From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [RFC PATCH] docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section Date: Tue, 12 Feb 2019 18:43:54 +0000 Message-ID: <20190212184354.GC20961@fuggles.cambridge.arm.com> References: <20190211172948.3322-1-will.deacon@arm.com> <20190211202218.GQ4240@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190211202218.GQ4240@linux.ibm.com> Sender: linux-kernel-owner@vger.kernel.org To: "Paul E. McKenney" Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Benjamin Herrenschmidt , Arnd Bergmann , Peter Zijlstra , Andrea Parri , Daniel Lustig , David Howells , Alan Stern , Linus Torvalds List-Id: linux-arch.vger.kernel.org On Mon, Feb 11, 2019 at 12:22:18PM -0800, Paul E. McKenney wrote: > On Mon, Feb 11, 2019 at 05:29:48PM +0000, Will Deacon wrote: > > The "KERNEL I/O BARRIER EFFECTS" section of memory-barriers.txt is vague, > > x86-centric, out-of-date, incomplete and demonstrably incorrect in places. > > This is largely because I/O ordering is a horrible can of worms, but also > > because the document has stagnated as our understanding has evolved. > > > > Attempt to address some of that, by rewriting the section based on > > recent(-ish) discussions with Arnd, BenH and others. Maybe one day we'll > > find a way to formalise this stuff, but for now let's at least try to > > make the English easier to understand. > > > > Cc: "Paul E. McKenney" > > Cc: Benjamin Herrenschmidt > > Cc: Arnd Bergmann > > Cc: Peter Zijlstra > > Cc: Andrea Parri > > Cc: Daniel Lustig > > Cc: David Howells > > Cc: Alan Stern > > cc: Linus Torvalds > > Signed-off-by: Will Deacon > > Hello, Will, > > The intent is to replace commit 3f305018dcf3 ("docs/memory-barriers.txt: > Enforce heavy ordering for port I/O accesses"), correct? Either way is > fine, just guessing based on the conflicts when applying this one. ;-) Yup, I decided to abandon the old patch: http://lkml.kernel.org/r/20190211153043.GC32385@fuggles.cambridge.arm.com Thanks, Will From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com ([217.140.101.70]:42070 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727303AbfBLSn7 (ORCPT ); Tue, 12 Feb 2019 13:43:59 -0500 Date: Tue, 12 Feb 2019 18:43:54 +0000 From: Will Deacon Subject: Re: [RFC PATCH] docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section Message-ID: <20190212184354.GC20961@fuggles.cambridge.arm.com> References: <20190211172948.3322-1-will.deacon@arm.com> <20190211202218.GQ4240@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190211202218.GQ4240@linux.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: "Paul E. McKenney" Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Benjamin Herrenschmidt , Arnd Bergmann , Peter Zijlstra , Andrea Parri , Daniel Lustig , David Howells , Alan Stern , Linus Torvalds Message-ID: <20190212184354.90h2-zQbkOD4txMvfCx-BS7gRqoeVaJrJDla_eMVFMc@z> On Mon, Feb 11, 2019 at 12:22:18PM -0800, Paul E. McKenney wrote: > On Mon, Feb 11, 2019 at 05:29:48PM +0000, Will Deacon wrote: > > The "KERNEL I/O BARRIER EFFECTS" section of memory-barriers.txt is vague, > > x86-centric, out-of-date, incomplete and demonstrably incorrect in places. > > This is largely because I/O ordering is a horrible can of worms, but also > > because the document has stagnated as our understanding has evolved. > > > > Attempt to address some of that, by rewriting the section based on > > recent(-ish) discussions with Arnd, BenH and others. Maybe one day we'll > > find a way to formalise this stuff, but for now let's at least try to > > make the English easier to understand. > > > > Cc: "Paul E. McKenney" > > Cc: Benjamin Herrenschmidt > > Cc: Arnd Bergmann > > Cc: Peter Zijlstra > > Cc: Andrea Parri > > Cc: Daniel Lustig > > Cc: David Howells > > Cc: Alan Stern > > cc: Linus Torvalds > > Signed-off-by: Will Deacon > > Hello, Will, > > The intent is to replace commit 3f305018dcf3 ("docs/memory-barriers.txt: > Enforce heavy ordering for port I/O accesses"), correct? Either way is > fine, just guessing based on the conflicts when applying this one. ;-) Yup, I decided to abandon the old patch: http://lkml.kernel.org/r/20190211153043.GC32385@fuggles.cambridge.arm.com Thanks, Will