From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751574AbdGYWh4 (ORCPT <rfc822;w@1wt.eu>);
        Tue, 25 Jul 2017 18:37:56 -0400
Received: from mail.efficios.com ([167.114.142.141]:54989 "EHLO
        mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751328AbdGYWhz (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 25 Jul 2017 18:37:55 -0400
Date: Tue, 25 Jul 2017 22:39:53 +0000 (UTC)
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>, Lai Jiangshan <jiangshanlai@gmail.com>,
        dipankar <dipankar@in.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Josh Triplett <josh@joshtriplett.org>,
        Thomas Gleixner <tglx@linutronix.de>, rostedt <rostedt@goodmis.org>,
        David Howells <dhowells@redhat.com>,
        Eric Dumazet <edumazet@google.com>, fweisbec <fweisbec@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Will Deacon <will.deacon@arm.com>
Message-ID: <2084231322.25815.1501022393937.JavaMail.zimbra@efficios.com>
In-Reply-To: <20170725215510.GD28975@worktop>
References: <20170724215758.GA12075@linux.vnet.ibm.com> <20170725165957.alykngbnrrwn3onw@hirez.programming.kicks-ass.net> <20170725171701.GS3730@linux.vnet.ibm.com> <20170725185320.uis4hxqaqlx7y7gp@hirez.programming.kicks-ass.net> <20170725193612.GW3730@linux.vnet.ibm.com> <20170725202451.GC28975@worktop> <20170725211926.GA3730@linux.vnet.ibm.com> <20170725215510.GD28975@worktop>
Subject: Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
X-Originating-IP: [167.114.142.141]
X-Mailer: Zimbra 8.7.9_GA_1794 (ZimbraWebClient - FF52 (Linux)/8.7.9_GA_1794)
Thread-Topic: sys_membarrier: Add expedited option
Thread-Index: aufEr3jCZ3O/uktLMrr8XC6QiKSZPQ==
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

----- On Jul 25, 2017, at 5:55 PM, Peter Zijlstra peterz@infradead.org wrote:

> On Tue, Jul 25, 2017 at 02:19:26PM -0700, Paul E. McKenney wrote:
>> On Tue, Jul 25, 2017 at 10:24:51PM +0200, Peter Zijlstra wrote:
>> > On Tue, Jul 25, 2017 at 12:36:12PM -0700, Paul E. McKenney wrote:
>> > 
>> > > There are a lot of variations, to be sure.  For whatever it is worth,
>> > > the original patch that started this uses mprotect():
>> > > 
>> > > https://github.com/msullivan/userspace-rcu/commit/04656b468d418efbc5d934ab07954eb8395a7ab0
>> > 
>> > FWIW that will not work on s390 (and maybe others), they don't in fact
>> > require IPIs for remote TLB invalidation.
>> 
>> Nor will it for ARM.  Nor (I think) for PowerPC.  But that is in fact
>> what people are doing right now in real life.  Hence my renewed interest
>> in sys_membarrier().
> 
> People always do crazy stuff, but what surprised me is that such s patch
> got merged in urcu even though its known broken for a number of
> architectures.

As maintainer of liburcu, I can certainly say that this patch never made it into
liburcu master branch (official repo at git://git.liburcu.org/userspace-rcu.git).
Paul is referring to a liburcu fork by a github user "msullivan", not the official
tree.

Thanks,

Mathieu


-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com