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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 49DA2C433EF for ; Tue, 7 Sep 2021 17:58:24 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C0541610F8 for ; Tue, 7 Sep 2021 17:58:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org C0541610F8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id C8A126B0071; Tue, 7 Sep 2021 13:58:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C38C7900002; Tue, 7 Sep 2021 13:58:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AB2716B0073; Tue, 7 Sep 2021 13:58:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 95B4F6B0071 for ; Tue, 7 Sep 2021 13:58:22 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 26CEA22BE2 for ; Tue, 7 Sep 2021 17:58:22 +0000 (UTC) X-FDA: 78561536844.03.4A4118A Received: from mx0b-00069f02.pphosted.com (mx0b-00069f02.pphosted.com [205.220.177.32]) by imf02.hostedemail.com (Postfix) with ESMTP id B09977001A05 for ; Tue, 7 Sep 2021 17:58:21 +0000 (UTC) Received: from pps.filterd (m0246632.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 187HsZgo027982; Tue, 7 Sep 2021 17:57:53 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : references : in-reply-to : content-type : content-id : content-transfer-encoding : mime-version; s=corp-2021-07-09; bh=qcO7MZthesZA8nMzsdYLNqPVTFTOFD5KjwzK9EXwvbs=; b=e3catQP5NG0ELPz5U2Pai1O4AOxjaFJDRdHM6QPrbCkT1QNvCsIGCtM3+g1KRlkOHs5E vxjIAAniihB3vvFvFB1ckQ6ypoal0rE71YIAWx5b3vkl7QptKs/TnBDlgKEgtUgdWAfD QFVDDAKF/O0zvTdx8Kd1b20MHHV+FfexM3bnLa7F/IsyHm0/asa7MYBcOmSz31k3RIRH LOL3n0NdKn9V7R6LezCWMaDIq5g+iUVkfMhyC9u1gBDac4Y4lmAXNCxun4NCXdC7wXyX iZ9GbaQzulOP/BCr5SUBRtRYgn9lmo+01fsdYkFJ7nTheGQG2ytvYjeA4ZEzM3g+Ro8y 2g== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : references : in-reply-to : content-type : content-id : content-transfer-encoding : mime-version; s=corp-2020-01-29; bh=qcO7MZthesZA8nMzsdYLNqPVTFTOFD5KjwzK9EXwvbs=; b=AyEjwiUDDu+pBSPkHyKON7eNAqQGIZN18ModHsrIt6SHS9/XjAj/Ps05uldNA+eLCuzy 9YiCO3K8Hx1/Pe076L+8m/MYkZHEMN7RwKHhMBV81Qd+S87Tnm0U0FSt3Bx7EMeyuPWp wYp3JpcgiGpuLr0Bi8VE9upECIEggO35MfBWxZ33NbcjfqGTDiMNI4DT0BTHh4SyPWPL mlO4dXsp/MA+AUf3IPtQooolm/wJOpH+ap2wfQN7DiXJTG6beFw0nNmZgHwQJO7zpIM1 1zQhAzfS6H4My98IPV0oRzJBRtkgJMuLjt9NLNK5DRxdmgcGP7EEQu2eYzg+tU0hHFtU Ww== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by mx0b-00069f02.pphosted.com with ESMTP id 3axcw680be-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 07 Sep 2021 17:57:53 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 187HuCkq086481; Tue, 7 Sep 2021 17:57:52 GMT Received: from nam12-dm6-obe.outbound.protection.outlook.com (mail-dm6nam12lp2174.outbound.protection.outlook.com [104.47.59.174]) by userp3020.oracle.com with ESMTP id 3axcpp8q1d-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 07 Sep 2021 17:57:52 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Vx/RKx1Lyuo1vmHN4hICPy4MGv/mDMgzUUI4+ZmM2YP0cYHNAbTbRAMyR3tH1m0BjeBncWmgOaX/B2d/a/SudJz+kq/zejajGlaxoD3B6dlO0/49QURVagU9Kkz7MbUHVZy+itPmQDnyP6uxDNH9ott01Toh5Uw3JIsY4GQN7GtT+zTVu8SjPNuMegm5ZzcxbCucqtHvg8wCjUHZS3DO/KaPP5F4FwRkJ8RE5LBsrfMsx1X8VTu6CZX5xiDpKImiSWE8szs0dFII5TyU5GJQKMG/qc3GiloeXsMQsIrktiN8oTmHdK163G9P55ErgmaeXORTiyJlxMotr+xobDnPjA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=qcO7MZthesZA8nMzsdYLNqPVTFTOFD5KjwzK9EXwvbs=; b=ShtBHM/1I2Zv2Et5hIBbbBlc32CV7LuEgUD+fzr4CzkTyjl292531DU4WehfTOekV3SKiNN3C4VRTxofidGB0tJPgd+9J6GwtbvXCZ6qyMxM4n/Tt8hFoIeDdfRj+jjOmAtqJ31XSyupaEq+bscRUoupXMYrfJnCZknDwQDyW0GViNbN5YMPbwZ7VOj+9IHPZELpDEo5iLTXzlj4qI/ynfF/PvVfwS965cPS/Z8syvUxWTKNO3Nmt5gAKBXFlkac7p/tqUg+FSWubGA8P5tgSDDOOW2l+Y9ljJw0T4QwU99GnV3qosFGt3+cg2Pfvznic5A9OijHFwA3yC6bViPL8A== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=oracle.com; dmarc=pass action=none header.from=oracle.com; dkim=pass header.d=oracle.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.onmicrosoft.com; s=selector2-oracle-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=qcO7MZthesZA8nMzsdYLNqPVTFTOFD5KjwzK9EXwvbs=; b=cIA8EBzrRn6kkLWB/6IBqOheq0h2XOGH8GVhHa8VhxIfbrOTQuNsmEFxdvJzQM4OjlS8ey2GTHrzIi1kTzbMcvtHum0vkxboAcXDb//XtlD6xtfG7reKH7S3qL6hBa4xevNI5MNXxR76rNWVB09TPXXeWKxPSuJ85Q2FzqLEMbQ= Received: from DM6PR10MB4380.namprd10.prod.outlook.com (2603:10b6:5:223::19) by DM6PR10MB3660.namprd10.prod.outlook.com (2603:10b6:5:153::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4478.17; Tue, 7 Sep 2021 17:57:48 +0000 Received: from DM6PR10MB4380.namprd10.prod.outlook.com ([fe80::f4b1:d890:7745:30a3]) by DM6PR10MB4380.namprd10.prod.outlook.com ([fe80::f4b1:d890:7745:30a3%4]) with mapi id 15.20.4478.026; Tue, 7 Sep 2021 17:57:48 +0000 From: Liam Howlett To: Steven Rostedt CC: Vlastimil Babka , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Michel Lespinasse , Matthew Wilcox Subject: Re: [PATCH v2] mmap_lock: Change trace and locking order Thread-Topic: [PATCH v2] mmap_lock: Change trace and locking order Thread-Index: AQHXoGpZMTHOHeoOlEi9q/cbKaDHwquXHvsAgAGx3ICAABIHAA== Date: Tue, 7 Sep 2021 17:57:48 +0000 Message-ID: <20210907175740.utkiu5folrdajmgs@revolver> References: <20210903022041.1843024-1-Liam.Howlett@oracle.com> <20210907125309.7af5cd19@gandalf.local.home> In-Reply-To: <20210907125309.7af5cd19@gandalf.local.home> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: f650b98a-4fd4-4c5e-4ee8-08d972290104 x-ms-traffictypediagnostic: DM6PR10MB3660: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:3968; x-ms-exchange-senderadcheck: 1 x-ms-exchange-antispam-relay: 0 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: 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 x-forefront-antispam-report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DM6PR10MB4380.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(7916004)(366004)(376002)(136003)(346002)(396003)(39860400002)(33716001)(122000001)(316002)(6512007)(54906003)(6486002)(4326008)(86362001)(66946007)(71200400001)(8676002)(83380400001)(9686003)(186003)(76116006)(91956017)(5660300002)(38100700002)(26005)(6916009)(66476007)(8936002)(44832011)(478600001)(64756008)(66446008)(38070700005)(53546011)(66556008)(1076003)(2906002)(6506007);DIR:OUT;SFP:1101; x-ms-exchange-antispam-messagedata-chunkcount: 1 x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?Wt6kY2gQjkkFu2oIJmfQrvMSPtX2u+gKfde3XioI232oTDVBZ1vivVkuLrCy?= =?us-ascii?Q?DIWcbajbOGiDr5dkm1ZGfYWSQznoPKilVHdYQ1PF74TDqU2W1oVDd1pjA4yp?= =?us-ascii?Q?QsSeTVvWjUsxMAy1qZYPZv+G8OnocS8uqexnf1Qr7W8P76aFn6HkWsSlD60s?= =?us-ascii?Q?9NS1Di9hZsLWgc8MMsWmLvted1x7aMhFck8FCw2XcQqrqOJtP1Xw1yhmGNQ0?= =?us-ascii?Q?cz0tUuVhCQnQaK/F5Hmoev0/57vkbEQBCefDYCrORLxOYaqJssRG1COaH6nY?= =?us-ascii?Q?Rhow7ezZF6nwfMsapgJn4W4aoaD3xCTJNsX3Vdn2OLCp0AiOxaaEMxU8bcwM?= =?us-ascii?Q?oB8LaJlLI/kGnki8bw15OQAHRLepIpw90UBy1LNS6tQkkZ7DN5PEsQWC1Z9Q?= =?us-ascii?Q?gWFhR2B8HJZRaSNSks0FHCUmEKou+BkicCkzot3XfMpBKTcKRSH2ARHiqVx4?= =?us-ascii?Q?RCGCNhesYK7/y6d9YdNE4s4sn17IAbIqPL3HZDDKo9vo/6aH6LZkzzmObOZw?= =?us-ascii?Q?YS0CKJCjE8VXqAo9x/Mo3tankUbNP06Rr6fFlqBUSXD3vq6TgH5KvC30dmX8?= =?us-ascii?Q?o14Pql6FZoL2v7AX3HLOSsp4MrmBbTJaVy6gM/fWXJzBgAyay8LOhLgMJgNW?= =?us-ascii?Q?quOgMinf8nVRmCgWXPpPgNqdVx3L7xC+L2bhyratAj/dR2Fc+3lalkPRIXxa?= =?us-ascii?Q?U0GSCFi/OvDdlycsqLYxPO1/COtHaIJP9R8Rb1llFGnW/UTBT19vMFjSRJeH?= =?us-ascii?Q?NayrPz3KQivkhHoJsujMnsQ2ktWZsv1TybAwNnFGuU4Dp6bTPZCnZaF9UiVY?= =?us-ascii?Q?z4/H7ZJUiE0x/EG8XwP2985YACPWwSF5RrQtZ8TPObEI/4Qyuw4sFcquYMPZ?= =?us-ascii?Q?piMkKEcuu/G9rGyiLNCpZWQkLutGRJzc1LD56Lj217LrJJHLYPVxPgErJmQC?= =?us-ascii?Q?p4rb2cBMEDeP/uIQ938HQ3ZeJ9kGjOU+v7Ba+iojIkfVs06RDAEnpN70RmUF?= =?us-ascii?Q?ZAp8L59t2M8UH7PEJSB07qAQ9wy1yyIFGQN7D4iyvEORITtKEG739AXwoKbt?= =?us-ascii?Q?Wfycx7yv85xRW7dRUNbON5PLIVwgXp5EpK8xKfXFsK0NlQMMClpTgnJcT/Th?= =?us-ascii?Q?3Og2wC66nh5FSUE2TE8tZdQIqT0PjD6/h1I+d97Yzmw6nZPMSN/1bisZJbYa?= =?us-ascii?Q?GRrzZHICVZ9SBsuRZdAExYIAjyy71Bx9JfFLsjQkFL/8U5V/PNu40E9CfOQ4?= =?us-ascii?Q?IwjbbABLoccnU5hECgGit5wmqkA96gzEDrATIi6fm7b/fVXQftuDIkHE8QOs?= =?us-ascii?Q?GZOeLsa5iAFBKbtAf74eMRTq?= x-ms-exchange-transport-forked: True Content-Type: text/plain; charset="us-ascii" Content-ID: <2C0053117978D94EBD06E68986C43A59@namprd10.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: DM6PR10MB4380.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: f650b98a-4fd4-4c5e-4ee8-08d972290104 X-MS-Exchange-CrossTenant-originalarrivaltime: 07 Sep 2021 17:57:48.5642 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: sW/UqeEF69WdZtS+/391zN9/lrmvAuRm+ILa4p8O6D2x5XbC7vqIz76YPsCUK4WpZBtJnW0duGvktHxPLGbY1g== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR10MB3660 X-Proofpoint-Virus-Version: vendor=nai engine=6300 definitions=10100 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 bulkscore=0 malwarescore=0 mlxscore=0 adultscore=0 phishscore=0 mlxlogscore=999 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109030001 definitions=main-2109070115 X-Proofpoint-GUID: FZDOmrEb_bP-IU3FxI3uyW62_YdJSvlk X-Proofpoint-ORIG-GUID: FZDOmrEb_bP-IU3FxI3uyW62_YdJSvlk Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2021-07-09 header.b=e3catQP5; dkim=pass header.d=oracle.com header.s=corp-2020-01-29 header.b=AyEjwiUD; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=cIA8EBzr; dmarc=pass (policy=none) header.from=oracle.com; spf=none (imf02.hostedemail.com: domain of liam.howlett@oracle.com has no SPF policy when checking 205.220.177.32) smtp.mailfrom=liam.howlett@oracle.com X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: B09977001A05 X-Stat-Signature: xdhzati86pyype4h7bkjj8q831a1khx9 X-HE-Tag: 1631037501-34316 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: * Steven Rostedt [210907 12:53]: > On Mon, 6 Sep 2021 17:00:18 +0200 > Vlastimil Babka wrote: >=20 > > On 9/3/21 04:21, Liam Howlett wrote: > > > Print to the trace log before releasing the lock to avoid racing with > > > other trace log printers of the same lock type. =20 > >=20 > > That description could use more details maybe? >=20 > Agreed, perhaps add something like this: >=20 > Due to the tracing of taking the mmap_lock happened outside the lock > itself, the trace can become confusing, making it look like more than one > task has the same lock: >=20 > task-749 [006] .... 14437980: mmap_lock_acquire_returned: mm= =3D00000000c94d28b8 memcg_path=3D write=3Dtrue success=3Dtrue > task-750 [007] .... 14437981: mmap_lock_acquire_returned: mm= =3D00000000c94d28b8 memcg_path=3D write=3Dtrue success=3Dtrue > task-749 [006] .... 14437983: mmap_lock_released: mm=3D00000= 000c94d28b8 memcg_path=3D write=3Dtrue >=20 > When in actuality the following occurred: >=20 > task-749 [006] - take mmap_lock > task-749 [006] - trace taking of mmap_lock > task-749 [006] - release mmap_lock >=20 > task-750 [007] - take mmap_lock > task-750 [007] - trace taking of mmap_lock >=20 > task-749 [006] - trace releasing of mmap_lock >=20 > Although the mmap_lock was taken and released then taken again by another > process, the lack of protection around the tracing of the activity caused > it to show the events out of order. If the tracing of the taking and > releasing of the mmap_lock is done inside the lock, it will protect this > from happening. >=20 > Andrew, I see you took this into your tree. Not sure if you sent it to > Linus yet. Perhaps add the above to the patch if you have not yet sent it > (with Liam's permission of course). Yes, I agree this change is useful. Let me know if you want a respin of the patch instead. Thanks, Liam >=20 > Seeing that the patch has this as a link in the commit, at the very least= , > the above explanation will be archived. >=20 > -- Steve >=20 >=20 >=20 > >=20 > > > Signed-off-by: Liam R. Howlett > > > Suggested-by: Steven Rostedt (VMware) =20 > >=20 > > Acked-by: Vlastimil Babka > =