From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932533AbcHKILt (ORCPT ); Thu, 11 Aug 2016 04:11:49 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:52979 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932289AbcHKILo (ORCPT ); Thu, 11 Aug 2016 04:11:44 -0400 Date: Thu, 11 Aug 2016 10:11:39 +0200 From: Peter Zijlstra To: Davidlohr Bueso Cc: "Paul E. McKenney" , Manfred Spraul , Benjamin Herrenschmidt , Michael Ellerman , Andrew Morton , Linux Kernel Mailing List , Susanne Spraul <1vier1@web.de>, parri.andrea@gmail.com Subject: Re: spin_lock implicit/explicit memory barrier Message-ID: <20160811081139.GT30192@twins.programming.kicks-ass.net> References: <1470787537.3015.83.camel@kernel.crashing.org> <4bd34301-0c63-66ae-71b1-6fd68c9fecdd@colorfullife.com> <20160810205202.GL3482@linux.vnet.ibm.com> <20160810222316.GA22336@linux-80c1.suse> <20160810225814.GR3482@linux.vnet.ibm.com> <20160810232922.GA24645@linux-80c1.suse> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160810232922.GA24645@linux-80c1.suse> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 10, 2016 at 04:29:22PM -0700, Davidlohr Bueso wrote: > (1) As Manfred suggested, have a patch 1 that fixes the race against mainline > with the redundant smp_rmb, then apply a second patch that gets rid of it > for mainline, but only backport the original patch 1 down to 3.12. I have not followed the thread closely, but this seems like the best option. Esp. since 726328d92a42 ("locking/spinlock, arch: Update and fix spin_unlock_wait() implementations") is incomplete, it relies on at least 6262db7c088b ("powerpc/spinlock: Fix spin_unlock_wait()") to sort PPC.