From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from BL2PR02CU003.outbound.protection.outlook.com (mail-eastusazon11011022.outbound.protection.outlook.com [52.101.52.22]) (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 A742419A2A3; Sat, 3 Jan 2026 00:41:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.52.22 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767400906; cv=fail; b=r/iTFEiZycdlB7P/ytYWqPlg/TpG3FWGUCgjq+f0ynx1q2X0sAUXTBR49LY6H5j9INejpG6P4lWvSjkTGRyNhM2ntxIGbq6safl8fYnflPrg1PKMEAjDkAQmJDaerd8OYVOlqoDXXUXND/XKmL4mLSvpo0lbXa/MgY+5bG1LvXU= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767400906; c=relaxed/simple; bh=phOBOxrXy0EHt8z/Ru35WnT491l9XqJiNzrjA2Y7ys4=; h=Message-ID:Date:Subject:To:Cc:References:From:In-Reply-To: Content-Type:MIME-Version; b=uPdh1IXM/DFWk2wpEhUaAkbHRxd0GJeZv4zpWjmdMkVRWXr9K3AEuxz4NvbzQ/J39n4yEVxb5ynCjRyI/TC9LTPksiiu/qvmx4We/E1bqp6SNhenS2M7dcyajd7eXtRNyVXuop2uN1jOnGpAqtOfOw3ys9PFxtcmo32mwjj5ZgI= 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=fHEfJa/K; arc=fail smtp.client-ip=52.101.52.22 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="fHEfJa/K" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=nEAFKkB6nb3HktKjuQ16gGNE00gM6XIXqZF9q0JKVwLq7heIXmurUG69usZHJs/+Nt6InTKml142YVKwzZleatEqvRLjCM/r9G/bkgRAxEi5HG7JUw9JeDyUhsZA97NU8GhdoA7hK7dt5ZCJW8cAwGNMIPfzHZHg+Hsn0NSjTsyCgIc7mAffUqywE1JQ7vpjawF1QRACoz0JT2rufs/cwz1LRz0a0c1PL+trY2I4e2STtljHzqbEcHaj4DDhlNqrHgpUw3dQHYkvGLj4Gw5jaUPIIZ6T0PbAHG5SEkJh61RSbdiGJ2wm1fQKI4yGhHbgt92k/wcEQg/RGFicaB4RvQ== 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=K/UR8mgy3ef+X91XCB5H5LU7Loazc1pKqYhe7wQ04vk=; b=U1CN5Rcq7p/e/ExkXOyNCXG0MCIc/uQB9sc22hR0EO430bLw/h8BckIaMu/9wRANs3eItWTW7Sh0TUUV5oqrzEVFzkOlPwfPQvEjxFFyCv/j7jkZctA4BwZM3mEJ3RPJKW73qIb1LQ0xLNZEIUCwXd1cKLG617Xu2NjMkif/EBfv8UvH3Zpvy64cV5anc2s9hB0tvu+PMPhd8WsXQznOMEUFkvExbVn1XzctQvEPWDzFxPnEKISXynegmMVxCl0soozFDz3bTG9PHnJ68D0bhC5m3r7ZgujbFaCnhx+FDYc3V/c9gKDDJFyEG0DSk2JqGTmqWmeAy4BT5ST5UV+m0Q== 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=K/UR8mgy3ef+X91XCB5H5LU7Loazc1pKqYhe7wQ04vk=; b=fHEfJa/Kyn6/vzzTZUE3g2oF4shtE9u2Mk+qj6bkAGgTjhKYLgrZ3oo2IBTzLLlXc0+V1LAz2c/OEQOSGwzJIVzbILmt06d8nPVVyMaPa+P1LfHuMvKBi+rZ9WnYnkTN6pM3wSOEP/fgGpe0VlHo9g27Qmu2olV53OtpxJ0IJ/fsc2m9UCcgCSuN0BMDBGBOGugEMDPE9wwPFkV62DYgeix8Py/lfd6uosXvWNyn0p4el0name2aS+cSo6/oZwZ8W9J2EYOz+OICP70kQYOHtVYWkPDmZWL6ji2DkrIcWfH5oWL5DmNUBQ6f4MBUVBptd3Uovpph/Ls1oYSmX+cREg== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from SN7PR12MB8059.namprd12.prod.outlook.com (2603:10b6:806:32b::7) by CY5PR12MB6454.namprd12.prod.outlook.com (2603:10b6:930:36::22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9478.4; Sat, 3 Jan 2026 00:41:40 +0000 Received: from SN7PR12MB8059.namprd12.prod.outlook.com ([fe80::4ee2:654e:1fe8:4b91]) by SN7PR12MB8059.namprd12.prod.outlook.com ([fe80::4ee2:654e:1fe8:4b91%2]) with mapi id 15.20.9478.004; Sat, 3 Jan 2026 00:41:40 +0000 Message-ID: <252063db-ec72-42df-b9e0-b8dc0aa6bef9@nvidia.com> Date: Fri, 2 Jan 2026 19:41:38 -0500 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH -next 1/8] rcu: Fix rcu_read_unlock() deadloop due to softirq To: paulmck@kernel.org, Steven Rostedt Cc: Boqun Feng , rcu@vger.kernel.org, Frederic Weisbecker , Neeraj Upadhyay , Josh Triplett , Uladzislau Rezki , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Shuah Khan , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Yao Kai , Tengda Wu References: <20260101163417.1065705-1-joelagnelf@nvidia.com> <20260101163417.1065705-2-joelagnelf@nvidia.com> <20260102122807.7025fc87@gandalf.local.home> <20260102123009.453dfb90@gandalf.local.home> <68b5b122-036b-475a-85bb-e39830f99fbe@paulmck-laptop> Content-Language: en-US From: Joel Fernandes In-Reply-To: <68b5b122-036b-475a-85bb-e39830f99fbe@paulmck-laptop> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MN0PR05CA0024.namprd05.prod.outlook.com (2603:10b6:208:52c::32) To SN7PR12MB8059.namprd12.prod.outlook.com (2603:10b6:806:32b::7) Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN7PR12MB8059:EE_|CY5PR12MB6454:EE_ X-MS-Office365-Filtering-Correlation-Id: 97cbf514-ecef-4209-d366-08de4a60dc2f 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?RjhVSkJidm56V3VQOHJwalRDV0xpYkc2eHUrOWljNk9DdTVWWlVHblYvV1hp?= =?utf-8?B?NEdBa0l4UnNpbjNGbmFRSmRiWlQrc2M5SmNaYW1lTjljV2NtQzBmcXBNRVh1?= =?utf-8?B?Q2JYaXVnb0hqTVhlUjdLVDQxcXJYeDZtbUduWW1xWEtXblZlS2ppMVNldWwy?= =?utf-8?B?ZTBhZkhUY3d0N0NIQ2N4cU4vRHljWDBNRXd3V3lLQ25acmdSSU1uUXM1eTBv?= =?utf-8?B?NzZrak5EOU9JU2hXQmVzOG52aWhUSmFvcDUwd2pTZHlWRUtYVUxCYmM5YXg0?= =?utf-8?B?OUxRNmFVbDI5OHJyTkFUVXlPeC9XSk5FRzBEN3BkcVNSNEIwL3RRK2RmdFZY?= =?utf-8?B?QTJQUUtIWTl2STd0S0NMRFRQOUpkTkFyczFqdmtpWjY2WG14RzdvV0dKbnRy?= =?utf-8?B?S3VuTkR6WGZzOVEvOXE2U1lrZ3lDdFZUa2t6RnVYcWY2Ukd5TmhlOWFTNWsz?= =?utf-8?B?ZGNKQnczMnpMQzRhazBNWXF2Q0VYSW81NTM2QjNDVDlWVTlZbXdHamQ2czcz?= =?utf-8?B?TkV5SjY3Zk5qcDJKcVArNXg5R1FPcjBTSzlieGRNeEkyMkFSVzlCQS93ZUFS?= =?utf-8?B?TnpnRDNzRDk3d3lxajgxeGRJY0tsZi9pVHM0YXVacEk5MkJ2U0hCdDB5VEMv?= =?utf-8?B?WXFNK3hMSjJ2OFZUd1RFODg0UzNiTVhWN3N6NkZqaGYxWUdRSE5lMG9OWmFS?= =?utf-8?B?ZmlsZDQ1TFlWNkZKSkpjNXlMZUV3UVI1WU1hZE5UaGtVeDZ1UlJnY1JOdkxH?= =?utf-8?B?TzNyRVBMYlArZnpNVGtVUFhXSXJTWlJBUkMrZ3NpcWdRS21vNDB1SjhWUGRH?= =?utf-8?B?VnlSeWRrd3lwczdmMzBTSEdtMDJhQTYrMmpuV1VTVzliMkEreVhHeXRDbCt6?= =?utf-8?B?cmRmRmRJRHArNVZyUzJBOGlLVFBjV2taZEg3bVpRM2tjZ1ErNmVXTXh2bnFU?= =?utf-8?B?dVZpYlVjVDk2bDlYcUlFVzBKVlhFME8xc0kwMVpHYWtYU3BYVEpiZC8wOHFE?= =?utf-8?B?bEthYjg3Zyt1ZG5TYWQ0bjZQRldCaWs2VFREMFRLK2RSSlkrMFVoSVZKN3B5?= =?utf-8?B?blMzdUowaDFMQm5iQzNKVFlIZkRoMkVTZkFxUis5TEJlazJib0lQTitXRGo0?= =?utf-8?B?aXhleUF4OVhQZjF0NDFMdlkxcHdsZ0tFZFN5aktsZXRNR0VHaWVkc2Q2TzYv?= =?utf-8?B?N1NsVXIwT1lQdHpXcnpjeDViS2hUMmZOa2JGMGhaSGJRaXU1UWF1YWJHbmJq?= =?utf-8?B?VG5pOXBZTS9zcWQ3QUJlOWNveTMxd0IzNW9kUGhnaEJPUEFBYnl4T1lYMzRW?= =?utf-8?B?TTM0WHN1NjhuZTQwbmxQa3E1TGpKT2hYbG4xbUpRdXlGQ0FmVFc3TXpheHl4?= =?utf-8?B?M3BrSlZIMUlIL2NkcVBrRUUzcVpTTG9HU3VqZGlITEV1dTBqQVdIa2hKNnBr?= =?utf-8?B?VmhYU0ZDT1lDZjBmSS8rVGxTem9ZaEZHTjlmK0VQYUhEN1VyNlRJM1djQlFu?= =?utf-8?B?MDdtUDQ4azNHWTRXS2JIYmpmdms0U3dDZ1dpTUJwcXlFcytzK3lFZEZSZFl1?= =?utf-8?B?a0tpS0NGNWo4dHhKRVZtd25XMnN0c2hoaEJhY2hmNlRmR3hWaUtUL2NlVlZM?= =?utf-8?B?eHlOYk5jL1Y3dkkxcTU5cEo2aHFwOVI4MmpkbXBKOVlMa1lKbUlYb1lDRG5C?= =?utf-8?B?bldNbUg4WFZ2emdoOTZuVUFyUEJaMkE1ME0yLzkzNTUrZ1hUM3ZHTmJDcEQz?= =?utf-8?B?b3ZvMWFoaVFPK2Z4V3c0K1l0a1pYRTdhcVRBTTFUeGpXbzAramMrc0FBbXE2?= =?utf-8?B?cnpmKy8zWXNQajc2Y2NsSFVLNklBLzlDNGw1UEF6OTg3QWZQTzVPb1puaUIw?= =?utf-8?B?OW1mS2FyUzQwTTFRSElhS1F1ejBNMHRWWkEwNUswRWZNTmhDSFVoaXlUeGtu?= =?utf-8?Q?r/B5FRYVAn5fwXq+xCcrcVpu1APOrT4Y?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:SN7PR12MB8059.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?bTRxR1E1T21xdnNrNE9WMURTZHViSXJKYlI1dG1Sd3QvdEtVMUU1SmFlZ2FP?= =?utf-8?B?bEhadkpIanVVeEVHdXlqMDdzZHVJMmF5TXZ4QmQ1bk9Lczc0bWdJUjZud3E5?= =?utf-8?B?bVFERGVYbTFNaDVvRmdTdW9EK1ZvMFVWejB4czZBVG5XYzIzRndXVUpYSVdw?= =?utf-8?B?T011SS9DOWVxWlUwc09HTzhsellWMWtWek94b1FheHk2VmpBSm16MEN5OEJ5?= =?utf-8?B?OGtISDhJWmZvZ3dMUjFxcHNWRGxxTjBERW8rQzlxellZaHQyWHB1QmpYNlVM?= =?utf-8?B?ZWtGY09ycytQdUxWclpTeWFVYXRYRittY2haQXhUY0pld1hkMHk1SU0yYVNO?= =?utf-8?B?RkVsd1kvdjA3ZjlwQUJyNGtOUE4vbEliVklqeDJGVmdzNkcvR3duTiswU2ZJ?= =?utf-8?B?RXd5SUc0VjMrSGRXMzFtWHFkVkpDZHZHQkFNVitFUmdmVGRLa3l3S3c1UElE?= =?utf-8?B?MFlKclNtNG1vQ2kvUGN0dmlCOVBIbkVwRWVNZk0vNGFOV2JjY25MT0x3SWxP?= =?utf-8?B?bDdwZWpKdWo1VmhFNTl1ZGMrM0I3SUFRZHY0UWd1VDJEMVJuNVNnV21BN2s2?= =?utf-8?B?SURrNlBUdER0dVp3eDRyUHRkeklBMDFiaUFOZGJaTnVSMFYwSTVjUzFWYk4w?= =?utf-8?B?bHpkeUx2dUsvQ0g4NmVEQ1dWS3N0RlBpWi8xM1F1aGlheUhSUDJJbFJnclU4?= =?utf-8?B?ODBnbVFQR0M5ckdLSUpEeGpwSnM5QkNleFNuSDU0QUswYWVpNW8zYlkydzcy?= =?utf-8?B?STlaQllDczE3Nm5wcXhhc3p4ZFFtL21MUEV3ZzMzN0tFY1BWaU5peHA5c0NZ?= =?utf-8?B?WWptZnd2T1dmb0VSSWttbVAvRjlEbXZDVUhsakxQeThqTkJWejhGZUFTNE5D?= =?utf-8?B?YWVrRmRGbEdOejRRZUxEWDBjNG9PL2FUNEV6bVB1c1lrcGNmdVJ6OEhaTi9C?= =?utf-8?B?VE5jUFZFVnVVVlVUNmZrbU5zajY2Z0I2bytVUmZCUFFhV3M0S09vSlEwUSty?= =?utf-8?B?ZHdiSG9LMFh5WE9MVUMzY051SE0vbUYrSlp6SXVmYWpSODhlSTh6bzFLd0JY?= =?utf-8?B?NW1BMzNIS3ZxY1ZaY1EvdU4vdnFSNHV3a0hnd3dXc1ZHVjdmNG1maXdvb3RJ?= =?utf-8?B?QW1OajNMakI0NFpOcmIyQ3IwVHRzdEROS3lBazhVU0lldDMvU2E2TXlHRms4?= =?utf-8?B?ZDFtOG5lTG01aTdLa2JvMTZzcHZNZHF0MTI1TlZtOEdONFhDNmhGTWlENEx5?= =?utf-8?B?NmdPL2RnZGYvSFVIZW51TFMxMy9YVmJGeC9KMjNHSU9JaTJydTRhM1lkQmRw?= =?utf-8?B?VkUzT1QrRUJYWHdYWGI5Z3lVQUtkalVabXprOVJaQm4xaXRTbEtCQm8xeE5Q?= =?utf-8?B?eU9XeVh6VVYvUmpBM05JOXd4Q2hTT3RleDJSZlRuakdrR0lVWGgzc3RlMFRh?= =?utf-8?B?dHphUWw1WEY4aVc0ekFtNnlIZktaRWRENTZRWFU0WkMvcHk3RWtVN1BTaUFk?= =?utf-8?B?elVESTZIWDJLK2FsTWZ4d3d1dnpqOHBzd01DMXJXOW01T2o4L1dTd2EwcmZ4?= =?utf-8?B?SmQzOVRYTk9HYXdScGx4MGxjdFFNcStSSVlPbk9qWVZvZ2JURnd6V1VMT2VN?= =?utf-8?B?OTdkSkR3Uk5pT3diamxaVTFIMnd0SXZSYXU3aHBrRnA4MDROSDV1ZUdNb3F6?= =?utf-8?B?d0JzZCs5OVNRdEJibG1aTzd5WkREeGs5bUVxb3hwNWp2azRDYVVDK21qRDdM?= =?utf-8?B?OHBWYnhubTBjWWxacjhpZG1nWGdOMm5uRlQ3b1BDSmZ2clhlMStQR00xY0Np?= =?utf-8?B?U2s0RnNhejhrRWUwMzQ3UDFtbitldWxFbG5RSlN4dHBKRWoyWlA3azgyMm9x?= =?utf-8?B?a1NZeDN2dE5xM1lZREtQNEhoR1BtYlYzVSthaERRRTZTdCtCNkI2QTNYaWNz?= =?utf-8?B?Z1ZvVmNiRGdNU0p3L2hxdUorUDFmSG53MGJKQnRhc3BUR3Jyb0Q4WDM3QXM2?= =?utf-8?B?clZtUGs2ejhlY2h4NkJJR1FuMkNWV3JiQnVTZTg2bjVhSDA3c1N4RUhpWWY4?= =?utf-8?B?U2JCdmNYdllMU3Nodnp5amJ4WGROWVcxTmw0UHFxRnR0RkZNV1RDN2xERVZN?= =?utf-8?B?UVpneFpmNzUxWDVtRDFTblArVHBPV1pTODJiVHVSYlduRHBkSW1WS29iOWZv?= =?utf-8?B?dmJ3UmlWQ2VpOXB1ZExXUjFtWHBtNlpHTmhpeFNveXVnaEg2V1NyY2pTK2VU?= =?utf-8?B?bTVjQzFPZkFVeEtxZmVLdkQ5VStmNWE1cmdzUkxjMERIekNSWmd4dllmUkRZ?= =?utf-8?B?Y0lNQ1hiejM4czlYeGpJUmRtRk50ZU5FNU9IbjZ3SmtsR25qZXh4dz09?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 97cbf514-ecef-4209-d366-08de4a60dc2f X-MS-Exchange-CrossTenant-AuthSource: SN7PR12MB8059.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Jan 2026 00:41:40.6007 (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: /mtrnZT/eBb85ALWy/MM1ocKlso+HKTqlfinED6cRNIspEwBQZioJr06UMBgoUufVm1kcl7Lo++hB5XI431kkg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR12MB6454 On 1/2/2026 2:51 PM, Paul E. McKenney wrote: > On Fri, Jan 02, 2026 at 12:30:09PM -0500, Steven Rostedt wrote: >> On Fri, 2 Jan 2026 12:28:07 -0500 >> Steven Rostedt wrote: >> >>> Stacktrace should have recursion protection too. >>> >>> Can you try this patch to see if it would have fixed the problem too? >> >> As I believe the recursion protection should be in the tracing >> infrastructure more than in RCU. As RCU is used as an active participant in >> the kernel whereas tracing is supposed to be only an observer. >> >> If tracing is the culprit, it should be the one that is fixed. > > Makes sense to me! But then it would... ;-) > Could we fix it in both? (RCU and tracing). The patch just adds 3 more net lines to RCU code. It'd be good to have a guard rail against softirq recursion in RCU read unlock path, as much as the existing guard rail we already have with irq_work? After all, both paths attempt to do deferred work when it is safer to do so. Yao, if you could test Steve's patch and reply whether it fixes it too? thanks, - Joel