Subject: Re: b44: regression in 2.6.22 (resend)

From: Maximilian Engelhardt <[email-masked]>
Date: Mon, 28 May 2007 16:12:12 +0200

On Monday 28 May 2007, Michael Buesch wrote:
> Can you also test the following patch?
> I think there's a bug in b44 that is doesn't properly discard
> shared IRQs, so it might possibly generate a NAPI storm, dunno.
> Worth a try.
>
> Index: linux-2.6.22-rc3/drivers/net/b44.c
> ===================================================================
> --- linux-2.6.22-rc3.orig/drivers/net/b44.c	2007-05-27 23:01:44.000000000
> +0200 +++ linux-2.6.22-rc3/drivers/net/b44.c	2007-05-28 12:48:27.000000000
> +0200 @@ -911,6 +911,8 @@ static irqreturn_t b44_interrupt(int irq
>  	spin_lock(&bp->lock);
>
>  	istat = br32(bp, B44_ISTAT);
> +	if (istat == 0xFFFFFFFF)
> +		goto out; /* Shared IRQ not for us */
>  	imask = br32(bp, B44_IMASK);
>
>  	/* The interrupt mask register controls which interrupt bits
> @@ -942,6 +944,7 @@ irq_ack:
>  		bw32(bp, B44_ISTAT, istat);
>  		br32(bp, B44_ISTAT);
>  	}
> +out:
>  	spin_unlock(&bp->lock);
>  	return IRQ_RETVAL(handled);
>  }

I did try this patch on a affected kernel, but I didn't notice any big 
difference. Perhaps the kernel is a bit less slow during the test, but It's 
hard to tell.

Maxi