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

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Date:	Wed, 30 Apr 2008 23:36:56 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
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

On Wed, 30 Apr 2008, Eric W. Biederman wrote:
> 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.

Makes sense.
 
> > 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 */

Your the third one to notice :)

Thanks,
	tglx

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