From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from EUR05-VI1-obe.outbound.protection.outlook.com (mail-vi1eur05on2081.outbound.protection.outlook.com [40.107.21.81]) (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 7E23818C93F; Fri, 9 Aug 2024 13:37:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.21.81 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723210667; cv=fail; b=fmYgwJsbl6p8GN7hjhZusxAeODrzNLd2tNgmtXM1EpHUGcWrniRG8U2BNRjUgeevjLbjIBfWZyPHzEv9GLF5ah+KgDmpJhS9kom2Yg8FUR/i+aF8BWuO5OUbf5cPEZwQRKKmvF34dt2KU65+Cb8ewq+NHUegBEiIaD1uJUdC4pk= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723210667; c=relaxed/simple; bh=lrJkLioVm5UeNdvRLjO/0X2kSIc1G2YxvXueyma2eeU=; h=Message-ID:Date:Subject:To:Cc:References:From:In-Reply-To: Content-Type:MIME-Version; b=Oi9mK+kYqk8x9J0KlyHCiIDW1m66d5Ah9Pdwtuu3rJlT5fNkJjsnMw4v1tCqWPGbdmQ/QdxQQiQ6k1rE6r/amxpNM8f3d9WhS3oj4JA5vB7Zt04cEpBjIIOz+fFNvLgNOx1GF6qbpEdva0TCWXqzzXnOxjttqvOK6VUEoXhUVYw= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nokia.com; spf=fail smtp.mailfrom=nokia.com; dkim=pass (2048-bit key) header.d=nokia.com header.i=@nokia.com header.b=fh0U9Zgz; arc=fail smtp.client-ip=40.107.21.81 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nokia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nokia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=nokia.com header.i=@nokia.com header.b="fh0U9Zgz" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=EXWXGS3LMqtdoAVPDWtouQtm5P0OXUbaHSpu/g7pKlWm5bgEn4WjpvPlYaf2A8KbwP4rnWB9uQDXBmLXeIL0no+MDAap5jfIjvAva2Hf9bI9oGiC7OeD01Thtl85+7lg4ywQG10xIYTjt5Ykga0JhtbJq+nFh1Yb7LnbTvBJ2f/71QKtnqAksQ3tSrISB485R8yKaDkehZcIY4fNL+KKblA4LrBPUooPq5tRS5sAuwY3gSaTibAZ3djxiockx65ERhA0zp+BKwHj3U4RfzfSrZNmC3S9gXlPzg4C6+vMr8nF2Iwfz5Oac4+uqtL8nYwZmWDBjdUVn1QK78UvjkSmeA== 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=1FR/iafYYJSJxzmG419L7tSuoxqSd7x6bzr9CFpcvK4=; b=kRAYH4S1wFxQc0VmJN+mjjUGKwQDWaT8d/TLxMBqI1IAYEvPIU47fXZqsxycYs6+rztjGto9LBcCRXGxM955j3KFVR1kOcr7tm8L26knk/qcoflNNc8j9UvGGyT+A/ChTEoKUhgM05boAVCWTsYt6PTP/OWhrOKBZfubHFnf0jlmLcOXtLyPBmpiTQM4G9ER70mzTuyS1NqpSIu/ZYhY/6HfRGPDvvBdB3xoIKmWMlqqcvD7gV9fowwXcaPFFALCDUUILfiNOVhEMPk96Pl+NFQzJEoS39F8yrID3wK292toaijEOTnr4Il3QZRnukScWobkQfji3eXAMRzV0s/E0w== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nokia.com; dmarc=pass action=none header.from=nokia.com; dkim=pass header.d=nokia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nokia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=1FR/iafYYJSJxzmG419L7tSuoxqSd7x6bzr9CFpcvK4=; b=fh0U9ZgzoocuFfjCxaz21WBJl4IfTG5xnYdump4kOpw9HQ9v/HE2zU0FUv5A/8wsB93FUzfsYYKcltyr+ng0itWWjJC2u7r5WnyA1RjfnmL8ucgRd2V98qEABsY4uxNRIgnT/fjrwC5eRCxpEfdfZJlte1z4hnBQ6DdwfsEON2aev6XfdsS1U0E10EHvsQux+emaEkH/Wz8KBYXNdg1/hnbKHMNdYvsm8UF7MRwJ8P26wqXXw05jY3MmvlP130XNn44GR9JF921P2h3nPwkSMKEYci7VfX5ueGTpf5eRfiL/XjagXHf6PyIadZnXnfrQ6O8xQl8o8AuCRA/AhCAWnw== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nokia.com; Received: from PAWPR07MB9688.eurprd07.prod.outlook.com (2603:10a6:102:383::17) by DBAPR07MB6757.eurprd07.prod.outlook.com (2603:10a6:10:19a::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7849.15; Fri, 9 Aug 2024 13:37:39 +0000 Received: from PAWPR07MB9688.eurprd07.prod.outlook.com ([fe80::6b9d:9c50:8fe6:b8c5]) by PAWPR07MB9688.eurprd07.prod.outlook.com ([fe80::6b9d:9c50:8fe6:b8c5%5]) with mapi id 15.20.7849.008; Fri, 9 Aug 2024 13:37:39 +0000 Message-ID: Date: Fri, 9 Aug 2024 15:37:38 +0200 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm: smp: Avoid false positive CPU hotplug Lockdep-RCU splat To: "Russell King (Oracle)" , Will Deacon Cc: Joel Fernandes , "Paul E. McKenney" , Josh Triplett , Boqun Feng , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , linux-arm-kernel@lists.infradead.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240307160951.3607374-1-stefan.wiehler@nokia.com> <66fdce3a-c7f6-4ef4-ab56-7c9ece0b00e2@nokia.com> <20240312221440.GA29419@willie-the-truck> <20240313003244.GA29568@willie-the-truck> Content-Language: en-US From: Stefan Wiehler Organization: Nokia In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: FR3P281CA0048.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:4a::20) To PAWPR07MB9688.eurprd07.prod.outlook.com (2603:10a6:102:383::17) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PAWPR07MB9688:EE_|DBAPR07MB6757:EE_ X-MS-Office365-Filtering-Correlation-Id: 63fdf15f-36ea-42e1-74af-08dcb8787009 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|366016; X-Microsoft-Antispam-Message-Info: =?utf-8?B?MjRDcXRZNlZBdnk2SGhNbnpYbHFvc01JVmJqdFprQkozQWNVVDlWckc4SGM5?= =?utf-8?B?TFhKWUJ0N05odVJKT0ZpdWpCYklrZGZmd2gwbjU1b0JOb1RrZS8wOEJjNTZP?= =?utf-8?B?R2h0TmlUc3lsU1dtV2VxMWVkSDdlT0xhWDFWNnFUZlRuamZjdzhTMjVyTkZI?= =?utf-8?B?UmxmOEp0WGdvb3FLWFJ6cHl2eU5oY01oaWQrZFhuNnVoNEs2VWZ0YjdoVUgz?= =?utf-8?B?bTd0UEptdDhwQnhFSlU2d1hmZVRKNlJUUU52M2ZEQmR6T1dKNHcrVk1OdW1X?= =?utf-8?B?RFBZM0UxNTZaU09DdjdmaGc5cy82M3RHOVV2cURiSmI4alZxaWZMTkI1WmVM?= =?utf-8?B?RVJSV1ZRdEJSempqdGcrbmlOK0w4QUgxVWtQZDUzL29MTUlOZTJjQUlQZVNT?= =?utf-8?B?Mm05dE1jb2JjQllBVUpJZkdqSFlPOXA4QXM0MVBpVHh5SEJGT2w2b0hJenFS?= =?utf-8?B?bVlWM1lYMXQyVkt3WERTMFFlSjJ3TzhmVVY1bmdNM1hibmRpaUpDUGs0SmIw?= =?utf-8?B?K0IxdzJZV1AyM1J3UW9IQ29vcSsrUEQ1ZnZlNklVUjdTVmNMcnFhNThzaHJS?= =?utf-8?B?K2hEdG1wbTE3QlQ3V0FZZ0RoR0VxTlJaOHp1c1R2MGV1a1RIS045UEd5ZmI2?= =?utf-8?B?YmpKNEFCRE5XNXhXTlppWHQxMjRmZ1ozWWwvenIyVEZkcjhJL0cxa0JkQmRH?= =?utf-8?B?M3ZzazdOVC9Hb2kyQmFVSy82MDRqMld1V1ZmQjF1WW5RUFJQKzQvRUdwTmFV?= =?utf-8?B?VWpSdm5GK21IZmdvK2pCOStzWDRNKzdoL3dha2I2UlRndkFTY3kybEZScGZ4?= =?utf-8?B?eUxUVmtXejhuT05FUDUyejRQelpRdW1PRlpHOWVvYjZ6N1lLeFd1QkE1aVJu?= =?utf-8?B?OWZ4T1JNQ1pENlJ6VTVNRTgvWlZJbkhwUVlrTmo4VlNSUmhXcFNBdXUxZkU2?= =?utf-8?B?ZmJ6REUrSWZuMUhnMXBWbnJaR25xS2xDdUF4NFMyREYxU3RoRlUweXVLVUly?= =?utf-8?B?OTkyU3lUNWJCbWl0K3B1dzFEOXZWWWlXSVJmODBsTkJYeGFJZGxsYWFHNVJL?= =?utf-8?B?Wk4zT0taUXpHNVgyK2cydlQ5S2JJS2tBQkc1bTdLcWp2ZldsQnVUVHVvRmJD?= =?utf-8?B?YWRvbTJIaUpFY0d5YmlWczZCUzN3dTRzOGYrSWdudWZxZk9EVmt1ZzQvWk0x?= =?utf-8?B?ZDk2T05DZUQzekF5a05JZDlJZjVRTURBRjN0M0hQeUtjbmdkd3FFM2FMdmxB?= =?utf-8?B?by9WODcxeDRKN3pkRHIvZFFnRUpZUmRqQUlhbkxEV3NhUksvbGRMSERTb0hw?= =?utf-8?B?eldvY0pMTmk0TVB3NktUaGZVR3V1UGxWc1AzMThwWjJYOU1FUksrMVNpSkp3?= =?utf-8?B?MEVnV2xZSkVSL3VidTd5Q0xHMUwzdmQxYjNYVmdla2h2LzBmdGFMeXJyZkF6?= =?utf-8?B?Q0tqVWlQRUhqY04xdzAxQ2NtclJhelg5NDlTQ1JKRjJ6Q3JIdXlRT25PT3hq?= =?utf-8?B?dVZBL0NCMzBONmdUdjJVZ2VBbExvMk9ERlpYNkdPLzlWS0tMZmZQN1c1aUc5?= =?utf-8?B?OVJkM0l4Y25EZzYyaWN6aDRsTUV2R2NuRXFackhqekUxQXU0UllLM2pjRXlj?= =?utf-8?B?b2xTNUNMR1BLMU9IWEhJaGVOdDRCSFo2VDRibXlobFlEMjdXRG5WdDZHN1NM?= =?utf-8?B?TnZSQlBEVmpvbU9jZ0dFM3hlM0NGRmQxWENtM2kzNkFLbCtrOXIwNUFpd2Nh?= =?utf-8?Q?V6LzyFmnzt84dETvnNatsdn3ZHM+/r2AaWyJvNj?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:PAWPR07MB9688.eurprd07.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(7416014)(376014)(366016);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?bUhCSzFOeHkwY0hhaS82NnVtYnJBUVI0dEIvYzVRMWRtN3RnYkNPaUZVeUFJ?= =?utf-8?B?a2NidG9WQ1JnajdVdGUwdk9DNUlsUlpKMkd0U2prYU9ZeVlNV3lvcGhWUTg2?= =?utf-8?B?K3BYUU56MEN4L2RlRVkxSG5WVTV3QUovbFpyb1JKcjI4OEhHVEhFYVNMUHMx?= =?utf-8?B?Y2hoSndyWXpaRG03UzhHNk1aTi9NMGFaWURkRjFNUXJkdnFDQ293bldBcnp6?= =?utf-8?B?TFRxK1VYemw0ZFBHbDVFOVErSzJXRGUvelB5L1pHZjhZRXJ2OFMxbGZpMU10?= =?utf-8?B?alZxMUh1eEJ0Y1dENW9OcmR5M29jRStJSE5iMjFvajVFSHhCSU9mT1hESG14?= =?utf-8?B?TDhud2QvQjlOOHpxaVBkLy9tQTJpaGNTRUkxbWFlSnZzdHpWMHREbWRXOHA1?= =?utf-8?B?ZTI3OGVia21PcDM1WTBVaHU0SzkxNGZaeFVOVE1SUDhQZlo3eVZ1VjJ1cVpJ?= =?utf-8?B?Q3RxVWx0emlrT0w5aGNGRUgxdnhndkNxeU54WXJEdE9YZW1pSzVkRG5ncTJw?= =?utf-8?B?Nlo3UmtNd0dYWHV3RUpNRUxmZitQSXJOY1RaOUFkUmJQOGtwZnI5ZDZ5U1Ur?= =?utf-8?B?aUlWaHFoNmNtZFBLaFFQWjc2OUdoT1J3b0o5cXRWSmdrc2VQTC9nMDV3ald1?= =?utf-8?B?Znd0UHJsdER4VWJqREtvbUFVY0k2UkhjMEtLR1dydEtDSmI0QlZRdG4rZEdM?= =?utf-8?B?NkZjQUVyZC9yZE5URGFqaDV3UUpCNkcrUU0wcGpJNUtVNGU5bFNRZGRBUzR5?= =?utf-8?B?TlcxYkQ3VVhRM3EwU1NsZmI4TlNvdzBPVDVYeGtZdjhFWDlCNE9rMGJuY1dy?= =?utf-8?B?VW9uK1VtT0FEQytqVU9ha21iSVdvV1BUcFdZYmZUWlNGYVBSSUU2c1dzd3ZG?= =?utf-8?B?RGlKSzdMbkVhcnVHdkJRSDJPWVJXT2h3QlVra3FRckJwOG9BYm5hZ3JNbVVl?= =?utf-8?B?dGdsMEZmRGFPdk5QTlRLSWRoNzFMMkRIYWVkMWpER1ErM1FKb0lPV2ZaWE5N?= =?utf-8?B?WUZPZUtMUENiYWVkSHFuSURGbjdyVWlJMnBpM254OUlSckZIcUdtYVRQWUor?= =?utf-8?B?dXpUY2pTSDRBVllQWXMzVkV1aVFqN2hmMk44ZlhUaDFsWGRsWUNUQ3ZNLzdj?= =?utf-8?B?SE0xY2FnV29wVWVRMGs2eG1QcW05T3VSdWhyQjI4Ykp5Um5hNkxiR2tmRDJD?= =?utf-8?B?S0hhN3V1K2hKenVXa0NFS0R0RjVnVmViZitZT3JBbDVsM0NOeEsyVUhrZ3NZ?= =?utf-8?B?V3poVWx2SkM2YjhPc2h5SkVjaXRIRjhaa1RoMzJLaGZZY2twbnEzQ3diWkZ4?= =?utf-8?B?NzBHS3p1N3pmL3diNmk4SThsNTc4TWZvNkN4TVdvbWpxbndiZm0zMEtoOERZ?= =?utf-8?B?Ty8xa3ZKSDRFUElCUy9IeUIzNUpxeG5XazVIb1gyZE8wRTJFc3RZVUc3OGRk?= =?utf-8?B?VVpNTlkzMkJyTWhqUlVoU2tLeUhlcTNab2lLNmlsczBvREVieHRySUYzK1FV?= =?utf-8?B?bzhCVmk3NWpkTzU1UCtPbCtEQXlDdkFwSXFGb09HZGZrVU05cXN2bDhrK0lS?= =?utf-8?B?VWJvSHpjd0Q5NktFUFc2dVZtMGNMSXh6NzdzWWZLK291Y3JjN3NqcmI0V1Qz?= =?utf-8?B?czlqNGwyaGhYRm5tR3hQbEI0L2I0ZWtTUGxNdGMxTUZaNWdqelMyOUkzYTNv?= =?utf-8?B?M3ZDTVZWYXVoeElRejc3d1BTMUJib3F4QUp1Z3V0RXJRTS9lMmkvUUp1Vmpr?= =?utf-8?B?eURQeGt3N0xpUzdNVzhUOWt2TjdlcW43eFIxTkRFWXdFaHkyWUg0ODR0NEt4?= =?utf-8?B?VFpNN0RtTEhmVjlCaVlDVFhpSlZkOXpXaXVZckRnSmVPZFk4eHFTRGY4dGhj?= =?utf-8?B?Mkx6OUpscGo4a1BLTVZrYUNpdTVkbEkwczNKekFtaTFnbGt5T3dlZ0JnS3M0?= =?utf-8?B?ZDZyM1BWWEtjVzBMN0xNR0RWdXE5Y0dZMUEzUWZJTG91TnlXV0tISG4xOXFZ?= =?utf-8?B?ak9JU05xNE9XbWl0aVZGdnJPdURLWHdFcGo5QTdNTHZiQm8yTm1zS2k3OFBB?= =?utf-8?B?WGc2MVpKTGRNc056QXR1WmUxR3BrMW5DYWFwUzJjWnk4cEt4eUZsU0MvSkd1?= =?utf-8?B?Vm1YU0k1RENUOG84N0lTUldiR0RZUWdSbTZDNjB3WEs0MWkzLyt0c0NQdzVN?= =?utf-8?B?cVFOUkNTMzZsVVhCYTZLZ3lrMnNZdit1T3RrV3BVVUpLZk9vdU42dVBIOHNq?= =?utf-8?B?Y05HUkl6aUg2YnlEVVJETnJBYXBBPT0=?= X-OriginatorOrg: nokia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 63fdf15f-36ea-42e1-74af-08dcb8787009 X-MS-Exchange-CrossTenant-AuthSource: PAWPR07MB9688.eurprd07.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Aug 2024 13:37:39.5906 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 5d471751-9675-428d-917b-70f44f9630b0 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: XDJaNDuBDhEbcMNe/dgUkPUNYxbHriBEjklbdNq+zpeFZcNb6ExcIfGiuRj9lAfWIIWuiL46lhgGI++LAWHl/HAjWlflKL7qW8R8tbHygpM= X-MS-Exchange-Transport-CrossTenantHeadersStamped: DBAPR07MB6757 I'd like to revive the discussion and quickly summarize our options to avoid a false-positive Lockdep-RCU splat when check_and_switch_context() acquires the ASID spinlock: 1. Briefly report CPU as online again via rcutree_report_cpu_{starting|dead}() 2. Replace raw_spin_lock*() by arch_spin_lock() 3. Remove ASID spinlock Both 1. and 2. are workarounds with different pros and cons/proponents. Regarding 3., the last comment form Russell is: > For 32-bit non-LPAE, I can't recall any issues, nor can I think of any > because module space is just another few entries in the L1 page tables > below the direct mapping (which isn't a problem because we don't use > anything in hardware to separate the kernel space from user space in > the page tables.) TTBCR is set to 0. > > For LPAE, there may be issues there because TTBR0 and TTBR1 are both > used, and TTBCR.T1SZ is set non-zero to: > > arch/arm/include/asm/pgtable-3level-hwdef.h:#define TTBR1_SIZE (((PAGE_OFFSET >> 30) - 1) << 16) > > so I suspect that's where the problems may lie - but then module > mappings should also exist in init_mm (swapper_pg_dir) and should > be global. Unfortunately I'm don't feel qualified to contribute to the discussion on option 3. Russell and Will, would you be able to spare some time to drive this further? Otherwise I would propose to make a decision on going for option 1 or 2. Kind regards, Stefan