Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932155AbbLNUcM (ORCPT ); Mon, 14 Dec 2015 15:32:12 -0500 Received: from casper.infradead.org ([85.118.1.10]:51802 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753201AbbLNUcL (ORCPT ); Mon, 14 Dec 2015 15:32:11 -0500 Date: Mon, 14 Dec 2015 21:31:54 +0100 From: Peter Zijlstra To: One Thousand Gnomes Cc: "Paul E. McKenney" , Will Deacon , Andrew Pinski , Davidlohr Bueso , Thomas Gleixner , Ingo Molnar , Linux Kernel Mailing List Subject: Re: Commit 81a43adae3b9 (locking/mutex: Use acquire/release semantics) causing failures on arm64 (ThunderX) Message-ID: <20151214203154.GY6357@twins.programming.kicks-ass.net> References: <20151211084133.GE6356@twins.programming.kicks-ass.net> <20151211120419.GD18828@arm.com> <20151211121319.GK6356@twins.programming.kicks-ass.net> <20151211121759.GE18828@arm.com> <20151211122647.GM6356@twins.programming.kicks-ass.net> <20151211133313.GG18828@arm.com> <20151211134803.GP6356@twins.programming.kicks-ass.net> <20151211223540.GA22277@linux.vnet.ibm.com> <20151214184931.7166827d@lxorguk.ukuu.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151214184931.7166827d@lxorguk.ukuu.org.uk> 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 Content-Length: 807 Lines: 23 On Mon, Dec 14, 2015 at 06:49:31PM +0000, One Thousand Gnomes wrote: > > But seriously are there any cases we actually care about this for osq ? So I think what PaulMck is worried about is that one would expect things like: mutex_lock(); MMIO(++var); mutex_unlock(); (the same example Linus gave but with a mutex instead of a spinlock) to just work. Now, I haven't checked the code, but I'm not sure we ever rely on osq to provide the mutex ACQUIRE barrier, since we always need to acquire the mutex variable itself after we've acquired the osq 'lock'. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/