean. Why open-code the first handler 
execution?

This is a sign (and side effect) of the logical model being slightly 
incorrect - see my previous mail to Jason.

	Ingo
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