netdev - Re: [PATCH] net: fix race in process

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Date:	Wed, 3 Oct 2007 09:15:26 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>, Jeff Dike <jdike@...toit.com>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH] net: fix race in process_backlog

On Wed, 03 Oct 2007 17:44:53 +0200
Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:

> Subject: net: fix race in process_backlog
> 
> The recent NAPI rework (4fa57c9ea9f36f9ca852f3a88ca5d2f1aebbc960)
> introduced a race between netif_rx() and process_backlog() which
> resulted in softirq processing to drop dead.
> 
> netif_rx()		process_backlog()
> 
> 			irq_disable();
> 			skb = __skb_dequeue();
> 			irq_enable();
> 
> irq_disable();
> __skb_queue_tail();
> napi_schedule();
> irq_enable();
> 
> 			if (!skb)
> 			  napi_complete();  <-- oops!
> 
> we cleared the napi bit, even though there is data to process.
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>

Acked-by: Stephen Hemminger <shemminger@...ux-foundation.org>


-- 
Stephen Hemminger <shemminger@...ux-foundation.org>
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