From: David Miller <davem@davemloft.net>
To: okaya@codeaurora.org
Cc: netdev@vger.kernel.org, timur@codeaurora.org,
sulrich@codeaurora.org, linux-arm-msm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, ariel.elior@cavium.com,
everest-linux-l2@cavium.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 3/5] bnx2x: Eliminate duplicate barriers on weakly-ordered archs
Date: Fri, 23 Mar 2018 13:04:18 -0400 (EDT) [thread overview]
Message-ID: <20180323.130418.2223623186761161723.davem@davemloft.net> (raw)
In-Reply-To: <4bd9ccd2-df8f-acad-2513-eefe065dc852@codeaurora.org>
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.
next prev parent reply other threads:[~2018-03-23 17:04 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-22 17:09 [PATCH v5 0/5] netdev: Eliminate duplicate barriers on weakly-ordered archs Sinan Kaya
2018-03-22 17:09 ` [PATCH v5 1/5] net: qla3xxx: " Sinan Kaya
2018-03-22 17:09 ` [PATCH v5 2/5] qlcnic: " Sinan Kaya
2018-03-22 17:10 ` [PATCH v5 3/5] bnx2x: " Sinan Kaya
2018-03-23 16:20 ` David Miller
2018-03-23 16:31 ` Sinan Kaya
2018-03-23 16:43 ` David Miller
2018-03-23 16:51 ` Sinan Kaya
2018-03-23 17:04 ` David Miller [this message]
2018-03-23 17:13 ` Sinan Kaya
2018-03-23 17:16 ` David Miller
2018-03-24 14:30 ` Chopra, Manish
2018-03-24 14:57 ` Sinan Kaya
2018-03-22 17:10 ` [PATCH v5 4/5] net: qlge: " Sinan Kaya
2018-03-22 17:10 ` [PATCH v5 5/5] bnxt_en: " Sinan Kaya
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