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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85098C433EF for ; Wed, 13 Oct 2021 13:42:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 66A4260F11 for ; Wed, 13 Oct 2021 13:42:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235492AbhJMNo3 (ORCPT ); Wed, 13 Oct 2021 09:44:29 -0400 Received: from mx0a-0064b401.pphosted.com ([205.220.166.238]:9328 "EHLO mx0a-0064b401.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233922AbhJMNo0 (ORCPT ); Wed, 13 Oct 2021 09:44:26 -0400 Received: from pps.filterd (m0250809.ppops.net [127.0.0.1]) by mx0a-0064b401.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 19DC03tH003533; Wed, 13 Oct 2021 06:42:18 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=windriver.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : content-transfer-encoding : content-type : mime-version; s=PPS06212021; bh=65krhgoCUj/ONJv4jCXUGa9wiynpcZwonBYO0JuHmHM=; b=i6KgWO7UY8OYuaHb6vZqXUHZBIjuXDAzHhclFI+AW0T6lP4fZocA1JxplMGj5Oe0P4tq +yGLej1fSQS0P5ZcfQv41Mqky2QLQK41DPPR3fHlOKljvSU+qB2BDRuPUrBr7gRczXN2 JUPK0o3+uAUet15H9fpGzfWxzFEcK0QLJAA72+S868dm6GhQzpN5QCh4pFoOigypoIuy rdUPt61Nog/uoaHo2HOj8cN/BKlQ5Gvv0DqOuGsRRrFPSaiAXDxsLTCArvEjLKyfQqmZ UnnwYYEYah3GzdUjPrbeQIIeVaL3Qrro/GtmU1McPlB1F7nlPo/FyXLW87JKMCHPnHd5 cA== Received: from nam11-co1-obe.outbound.protection.outlook.com (mail-co1nam11lp2175.outbound.protection.outlook.com [104.47.56.175]) by mx0a-0064b401.pphosted.com with ESMTP id 3bnka70k5v-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 13 Oct 2021 06:42:18 -0700 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=b6dwcnG8MORjXHRq6uJbBef2S1bUaqQ2+T3u4zagoWdVo+A7bjJ9nquWPj+HQoEeaOo8rNPR9GXmWhgWJ6SVT0brQlbX2cpOLc3eGDy2gea3MgBiPvQw2PgLMNxN73T5QSfbGUS5HlYHlGRHY/eScVJ2d9WJnP+QRBtlfJ2H65A1jD9u2/jwAwW8Dp2BrYqnq7lx03ND2TOVZ88TeUltssrvd0CoXOSBybrJ4XDgYuezAAH1CzKt/Q1lrymQxz9rt4g84vef5iHKDSvk2MsHZuMLI4klgcl8Veef3syfFj60o0LnnwTE/rkif+gqLYptbbT+zyc+zBxxq++5x2ZFuw== 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:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=65krhgoCUj/ONJv4jCXUGa9wiynpcZwonBYO0JuHmHM=; b=mPxU6P/ji3uzJu43/FaiBmZaIzmVRNUzgXAT5rEQyUxjt7FOgGXTY3F6d1/IK+d3O2TRxbNKgBU8dDkdk9h3qXsDsqxETWpU2754MsZp/oOiKq/dEKE3jIX76V+3MNdKT+V4UrurJ9fY5lIKvCgRu+aPX28UEpOevQN4g9HXu6Vtuf4ckTMeaMun8uUEuYwJk3kFe4nNqYQT9ZE/L+QaOOoT/RMOfyhnCDkGzkCqSC26mqw0BdS9K3FBW5SkXNl01mLQtY548DxCtIuVuoKdOXftRg9dExhyy06Lcm5HT3iunV/NWittL7qqpKbf5u5mHyIFH7I6vJR0F2JemSliSw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=windriver.com; dmarc=pass action=none header.from=windriver.com; dkim=pass header.d=windriver.com; arc=none Authentication-Results: infradead.org; dkim=none (message not signed) header.d=none;infradead.org; dmarc=none action=none header.from=windriver.com; Received: from DM8PR11MB5734.namprd11.prod.outlook.com (2603:10b6:8:31::22) by DM6PR11MB2715.namprd11.prod.outlook.com (2603:10b6:5:be::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4587.22; Wed, 13 Oct 2021 13:42:17 +0000 Received: from DM8PR11MB5734.namprd11.prod.outlook.com ([fe80::5db7:737e:8ef0:c831]) by DM8PR11MB5734.namprd11.prod.outlook.com ([fe80::5db7:737e:8ef0:c831%3]) with mapi id 15.20.4608.016; Wed, 13 Oct 2021 13:42:17 +0000 From: Yanfei Xu To: peterz@infradead.org, mingo@redhat.com, will@kernel.org, longman@redhat.com, boqun.feng@gmail.com Cc: linux-kernel@vger.kernel.org Subject: [PATCH V2 3/3] locking/rwsem: fix comments about reader optimistic lock stealing conditions Date: Wed, 13 Oct 2021 21:41:54 +0800 Message-Id: <20211013134154.1085649-4-yanfei.xu@windriver.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20211013134154.1085649-1-yanfei.xu@windriver.com> References: <20211013134154.1085649-1-yanfei.xu@windriver.com> Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: HK2PR02CA0148.apcprd02.prod.outlook.com (2603:1096:202:16::32) To DM8PR11MB5734.namprd11.prod.outlook.com (2603:10b6:8:31::22) MIME-Version: 1.0 Received: from pek-lpggp1.wrs.com (60.247.85.82) by HK2PR02CA0148.apcprd02.prod.outlook.com (2603:1096:202:16::32) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4608.15 via Frontend Transport; Wed, 13 Oct 2021 13:42:15 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: b10941c0-7c0a-49b4-c39c-08d98e4f457c X-MS-TrafficTypeDiagnostic: DM6PR11MB2715: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:473; 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:DM8PR11MB5734.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(366004)(1076003)(6512007)(83380400001)(86362001)(2616005)(52116002)(5660300002)(316002)(44832011)(8936002)(956004)(8676002)(6666004)(6486002)(6506007)(2906002)(186003)(38350700002)(38100700002)(66946007)(508600001)(26005)(4326008)(66556008)(36756003)(66476007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?mIhB7kdP87eDyyEVGGgGYo0l6h+qaXyv2LeX51QA8KnXogVUoJ2ZXjYycHRl?= =?us-ascii?Q?RLsN6XTLllit5WFibupmjfVH4DaBZzpH11GPVuEGspmwf7g/0Ae8KNVmuQe/?= =?us-ascii?Q?8ro8tj2PsaCRy9g3ufzXJADvY73rGzAcfyCYl3nIQRttTdbQSy9O3ztAg+7C?= =?us-ascii?Q?zcNpvOt01IuXkhwP0mPy6ZFTw2lxnR7bsVxqIZdAE0nm2K+kBqrvY1xiFQJ8?= =?us-ascii?Q?IWDe0OY2SRE78YAOJmWBAwsrwD1/OsFrMMIkXuVF9EJmcuvyJZHN+Vf+r/yC?= =?us-ascii?Q?gbi+yEmj4EcaquC326fS031ClLct3IwpohUF+jfhjMeUs/G5InsVejID/eSd?= =?us-ascii?Q?W2CGIXMnlFNc4DpEYlIRqVFzf2vTjJAYwF6Ybo6VTy5yD8rzrVYTm0iSCmDm?= =?us-ascii?Q?ztMN29HDMdAHeFCvvtApD7V9HY/+JQR+Y0FuuLqhqdIwKT91XpPOXGvt7l6i?= =?us-ascii?Q?0hJ5Dm9WuqWAClgGcCKSsYxaqxqlz1Z/Z0EJRXG+VfV5MlchKhzdbEhwqPmh?= =?us-ascii?Q?x4KP/DULpDRzCX6leTjPfVUDNTvj8KGYjQWSOAzzbkhf+MNrqU8r+sjJRVhB?= =?us-ascii?Q?pKTDiltS+0o645FufsddT08gaZDJXurOLZGhvWI2kPiDlpChMdPTb2eR0Jcj?= =?us-ascii?Q?bllxveqrDhHQvOtnmdQgp3nUKcqU+cyaWaqIyQN92aOpybD8uY1kvTMqx+vR?= =?us-ascii?Q?7CPnVBHiW/ZOsjEUEC8D5XT1mrqhonBXLcKOnGYkH1E5j8tBICrjjdKfnWbD?= =?us-ascii?Q?dd7maz++8cEV8XgJXsiWtkhMC11U0QQcWYryOPjC5VQlxA6O1kNBGb6gw7Vz?= =?us-ascii?Q?Eeju4h3t1bxArF5pEOk62Tn3lQqO+0EgJm9OBwK8G+NwJDXVYj5nRLjoFdqY?= =?us-ascii?Q?LwkpXspeNLNbz6SAGjNHnKc5N5QxmdEW56SB4Xdpy43Vj3v2kzq+XPS6muM/?= =?us-ascii?Q?Z7d0C1ywJxgm6seew5+QeoQ8wMZRQfhQXDRfQ/AitY+lz23PFME+BI551mcm?= =?us-ascii?Q?Q/4XwgwYVgkr4GaLlLNLkIqAR59hvd8bmdzCRqc6HJt5E/TexIXLz7DGsq3c?= =?us-ascii?Q?TwuXaUu/quWR3iy6yg04rLP1r6+UarZGIfduX0UTeDxUjrkkIfCxoQtNOhx9?= =?us-ascii?Q?96XEZMOKbcZilZtVI31MOCbhT4ff6Ff2z12s4LcsyM4zYknBU8kJxUMpmlVQ?= =?us-ascii?Q?3JczEKnTlAKhuevJEVjOyhClsgm13uRKo4SEKGkv0ykIMPqhnPpNcOUbmWYt?= =?us-ascii?Q?8LyQ1vSfiRocsz/KprU8PkFUI+QlWfWD00pBXRargRof9+1hFK0MTAY8f+/u?= =?us-ascii?Q?YNc6IFNPBne40Wb+tLedc5k/?= X-OriginatorOrg: windriver.com X-MS-Exchange-CrossTenant-Network-Message-Id: b10941c0-7c0a-49b4-c39c-08d98e4f457c X-MS-Exchange-CrossTenant-AuthSource: DM8PR11MB5734.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Oct 2021 13:42:17.1748 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ddb2873-a1ad-4a18-ae4e-4644631433be X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: XChc3Xfs23b/nE+n7uKXBZdkn0C3iiDEEpgEXnurjRyt7cWAP+q7Pmv9bgbR1iZEeu5CXb/f3borF4jbP3HCvg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR11MB2715 X-Proofpoint-GUID: F40Ty0WdAx0rQFLLLVQd5101_lBA2wk9 X-Proofpoint-ORIG-GUID: F40Ty0WdAx0rQFLLLVQd5101_lBA2wk9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.182.1,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.0.607.475 definitions=2021-10-13_05,2021-10-13_02,2020-04-07_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 impostorscore=0 bulkscore=0 clxscore=1015 suspectscore=0 adultscore=0 mlxlogscore=889 spamscore=0 malwarescore=0 priorityscore=1501 mlxscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109230001 definitions=main-2110130093 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org After the commit 617f3ef95177 ("locking/rwsem: Remove reader optimistic spinning"), reader doesn't support optimistic spinning anymore, there is no need meet the condition which OSQ is empty. BTW, add an unlikely() for the max reader wakeup check in the loop. Signed-off-by: Yanfei Xu --- kernel/locking/rwsem.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 06925b43c3e7..2bd914187399 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -56,7 +56,6 @@ * * A fast path reader optimistic lock stealing is supported when the rwsem * is previously owned by a writer and the following conditions are met: - * - OSQ is empty * - rwsem is not currently writer owned * - the handoff isn't set. */ @@ -485,7 +484,7 @@ static void rwsem_mark_wake(struct rw_semaphore *sem, /* * Limit # of readers that can be woken up per wakeup call. */ - if (woken >= MAX_READERS_WAKEUP) + if (unlikely(woken >= MAX_READERS_WAKEUP)) break; } -- 2.27.0