Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756368AbdDMJYb (ORCPT ); Thu, 13 Apr 2017 05:24:31 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:38445 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756092AbdDMJYa (ORCPT ); Thu, 13 Apr 2017 05:24:30 -0400 Date: Thu, 13 Apr 2017 11:24:18 +0200 From: Peter Zijlstra To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, Will Deacon , Boqun Feng , Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH tip/core/rcu 02/40] rcu: Make arch select smp_mb__after_unlock_lock() strength Message-ID: <20170413092418.a2rudzukbgookior@hirez.programming.kicks-ass.net> References: <20170412174003.GA23207@linux.vnet.ibm.com> <1492018825-25634-2-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1492018825-25634-2-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 560 Lines: 10 On Wed, Apr 12, 2017 at 10:39:47AM -0700, Paul E. McKenney wrote: > The definition of smp_mb__after_unlock_lock() is currently smp_mb() > for CONFIG_PPC and a no-op otherwise. It would be better to instead > provide an architecture-selectable Kconfig option, and select the > strength of smp_mb__after_unlock_lock() based on that option. Why is this better? Do we want to have more of this? I thought we still wanted to convince PPC to go RCsc and eradicate all this RCpc 'fun'. But instead now you're making it look like its OK to grow more of this pain.