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SubjectRe: [PATCH v5 3/3] RDMA/qedr: eliminate duplicate barriers on weakly-ordered archs #2
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On 4/3/2018 3:42 AM, Kalderon, Michal wrote:
> The wmb before writel are used to make sure the
> HW observes the changes in memory before we trigger the doorbell.

According to Linus, writel() guarantees observability. No extra
barrier is necessary.

https://www.mail-archive.com/netdev@vger.kernel.org/msg225806.html

There shouldn't be any wmb() in drivers unless it is used for a
very well-known reason.

APIs like readX() and writeX() guarantee observability.

--
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.

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