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[209.85.167.52]) by smtp.gmail.com with ESMTPSA id h6sm4427720lfj.77.2019.04.05.08.55.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 05 Apr 2019 08:55:56 -0700 (PDT) Received: by mail-lf1-f52.google.com with SMTP id o19so4745897lfl.4 for ; Fri, 05 Apr 2019 08:55:55 -0700 (PDT) X-Received: by 2002:ac2:485a:: with SMTP id 26mr7146710lfy.128.1554479448457; Fri, 05 Apr 2019 08:50:48 -0700 (PDT) MIME-Version: 1.0 References: <20190405135936.7266-1-will.deacon@arm.com> <20190405135936.7266-18-will.deacon@arm.com> In-Reply-To: <20190405135936.7266-18-will.deacon@arm.com> From: Linus Torvalds Date: Fri, 5 Apr 2019 05:50:32 -1000 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 17/21] drivers: Remove explicit invocations of mmiowb() To: Will Deacon Cc: linux-arch , Linux List Kernel Mailing , "Paul E. McKenney" , Benjamin Herrenschmidt , Michael Ellerman , Arnd Bergmann , Peter Zijlstra , Andrea Parri , Palmer Dabbelt , Daniel Lustig , David Howells , Alan Stern , "Maciej W. Rozycki" , Paul Burton , Ingo Molnar , Yoshinori Sato , Rich Felker , Tony Luck , Mikulas Patocka , Akira Yokosawa , Luis Chamberlain , Nicholas Piggin Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 5, 2019 at 4:01 AM Will Deacon wrote: > > mmiowb() is now implied by spin_unlock() on architectures that require > it, so there is no reason to call it from driver code. This patch was > generated using coccinelle: > > @mmiowb@ > @@ > - mmiowb(); So I love the patch series, and think we should just do it, but I do wonder if some of the drivers involved end up relying on memory ordering things (store_release -> load_aquire) and IO ordering rather than using locking... Wouldn't such use now be broken on ia64 SN platforms? Do we care? So it might be worth noting that a lot of the mmiowb()s here weren't paired with spin_unlock? Linus From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: [PATCH v2 17/21] drivers: Remove explicit invocations of mmiowb() Date: Fri, 5 Apr 2019 05:50:32 -1000 Message-ID: References: <20190405135936.7266-1-will.deacon@arm.com> <20190405135936.7266-18-will.deacon@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20190405135936.7266-18-will.deacon@arm.com> Sender: linux-kernel-owner@vger.kernel.org To: Will Deacon Cc: linux-arch , Linux List Kernel Mailing , "Paul E. McKenney" , Benjamin Herrenschmidt , Michael Ellerman , Arnd Bergmann , Peter Zijlstra , Andrea Parri , Palmer Dabbelt , Daniel Lustig , David Howells , Alan Stern , "Maciej W. Rozycki" , Paul Burton , Ingo Molnar , Yoshinori Sato , Rich Felker , Tony Luck , Mikulas Patocka List-Id: linux-arch.vger.kernel.org On Fri, Apr 5, 2019 at 4:01 AM Will Deacon wrote: > > mmiowb() is now implied by spin_unlock() on architectures that require > it, so there is no reason to call it from driver code. This patch was > generated using coccinelle: > > @mmiowb@ > @@ > - mmiowb(); So I love the patch series, and think we should just do it, but I do wonder if some of the drivers involved end up relying on memory ordering things (store_release -> load_aquire) and IO ordering rather than using locking... Wouldn't such use now be broken on ia64 SN platforms? Do we care? So it might be worth noting that a lot of the mmiowb()s here weren't paired with spin_unlock? Linus