netdev - Re: 2.6.29 forcedeth hang W/O NAPI enabled

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Date:	Wed, 25 Mar 2009 22:24:42 -0700 (PDT)
From:	Adam Richter <adam_richter2004@...oo.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	davem@...emloft.net, netdev@...r.kernel.org, berkley@...wustl.edu
Subject: Re: 2.6.29 forcedeth hang W/O NAPI enabled


--- On Wed, 3/25/09, Herbert Xu <herbert@...dor.apana.org.au> wrote:
> Hi Adam:
> 
> Any chance you can test this patch instead of the previous
> one?

OK.  I tried your patch.  It seems fine.  I was able to do "ping -f" for five minutes with no problems, and surf the web during that time.

I preserving the rest of your message below, just to be clear about which patch I tested.

Adam


> 
> net: Fix netpoll lockup in legacy receive path
> 
> When I fixed the GRO crash in the legacy receive path I
> used
> napi_complete to replace __napi_complete.  Unfortunately
> they're
> not the same when NETPOLL is enabled, which may result in
> us
> not calling __napi_complete at all.
> 
> What's more, we really do need to keep the
> __napi_complete call
> within the IRQ-off section since in theory an IRQ can occur
> in
> between and fill up the backlog to the maximum, causing us
> to
> lock up.
> 
> This patch fixes this by essentially open-coding
> __napi_complete.
> 
> Note we no longer need the memory barrier because this
> function
> is per-cpu.
> 
> Signed-off-by: Herbert Xu
> <herbert@...dor.apana.org.au>
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index e3fe5c7..2a7f6b3 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -2588,9 +2588,10 @@ static int process_backlog(struct
> napi_struct *napi, int quota)
>  		local_irq_disable();
>  		skb = __skb_dequeue(&queue->input_pkt_queue);
>  		if (!skb) {
> +			list_del(&napi->poll_list);
> +			clear_bit(NAPI_STATE_SCHED, &napi->state);
>  			local_irq_enable();
> -			napi_complete(napi);
> -			goto out;
> +			break;
>  		}
>  		local_irq_enable();
>  
> @@ -2599,7 +2600,6 @@ static int process_backlog(struct
> napi_struct *napi, int quota)
>  
>  	napi_gro_flush(napi);
>  
> -out:
>  	return work;
>  }
> 
> Thanks,
> -- 
> Visit Openswan at http://www.openswan.org/
> Email: Herbert Xu 许志壬
> <herbert@...dor.apana.org.au>
> Home Page: http://gondor.apana.org.au/�herbert/
> PGP Key: http://gondor.apana.org.au/�herbert/pubkey.txt


      
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