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SubjectRe: [PATCH v5 3/3] RDMA/qedr: eliminate duplicate barriers on weakly-ordered archs #2
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.

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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