From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from BL2PR02CU003.outbound.protection.outlook.com (mail-eastusazon11011024.outbound.protection.outlook.com [52.101.52.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C98FC13DDAE; Fri, 6 Feb 2026 01:23:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.52.24 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770340981; cv=fail; b=Os6RlMv5oxGldyDwt8Kyv0SDtb0Me8lrOP5GdKeNL27Gi2JJcejFt2ETNk0H8axP11nznqcWNZcjO3SFqSq1p5TB/p6Ubk34knbNNXNhbYpCETX+amHFzfCcsHkf7DArsFylJMf7/yG5fzIATv4rN4yANQTVcUHE1gKDze0Xm5E= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770340981; c=relaxed/simple; bh=jrsIV/7kCdT4J8NA34NzXDjBS8JMV6NH2GZMjW7EZQI=; h=Message-ID:Date:Subject:To:Cc:References:From:In-Reply-To: Content-Type:MIME-Version; b=YeID8EB5Rz+OG5NJ1dKiVOeoWmbtpGGNBQ/Y7r1UPGErRTHgGitBIvlLDMcJqpyiqUv+2ZhdI3Fz9bwAVgNwtxqAY3sIcBzWjXW+Bqzf60mBM0GMaLMPCQewkAqdanSXSigYJJY57ioXhMAUwxwt7/PRLbgSZH25CMF1yKJx494= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b=EfmohupS; arc=fail smtp.client-ip=52.101.52.24 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nvidia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b="EfmohupS" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=gLcNzr20hwnPOHLV87VCYkkOjG3zcJAorvsh5QoMpgaUU7kanlx/Da2F4YP2tquQJF7RLVsSbBo01abrpKUhsLrFlQAK79d3aTggqXo4ra9+xnac4awNixqLhqs8v9qfmAq/5wWDIn7d/d5FYrndf6jakX3acg1S2Klaw7gaA+dJ9z8Ba1HcBwfw/asfPFfwHmDpwX8e2dnooM5OCbFwO3Ldqeby/QJOmPbithMooGQL/jmcas+ZqbIjWVSASXuRRxyQeoHOWOLZcmI2dzQdlFh1AZjktdAOd39Vy8SJZvdO+kroUchvbTZXdkmjwaNM1C922Ay8qnfw/UEN7cklww== 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=DJJ2xseVH62H+qTy/v+7yaqXXNz7cEcu3h49e+gCFQk=; b=KhwFtoso6kARVvG0r0FqgPqgaxXo1G99ojhuZFaoILnh35L13Rmj5RYfK80s/vz1nFp1ua3vg99wK5y3LWCE+2HvrSB/taEGT0TJJu8tVLinrtLjsn8FOsXyCFrl8mCogxxFljTlV9kg6FHcMM36wsfn78zmaCYp+ZdKRy4mEPaJhJCKhqumICXMmByjCF3g55udR+kYG2u9uqgduDjlO6snWc412i9XSOYd08x7G1MWExW8YLc2ZD4hPuQHQAMCidBqYF94/PAF1w1GjH68xPEuEu8vdqd2H2XRa+vPGz4Vln7Mz600yRJHC4h7yWrm+mJ6KaLYiS3nCzdiKcTEuA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=DJJ2xseVH62H+qTy/v+7yaqXXNz7cEcu3h49e+gCFQk=; b=EfmohupSDq+ehQnMyPmJRd0aUa5DVLjtd2hOEmh1UkvgA0eJkqbsd8GoErcY202copOdMUyg9L7cZlQKzEHbWhuOb2IRjFIDQNZCKbw90Q2QY1yKUW3Qc4VwJCIwuj1rNtaPVjYeNjy/lBgT7jUBevqEUu3DBjTyoWF52ypH+KistH5wZRfFWwbCMIP4cucH2euxPjYGKNlWhu+jryR4dvTm1zxjehS22o8Nbodk3vjlRxGNX84W0fjDYiS2/7mcBIejoyCzxpKKaxx1Uh/GUBtYMRquFvTJqBEZfoamM3mZ6pE9i66cZxnTgq7Owo/DITL9OlL6AunhdE1Gu1sLFQ== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from DS0PR12MB6486.namprd12.prod.outlook.com (2603:10b6:8:c5::21) by DM4PR12MB6087.namprd12.prod.outlook.com (2603:10b6:8:b1::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9587.15; Fri, 6 Feb 2026 01:22:48 +0000 Received: from DS0PR12MB6486.namprd12.prod.outlook.com ([fe80::88a9:f314:c95f:8b33]) by DS0PR12MB6486.namprd12.prod.outlook.com ([fe80::88a9:f314:c95f:8b33%4]) with mapi id 15.20.9587.010; Fri, 6 Feb 2026 01:22:48 +0000 Message-ID: Date: Thu, 5 Feb 2026 20:22:46 -0500 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v17 02/16] preempt: Track NMI nesting to separate per-CPU counter To: Peter Zijlstra , Lyude Paul Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Boqun Feng , Daniel Almeida , Miguel Ojeda , Alex Gaynor , Gary Guo , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Andrew Morton , Ingo Molnar , Will Deacon , Waiman Long References: <20260121223933.1568682-1-lyude@redhat.com> <20260121223933.1568682-3-lyude@redhat.com> <20260203114454.GM1282955@noisy.programming.kicks-ass.net> Content-Language: en-US From: Joel Fernandes In-Reply-To: <20260203114454.GM1282955@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BLAPR03CA0017.namprd03.prod.outlook.com (2603:10b6:208:32b::22) To DS0PR12MB6486.namprd12.prod.outlook.com (2603:10b6:8:c5::21) Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS0PR12MB6486:EE_|DM4PR12MB6087:EE_ X-MS-Office365-Filtering-Correlation-Id: 1c3dbddb-34a7-4370-3add-08de651e3d2d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|366016|1800799024; X-Microsoft-Antispam-Message-Info: =?utf-8?B?bkx1SVFDOHdPNk12QXpVaFFsUVZHdG1MdEhSc1hxUjJDdWRaamZybUNBZThI?= =?utf-8?B?WmlsOXplTGhDZDkzNTFqcjJSZEQ5dzFrTjdGQnhxQlpWWFZqdXAyWW1yQXRP?= =?utf-8?B?UDkzWFU5QUlUMGFBZGlLU0NyOHZKMTFvR0dabHJkQjZqQWVDZktBQjEwWUs3?= =?utf-8?B?b0Q1dUdRRTRMRXdSbUFOZ0g4VnRmdWRDVVA2MlpuMGFoMkVwb291SWdRQ2sw?= =?utf-8?B?bjkxREdHUnFueTk3cTJBYWhOWjNjOUlWTml5b3hPRzlBdzNEdzJpZWNFbjV4?= =?utf-8?B?enpxeGlYUlNtcDh3S0ZrU0hPVzVPS1h5YVBCRE9tek1uTDI5VE1EQ3gyVlVu?= =?utf-8?B?Y0NWTXoyaFNFSm0yNDV3RXlLcU1GNEtWUTRnZHBoMlV2TW81ZzBxRVZuZmt1?= =?utf-8?B?cGhNVTFZOVVlb2ZlMlV2ckVob1EzOUMvcGtMUXpZMi8xM2YxSm1SRnBKNEk3?= =?utf-8?B?MWtKc2RNWTdmLytqRExSY1BqSzEyMHNSQ054eGJYMDlCc0hnV2pKODhTejlD?= =?utf-8?B?WWVjMnV2VHEzaCtUWEZOc1ppTS9icjMyU29IUm5qdlB2TXV3VHAyRFZnWlk5?= =?utf-8?B?RWZpa3JocDJYc1hxVzRxZWN4WE9xR0pYaitNUU5KSkhOaVlxdEw2T09rUWtx?= =?utf-8?B?clhPWkNqNk1STS9LRlhWeW5mUERSV2lxdGxDNzhId1VxYU5nUk1DZ2JUVjlm?= =?utf-8?B?M0wrbjlQYmRWdmN4bDEvNXY1T09IdkN2RnY2a1NDS05KMm5hUEVPWDZ4Y2pI?= =?utf-8?B?OWpvTnVEU0tOZkFrdGc4WFV6K0NTTEFybWxRNXkzT3hBRUwyZVNqL1dObHJq?= =?utf-8?B?cnRjNElIalRyL2t2aW1FYXBiVHh4UlZsTTFuUStEL1h3VE43STZvMEdaTkhI?= =?utf-8?B?R3A5KzRJd2RyMjZWdjNjVk1RdmlEUFBSbmU2NXg5WlRBWFhQeDBzYlRjSEhI?= =?utf-8?B?dFUrbmpmNGUvMGNTZHZuOVozODFrdXFwL1I1N3BSc1Rjckp0NlVrU2JOU29Y?= =?utf-8?B?aGFFdDMzaG1kbnZQUHp6TTIzZDZWRUg5V0E4UmJDUWFIVUdRaXJRK1pGN25M?= =?utf-8?B?WDdsd2JpSWVRWWJCK2t1anlMemRGQTF5Z0xacWl5d2grU3hZN050VGNETFdi?= =?utf-8?B?a1lVY2VhYmlTamJ1eEs0MkN2bkU0dkJ1S29KelRXeUhPeVEraHpiaUxJODRj?= =?utf-8?B?aCtLMGs3SG5YMnA1UnpHOXZNNDRxRElaWDR3N1lLTjUrN3dUd3d0OEJPWDND?= =?utf-8?B?aXVHZHpqdXh2MllVT2cyaGtBMS9xaEFNWFVvZlhpcUo3Rmt1MEJDd3JRZWQy?= =?utf-8?B?NmF2TnhwSXpmUHJMRytnUGZtY0JhSjJXdDZ5MmlRRHZRbnhOUHh1LzdCUmxC?= =?utf-8?B?WkxVRUdSd3NNSEZTdnBUdlJCUGlPVy9uQXdqTThvRFdGMjNxR0RmVmJqOXMy?= =?utf-8?B?Zkp6bUtUMGxEWUUycVNDa2gvanJiNFRleXR4UzJ2SEd0ZmRkVXpSYmJZd29v?= =?utf-8?B?R2cyb200WTZ5Vko3QTNHL0REZ1BaeEk2c1oydlNBaER3Nno0Y1NpMVZkSnJH?= =?utf-8?B?WjBIY2hPREFsMlRWTEpxMllCZldxQkM0MStFdjVEQnkySk5lM1JSYnFGR3Jj?= =?utf-8?B?Wk1WcGJDTmc2Q1YyMlZ5TmVFdjJsK2J4RzZOdmYwdHNIZHZMQ3pkQkhiMUlx?= =?utf-8?B?eUx5Nzg5VXE5ZnZUZEJNdVNsRmVUdnFpeXRlV0I3ZUp3UFRNTjcxM21tQkR0?= =?utf-8?B?OU5Id3MxZ0pzK1Y3YXBmeTR6RXhBSk9NazM5MSttMDEvWU1QaWl2UHI1TTlB?= =?utf-8?B?dzZDSk9sdjdiaWxXQzV2VzFHbTEvSUtXd2tUcnpPV084UmlXT29NSjJaNUti?= =?utf-8?B?WFRUZnpHUXRnSlo5cm8rVEFWMzVsSVhvcVhvbEptcDVzVXJGTWY4NUJlOTgr?= =?utf-8?B?bW9qeG11UjNpUFd3cjQwME9YWklJOVpNdStRUTdFdHFzMlBJQisvYkRCVzkr?= =?utf-8?B?UTFHM2xOUnc1ODF0VStmR1JJQk5md1lPcGNpTGZPblNiZ21zRnk3eWNEcjNQ?= =?utf-8?B?SVBIWGhqcWZhbk1nU0VyOStpRGJZN1FKU3lCRzlWem13eHFKd2FVZ3RlQmRL?= =?utf-8?Q?R55g=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS0PR12MB6486.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(7416014)(376014)(366016)(1800799024);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?VFI3Z3dZUGhGU3RFMlIvNlE1bGJMT0hrUVlNTzJtOXlQeXNZMCtMdEJFajc0?= =?utf-8?B?b3dSRSt6N0d4UTVGaEtHQVdnKzI0TmZqWEVrYU9YMWRqV054YkFETzEyOW5W?= =?utf-8?B?VlkyS0l3TE91dWxxYnJ2Rm5qa1I2MmxVRUpOZEdadHFXZTk3ak84WVZwNS9n?= =?utf-8?B?cnB4cG9rOHZJS0JzdUd0ajMvNW5QbUxubXVibTNTNGxQT0FNamo1SlpzOE1u?= =?utf-8?B?cnA5MEM5SG9ucWFXU09Tc3V2bDJ6R2IvQXVYNEc3MCsvT0szejNnSWxPQjhi?= =?utf-8?B?aFh5VTMzdDJDYkszOGxZMWpvbHBlY1p2VTdseXhJTDBacjdMZWFFRm1YZHMy?= =?utf-8?B?c25QT2syQ0YwcWppd0FRRnQydUZ5aGM5Y0taY05iaGhyVkl0RGV0dWJpVGFh?= =?utf-8?B?UVhYL1g3aXY5dVVDcW9UNDhFVHBIVXBYSFZCeng3cUdaUTNHSlhmMTJMUnlr?= =?utf-8?B?eHlKaXdEMVlWbnB3NGloV1pLdDdvc2gvcUtMbS80NEQ0RUc5c2g4Z3dvQXNQ?= =?utf-8?B?YVNCc1JzaytLdlV5QnpyS3lhVUd4RUlrNk1MbkwydGhudUtXbHFvNkoxSU1v?= =?utf-8?B?eDJhU1hSNjZDcG5mM2Y5RkM1WndSS0srWVNVTVJia0VVbitrU2pzbUJ0R1lq?= =?utf-8?B?OHU0aHQ5dU1JblFsV0xYZXNaMVNyVTdWZVpHVzJTOU5lQ080YWlma0VGSE81?= =?utf-8?B?dVN4dVJ4Rm9BQzJnN2VKbzdaSVhRb2VZSytEYWkyQUZWcVBOd0RGVUdubUJm?= =?utf-8?B?UFFPcXVoTjl0V3VQWkVEL0ZkN2MyaEQ3SkplMlBNNTBoditHb1VadEp0SHR2?= =?utf-8?B?dG1scCtRNDg0RXlLTDVLSkROdC8yOWhiWkVtNDVIV1pDSnBYYjdkb3JmNHBa?= =?utf-8?B?bFBKOC92M3F3elVFcVZBYjJiOHA3cml0TjE2alZoZ3RLeThsc3dKNXcrVjlo?= =?utf-8?B?L1Q4SUh5bFRMeHNsRTkvNUpmeDBNQy80TkJPY2dIZXFpSjloT2cyNW5rNUd4?= =?utf-8?B?SEI0ZEhtN0crTmNtU1lyZ3RQKzg3ejFTL2RrSUxhYjh2V1p6b1hLZlJUMi9J?= =?utf-8?B?RjlVU3pLZFpCTTg3b0hDS1Z3TktkY0ZjWVJoVVVrZmhXajdUNXZ2b3EvdU1O?= =?utf-8?B?NGlnam1ON0h5cFJvQUJ4OGQrV2RjRlZKbGJLS292VmtndlhSdXFOTUJTVEpR?= =?utf-8?B?YjhmakZPMmFCaEp6T1VUY1BoT3lJbUZLbi9wYy8wdjd6aSs0TkJYOFBDdGlo?= =?utf-8?B?bEpaeVNwUXVSUkhsNTlqd3BWMFVxWUpVUGJmcXdxRitlcnlBZUIyVGF4UUN4?= =?utf-8?B?dUcwOVJFVGplT0N4bXVueFZmeElBbmU3czd0dFpiOHFNTGVmSE5iVjFUOFor?= =?utf-8?B?SUYrSXRMekppK0ZxOXIrd3NwRmo4NmE2Nm9KUWVpRlBPanFXYWFkd2toZ25r?= =?utf-8?B?TXBpMVB5dkR1WDJweGJ4M0dlUTBqNGIvalpUNytlZW8vZlVQM1Q0M3NTaWxI?= =?utf-8?B?ZHVreDZOcVE0SFM2Z1EvVTA4YytRS2YxUFZOUjdMekIyd3dMUHZJcUdHQkp6?= =?utf-8?B?Nml1NG8wbUFBYWlKZGN5TDhPcklZSzlZV0tXMTd2MG1qSHFYSTREbmJrSUls?= =?utf-8?B?cjlsMGpucERvTVd0NCtQUDdic0VxKzNKWUpZblRxNjBvemhIZm9KOVBHblYx?= =?utf-8?B?Ujg5OHp4YXhFZWZlNkx0Z2RKeVRSbHdZM0l4SWM3Um9zTUc5NzJZdG50WHND?= =?utf-8?B?NXpxL0taQVFQN3lLa0NMeDk0bTBmeVZtRkFhSGJuN2VuMVJWNUxldzkxMStP?= =?utf-8?B?QTJObkVXTXNkVGdUdklhK05vclhyV3paR3hjTzhqMjhQM0ZqMXF0M3lZNm5s?= =?utf-8?B?UlV6VXQ1cHQxUTFGcTI2QklkVG5relN6RklhMHA4USt2U0o5WERmNGdZVm9F?= =?utf-8?B?Ymx4dVdqZ3lEN2RNaElsdjd3THR0SkZ3dkk3TkhjSytINThhT25vajlnS3ZG?= =?utf-8?B?Uk1yT21EVmY0L0FKU2pJcklVSzdVVHI2Mng4WFJvU2g3MnlGQ2lxakQrWnlZ?= =?utf-8?B?b05iRk9HSGxCVHM1TTVhL3BoeXgyQkV3OEw1YW56MzhPUzZ4UUtsbk9TQWRZ?= =?utf-8?B?eUF5UmE5azc2d0Ryay91djdHNkJwVFAyNEkxUTRjeDJwbWVoc29qdGZKMDhZ?= =?utf-8?B?UVJVWUxUckxoWCswVnB4bWh4ci9teFdMNURRR0xmYUhKWjhoK2o0VmFXblNo?= =?utf-8?B?eG1sRjc4Q3R0d2grRVhQU3ZRV1FCU2JBYkZ3a1Jva1gydC92WHVxcDd6OG5K?= =?utf-8?B?RjA3VUtDRDZKRnNJRGVmM0VsVU1DM1dLMm5HVDRHWnMySVhmMUh4QT09?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 1c3dbddb-34a7-4370-3add-08de651e3d2d X-MS-Exchange-CrossTenant-AuthSource: DS0PR12MB6486.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Feb 2026 01:22:48.4483 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: oyRXJ5sK6nR07GrJNrhIkpRwdwtGer0tLIytNhuOV/kMRyIeNDUq73hErCRqzLL11vMuEU2M0xerZHdXlaGurA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6087 On 2/3/2026 6:44 AM, Peter Zijlstra wrote: > On Wed, Jan 21, 2026 at 05:39:05PM -0500, Lyude Paul wrote: > >> diff --git a/kernel/softirq.c b/kernel/softirq.c >> index 77198911b8dd4..af47ea23aba3b 100644 >> --- a/kernel/softirq.c >> +++ b/kernel/softirq.c >> @@ -88,6 +88,8 @@ EXPORT_PER_CPU_SYMBOL_GPL(hardirqs_enabled); >> EXPORT_PER_CPU_SYMBOL_GPL(hardirq_context); >> #endif >> >> +DEFINE_PER_CPU(unsigned int, nmi_nesting); > > What happened with putting this in the same line as preempt_count? I can try to do that again if we still want to go with this patch. When I tried that last, I ran into issues I can't remember now (the space being limited?).