linux-kernel - Re: [PATCH] let setup_irq reenable a shared irq

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Message-ID: <m1d4o7kpme.fsf@frodo.ebiederm.org>
Date:	Wed, 30 Apr 2008 14:19:05 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Uwe Kleine-König <Uwe.Kleine-Koenig@...i.com>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] let setup_irq reenable a shared irq

Thomas Gleixner <tglx@...utronix.de> writes:
 >
> Subject: genirq: reenable a nobody cared disabled irq when a new driver arrives
> From: Thomas Gleixner <tglx@...utronix.de>
> Date: Mon, 28 Apr 2008 17:01:56 +0200
>
> Uwe Kleine-Koenig has some strange hardware where one of the shared
> interrupts can be asserted during boot before the appropriate driver
> loads. Requesting the shared irq line from another driver results in a
> spurious interrupt storm which finally disables the interrupt line.
>
> I have seen similar behaviour on resume before (the hardware does not
> work anymore so I can not verify) and this spurious irq issue is
> raised on a regular base in bugreports.

This case also happens on a regular basis in kdump kernels where we
deliberately don't shutdown the hardware before starting the new kernel.
This patch should reduce the need for using irqpoll in that situation
by a small amount.

> Index: linux-2.6/include/linux/irq.h
> ===================================================================
> --- linux-2.6.orig/include/linux/irq.h
> +++ linux-2.6/include/linux/irq.h
> @@ -61,6 +61,7 @@ typedef	void (*irq_flow_handler_t)(unsig
>  #define IRQ_WAKEUP 0x00100000 /* IRQ triggers system wakeup */
>  #define IRQ_MOVE_PENDING 0x00200000 /* need to re-target IRQ destination */
>  #define IRQ_NO_BALANCING 0x00400000 /* IRQ is excluded from balancing */
> +#define IRQ_SPURIOUS_DISABLED 0x00400000 /* IRQ was disabled by the spurious trap */

Looks like a duplicate define here. Don't you want:
+#define IRQ_SPURIOUS_DISABLED 0x00800000 /* IRQ was disabled by the spurious trap */
--
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