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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 46D89CA9EBB for ; Fri, 9 Oct 2026 21:56:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 017706B0092; Fri, 9 Oct 2026 17:56:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id F031B6B0096; Fri, 9 Oct 2026 17:56:12 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DA4166B0098; Fri, 9 Oct 2026 17:56:12 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id A77FE6B0092 for ; Fri, 9 Oct 2026 17:56:12 -0400 (EDT) Received: from smtpin18.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 33CC6A0545 for ; Fri, 9 Oct 2026 21:56:12 +0000 (UTC) X-FDA: 85304446584.18.BA0825A Received: from CWXP265CU010.outbound.protection.outlook.com (mail-ukwestazon11022116.outbound.protection.outlook.com [52.101.101.116]) by imf18.hostedemail.com (Postfix) with ESMTP id 365781C0004 for ; Fri, 9 Oct 2026 21:56:09 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=garyguo.net header.s=selector1 header.b=l3QQTq4n; spf=pass (imf18.hostedemail.com: domain of gary@garyguo.net designates 52.101.101.116 as permitted sender) smtp.mailfrom=gary@garyguo.net; dmarc=pass (policy=none) header.from=garyguo.net; arc=pass ("microsoft.com:s=arcselector10001:i=1") ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1791582969; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Dh4YcTw8JbaNUhW/j/fMV1f/mSLIk4EOiM7Jyoi4eX4=; b=1+xWSRiu/WpueptGO+kbnisvtPpR5hWGzczrCLtf4gT2/F4ILn3jFe7cZ6geAs1gTRFpRP esvBsfGyF6HhPVKfkzQTMOI4NuyDg1uMerXW/5Qm4Kc2yR74B7/49w+OXxARTchN2tAnOq e1zl8Xlq1o0iyooOnKtzYdWoq6dtzcw= ARC-Seal: i=2; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=pass; t=1791582969; b=fqnqwJpYve8AvrCwdT0ogzmVix2HInkycQABq17961UBRLuNlECQ8+RKhsLYr+DuRqGbXE lThNeiPVD+a5ySS9lzbOcZRTmGfRFkQeIaMYLNDJB2At6G/yuvhyP9fJLmYVfC9WG9E1uB 9V4Vnr7NCMc+hstDLfJDXmAciOYjFG0= ARC-Authentication-Results: i=2; imf18.hostedemail.com; dkim=pass header.d=garyguo.net header.s=selector1 header.b=l3QQTq4n; spf=pass (imf18.hostedemail.com: domain of gary@garyguo.net designates 52.101.101.116 as permitted sender) smtp.mailfrom=gary@garyguo.net; dmarc=pass (policy=none) header.from=garyguo.net; arc=pass ("microsoft.com:s=arcselector10001:i=1") ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=r8r67xD0daZ8TM+DWhGJeiL33ih0z+9yYaMDB0o1WI6tal9xOZ1PuffYoh1VSO4nrYI+9bhlWlpxdbNKSgCt3jmLjHa87o2oQPiTcOy6UE8xR2L5gT5tJt+B448lm308yR8OtoW3zpAV9RrPNd5nRQlHdiMJTfxHhJM4bHoceo2t65dfLadEVG7+s0zrfOaAesW5j+m9VmGaPB0mEOMn9KqZOLiOesyCupASgcETJ0oJwNgSk5r2Ajr9WaGmDRxFj+L6BEmUV1kfO/7BXb9lG2oB99p05LKsGsNs1ne1wn4cTe8K0yarTMUOXNbDhCZIkA/zxOdAmnEcw8UqytKgdA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; 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=Dh4YcTw8JbaNUhW/j/fMV1f/mSLIk4EOiM7Jyoi4eX4=; b=sjcFxc6oDathWllHCk3/f+KnNCV63KmB0s8a/HsvLuTVSbE5vpUC93sCLLoQeAfvesqa7i2GchN9CvU7IMSJ77e9qiYvzt6TsgyQC7zkOMMcWyUkJxezgw8lWRqBUi+F4sqNUfe68PpQ1VhDrhY+RMK4OJHwhv43Z3gPuRCCUanH0csFqJa2MbrpY6tskvNlW1k0QHZnWSZ0rBkAOWie65DIS/azhCb1vaRL/+Br8IHvlVzatQpB+djq9WkMRF+k4Kh2FoZl7eAGIgHp1ZXVaaA7jb8UYI84rOqm4GMknk3Yjdln2jNCwGGv3CEWj/7ueRLur2OqkIxAtcCs3tCWjw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=garyguo.net; dmarc=pass action=none header.from=garyguo.net; dkim=pass header.d=garyguo.net; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=garyguo.net; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=Dh4YcTw8JbaNUhW/j/fMV1f/mSLIk4EOiM7Jyoi4eX4=; b=l3QQTq4nvoEmPKX0BYeFNJWQ2l5DkKIm9v1hFZDTm2aFphuhOt8aI/kv7LY96f74P5K5tG9aAdSRZG/CoQblPOP0n/YsFi4XyfErEHouXllj82hzlatDShy3YCvPNelmoSqAsmAIZ7RmzS8qGp2ydV8oXjOrakjN3ZnnMTc8iyA= Received: from LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:4ab::19) by CWLP265MB6184.GBRP265.PROD.OUTLOOK.COM (2603:10a6:400:182::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.496.18; Fri, 9 Oct 2026 21:56:02 +0000 Received: from LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM ([fe80::f60b:1537:68d7:4fc1]) by LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM ([fe80::f60b:1537:68d7:4fc1%6]) with mapi id 15.21.0496.015; Fri, 9 Oct 2026 21:56:02 +0000 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Fri, 09 Oct 2026 22:55:58 +0100 Message-Id: To: "Mathieu Desnoyers" , "Paul E . McKenney" Cc: , "Linus Torvalds" , "Boqun Feng" , "Greg Kroah-Hartman" , "Sebastian Andrzej Siewior" , "Will Deacon" , "Peter Zijlstra" , "Alan Stern" , "John Stultz" , "Frederic Weisbecker" , "Joel Fernandes" , "Josh Triplett" , "Uladzislau Rezki" , "Steven Rostedt" , "Lai Jiangshan" , "Zqiang" , "Ingo Molnar" , "Waiman Long" , "Mark Rutland" , "Thomas Gleixner" , "Vlastimil Babka" , , "Mateusz Guzik" , "Gary Guo" , , , , "Nikita Popov" , , "Lian Wang" , "Kunwu Chan" Subject: Re: [PATCH hazptr v2 2/4] ptreq.h: Introduce ptr_eq() to preserve address dependency From: "Gary Guo" X-Mailer: aerc 0.22.0 References: <20261009182142.6311-1-mathieu.desnoyers@efficios.com> <20261009182142.6311-3-mathieu.desnoyers@efficios.com> In-Reply-To: <20261009182142.6311-3-mathieu.desnoyers@efficios.com> X-ClientProxiedBy: LO4P123CA0537.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:2c5::17) To LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:4ab::19) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LOAP265MB8560:EE_|CWLP265MB6184:EE_ X-MS-Office365-Filtering-Correlation-Id: 19e20ae1-a5e7-4a6a-233b-08df26501c54 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|23010399003|366016|1800799024|56012099006|4143699003|10067099003|18002099003|22082099003|6133799003|3023799007; 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:LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM;PTR:;CAT:NONE;SFS:(13230040)(376014)(7416014)(23010399003)(366016)(1800799024)(56012099006)(4143699003)(10067099003)(18002099003)(22082099003)(6133799003)(3023799007);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?SGE2V0toT05mL1FRWnY3TlFYTE1UcCswdGV3blhlSE5KSWFELzRmUE8vOGlZ?= =?utf-8?B?L0tBR3p4cWI5ZXd2bnhQV0c4VFlNamRXb0FMWFJVWDFJYUMyWE9rM3BrRjd6?= =?utf-8?B?QW9aclMzUXliaTM3NSt6TEZJazJZSXd4ZjNBcGcydXdKa1hVUnYzKzZBZlJU?= =?utf-8?B?YnVZbDFMVVk3QVlmbzNqT2E3THJNb3FVMTlNUkJoUW1NYkV5R1Z1WXdsNFV2?= =?utf-8?B?OEZDQit0OEhlRGRxRDlVekYvQ1c0bGFwRzFYUEVZK0pnQm5SQnMrVDhYZ2Nq?= =?utf-8?B?ZDJSNUg2MXB6cUxBZytPWVByclpXSVN6WTBHSjM1ZTlEaCs0WUFYVzZ3OVkx?= =?utf-8?B?ck1hVGRtNWxqNVVmZHJiSk16RTY5SERmNGxRMnJ5WGxPSDhCcmZQWDFpTWZt?= =?utf-8?B?Y0lubXMyYWMvSi9BSzdkUCtEL2NqMVpVdzg1YytFemdvdWJFZGJYbVZWN3pD?= =?utf-8?B?NXFDVzg1aXBiTUwwaS9sNUFJa21WSW1TSVVReldrZEhwYzl0R0lFb3JoaExv?= =?utf-8?B?VVVsM3NQYmo5NFo0Tjgwa0daRkc4NEdReFNFcUtFSDVJK253bEk1VkNIZ2lV?= =?utf-8?B?SmgzNFJJTG5ReGdjZithdEQvNnU0blF5cUxibllvS0ZPKzhpazVXeU4rK0xN?= =?utf-8?B?NHdMcS9COTJWcGc0djQrOVBuTWZiOHY5emNDWTc1ei83OU1PbXg5a1UyV1Zo?= =?utf-8?B?cTNjTzVpZTE0Q05UMVIraFFMYXZZNU9tcCs5ZVh5SityL3JJM3R1bFE2dXpY?= =?utf-8?B?VjM1a2g4bzV2NWQwYzdQN0kyVldTVVY5aC9LZ2Y0ZXRNdVF3QUNwVWFCc3Fu?= =?utf-8?B?T1JhOUI5TmdLclR1Yk5LQWdrWG1tTkRYT05QWExVLzAwYTdGTzVEelVjajVF?= =?utf-8?B?alJQMU9XMFhCMmJQOW5ITGdtR1I1dDd0ODVjS3VaZDVjdWdSWUJXdkdvQmJw?= =?utf-8?B?bVZnZjFQTjBZcmdpTnNIYzc4MUJTZmgxYVBURmNrckk1MU0yQmE3TFFOSGJG?= =?utf-8?B?cDdwSU1sUldVK3ZDZFArSW1MOFVXMXVqMFVmaFA0UVJiYzVmcElOSDhFaG52?= =?utf-8?B?clFENFRMYW55NlhRYmNLZWlzQ1NUZStlakg4dEhBYW5ZNFllbWprYkZEaUM4?= =?utf-8?B?NzBKK1J3Vk9kVEhETmxObFRtUHY1TXFuVy9oV1RYUExIVVVpUEdnNDRLKzE4?= =?utf-8?B?NTBybzdyZlNZaFg2bUE3dityVENLNTc1b2xqQUpwSStnSUZCdVpGRHZaZy9C?= =?utf-8?B?emluell4Z2RHSWJzMHA1LzZOclNvZkQ2blBscHl3WHlNVkcyU1RYbHI4KzFU?= =?utf-8?B?cUJDNnJMUnlYQ29ES0x1SGo5cGFRRk1nOGRkOHJYZCtNNXRQZXVvQ2g0R3RI?= =?utf-8?B?WkJOWG9BcjJuUkV4VEVrZVE3QUJybEkrVGQydXhoZnM5SE9KT2xDS3VCMHp0?= =?utf-8?B?Q2FZK1VLdldPQlVJYXBpSGovb1JaOXB4VTNuTjBDSkNUcENQN0hSd05zUkNS?= =?utf-8?B?d2YveEE5QW42Si96Yy9GRTZLQTAzV0hOWlhlNk5GbDRVRFY2aEtCc2huWE9j?= =?utf-8?B?U045aVJWU3Z0dlRNaGowSTFXNjJoVUN5SGJqWXVnejBOZU9QMENzQS96YUVx?= =?utf-8?B?ZXFXMzM4UGdsc3p2cWEzcU1acldhZlRIRmx1b2NseTd2TlMremxvcGxhOE9P?= =?utf-8?B?ZWlzSlBTbFhWVzdCenpnRkM2b25razdEcDRQV05SSnVRd3d6YzNhUStMMllq?= =?utf-8?B?ZWZlZFcwVDNpTDdGU2xaWmNzNFk0THZNUXFYOWF6a3VhTURlazRkUnhtekhh?= =?utf-8?B?aHJlUjk1Q3pURXlKbDJnamFCZEEwNkhZenU5bXAxTTFhUFRydVVHV2NTTC93?= =?utf-8?B?MVRwOXJZMS9McUZUS3o4ZEhRSUJScnphZ09TRkprNWVud0o4T2tUUlUzcGZy?= =?utf-8?B?RXdtdmRtUVBVTzV5dWZoMU43eG9mZlJiaXFyMjR6ZE12ZFhmZnV4N1E5Mmhr?= =?utf-8?B?NUh5RUNxOGt4L1M2V04wNTNDbDNaeGhUWmRLbG1jdkh1aVk1OGRkWmtiWTc0?= =?utf-8?B?S01OakE1Q0ZQMW5ZQ1RzYlowZkloT3BDeG1lS1c5OWRhZTd0SmFXbTZXVFhq?= =?utf-8?B?Lzd3UGRvbWkyZHBwd0J0TENHOGpOaHh6SVV4WGZFS0U4NlNoK01KVkM2K0xn?= =?utf-8?B?VjRLRlF0Tm9GZWVMYkZGZEN4S3J5WThMbVVFWHBtUnlwVkpkb21lM1NzRWtK?= =?utf-8?B?MWtOb0s0Ny96MnQ5S05WL0FYb29ZRVY0MTRlTU5nc1E1UWpTSGovdlZrYVQ2?= =?utf-8?Q?yFXglUqAtC/Fw4k48N?= X-OriginatorOrg: garyguo.net X-MS-Exchange-CrossTenant-Network-Message-Id: 19e20ae1-a5e7-4a6a-233b-08df26501c54 X-MS-Exchange-CrossTenant-AuthSource: LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Oct 2026 21:56:02.5485 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: bbc898ad-b10f-4e10-8552-d9377b823d45 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: HFPUYYWwsv3nCiaJRAowTMwdXGNnG/Z3HxTRRavqlevQcYKyZKE8lzO/CVtPc7vo+FvNXvC9cqo788ERUJHiNg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CWLP265MB6184 X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 365781C0004 X-Stat-Signature: nfymg13c5ua46ur6r394uh6ky1hszidm X-HE-Tag: 1791582969-8296 X-HE-Meta: U2FsdGVkX19dut899wLuikWV1GGcxc70NKOeAfEOD7OJZrziAtTp2f/9klT/vlShd/9yukMoB1ggoM16JYu6ClWmXuxY0nxspqWhBzI/5DFFb7uLPqZAhoNalcgqbbvKdjYUf8n6EGEVqSdYV5IiRuHPbb6GpXEQGK6XFDlcJniOgpPd3cYxGjxLXBEk7zfhzlr558B98ugJVPNNwSQEs3H6SNvDSUVwsgAgr8XL6J0NmN2nOEQPy55S3i9J3D3gNRrBj2+gnseRT9aSE3lYFHDEBfsbCYXsOE+GJ3vsEMfzliKtV2rukOfYs9bz+ejFSpcc8JU8NcG1g0eORs2CspgOWdLJfzWs7D8r/btdgzme57PZvmMY5CD361gRlAiNkloFCvM9CQl9LvQghBgEsvr67TQ0TaS9rN6s0aQGnwE5pf4m8pNtdUyM6T0+KDqyasM3cU1z6zaZHvA7RLOxLcchYN1oV5HZ+K3G9B9l/LQW+2Dj0969j2Yw6Ppcl1JqW05UtkLHcRK4T7+uzW5LP0m96dFsZxd9h5i6Ai67cJ2X3dT4uS1i25KpYxhS/9ZE38qk9f1By7+MejRVqnGdO8wCXdxN4Cddt0RrhzmYMmLA1bC0mbAZyHv0BCRnUNE2kjIbj4wCLD3BNU4YbmzfFNV02/gFjZyyZGY9Jdb+PLuOhCMIrfKVBrcpdYEuN5WY3zJjGjkfQ+IiE43VcrLa+q/13R2sXbZjToQcKlFKl90VfRMHXgVmUnE04namnYYtDcv+n7XYiswjQAFSbcBYOWyx6iPrP4DCWLCx1TGPVk9g+i3dYlUjg1qfnqHiWXNyxKBMW6AYsqiPQVK66tucuPp9uuZvTLf3RqtPqdqQBio1BPuE3l6WxuJXNsZMkTLLKNTXece5ewiDsnp918hwV4AyVBU8W7FiIDtUVdIO9QZrOpx6bmtjui5voLUpNx8YWENQHR+ze01n5pFFck8 BrYscP8s lIgT6+5q8X5K5RLTpDbvRoeub0zESwrBA6o8DL5dqdvjsAP7CdmwwokQvX5S7BAaeovUI7N8Dc6Ip8nmpT24oDDy1yuRSxZ3tta2h3OdZIx/Nh8EsOEbTtBNQxvSwQBqWKY5SBPcjL06LYvpQUww993FApug9aLg8WW5U3IfotOc9p2WzNYIDx/MdBVf90qK9D3T4kAqVa0XTfoRPtXUcOzIFRqcL/pKJwTjZkUN0X//XZosioVH7CX74TXkRfZRcd61au9P3FXaVBJhtqOdS5jJCA+7GA03zN3/r44bHYRIup7iaVyhhYwCo1Ogt99UeVhl00w1pQOQwiUcxZcWlq+1WLY+hq+VuiULBhvRi+ppTwlvv66TgwohRk4gkmoNrQAR0t3D1wz31+rnAvzxY6dLEo03/8HvdYzE1sMjpfcJ8ldwqdkr6y6owp3EZiT4We5iCbf6EsXBCIo/v25Ds6wgTxwsjrq0r1s2tGSP4lq0UsUOCW2EXwXq1vO4CH7C5FIFIzmUQ/AL3XGXsfwJYADPSI5KQZUfK4BtfaNfISL8q8zquwvjC3vP24CzHLotz+1GS9xsqr/WO/vAAw2RreOh4wktIXPNrve9ZuI3YlFybLCkd8hz9gwyRrm2Riyp9iXqzwipuGY5bHVtDpS0q/sMd0lDykIL8pUoQZwHb44IgQU2JQkTCaxSDZYGH/GGOlasjjFzOfL/0nHM4YalpwF0yi7P4ptN5usYpuxnNR3L2TCky9iwS0tlVTBdqLKXMy/jOiT0UGO9tCyBOj69Nbbe2d7DZOQ3XL2ghrYp0yOAo4Nj7ryxbl7iEp7DMyBeHKwHQ7tf2lEf7C/lhoCkDxUSjo5dd1VQIyNi3CNsNCMoIAHQC4Eimf4tOwKpKphQTnziTC4OWLdlWdpn7LHmuO+tnoxufUmj5KuJk4raguJuhBP50Dj//vpb3y6ELt6PH6IlLwIaRm+hHULGxTV2KLfxDSXGR 8dMs01gq iX65NllnNl/D+jDU5gh5HS+PxontHvkpwQXtu+hjfsGoyMPoyirrRw6KYOIUsW62VyVE3ozXdVFyOsuSG1yXUdKSsrKcKGXFfWUypfOHx67qGX4e2LmHMrmhmbBTL2/4F65X2+tKvF9ACb8CeBWvInVMOdAIIj3/pfjaZ5RxvdWZdLYzAl9i6WgCCg9MYZmbtD/OFQM1I/0ROY7mWX0+Fw5QAm1dzFJPG9KQejF8hhgNn9ALpBMMHGDLlsq2ClZUxCJWMejNsL0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri Oct 9, 2026 at 7:21 PM BST, Mathieu Desnoyers wrote: > Compiler CSE and SSA GVN optimizations can cause the address dependency > of addresses returned by rcu_dereference to be lost when comparing those > pointers with either constants or previously loaded pointers. > > Introduce ptr_eq() to compare two addresses while preserving the address > dependencies for later use of the address. It should be used when > comparing an address returned by rcu_dereference(). > > This is needed to prevent the compiler CSE and SSA GVN optimizations > from using @a (or @b) in places where the source refers to @b (or @a) > based on the fact that after the comparison, the two are known to be > equal, which does not preserve address dependencies and allows the > following misordering speculations: > > - If @b is a constant, the compiler can issue the loads which depend > on @a before loading @a. > - If @b is a register populated by a prior load, weakly-ordered > CPUs can speculate loads which depend on @a before loading @a. > > The same logic applies with @a and @b swapped. > > The header "linux/ptreq.h" is the expected include target. It > contains the documentation of the ptr_eq() API. > > An architecture specific implementation of the pointer comparison > can be implemented by each architecture as asm/ptreq.h. The x86 > implementation is provided initially. If no implementation header is > present for the architecture, an arch-agnostic fallback based on > OPTIMIZER_HIDE_VAR is included from asm-generic. > > Suggested-by: Linus Torvalds > Suggested-by: Boqun Feng > Signed-off-by: Mathieu Desnoyers > Cc: Greg Kroah-Hartman > Cc: Sebastian Andrzej Siewior > Cc: "Paul E. McKenney" > Cc: Will Deacon > Cc: Peter Zijlstra > Cc: Boqun Feng > Cc: Alan Stern > Cc: John Stultz > Cc: Linus Torvalds > Cc: Boqun Feng > Cc: Frederic Weisbecker > Cc: Joel Fernandes > Cc: Josh Triplett > Cc: Uladzislau Rezki > Cc: Steven Rostedt > Cc: Lai Jiangshan > Cc: Zqiang > Cc: Ingo Molnar > Cc: Waiman Long > Cc: Mark Rutland > Cc: Thomas Gleixner > Cc: Vlastimil Babka > Cc: maged.michael@gmail.com > Cc: Mateusz Guzik > Cc: Gary Guo > Cc: rcu@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: lkmm@lists.linux.dev > Cc: Nikita Popov > Cc: llvm@lists.linux.dev > Cc: Lian Wang > Cc: Kunwu Chan > --- > Changes since v1: > - Move to linux/ptreq.h, implement x86-specific comparison > and asm-generic header (fallback). > > Changes since v0: > - Include feedback from Alan Stern. > --- > arch/x86/include/asm/ptreq.h | 16 +++++++++ > include/asm-generic/Kbuild | 1 + > include/asm-generic/ptreq.h | 16 +++++++++ I agree with Boqun that this should be ptr_eq. There is no need to save tha= t character :) > include/linux/ptreq.h | 63 ++++++++++++++++++++++++++++++++++++ > 4 files changed, 96 insertions(+) > create mode 100644 arch/x86/include/asm/ptreq.h > create mode 100644 include/asm-generic/ptreq.h > create mode 100644 include/linux/ptreq.h > > diff --git a/arch/x86/include/asm/ptreq.h b/arch/x86/include/asm/ptreq.h > new file mode 100644 > index 000000000000..593b45f80451 > --- /dev/null > +++ b/arch/x86/include/asm/ptreq.h > @@ -0,0 +1,16 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef _ASM_X86_PTREQ_H > +#define _ASM_X86_PTREQ_H > + > +#include > +#include > + > +static __always_inline > +bool ptr_eq(const volatile void *a, const volatile void *b) > +{ > + bool ret; > + asm(__ASM_SIZE(cmp) " %1,%2" : "=3D@ccz" (ret) : "r" (a), "r" (b)); > + return ret; > +} > + > +#endif /* _ASM_X86_PTREQ_H */ > diff --git a/include/asm-generic/Kbuild b/include/asm-generic/Kbuild > index 2bc00c67dc54..e1d95dea09d5 100644 > --- a/include/asm-generic/Kbuild > +++ b/include/asm-generic/Kbuild > @@ -47,6 +47,7 @@ mandatory-y +=3D percpu.h > mandatory-y +=3D percpu_types.h > mandatory-y +=3D pgalloc.h > mandatory-y +=3D preempt.h > +mandatory-y +=3D ptreq.h > mandatory-y +=3D rqspinlock.h > mandatory-y +=3D runtime-const.h > mandatory-y +=3D rwonce.h > diff --git a/include/asm-generic/ptreq.h b/include/asm-generic/ptreq.h > new file mode 100644 > index 000000000000..db5a88628b1e > --- /dev/null > +++ b/include/asm-generic/ptreq.h > @@ -0,0 +1,16 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __ASM_GENERIC_PTREQ_H > +#define __ASM_GENERIC_PTREQ_H > + > +#include > +#include > + > +static __always_inline > +bool ptr_eq(const volatile void *a, const volatile void *b) I suppose this is `const volatile` to take advantage of implicit conversion= that adds cv-qualifiers to be added implicitly. Might worth a mention in somewhe= re (commit message maybe) because I was confused for a second on why this need= s to be volatile. > +{ > + OPTIMIZER_HIDE_VAR(a); > + OPTIMIZER_HIDE_VAR(b); > + return a =3D=3D b; > +} One thought on inline assembly. For RISC-V, branching with comparison is a single instruction, but there's no instruction for obtaining the boolean fo= r a =3D=3D b. One option is to do static __always_inline bool ptr_eq_likely(const volatile void *a, const volatile void *b) { asm goto ("bne %0, %1, %l2" : : "r" (a), "r" (b) :: not_eq); return true; not_eq: return likely(false); } and then the optimizer can turn a ptr_eq call + a branch to a single instruction. This, however, would require likely + unlikely variants. Alternatively, we can just not have all the complexity, and just emit one e= xtra instruction: static __always_inline bool ptr_eq(const volatile void *a, const volatile void *b) { unsigned long diff; asm("xor %0, %1, %2" : "=3Dr" (diff) : "r" (a), "r" (b)); return diff =3D=3D 0; } Thoughts? Best, Gary