From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from BL2PR02CU003.outbound.protection.outlook.com (mail-eastusazon11011009.outbound.protection.outlook.com [52.101.52.9]) (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 67E9414A60C for ; Mon, 10 Nov 2025 06:57:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.52.9 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762757862; cv=fail; b=lvEFJZ/YiAE9AXMUrgCWjKYqY3sYoGTcGaDc90THvUysLzw/xObQwn5dDAn5PtKsBeUTGm6RqBwTveyOZEB5a283pysMZP/xwl8JZaTgHUXdRrTQ083kTPgDB+lHc5hJTlmhGNe27Gh+/lQ6BuiJWS+n34Ezs8rQzzltxqeqFCk= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762757862; c=relaxed/simple; bh=w+7wwbVTvf8HjGj91B27dWbutXlwL8Rp70bZ7eERA2s=; h=Date:From:To:Cc:Subject:Message-ID:References:Content-Type: Content-Disposition:In-Reply-To:MIME-Version; b=swDnu8xHbPo38h7/UJLnaIRPhWZh+FLpQeugE+T58yAYO1YXmP421lKIiK0DxEq1jz6oIkhH/txXUKplRhNQnOMfzq8ttCDSDeLQzgqcjb2RpSGGfbqPJ/TjbyzVShbhAH+PFNY2TzT1ucRGWb5+RdqVanfMxWAqE5aRDR4HGfA= 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=pw8UCTec; arc=fail smtp.client-ip=52.101.52.9 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="pw8UCTec" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=s6h3+nWIeajUT2tf9Z+OqWBz/NHqiT/Jc0r5ESozpXh7tUTjgSZGAcY3/BMtEbaRcRzUyIbJckKX9ByBMFMgYxAGvKIQqw9DYVHPFBe5QhzvFn5QJeXbIPZOrds+hA0YoIe9/TwsNLabGtwCyQevj51kWrbitCT9SlchV+e2+1/Wgz9OP7HczABH8NoB7GQqJXtKlLw32o4tOcqpqXM4POQSiYyFydHMlzPcoGB1gCewLcf5KuXXmY2BHds6iiG0gkCDTAMwmtkGI3EQDfJ43nazMOjdio1QiGyAgU5rF2YgTs9fbcmTbA8cV6FbC7qTu6W15YKhECKTn++Xb425zQ== 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=fcK7kCRwnHAhjmpUKMMcv9v/U7Zn7Zuxw+n+cRxLlYI=; b=dQUXu2e284qgeHarAJ9GaWTQ4WzYOAiuf9Opbn3kdiATlzNtog4b1TQedqrlkglmDpvIh7egTtVdA9YXUwfp3jIKoAK1tDoePXSZBkz9BaYBdqdeeNfe5laD1ryWG/HyebKxxB81G+HNsdM9IPMoDl4tvGzLmQVWmytnpExxzAhPRwVWyFoUwmBF2s2RTWigxMV5avfE7u/lRefjOMh8y7R0eP7CvXEotFpJ28ykuDAVQchj7osKLBJe2BMYcX2maJZ0qeNttnQ8/3dNs1dBMUpe/tMDH9e+asFPOtFFjfu7LypwhHAOKtQv3QqW+2zEGAKO6kSIHMlulvHzA+vDng== 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=fcK7kCRwnHAhjmpUKMMcv9v/U7Zn7Zuxw+n+cRxLlYI=; b=pw8UCTecWTmj45jSsT6Czls7r4d646KNqoA+56+U1iDxTuK+TCnGfQi7aavCWCjMXiXKTWLugOhMrxA3SE8S6CdR00sBIh/PkuXITq4vGrUMKAwY0OJvL1XONpIqGk97e4HofoDzR9HU7bnToUZ5oSz76Q7q6jkTuSbWe4G5n379EE/Xr6yf0ijN9dlRGU0H10cux/tEBK9a4sKSfiAeueTiVGip7v21mYfeANQUL7qsqIZDtWjSwvl+5ZDzEuQhLEZEe0D3VPx4Q5JXHCwFKeWBpsvvyrTXfJsLl3rUXjxE6i9ikTfDCELxneZyRk8vQldY27L6ngAzrjnz1acv3w== 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 SA1PR12MB7200.namprd12.prod.outlook.com (2603:10b6:806:2bb::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9298.12; Mon, 10 Nov 2025 06:57:37 +0000 Received: from LV8PR12MB9620.namprd12.prod.outlook.com ([fe80::1b59:c8a2:4c00:8a2c]) by LV8PR12MB9620.namprd12.prod.outlook.com ([fe80::1b59:c8a2:4c00:8a2c%3]) with mapi id 15.20.9298.015; Mon, 10 Nov 2025 06:57:36 +0000 Date: Mon, 10 Nov 2025 07:57:18 +0100 From: Andrea Righi To: Tejun Heo Cc: David Vernet , Changwoo Min , Dan Schatzberg , Emil Tsalapatis , sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org, Patrick Lu Subject: Re: [PATCH 01/13] sched_ext: Don't set ddsp_dsq_id during select_cpu in bypass mode Message-ID: References: <20251109183112.2412147-1-tj@kernel.org> <20251109183112.2412147-2-tj@kernel.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251109183112.2412147-2-tj@kernel.org> X-ClientProxiedBy: MI1P293CA0001.ITAP293.PROD.OUTLOOK.COM (2603:10a6:290:2::8) To LV8PR12MB9620.namprd12.prod.outlook.com (2603:10b6:408:2a1::19) 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: LV8PR12MB9620:EE_|SA1PR12MB7200:EE_ X-MS-Office365-Filtering-Correlation-Id: 382abcb0-b949-4134-0afe-08de20266e32 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|366016|1800799024|7053199007; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?t9F3AIJOCfYhZPs7iIe2o9GetklzUXHeYQGLWk1O3mwJ2Q0+Dnjuuz9n3GNS?= =?us-ascii?Q?crc87ScCbxbs4gnaH8c9FA7pSxF1ludXZsHKUSXQoF3bIGkjA8mNCklRz+xx?= =?us-ascii?Q?x8n0V56VKML9a2f7ljRDzGVlI6xo09n9kUEEIrr2xl2Jnn/bUNPDtbuZIF26?= =?us-ascii?Q?rzmU7bKR3iSrrDX98dsiO8nfzy4dWjG5r2zYKhC/WCnNUDH+xD1xRy4x7U2Z?= =?us-ascii?Q?qrO/gM2nKKnV5U/vg7czjTvBZ1hfetVBz0yGDWuzvJM/KIBnKNcIjWauy83S?= =?us-ascii?Q?9bMlWCZIHqEo151HlQrHxEQasBrgCvqYab1rGa5UmximaNvtdgSYJMX+NwCM?= =?us-ascii?Q?N72OONLHW13faXD/NQdxva9GSdZ+0VtjVoR3VujGSivUc6cNNgo4ySUg78Rw?= =?us-ascii?Q?eBZdfmH/qR2QAOLHWPvmUVdCOU9ktuCBlba7sgOrCcGn62wgQAX+VkP52Cqe?= =?us-ascii?Q?kDHG35sq1rUuDASJbXJyno8zkInKgpAHmMETjIhF7Y3cMps9lJ/xP6lkWpu/?= =?us-ascii?Q?i1TKbjB2ZwBHY0YNVlzrPfRkT7KbPgW2i7WYJLnOFTKKSus8lOnrCzXvQIuT?= =?us-ascii?Q?PY/pRmLYaLg85fcU2ZlU6DnpiAm/kR2QiiPbPNTAgVTwCOlIl+MnXPbMN3xH?= =?us-ascii?Q?B52cmOpHU+Ws+hK5tUPvimKzt8IkKegg5SFH9F+/ql8+ux9XyXWFgT8e6Iza?= =?us-ascii?Q?3vjyZOIY9D53Ukq32Jcp3lp7DQ6ZS0eKFIgURG4ctBqMK2c3asntdEQ92X0/?= =?us-ascii?Q?XnZM1RE3Urwqf87ysGbHZL6LMqnv1qOXeSAnH2labYdMDJcZrAaiVv3p5yNy?= =?us-ascii?Q?mzUZJ0NkxxJwOczxg302BYuWmmXtb+axZafeAS3hD34CYVbbO1vRMva00JbF?= =?us-ascii?Q?RMIu0yAPyXA+rCKLrtZDhVmQYEzx7aoLrpDWHccaFEepsEeFMWniIZwYzYOI?= =?us-ascii?Q?pfzxinQQcbj9ZuoOG2SRSiTUlzN6N7bC57k7BvnpCiZzOPccfTmWxytDDBsM?= =?us-ascii?Q?g0iGw+t8fWIPZPDoLfr3BeKW/2zHjCKeBDWmaIWPeg1xsrS2UXAkiwFJUyqw?= =?us-ascii?Q?SZI7DhNWX0OzaPEJ1plp6MuBaejZqkFv3VHWR1rbAeReWOE1orj4Ys9SM1xJ?= =?us-ascii?Q?gYhuOJ3k25hEmqORXwZtMyNzC3rZhp3I22Rsu+vgWaS4RSPeyyY9OYnk77Z9?= =?us-ascii?Q?T28tHPjkotnVisUzdePKperI7k1xlu3HDT44nER3CD8ZppsR+T03Ep56BEvB?= =?us-ascii?Q?jTaAc8c+Wh9iYidzgKfjtcxYVt95s8ejjR4z4e7JW/hxOvHMoCk+GgN16s+w?= =?us-ascii?Q?KJGVX7mQF9dAFMjGkhP8lKb28kqi/Q1w2c3172ITnbWzAYuXPSBR6xfVwWjw?= =?us-ascii?Q?XiGzFpTe4HaXbgBFomP529Z0l5nxap794UF2Vg9GVE8/ETacdx8h1xaTnqYb?= =?us-ascii?Q?MUlvGy2ZjIUjK5RGxoLBsuQxBvbrtIzsSPFyELHJU1setw9VDXxz+A=3D=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)(376014)(366016)(1800799024)(7053199007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?ERPVAtyHJdQBVO24GZgyFCNmDg4jZThwWFjfD3USkKteZPLKRQi4N/0wKF1C?= =?us-ascii?Q?rIup+DXZdG14QRhilmpYHLUVPGM/JcautCeKOMoJWTP/az8fvOOkeU2TfAcJ?= =?us-ascii?Q?dHItunffgGmlTWTzTTVNZYnXOJmvUzRlOgMCqKZUejZNcHziLkQi79HzzwyD?= =?us-ascii?Q?4eNz2nYExY7E5vGdw3lgpNliglnNqyH+eIAYhhor//Up8hRjEsuETjThIF0X?= =?us-ascii?Q?eq/OM6NbjyYcgs2WROXGc+BAZI+3BVC0bvyii4LNPe9r9vaSjwEVLcEnhmm2?= =?us-ascii?Q?2tWMD7781ccyMlJrHbrjskRNYT5yWoGOI0o7Tf2K4rK5YksjkMwHYucbXQVF?= =?us-ascii?Q?7ZskA03Sa8EjTZmRVKJridKEkviyLScmJWqATbZglv85GCYUcELX8F9QuIks?= =?us-ascii?Q?6QITHArJQmhSpdYGn7w5RUSRwLJVRtvx7PtU+KhHz+qMrqyvmoUAmpM/c/w4?= =?us-ascii?Q?NoMjOhEy6ByBNdBXU3KwO/PXTT+hz6CX7pvypByMYCWpNgd8Jdfn6ZDY2a5g?= =?us-ascii?Q?iL5xybhKNccxNW0fFxB9Hw3Cg6zN2HngScYyYLdy0hbqKf9+795NPXT3IuWg?= =?us-ascii?Q?uGwK1vQb8PAtaQAI6jUiwGYad/WLaKIOks/qlDIncWVlUQvwR9vOttPqihmg?= =?us-ascii?Q?NXu+gT1oB9HmBPLIHk3v/+hLYbuNOFPLWhjl3Ljt9YCbe+5ivsPxHiTVjAyV?= =?us-ascii?Q?3aVM+/I6kFYAmlbxtp8yDuRfM/LjYj7WQZ2SxMDzBz8MZ3EVpC5MEGAsHiur?= =?us-ascii?Q?FcUmMJP0i6Qg7n0yrxv4/3b38uRQKCGm4PBx4i7M7tnXkEUl7dphnJzcZrc7?= =?us-ascii?Q?6LRmg4DZrAUVj0dgqWrGpsDlo1IkbNJJmObfMNqq/5g4Dv+p+OmQNc8LMVXi?= =?us-ascii?Q?VZQBE7bhhnWdGzaXaYpluQg0Ymh5AEp8E8pY1FcDzWpFfC0GReR68wLQmE6w?= =?us-ascii?Q?mfXgpFFIx2qyu5nezMEdjQc01dKCYQ/RqiR35PpR2zR39pVw+SohQVvhgcrU?= =?us-ascii?Q?B6A4IG6ilcRBxbpN4RBouVWy5iqGrn/xRBShJRWu3j6PVldauQp3m3ThJzmB?= =?us-ascii?Q?rjeZGZghkIc4xFIQYxbbC3gXpzLBl1IT5A3WQgurxM+hcsgbcRv6VlspdZFx?= =?us-ascii?Q?rxhVAvE0YO8H9+J8K7A6x5p3G38Noj+tiNJuPb8ror7Jr8bYRF5zyLu8WxHF?= =?us-ascii?Q?PlcNOYjGPmoBeiO1ki/NqZAkf69Xz/5E5eb36rR8BuszzUcSOJjLn+lM0ldH?= =?us-ascii?Q?hENwxGB8J+kzDwE299r07KZL+5yMEoo176e/YqLhzpOU1sUHtR05LRDFVjqZ?= =?us-ascii?Q?bXdZ48YJ9AnSrDeWXTJHRJy5ndQxbq/0is3cDcJR+TF/2HRcMjfEY8khGdf0?= =?us-ascii?Q?t7klp22wNC2Pv1kejGqcYDQRwSybqvWHlOcKe8Ouz2HqEBnMZ82OyePILlNn?= =?us-ascii?Q?vlEQyYHuHd4CCaKZqU2PwWWHCVd6IiVh2mUkT2kZzdH/jn1ROFAoTp811ELD?= =?us-ascii?Q?LP9R0N+zhh7yQOZVVmL18umRL1GIVGYqOu4J0x+hPBP/dAFJ+aaZpDLxspRG?= =?us-ascii?Q?0VVQs5pko+7keQpoUpvplLeKAF1oDwHeF5bSZfVI?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 382abcb0-b949-4134-0afe-08de20266e32 X-MS-Exchange-CrossTenant-AuthSource: LV8PR12MB9620.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Nov 2025 06:57:36.6072 (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: d8dj+t40EnAU5PFnxPyt032Ib/OEo9TT35l/WZ+Tt1Qr4LmK7DaaVVxIjuhXA7u3NW66uL5SqmbrtQx8ZmBPkQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB7200 Hi Tejun, On Sun, Nov 09, 2025 at 08:31:00AM -1000, Tejun Heo wrote: > In the default CPU selection path used during bypass mode, select_task_rq_scx() > set p->scx.ddsp_dsq_id to SCX_DSQ_LOCAL to emulate direct dispatch. However, > do_enqueue_task() ignores ddsp_dsq_id in bypass mode and queues to the global > DSQ, leaving ddsp_dsq_id dangling. This triggers WARN_ON_ONCE() in > mark_direct_dispatch() if the task later gets direct dispatched. The patch makes sense and I was actually testing something similar to fix https://github.com/sched-ext/scx/issues/2758. However, in dispatch_enqueue() we're always clearing p->scx.ddsp_dsq_id (SCX_DSQ_INVALID), even when we're targeting the global DSQ due to bypass mode, so in this scenario we shouldn't see a stale ddsp_dsq_id. Am I missing something? Thanks, -Andrea > > Don't use direct dispatch from bypass. Just return the selected CPU, which has > the effect of waking up the picked idle CPU. Later patches will implement > per-CPU bypass DSQs to resolve this issue in a more proper way. > > Reported-by: Patrick Lu > Signed-off-by: Tejun Heo > --- > kernel/sched/ext.c | 6 +----- > 1 file changed, 1 insertion(+), 5 deletions(-) > > diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c > index 652a364e9e4c..cf8d86a2585c 100644 > --- a/kernel/sched/ext.c > +++ b/kernel/sched/ext.c > @@ -2521,12 +2521,8 @@ static int select_task_rq_scx(struct task_struct *p, int prev_cpu, int wake_flag > s32 cpu; > > cpu = scx_select_cpu_dfl(p, prev_cpu, wake_flags, NULL, 0); > - if (cpu >= 0) { > - refill_task_slice_dfl(sch, p); > - p->scx.ddsp_dsq_id = SCX_DSQ_LOCAL; > - } else { > + if (cpu < 0) > cpu = prev_cpu; > - } > p->scx.selected_cpu = cpu; > > if (rq_bypass) > -- > 2.51.1 >