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Date:   Fri, 23 Mar 2018 13:04:18 -0400 (EDT)
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Subject: Re: [PATCH v5 3/5] bnx2x: Eliminate duplicate barriers on
 weakly-ordered archs
From:   David Miller <davem@davemloft.net>
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From: Sinan Kaya <okaya@codeaurora.org>
Date: Fri, 23 Mar 2018 12:51:47 -0400

> It could if txdata->tx_db was not a union. There is a data dependency
> between txdata->tx_db.data.prod and txdata->tx_db.raw. 
> 
> So, no reordering.

I don't see it that way, the code requires that:

 	txdata->tx_db.data.prod += nbd;

is visible before the doorbell update.

barrier() doesn't provide that.

Neither does writel_relaxed().  However plain writel() does.

Therefore the code is only correct as-is, and your change potentially
adds a reordering problem.