netdev - Re: b44: regression in 2.6.22 (resend)

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Date:	Mon, 28 May 2007 16:12:12 +0200
From:	Maximilian Engelhardt <maxi@...monizer.de>
To:	Michael Buesch <mb@...sch.de>
Cc:	"linux-kernel" <linux-kernel@...r.kernel.org>,
	"linux-wireless" <linux-wireless@...r.kernel.org>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Jeff Garzik <jgarzik@...ox.com>,
	Gary Zambrano <zambrano@...adcom.com>, netdev@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: b44: regression in 2.6.22 (resend)

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

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