From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e39.co.us.ibm.com (e39.co.us.ibm.com [32.97.110.160]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 22B771A006B for ; Sat, 6 Sep 2014 06:09:33 +1000 (EST) Received: from /spool/local by e39.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 5 Sep 2014 14:09:31 -0600 Received: from b03cxnp08025.gho.boulder.ibm.com (b03cxnp08025.gho.boulder.ibm.com [9.17.130.17]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id 6422219D8040 for ; Fri, 5 Sep 2014 14:09:15 -0600 (MDT) Received: from d03av06.boulder.ibm.com (d03av06.boulder.ibm.com [9.17.195.245]) by b03cxnp08025.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id s85K9SwC24117356 for ; Fri, 5 Sep 2014 22:09:28 +0200 Received: from d03av06.boulder.ibm.com (loopback [127.0.0.1]) by d03av06.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id s85KDq3d022094 for ; Fri, 5 Sep 2014 14:13:53 -0600 Date: Fri, 5 Sep 2014 13:09:26 -0700 From: "Paul E. McKenney" To: Peter Hurley Subject: Re: bit fields && data tearing Message-ID: <20140905200926.GW5001@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <063D6719AE5E284EB5DD2968C1650D6D17487172@AcuExch.aculab.com> <1409824374.4246.62.camel@pasglop> <5408E458.3@zytor.com> <54090AF4.7060406@hurleysoftware.com> <54091B30.2090509@zytor.com> <20140905081648.GB5281@omega> <20140905180950.GU5001@linux.vnet.ibm.com> <540A05F7.1070202@hurleysoftware.com> <20140905190506.GV5001@linux.vnet.ibm.com> <540A0DF3.8030802@hurleysoftware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <540A0DF3.8030802@hurleysoftware.com> Cc: Jakub Jelinek , "linux-arch@vger.kernel.org" , Tony Luck , "linux-ia64@vger.kernel.org" , Michael Cree , linux-alpha@vger.kernel.org, Oleg Nesterov , "linux-kernel@vger.kernel.org" , David Laight , Paul Mackerras , "H. Peter Anvin" , "linuxppc-dev@lists.ozlabs.org" , Miroslav Franc , Richard Henderson List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, Sep 05, 2014 at 03:24:35PM -0400, Peter Hurley wrote: > On 09/05/2014 03:05 PM, Paul E. McKenney wrote: > > On Fri, Sep 05, 2014 at 02:50:31PM -0400, Peter Hurley wrote: > >> On 09/05/2014 02:09 PM, Paul E. McKenney wrote: > > [cut] > > >>> ------------------------------------------------------------------------ > >>> > >>> documentation: Record limitations of bitfields and small variables > >>> > >>> This commit documents the fact that it is not safe to use bitfields as > >>> shared variables in synchronization algorithms. It also documents that > >>> CPUs must provide one-byte and two-byte load and store instructions > >> ^ > >> atomic > > > > Here you meant non-atomic? My guess is that you are referring to the > > fact that you could emulate a one-byte store on pre-EV56 Alpha CPUs > > using the ll and sc atomic-read-modify-write instructions, correct? > > Yes, that's what I meant. I must be tired and am misreading the commit > message, or misinterpreting it's meaning. Very good, got it! Thanx, Paul