netdev - Re: RFC on writel and writel

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Message-ID: <1522249996.21446.25.camel@kernel.crashing.org>
Date:   Thu, 29 Mar 2018 02:13:16 +1100
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     okaya@...eaurora.org,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Alexander Duyck <alexander.duyck@...il.com>,
        Will Deacon <will.deacon@....com>,
        Arnd Bergmann <arnd@...db.de>, Jason Gunthorpe <jgg@...pe.ca>,
        David Laight <David.Laight@...lab.com>,
        Oliver <oohall@...il.com>,
        "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" 
        <linuxppc-dev@...ts.ozlabs.org>, linux-rdma@...r.kernel.org,
        Alexander Duyck <alexander.h.duyck@...hat.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        netdev@...r.kernel.org, linus971@...il.com
Subject: Re: RFC on writel and writel_relaxed

On Wed, 2018-03-28 at 07:41 -0400, okaya@...eaurora.org wrote:
> Yes, we want to get there indeed. It is because of some arch not 
> implementing writel properly. Maintainers want to play safe.
> 
> That is why I asked if IA64 and other well known archs follow the 
> strongly ordered rule at this moment like PPC and ARM.
> 
> Or should we go and inform every arch about this before yanking wmb()?
> 
> Maintainers are afraid of introducing a regression.

Let's fix all archs, it's way easier than fixing all drivers. Half of
the archs are unused or dead anyway.

> > 
> > The above code makes no sense, and just looks stupid to me. It also
> > generates pointlessly bad code on x86, so it's bad there too.
> > 
> >                 Linus