From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 923F6C169C4 for ; Thu, 31 Jan 2019 16:52:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 68CED218AC for ; Thu, 31 Jan 2019 16:52:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388671AbfAaQwh (ORCPT ); Thu, 31 Jan 2019 11:52:37 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:37248 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1733267AbfAaQwg (ORCPT ); Thu, 31 Jan 2019 11:52:36 -0500 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x0VGmxfG111560 for ; Thu, 31 Jan 2019 11:52:35 -0500 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 2qc4sjre55-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 31 Jan 2019 11:52:34 -0500 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 31 Jan 2019 16:52:31 -0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x0VGqTuH40763504 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 31 Jan 2019 16:52:30 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CB55052059; Thu, 31 Jan 2019 16:52:29 +0000 (GMT) Received: from osiris (unknown [9.152.212.95]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTPS id 6D4E25204F; Thu, 31 Jan 2019 16:52:29 +0000 (GMT) Date: Thu, 31 Jan 2019 17:52:28 +0100 From: Heiko Carstens To: Thomas Gleixner Cc: "Paul E. McKenney" , Sebastian Sewior , Peter Zijlstra , Ingo Molnar , Martin Schwidefsky , LKML , linux-s390@vger.kernel.org, Stefan Liebler Subject: Re: WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggerede References: <20190130125955.GD5299@osiris> <20190130132420.spwrq2d4oxeydk5s@linutronix.de> <20190130210733.mg6aascw2gzl3oqz@linutronix.de> <20190130233557.GA4240@linux.ibm.com> MIME-Version: 1.0 In-Reply-To: X-TM-AS-GCONF: 00 x-cbid: 19013116-0008-0000-0000-000002B96ECD X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19013116-0009-0000-0000-000022257265 Message-Id: <20190131165228.GA32680@osiris> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit Content-Disposition: inline X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-01-31_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1901310129 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 31, 2019 at 01:27:25AM +0100, Thomas Gleixner wrote: > On Thu, 31 Jan 2019, Thomas Gleixner wrote: > > > On Wed, 30 Jan 2019, Paul E. McKenney wrote: > > > On Thu, Jan 31, 2019 at 12:13:51AM +0100, Thomas Gleixner wrote: > > > > I might be wrong as usual, but this would definitely explain the fail very > > > > well. > > > > > > On recent versions of GCC, the fix would be to put this between the two > > > stores that need ordering: > > > > > > __atomic_thread_fence(__ATOMIC_RELEASE); > > > > > > I must defer to Heiko on whether s390 GCC might tear the stores. My > > > guess is "probably not". ;-) > > > > So I just checked the latest glibc code. It has: > > > > /* We must not enqueue the mutex before we have acquired it. > > Also see comments at ENQUEUE_MUTEX. */ > > __asm ("" ::: "memory"); > > ENQUEUE_MUTEX_PI (mutex); > > /* We need to clear op_pending after we enqueue the mutex. */ > > __asm ("" ::: "memory"); > > THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); > > > > 8f9450a0b7a9 ("Add compiler barriers around modifications of the robust mutex list.") > > > > in the glibc repository, There since Dec 24 2016 ... > > And of course, I'm using the latest greatest glibc for testing that, so I'm > not at all surprised that it just does not reproduce on my tests. As discussed on IRC: I used plain vanilla glibc version 2.28 for my tests. This version already contains the commit you mentioned above. > I just hacked the ordering and restarted the test. If the theory holds, > then this should die sooner than later. ...nevertheless Stefan and I looked through the lovely disassembly of _pthread_mutex_lock_full() to verify if the compiler barriers are actually doing what they are supposed to do. The generated code however does look correct. So, it must be something different.