From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752381AbcEVKmc (ORCPT ); Sun, 22 May 2016 06:42:32 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:40733 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752213AbcEVKm3 (ORCPT ); Sun, 22 May 2016 06:42:29 -0400 Date: Sun, 22 May 2016 12:42:23 +0200 From: Peter Zijlstra To: Peter Hurley Cc: Jason Low , Waiman Long , Davidlohr Bueso , Ingo Molnar , linux-kernel@vger.kernel.org, Dave Chinner , "Paul E. McKenney" , Scott J Norton , Douglas Hatch , jason.low2@hp.com Subject: Re: [PATCH v4 2/5] locking/rwsem: Protect all writes to owner by WRITE_ONCE Message-ID: <20160522104223.GO3193@twins.programming.kicks-ass.net> References: <1463534783-38814-1-git-send-email-Waiman.Long@hpe.com> <1463534783-38814-3-git-send-email-Waiman.Long@hpe.com> <20160518140436.GA6273@linux-uzut.site> <1463592095.3369.10.camel@j-VirtualBox> <573CB496.4010707@hpe.com> <1463601515.2587.24.camel@j-VirtualBox> <574086FE.6080807@hurleysoftware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <574086FE.6080807@hurleysoftware.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, May 21, 2016 at 09:04:14AM -0700, Peter Hurley wrote: > And by the way, it's not just "here" but _everywhere_. > What about reading ->on_cpu locklessly? In the smp_cond_acquire() rework that I have pending that one is actually 'fixed'. But yeah, the whole load/store tearing thing is giant pain inflicted upon us by C language and GCC people :/ And the problem is that the 'regression' is now so old it doesn't matter they fix it or not, we have to support compilers that think its fine to generates tears :-(