linux-kernel - Re: [RFC patch 3/5] genirq: add threaded interrupt handler support

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Date:	Thu, 2 Oct 2008 01:01:35 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Thomas Gleixner <tglx@...utronix.de>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...l.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Arjan van de Veen <arjan@...radead.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Jon Masters <jonathan@...masters.org>,
	Sven Dietrich <sdietrich@...e.de>
Subject: Re: [RFC patch 3/5] genirq: add threaded interrupt handler support


On Wed, 1 Oct 2008, Thomas Gleixner wrote:
>  #define irqreturn_t	enum irqreturn
> Index: linux-2.6-tip/kernel/irq/handle.c
> ===================================================================
> --- linux-2.6-tip.orig/kernel/irq/handle.c
> +++ linux-2.6-tip/kernel/irq/handle.c
> @@ -143,13 +143,34 @@ irqreturn_t handle_IRQ_event(unsigned in
>  			ret = IRQ_NEEDS_HANDLING;
>  
>  		switch (ret) {
> -		default:
> +		case IRQ_NEEDS_HANDLING:
> +			if (!(action->flags & IRQF_THREADED)) {
> +				ret = action->handler(irq, action->dev_id);
> +				if (ret == IRQ_HANDLED)
> +					status |= action->flags;
> +				break;
> +			}
> +			/*
> +			 * Warn once when a quick check handler asked
> +			 * for invoking the threaded (main) handler
> +			 * directly
> +			 */
> +			WARN(!(action->flags & IRQF_WARNED_THREADED),
> +			     "IRQ %d requested to run threaded handler "
> +			     "in hard interrupt context\n", irq);
> +			set_bit(IRQF_WARNED_THREADED, &action->flags);

Do you purposely fall through to the next case statement here?
If so, could you please add a comment.

			/* fall through */

or something similar so we know it's not a bug.

> +
> +		case IRQ_WAKE_THREAD:
> +			set_bit(IRQF_RUNTHREAD, &action->flags);
> +			wake_up_process(action->thread);
> +			/*
> +			 * Set it to handled so the spurious check
> +			 * does not trigger.
> +			 */
> +			ret = IRQ_HANDLED;
>  			break;
>  
> -		case IRQ_NEEDS_HANDLING:
> -			ret = action->handler(irq, action->dev_id);
> -			if (ret == IRQ_HANDLED)
> -				status |= action->flags;
> +		default:
>  			break;
>  		}
>  		retval |= ret;


-- Steve

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