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SubjectRe: [PATCH v5 3/5] bnx2x: Eliminate duplicate barriers on weakly-ordered archs
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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.

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