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Date: Fri, 21 Apr 2006 17:11:40 -0700
From: Eugene Surovegin <ebs@ebshome.net>
To: Linas Vepstas <linas@austin.ibm.com>
Subject: Re: [PATCH 2/2]: Spider ethernet driver -- protect chain head
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Cc: Maxim Shchetynin <maxim@de.ibm.com>,
	Arnd Bergmann <arnd.bergmann@de.ibm.com>,
	linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org
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On Fri, Apr 21, 2006 at 06:45:51PM -0500, Linas Vepstas wrote:
> Prevent a potential race. If two threads are both calling
> the transmit routine, both can potentially try to grab the
> same dma descriptor. Serialize access to the head of the
> tx ring with spinlocks.

Two threads cannot be in spider_net_xmit() simultaneosuly because 
hard_start_xmit entry point is already protected by net_device 
xmit_lock, see Documentation/net/netdevices.txt

-- 
Eugene