netdev - Re: [PATCH net] amd-xgbe: Fix race between access of desc and desc index

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Date:	Tue, 27 Oct 2015 19:50:07 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	thomas.lendacky@....com
Cc:	netdev@...r.kernel.org, alexander.duyck@...il.com
Subject: Re: [PATCH net] amd-xgbe: Fix race between access of desc and desc
 index

From: Tom Lendacky <thomas.lendacky@....com>
Date: Mon, 26 Oct 2015 17:13:54 -0500

> During Tx cleanup it's still possible for the descriptor data to be
> read ahead of the descriptor index. A memory barrier is required between
> the read of the descriptor index and the start of the Tx cleanup loop.
> This allows a change to a lighter-weight barrier in the Tx transmit
> routine just before updating the current descriptor index.
> 
> Since the memory barrier does result in extra overhead on arm64, keep
> the previous change to not chase the current descriptor value. This
> prevents the execution of the barrier for each loop performed.
> 
> Suggested-by: Alexander Duyck <alexander.duyck@...il.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>

Applied, thanks.
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