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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Sun, 28 Oct 2018 21:20:41 -0400 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp22034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w9T1Kfr757737262 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 29 Oct 2018 01:20:41 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E456AB206C; Mon, 29 Oct 2018 01:20:40 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C0F57B2068; Mon, 29 Oct 2018 01:20:40 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.85.185.180]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Mon, 29 Oct 2018 01:20:40 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 82FC216C35A9; Sun, 28 Oct 2018 18:20:42 -0700 (PDT) Date: Sun, 28 Oct 2018 18:20:42 -0700 From: "Paul E. McKenney" To: Andrea Parri Cc: Peter Zijlstra , Josh Triplett , linux-kernel@vger.kernel.org Subject: Re: [RFR] Store tearing Reply-To: paulmck@linux.ibm.com References: <20181028230627.GA3420@andrea> <20181028231003.GA4021@andrea> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181028231003.GA4021@andrea> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 18102901-2213-0000-0000-0000030C02A3 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009946; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000268; SDB=6.01109425; UDB=6.00574771; IPR=6.00889518; MB=3.00023942; MTD=3.00000008; XFM=3.00000015; UTC=2018-10-29 01:20:43 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18102901-2214-0000-0000-00005C0E39CE Message-Id: <20181029012042.GR4170@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-10-29_01:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=484 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1810290012 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 29, 2018 at 12:10:03AM +0100, Andrea Parri wrote: > Hopefully, with Paul's proper email address this time, > > Andrea > > On Mon, Oct 29, 2018 at 12:06:27AM +0100, Andrea Parri wrote: > > Hi, > > > > memory-barriers.txt says: > > > > [on "store tearing"] > > > > "In fact, a recent bug (since fixed) caused GCC to incorrectly use > > this optimization in a volatile store.". > > > > I was wondering if you could help me retrieve some reference/discussions > > about this? This was quite some time ago, but it involved a 32-bit volatile store of a constant such as 0x10001. The machine in question had a narrow store-immediate instruction, so the compiler emitted a pair of 16-bit store-immediate instructions. This bug was fixed, though only after significant screaming and shouting. Thanx, Paul