netdev - Re: [PATCH net 2/3] ibmvnic: remove unnecessary rmb() inside ibmvnic

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Message-ID: <CAOhMmr4r0OvSvbr68B8483mwJKtm=8BjiYUQa3gtin8ajZQ-5w@mail.gmail.com>
Date:   Sun, 24 Jan 2021 22:38:02 -0600
From:   Lijun Pan <lijunp213@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Lijun Pan <ljp@...ux.ibm.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net 2/3] ibmvnic: remove unnecessary rmb() inside ibmvnic_poll

On Sat, Jan 23, 2021 at 11:11 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Thu, 21 Jan 2021 00:17:09 -0600 Lijun Pan wrote:
> > rmb() was introduced to load rx_scrq->msgs after calling
> > pending_scrq(). Now since pending_scrq() itself already
> > has dma_rmb() at the end of the function, rmb() is
> > duplicated and can be removed.
> >
> > Fixes: ec20f36bb41a ("ibmvnic: Correctly re-enable interrupts in NAPI polling routine")
> > Signed-off-by: Lijun Pan <ljp@...ux.ibm.com>
>
> rmb() is a stronger barrier than dma_rmb()

Yes. I think the weaker dma_rmb() here is enough.
And I let it reuse the dma_rmb() in the pending_scrq().

>
> also again, I don't see how this fixes any bugs

I will send to net-next if you are ok with it.