From owner-freebsd-current@freebsd.org Tue Jan 10 00:16:46 2017 Return-Path: Delivered-To: freebsd-current@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id E4190CA8FC9 for ; Tue, 10 Jan 2017 00:16:46 +0000 (UTC) (envelope-from anindya49@hotmail.com) Received: from BAY004-OMC1S6.hotmail.com (bay004-omc1s6.hotmail.com [65.54.190.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (Client CN "*.outlook.com", Issuer "Microsoft IT SSL SHA2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id B07841604 for ; Tue, 10 Jan 2017 00:16:46 +0000 (UTC) (envelope-from anindya49@hotmail.com) Received: from NAM03-DM3-obe.outbound.protection.outlook.com ([65.54.190.60]) by BAY004-OMC1S6.hotmail.com over TLS secured channel with Microsoft SMTPSVC(7.5.7601.23008); Mon, 9 Jan 2017 16:15:40 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=hotmail.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=BJC8TswqiwZlKinmDb/wlqeQVbYWBziS1X/xDbic0/8=; b=LeG1HwH6xbdYEA8dXqpRrdEkZFB8FjCGqOVDKHu4wA0LDSLh37PtAXiHorc7jfB9cjrf7xZz02GhlTQ63O4FyJRHQsi8Aw3VuR8aAE1gWC4vkBVL9IQQYXMOQ2u/AvZ1psS1QvQIGmYhEYF6OCJQMbT9zRmUdrSPuMfFzSa7ClA+bFTrZAc6U4k5DuojjAI+rcuT15VsFes9P8H7XPg4tWthq8xVzH76nONFLiicYDlAHSIbg5DqS00MgfaQ0kErAI7n+gKAqspGPh2RlF4xN85UnLaPTcu1mdPiik5id4Q2RlJUrYO3n4CKEJG//SypIu5w6leKdBe9RJwTa/PEBA== Received: from CO1NAM03FT055.eop-NAM03.prod.protection.outlook.com (10.152.80.52) by CO1NAM03HT216.eop-NAM03.prod.protection.outlook.com (10.152.81.129) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P384) id 15.1.803.8; Tue, 10 Jan 2017 00:15:39 +0000 Received: from BN6PR22MB0802.namprd22.prod.outlook.com (10.152.80.57) by CO1NAM03FT055.mail.protection.outlook.com (10.152.81.162) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P384) id 15.1.803.8 via Frontend Transport; Tue, 10 Jan 2017 00:15:39 +0000 Received: from BN6PR22MB0802.namprd22.prod.outlook.com ([10.171.180.21]) by BN6PR22MB0802.namprd22.prod.outlook.com ([10.171.180.21]) with mapi id 15.01.0829.013; Tue, 10 Jan 2017 00:15:38 +0000 From: Anindya Mukherjee To: Benjamin Kaduk , Anindya Mukherjee CC: "freebsd-current@freebsd.org" Subject: RE: New Lock Order Reversal in 12.0? Thread-Topic: New Lock Order Reversal in 12.0? Thread-Index: AQHSag/a8ajcUxWClUK1AyeooZ2LxKEvT7sAgAAY/m+AAUjWAIAAJxsy Date: Tue, 10 Jan 2017 00:15:38 +0000 Message-ID: References: <20170109004717.GE8460@kduck.kaduk.org> , <20170109215342.GI8460@kduck.kaduk.org> In-Reply-To: <20170109215342.GI8460@kduck.kaduk.org> Accept-Language: en-CA, en-US Content-Language: en-CA X-MS-Has-Attach: X-MS-TNEF-Correlator: x-slblob-mailprops: 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 authentication-results: mit.edu; dkim=none (message not signed) header.d=none;mit.edu; dmarc=none action=none header.from=hotmail.com; x-incomingtopheadermarker: OriginalChecksum:6249DA48F958634354ED8B28243BA0E0DE745000AF38201F403FEAE819B76416; UpperCasedChecksum:9A5D02A779C1A0B995887358A28F7CC742DFA636F53923706AB2E6D315E3B407; SizeAsReceived:8475; Count:41 x-ms-exchange-messagesentrepresentingtype: 1 x-tmn: [din/GwJ0AVb/rkcnOjM5w0AkLJcmPtrx] x-incomingheadercount: 41 x-eopattributedmessage: 0 x-microsoft-exchange-diagnostics: 1; CO1NAM03HT216; 7:ZJfCDYzMXm+Q+djfNMegvIH5eOwZVHEqRBvRmL7JXx9JpV/RWnf8phZe6YOskqxhfO7jKw6tPOKntLhTvKbToQsE8bMCjq/7gezSiG0mu0X2C3miF8dg4gce1A3U2MeQT7ETSfNqKgwl74sxFMIDNndgE8Xy5hU/MIoTtCDM3iJYPXfEKtSrTjIo7/b2xthiHBp/SiCgFSyMZhioM1Jv9w6K7ajCGj0kWGystIFhPGdKR/rmVBcwBz76bCqjvW1UPCflBSncqVGPqdl+j0ncqu13VhVB+QheHemepo++V68WwWYaHy4Zz3Q076zgBKcSydkGE7NGZFPd5b2oyXc1dxQvhhiU5tJwDNGIMtWGlB6Df6zdlHut6yNlwGTM7ZpOgZ0+290zWGIS36AmNYiVRBcG+ZJrZE/TuH81MEL+QWr37UlZqC7wXaK+24ePv5X7PsgcKSJ09xe7FF3Ex/RRvg== x-forefront-antispam-report: EFV:NLI; SFV:NSPM; SFS:(10019020)(98900003); DIR:OUT; SFP:1102; SCL:1; SRVR:CO1NAM03HT216; H:BN6PR22MB0802.namprd22.prod.outlook.com; FPR:; SPF:None; LANG:en; x-ms-office365-filtering-correlation-id: 5cc98675-7c5c-4a05-4a5d-08d438edce28 x-microsoft-antispam: UriScan:; BCL:0; PCL:0; RULEID:(22001)(1601124038)(5061506270)(5061507270)(1603103113)(1603101340)(1601125047)(1701031023); SRVR:CO1NAM03HT216; x-exchange-antispam-report-cfa-test: BCL:0; PCL:0; RULEID:(444111334)(444112120)(432015012)(82015046); SRVR:CO1NAM03HT216; BCL:0; PCL:0; RULEID:; SRVR:CO1NAM03HT216; x-forefront-prvs: 01834E39B7 spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: hotmail.com X-MS-Exchange-CrossTenant-originalarrivaltime: 10 Jan 2017 00:15:38.1202 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Internet X-MS-Exchange-CrossTenant-id: 84df9e7f-e9f6-40af-b435-aaaaaaaaaaaa X-MS-Exchange-Transport-CrossTenantHeadersStamped: CO1NAM03HT216 X-OriginalArrivalTime: 10 Jan 2017 00:15:40.0603 (UTC) FILETIME=[AD0D20B0:01D26AD6] X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 10 Jan 2017 00:16:47 -0000 Good, that makes me feel better :) The system is running fine, so I think y= ou're right and it's nothing to worry about. Thanks again for your response= s. Best, Anindya ________________________________________ From: Benjamin Kaduk [kaduk@mit.edu] Sent: January 9, 2017 1:53 PM To: Anindya Mukherjee Cc: freebsd-current@freebsd.org Subject: Re: New Lock Order Reversal in 12.0? On Mon, Jan 09, 2017 at 02:31:39AM +0000, Anindya Mukherjee wrote: > Hi Ben, > > Thanks for your reply, and yes, I did notice #238. I should say at this p= oint that I'm a newbie when it comes to kernel code and am trying to learn = about it (hence current). Understood. It's good that you are ready to try! > The entry you refer to does look a bit like the one I've got, but I'm not= totally sure if the same code path is being followed to arrive at this LOR= . An inode is being created in my case, vs a directory creation (entry + in= ode probably) in #238, and then a sync is being attempted, which causes loc= ks to activate in the softdep code. I've read a bit about this from McCusic= k's book but the details are still fuzzy. > > Perhaps you are trying to tell me that it's benign? I know that WITNESS h= as false positives, an example being #236 where due to shared vs exclusive = vnode locks required on the two ways to lock bufwait and dirhash a deadlock= never happens. Well, it's hard to say for certain, but there are a few ufs/bufwait/ufs LORs that are very commonly reported as WITNESS output but have never (IIRC= ) been identified as causing a deadlock. So, it seems pretty likely that thi= s one is similarly benign -- I, for one, do not plan to put in time trying to analyze it until there is a hang or deadlock associated with it. -Ben