netdev - Re: [PATCH 3/7] RDMA/qedr: eliminate duplicate barriers on weakly-ordered archs

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Date:   Wed, 14 Mar 2018 08:06:32 -0400
From:   okaya@...eaurora.org
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     netdev@...r.kernel.org, timur@...eaurora.org,
        sulrich@...eaurora.org, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Michal Kalderon <Michal.Kalderon@...ium.com>,
        Ariel Elior <Ariel.Elior@...ium.com>,
        Doug Ledford <dledford@...hat.com>, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] RDMA/qedr: eliminate duplicate barriers on
 weakly-ordered archs

On 2018-03-14 00:12, Jason Gunthorpe wrote:
> On Tue, Mar 13, 2018 at 11:20:24PM -0400, Sinan Kaya wrote:
>> Code includes wmb() followed by writel() in multiple places. writel()
>> already has a barrier on some architectures like arm64.
>> 
>> This ends up CPU observing two barriers back to back before executing 
>> the
>> register write.
>> 
>> Since code already has an explicit barrier call, changing writel() to
>> writel_relaxed().
>> 
>> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
>>  drivers/infiniband/hw/qedr/verbs.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> Sure matches my understanding of writel_relaxed
> 
> This is part of a series, should we take just this patch through the
> rdma tree? If not:
> 
> Acked-by: Jason Gunthorpe <jgg@...lanox.com>

Feel free to take pieces.


> 
> Thanks,
> Jason