From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [RFC PATCH] docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section Date: Tue, 12 Feb 2019 11:24:05 -0800 Message-ID: <20190212192405.GU4240@linux.ibm.com> References: <20190211172948.3322-1-will.deacon@arm.com> <20190211202218.GQ4240@linux.ibm.com> <20190212184354.GC20961@fuggles.cambridge.arm.com> Reply-To: paulmck@linux.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190212184354.GC20961@fuggles.cambridge.arm.com> Sender: linux-kernel-owner@vger.kernel.org To: Will Deacon 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 Tue, Feb 12, 2019 at 06:43:54PM +0000, Will Deacon wrote: > 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 x86-centric, out-of-date, incomplete and demonstrably incorrect in places.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 Got it, and thank you for the reminder! Thanx, Paul From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:46196 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729845AbfBLTYM (ORCPT ); Tue, 12 Feb 2019 14:24:12 -0500 Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x1CJEBmL113981 for ; Tue, 12 Feb 2019 14:24:11 -0500 Received: from e16.ny.us.ibm.com (e16.ny.us.ibm.com [129.33.205.206]) by mx0a-001b2d01.pphosted.com with ESMTP id 2qm2u1bqr2-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 12 Feb 2019 14:24:11 -0500 Received: from localhost by e16.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 12 Feb 2019 19:24:10 -0000 Date: Tue, 12 Feb 2019 11:24:05 -0800 From: "Paul E. McKenney" Subject: Re: [RFC PATCH] docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section Reply-To: paulmck@linux.ibm.com References: <20190211172948.3322-1-will.deacon@arm.com> <20190211202218.GQ4240@linux.ibm.com> <20190212184354.GC20961@fuggles.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190212184354.GC20961@fuggles.cambridge.arm.com> Message-ID: <20190212192405.GU4240@linux.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Will Deacon 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: <20190212192405.x6OEoXY4xwpxaXgNpqhCygEOHVNqVL79xnZ_rgLCUj4@z> On Tue, Feb 12, 2019 at 06:43:54PM +0000, Will Deacon wrote: > 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 Got it, and thank you for the reminder! Thanx, Paul