From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from NAM10-DM6-obe.outbound.protection.outlook.com (mail-dm6nam10on2061.outbound.protection.outlook.com [40.107.93.61]) (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 CB8252877CD for ; Wed, 16 Jul 2025 19:30:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.93.61 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752694222; cv=fail; b=uozYaUksP5OzoMWUFaMMsQ24ESZG6WYFMxQzgZKA7zfWQEx1Gn7JUaFkY+ETBYoM2583NqBE/gfInSTO5zGBi2ZllYZH7DMdPvmKO2mat9W8LPo730JEcppKtPpT0qBWSuK21+thdjqSskIwG2kVSuoG9kvkyn512ll81m5e8Bc= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752694222; c=relaxed/simple; bh=3nB5mNhVZU3QCVueHkxj2mZQxct7tVASFLaT/lxjaNY=; h=Date:From:To:Cc:Subject:Message-ID:References:Content-Type: Content-Disposition:In-Reply-To:MIME-Version; b=EAej8GUGvhoZzU0TrXfq9g8nUy7sZyFsjMsoqvbw3QWtZVoCyze7kXCqvsXIAk1XPZiT/MlVJYhCOp0bReBS69Go+u2Ltcb5x0nDVleC/gzR6DgwoIK9UtBl/lKL0S5jOdkdbUBPIXMriDWjMvarHgLgtMxS5ce2h9Me5HK0Rak= 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=bOEdk6UX; arc=fail smtp.client-ip=40.107.93.61 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="bOEdk6UX" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=Du69Ib3qA89aCRe0pPMM92JUO46XVLIb1NqwiuQ8QY4kMgI2MbMaNH460Bbo0uZ7hNSZAdkzqAMpYS1275dFB43qkFIVcY4OpFvhmOpv76V8s129tos7NMxvAJLJGyckYP/BNBQ6oSfb/tPyqdTFjLKMTvQzyA3BiG0zBExnuTVrJyZAZTec6srM7G6SYqBwYA1eoKWMEUrRx1F6PD+1X+fBGKBkGgIWOeVBUHaZgN22+tZVCK+3kShzaiOEzmTHsrnZ4Vxbv3PvWJ2xa+Qpz9NeahueiLH/lVTAu8PYW1y5pQxpBmRsI+UBr/7toDMrAazHpcXp0e3+K1bxxQ2jsg== 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=x47Zjf3y90ONW1OXTlOa8J7nv9pqeNdNkwMZrzZYqQE=; b=OmO9KzSjcWtGEhdi78E5fbFiEucVMNLM2pxregExY1d8ZF640lkVFLk2xodsmkUX0GzxrHbUzkaue+bK9L1KQGjvoUmt6jN47frp760DwjWLBJopgaV85h4xRi//IwmYNa1ge96uig5SsIqKFRLJe1VhuYjoQaI6de3jkVXqRNd+2yN7fHbA67lGe1qP6IhP5fPvptmk6dRQw2Wd9Ce10rOa/8Hc4G/Ml37NSdnSJO37/i3JNgVKTTpMWSmg7TJf0VWglnind5mYERW+pRt6JfUij7tTJIuRroo1l92NgJ18Pk1sFgvlR3zYzxLeXIcHB++GU2FaEDX60/rksOwsRw== 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=x47Zjf3y90ONW1OXTlOa8J7nv9pqeNdNkwMZrzZYqQE=; b=bOEdk6UXGhsiaShkSHIQmi4I4r6Ynnh45ui8hOAOOIsDBx2+aVsDSkc+g9SOKvM6xuK9f41rerBFFt584uhwwzKc8VbokWDqwy++kxWa8f07qYjT0pL6yjGiijJSe+RRH+gWwKK/5J9XOSD+6Ja4YvadQnmDj+RvXNXKVh43vnZaTLckx/yLZhpLjI6xhs0JEp3byArdlW5voVpn0Bmd9oA7xjf0KhTGS8XQnipKziHQmED3p2AxOKj+3lFvP4Mt0IGzPZ7n6CXIm1viKLM1rhKz3OgoirsjgYCprcpYWQj7AagFM8zMFV1Ipps//iUAyjA74Fzn+IrAwFusTo24GQ== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from LV8PR12MB9620.namprd12.prod.outlook.com (2603:10b6:408:2a1::19) by PH8PR12MB7277.namprd12.prod.outlook.com (2603:10b6:510:223::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8901.35; Wed, 16 Jul 2025 19:30:13 +0000 Received: from LV8PR12MB9620.namprd12.prod.outlook.com ([fe80::1b59:c8a2:4c00:8a2c]) by LV8PR12MB9620.namprd12.prod.outlook.com ([fe80::1b59:c8a2:4c00:8a2c%5]) with mapi id 15.20.8922.028; Wed, 16 Jul 2025 19:30:12 +0000 Date: Wed, 16 Jul 2025 21:29:58 +0200 From: Andrea Righi To: Breno Leitao Cc: Tejun Heo , David Vernet , Changwoo Min , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org, jake@hillion.co.uk, kernel-team@meta.com Subject: Re: [PATCH v2] sched/ext: Prevent update_locked_rq() calls with NULL rq Message-ID: References: <20250716-scx_warning-v2-1-1d015b2d8efa@debian.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250716-scx_warning-v2-1-1d015b2d8efa@debian.org> X-ClientProxiedBy: MI2P293CA0009.ITAP293.PROD.OUTLOOK.COM (2603:10a6:290:45::6) To LV8PR12MB9620.namprd12.prod.outlook.com (2603:10b6:408:2a1::19) Precedence: bulk X-Mailing-List: sched-ext@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV8PR12MB9620:EE_|PH8PR12MB7277:EE_ X-MS-Office365-Filtering-Correlation-Id: f42dd777-6ec0-47a9-0ddc-08ddc49f2ead X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|7416014|7053199007; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?2AYH56zezcA6MMwGgnpuEiyCLlPG3cBekzvYVxCX06rYio/KDTtck3+aZ5+k?= =?us-ascii?Q?U8SuoJzqgtV9GgAlWdbOoOX1Ep6rCdvtIKIl97iHaN/2R+64QgqNOfQQm9ob?= =?us-ascii?Q?acAm+2INdkxBh/UsMpVKzhc79l1WWZ+v9Qpg2MwYZ5zzyX7Hc0/rdUomNmi5?= =?us-ascii?Q?Lwb0KnztSAGQTxJq2FRQX0iD7LFuqIPBnFDgiQRKyDOA8v/X9c+qQj18TJ4a?= =?us-ascii?Q?XtPV0BgFb1OArsa4azIf8wVKbqfzTwsG3t8u2thAl1blbdLwXW0UrtdEBa3Q?= =?us-ascii?Q?AGxuhMbt6zQMCndOoPC/+sEGj1O2TLL7ckcPS5dak5F/obHL+8BCTnIyIWHl?= =?us-ascii?Q?TUNFAtADPzVwKz4fBIVt9pKsQe776i8Xau1JjlWVKt8qGmNEyb25/Mwf8bMc?= =?us-ascii?Q?qGHa3iddbiSz9usL2ZMtgNbbhcvBnXo0kfSd8z0Nr/NradOqnP8/kFluANEB?= =?us-ascii?Q?zETOkpYWXcLlkbR5EgvUWFGE9XMIrJ+nLGyMmEmrFIRaj3StlTeqU4AVzFWA?= =?us-ascii?Q?Mxe+yHsnGeiXn/wkPUIhPMBw2nMsw1nbI/GZX4iCrLyx6EsX8JLzDyX9AI/P?= =?us-ascii?Q?BBHIfuwbAmCzke3TjCWRstiuXtnXJ1oy4v8/aga0yEEbZjK3JU/lXWUMZPQk?= =?us-ascii?Q?IyOT+g1L6vMJdVlmxfKnCUUTrvXOJ9kqBj7ErTYK5fc3RrGiWKve9WLjSbra?= =?us-ascii?Q?KYWQGj0J4TTXETdbLJyWWQGYjfA83Ulk2lxVDmvYFeS2E7qO6SkcjAap8+sL?= =?us-ascii?Q?HfY7e2FFOIQabwopPqQbNovx19fLdVSValFrYyf+XiYP+ZEH5fsfEn1kTuQi?= =?us-ascii?Q?mz34KGyNRwl/vjsJ4JWhsX0g4+Q5mYbRu8E3slN3uqYnAyJzaqiLjdDANWMb?= =?us-ascii?Q?R2nxYF6oF0vCzI/09N2FpT0T/KIRFsI6wCou4Qj4fzIwp2Yz7Z0FF09/Rk8q?= =?us-ascii?Q?F+c53JrKCbxzLiMsKIUonuHx5vdF2A3yoCe3W7t7czwQiOOj//acumeMmsiB?= =?us-ascii?Q?CXA7RIRg0m1rqTRmIvNo9j48e7vYcByVWxM+XI6yzotj225415f/zAc5T7Ku?= =?us-ascii?Q?Xh4WQU3/QEabNKJO6RBbkWrIAZgHhOCGcAvAVQF4wYrokhFthqpW0enuJWf4?= =?us-ascii?Q?MowW7nZw9gEG4cD2uwp41rA3Ce5VpQCxBic0wm8AtJBiHTGmX/Uap5gKQDiu?= =?us-ascii?Q?iqiTrbn1LUWiMbWDcip7KtAfwbPIfy8TnV9z763GXYkW2LKND4B3f4O/5jiq?= =?us-ascii?Q?Vzfg8h0JhaNy4G3BeUGNBM8js7F9BK9EuLeC31HL5fUhk+2poih7/mLc5W8u?= =?us-ascii?Q?b7ygcrnTHsbQi0+TwVROyTDeVYac5mgywW+LxG3hvjaXcQYnyn5OVMG48JVy?= =?us-ascii?Q?HgVosLnMdKMjX4kt9TcAo1OwzcSyZbuw4QsNt7DTzSZha5MT0mZV/06AbkOq?= =?us-ascii?Q?lT8/2s/X83o=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:LV8PR12MB9620.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(376014)(7416014)(7053199007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?hHMtceUT/8IFEvnuW/7kiE5pCbeuqVoCUpYvj7QoxDotBmUjurAdV5AezHpd?= =?us-ascii?Q?yBoDYAF4uzDwDFUgGpkuoEPspWiNRatGJVsK5/e1KWxxl6J4K6FaVaZmuHYS?= =?us-ascii?Q?EQLBFQ+eynzAkzDj0AAZ4zYfmATVGp5vDmaym/GTJJssXVyND+deLhxsgP15?= =?us-ascii?Q?QWS0uYMsqAIr6BFae6PZNE4b/jvBhkGv53c706SR7oD3X26Sz38ifl5T5Fsl?= =?us-ascii?Q?dudbucJADwrc/Ds7NH7dsoqhtkr9rDaaq8msXlhtlp50OKJFGOXKhn+gLpjR?= =?us-ascii?Q?vjHtzse9i2icMF9CvcAKoGRQh7A8wIeVx2zOvD4wQDYtLW9vRIafFhBuBloE?= =?us-ascii?Q?93qyV73PGmSNFcdlWaE0/MbeZV8ln8fnswPXklQQQv2QxSFo3XvCESR8ntJW?= =?us-ascii?Q?Sqz1iokAWJziWAewpthn0fMa5L/3Wiof0Q7vMRpbTXytsIrx2g/0kXg7wMaZ?= =?us-ascii?Q?ktNG2wIciz02bHI5FBFl2coXJ7VEl2oYdZh0pY9jRWU/Q6DYGqp0BPDPbwAb?= =?us-ascii?Q?gaVg5CamoaC5OG23RDV+dP65bD5WDTjmOl8J1H+/n612K1/io3O25rhy1Yru?= =?us-ascii?Q?ij43iIgsTYkFnGHU+1tMgO3JhJHFRCUuHRYhza09LMAGrJF13EclT2qc+qcI?= =?us-ascii?Q?673J0FTDGIfVdnaWN75tx3PhDSQMk4bNGgW3duK5drHmvEJhOKDQYevQX5Rr?= =?us-ascii?Q?Ks1jNjqW5HqwogUVAJKE3cYiIMcYiQaXGxzSlC8/TbcxUOprDVN606LaOdtL?= =?us-ascii?Q?7enCU08GYuqDjSuahudZ2DZ0zcI4S+o0IJ2fUpwlIoOjKmPoFlS1bghT7FjH?= =?us-ascii?Q?duBn4HfmFMGhzEgzdaJve3ZMJbbG+9H9kRGJjb94lYaObdzyard7XAI416u6?= =?us-ascii?Q?PAoULy+Tlo9NxzDTN4qQ0cBBgECSpSez6g5l3zzmgXTU/PjTCQ938QwTrWdr?= =?us-ascii?Q?H1XuKr1LomIteCsiLrZBXOSvW+wqxy+ZdrYRT8tQ4ITH+g4kQRXSiI8xYnuE?= =?us-ascii?Q?Qoo25VR7WZk7KTZXwJBcU8nJIh9eRdYzdMPYaoDdzEdxAufR3BWe3jkyuloB?= =?us-ascii?Q?yq8TNrDu1Q5Ve3JZbtd3ip+3vRVDUX0rB8f/oJvIb4kFrb+Yjsdj1CXpl3GO?= =?us-ascii?Q?KDX6IezkiYG49h69PTntqwwMXywg3VFUCGwqQMiXnFGsY5+7pIO5nLkk2fkG?= =?us-ascii?Q?YVRUcxqCnPfCTAcnDvYhCxvhqfa19caldjJo+5mX87vJdvXdA54iWZ7O1pim?= =?us-ascii?Q?zCG7ud/vUb4dekxqaxnamV04h9+ABS/ToxE9UOIn5tZnu3YrNcYOx7vLoviq?= =?us-ascii?Q?JqdWXZpXcu+230SpmU/SaqAhVtktAU5Pll+ZmSWbQBXhQiyfNuoxWPmJNXc9?= =?us-ascii?Q?wWThBgIyEJPBu8SF4uKg/G2q4Hho/8p7kJKYCr1JijIFiIfoeYJVQ2JPqIxc?= =?us-ascii?Q?Sl1gm3RK+CLEzpYLKfnfTgays78pfHtyi3i6KEGD8LVfOHbtvRyBPyzJAf8B?= =?us-ascii?Q?OwAY7pEbiKBrr6cg1D3tk/f/2+THqeAKVt7SHG7wK7ZR6tvOSTV4a5va3+tw?= =?us-ascii?Q?eYMsQG5TxF3oHlFfFjFDRtK2z9FiYe83O0GG1pfb?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: f42dd777-6ec0-47a9-0ddc-08ddc49f2ead X-MS-Exchange-CrossTenant-AuthSource: LV8PR12MB9620.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Jul 2025 19:30:12.0056 (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: FuMIpiNbhnr18aGoCrBXqmtECMr8zegAigUqNC+UvC8+TQVcASGTR3cQHaBD/cKd4x90Y8HPhB5K+TWcm42kEw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH8PR12MB7277 On Wed, Jul 16, 2025 at 10:38:48AM -0700, Breno Leitao wrote: > Avoid invoking update_locked_rq() when the runqueue (rq) pointer is NULL > in the SCX_CALL_OP and SCX_CALL_OP_RET macros. Maybe it'd be useful to clarify that rq == NULL indicates a callback invoked from an unlocked context. In that case, we don't need to store any rq, since the default is already NULL (unlocked), and we can avoid unnecessary updates. With something like that: Acked-by: Andrea Righi Thanks, -Andrea > > Previously, calling update_locked_rq(NULL) with preemption enabled could > trigger the following warning: > > BUG: using __this_cpu_write() in preemptible [00000000] > > This happens because __this_cpu_write() is unsafe to use in preemptible > context. > > Ensure that update_locked_rq() is only called when rq is non-NULL, > preventing calling __this_cpu_write() on preemptible context. > > Suggested-by: Peter Zijlstra > Fixes: 18853ba782bef ("sched_ext: Track currently locked rq") > Signed-off-by: Breno Leitao > --- > Changes in v2: > - Avoid calling update_locked_rq() completely on preemptible mode (Peter Zijlstra) > - Link to v1: https://lore.kernel.org/r/20250716-scx_warning-v1-1-0e814f78eb8c@debian.org > --- > kernel/sched/ext.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c > index b498d867ba210..7dd5cbcb7a069 100644 > --- a/kernel/sched/ext.c > +++ b/kernel/sched/ext.c > @@ -1272,7 +1272,8 @@ static inline struct rq *scx_locked_rq(void) > > #define SCX_CALL_OP(sch, mask, op, rq, args...) \ > do { \ > - update_locked_rq(rq); \ > + if (rq) \ > + update_locked_rq(rq); \ > if (mask) { \ > scx_kf_allow(mask); \ > (sch)->ops.op(args); \ > @@ -1280,14 +1281,16 @@ do { \ > } else { \ > (sch)->ops.op(args); \ > } \ > - update_locked_rq(NULL); \ > + if (rq) \ > + update_locked_rq(NULL); \ > } while (0) > > #define SCX_CALL_OP_RET(sch, mask, op, rq, args...) \ > ({ \ > __typeof__((sch)->ops.op(args)) __ret; \ > \ > - update_locked_rq(rq); \ > + if (rq) \ > + update_locked_rq(rq); \ > if (mask) { \ > scx_kf_allow(mask); \ > __ret = (sch)->ops.op(args); \ > @@ -1295,7 +1298,8 @@ do { \ > } else { \ > __ret = (sch)->ops.op(args); \ > } \ > - update_locked_rq(NULL); \ > + if (rq) \ > + update_locked_rq(NULL); \ > __ret; \ > }) > > > --- > base-commit: 155a3c003e555a7300d156a5252c004c392ec6b0 > change-id: 20250716-scx_warning-5143cf17f806 > > Best regards, > -- > Breno Leitao >