From nobody Wed Feb 11 01:27:33 2026 Received: from SJ2PR03CU001.outbound.protection.outlook.com (mail-westusazon11012047.outbound.protection.outlook.com [52.101.43.47]) (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 221CB1F12F8; Sat, 3 Jan 2026 00:23:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.43.47 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767399838; cv=fail; b=QeH6qJNDQigkniRPTB0do6l2tBIVt9spMKV4dLlw1MDTosHkPLraXi8LLno7cZsOnyOkJnhxgyK70Ln6y2KOu/W7aAu3tGJxQXXKJ8SBCa/iALA6tMWdWGmDNJWTravnZXR7j88XOQqygVUC3GKYoQjof78t0RVgyKxIYFTkC60= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767399838; c=relaxed/simple; bh=ExcAwuJ2csLNXiS13QHqPi/N+MxLxiKs+x9M5EunpfA=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: Content-Type:MIME-Version; b=Dt8Teg67CxJymC6oVXy2LcOXsgTOwHfbldrRBJD0q9v1p9lpby7Gnj1BQ7xtehGyvX/bAH+WUgfkSm3IvOLeolzKyiHvNr16fklq9/eihYZsCVrbBDAFBjXt85u/W1RtWJPW/+x0U6bNpktG1Qb92fIaF0kEBqMR42f3wl7xlnk= 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=aYOqufjb; arc=fail smtp.client-ip=52.101.43.47 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="aYOqufjb" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=Ebb5JgUACX4+tXuPtZZtEsZekF3bFSszWtCZAqTesXD12vCQ0hCIw29g8edjcyrauv5NKdgnrCzGbp0/6mblQevahS0E26x/23gPSq602L/V97F0hPaZlXtjDgWFkhkQElaDbHOxrt06LVpsdrQRRCnwVqZzlNncgZUF1WtEqavD55XCKvQkrCLTwn7hnHsaUKssFsBzs9mqmURdvX9jp3+Nnat9tDrs1zu2xesyzhKXKVWAgq0iQDLHv0axXcFoGiKKdLTJ1rA2VBTg3DZGYQyogZd0X1fQjxmGk+o73ZnPnGCBcuIR4ZvU4c/Onjinr/1OwDfZxGAq2gZ8yu7TCA== 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=90vscRQZ/II7DHa0WnbCqijbVsbgy9+W9TxBcfWWipc=; b=tCd/Z0ykjLHhuXM1qwZJ87uz4Og9vhR3ulzQluqry1OxgOZubpdzmSItc5YUcYkPy4+8+HIIbCumfHwEjUl4d9YIBsWe50UWM/9y6Wt/EkYvauIZcA6nF6rn3fSTqb2/8HIg8oKUGp5tZUQCJx9f2MjanRf1Wq5UKgOUIWd74NbeZCWs3BXhyOx8g3enzNvAFzMFFa9vcDL+ezUDg0tVAcxCz4GmKJ6h5HSmhJEIn7R77vmcwMi45OiDo/wyTAljCeiazeqkEDaTaaAmcugDWtW+bGCSDN+JJx1SVHYfUGnWAtazRvz8s2//QrytYlthBxTdNOxDB6cTn+6Prki8fw== 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=90vscRQZ/II7DHa0WnbCqijbVsbgy9+W9TxBcfWWipc=; b=aYOqufjbcwwWel7RjvArXlTwM7mZwVU7D5l9gM5ypgKdV6dVGp/kxGZ9HahECJr7Ye0p6r+jqeV4j4WlPYzkadYOBSRbysKz9QTRBXoT5mjpo7Vtg/0HQcO23Q2WU+1Nsu0MFOFycJ44xTKChN6Vg6zKBmQ7FGdt4JAIzreshyzIu6eObzg0LL72/ciAcENScDFbaESASUbA9HKs6gp+BFXgPHQrIsy7+gGGLivy0o0H832hPJqzi5Bqd20uvYrQ1uPpziqGL8fOm98wBoWhvZxGoePQpvW0m8Y7Q2jBLjLOUO54r5NFwa74TDNww/X/rmgYfsVIgwowTlDx+5bXyQ== 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 CYYPR12MB8872.namprd12.prod.outlook.com (2603:10b6:930:c8::14) 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 00:23:53 +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 00:23:52 +0000 From: Joel Fernandes To: linux-kernel@vger.kernel.org Cc: "Paul E . McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Uladzislau Rezki , joel@joelfernandes.org, rcu@vger.kernel.org Subject: [PATCH RFC 01/14] rcu: Add WARN_ON_ONCE for blocked flag invariant in exit_rcu() Date: Fri, 2 Jan 2026 19:23:30 -0500 Message-Id: <20260103002343.6599-2-joelagnelf@nvidia.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260103002343.6599-1-joelagnelf@nvidia.com> References: <20260103002343.6599-1-joelagnelf@nvidia.com> Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: BL1PR13CA0178.namprd13.prod.outlook.com (2603:10b6:208:2bd::33) To SN7PR12MB8059.namprd12.prod.outlook.com (2603:10b6:806:32b::7) 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: SN7PR12MB8059:EE_|CYYPR12MB8872:EE_ X-MS-Office365-Filtering-Correlation-Id: 2869a382-d6cf-4b0b-eb0f-08de4a5e5fd4 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: =?us-ascii?Q?ElHraaGc1cCgAbcaEuTjkqzghLX/c5Hu0I1EbXNnHNmhy66Ml2bqjiMYhihU?= =?us-ascii?Q?2UczMflupsDzcEXvRnIeOOMllFStPizhVKg5BrMlUsmHaOQnc/D1ATIChNBQ?= =?us-ascii?Q?8EdxSeyGG3DG0bnd8wSxt8KVp5jYdcjKAKqX2N6m2K0LMWC4+3+AOkdhOsud?= =?us-ascii?Q?qgwnBaQFzXLnHNxZYfATPMXqxkcU2muzqMl9ipwIW6B4p/ZYU2bSn+azB4Ru?= =?us-ascii?Q?nT1JF8W8IA4D71K6tjihk4z2AIrwwNtgJFRHBQVDvzQcS+vCZsdVUsahCOwN?= =?us-ascii?Q?lzCtAI6xWn1dWMxbUIbomjOKai7F+D5c8WkswssgwZmBLTlUb5olKD7jZBhy?= =?us-ascii?Q?EL2iH8aj96x2oaByRLuM8hpR0qJDfDnb9Y/YZZoHrgLVyGAwphbOa1VCaH6H?= =?us-ascii?Q?P/pi9xTDtz+wdeIb0U5btNnOdUQuoUra/YRjQ9irAFdBY5rkazpFOVlUQy/n?= =?us-ascii?Q?h6CShsigJYoPMiEYPVBHnC+/e1tEThFBrJkxNTfZqj4pVW7QXyOJIs4qExe5?= =?us-ascii?Q?zbCHTI38Hxyr9I01udyw9bpidDlomDObJvougmYU4cMBtKtTx9Qu51ouA9f2?= =?us-ascii?Q?Jjo8J5HM9mdZ8iq3O+vCD0okm6OKGqbrUDZlueXL7UI4MG3biIPM6KFW19Jy?= =?us-ascii?Q?urCj8U6aqOuAAolFC1HrAPIh0kLi39EahGFR/oeA4j35aOpcgIZ05lWIWvAJ?= =?us-ascii?Q?XAdK2wA9dQ7jD0Z89oSBTFKnxfgvaJMMi9SzHu1PhWvYJTfk0xRrola2Dtax?= =?us-ascii?Q?6HTvCWtTmWpNpb1fcBAaP5PAfxjSVWZd4Zc88zLEE14sdX+F0iz5RTsxPe8V?= =?us-ascii?Q?riDrsMB0m1/4M+vn6h/8oxoVFmLHUjZep4dGXNl54sGUDpk5RBm0UCVnq+lS?= =?us-ascii?Q?NwlN8ybr6U9G+pxFoE3bLeLOuiSefeN+o1zm3lQDuMge7lkl/YSo999OYcun?= =?us-ascii?Q?MjBis/n5ac1uRHypOg1FIx4odgZAZPz42g2018RHcHaVj4AJOFK2ma5bZ5Hi?= =?us-ascii?Q?zuJpqmic6ptm7BsuCfLWgymM9wtynTtYqaCzU7Vbrr7RspioQk8ahK82MiPO?= =?us-ascii?Q?vpScLPgE/fNM0UJXBEbD/wsbZN3N7bH8K8D/RvQbPHGFsPPje06I5TqX/CGX?= =?us-ascii?Q?YKHcwqZuyUECiS/TT4hphIBCh4hpHuVK5erzH1rE2qbAvDGWiomBB/gjdYrR?= =?us-ascii?Q?AO/mb9dS816Mtf5YQw09YYTiim4/RYGhQJf64GHrFYE27LqDc8IXTeClEKDT?= =?us-ascii?Q?AXWIpysi9ajmYKcgxrdoy5F0cNnWcLMhhj7clz6jvvJY/HU3lcypbn1RobHO?= =?us-ascii?Q?7+j9mH8FLQPFAQF9CWjSl819stAfBCtrzA0zVcR9E8vEObtt0CMy+GZvOsGn?= =?us-ascii?Q?wc81NjA/rYwR/VfqRq5neX07H46cQczlAWIaJNb46sSfeDGRwcGJLz4BOM9E?= =?us-ascii?Q?6TFUyXsGQ1WQAXQyIb9+ZYFBuBSoSABH?= 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: =?us-ascii?Q?QsjgvLbl4bLv87AjjKOq8LRAlC2gVgYbk5GU1a+e2iWk44sguIerCF2zzycj?= =?us-ascii?Q?pseWfyfo0e6NZGbz+tWcZ4OhbhxlWNgkQoihNlY4cHYtbNfJ1H9D+m03S/wp?= =?us-ascii?Q?lTQbwS3IuB8SEI9mdhCc1kQXqL3BueoQT0cCbZMs5upIq3ZenbIs2rXi/qFc?= =?us-ascii?Q?tERIlSrPvqY9n3bTFIazWljf7WtKojeT5sk3hJeKcr6eIEOE7htDhuikovm/?= =?us-ascii?Q?raK2FJ53umzC3TPRESg1G2jQy/YVwFIWQramCQYCaLBzTfu97POTUH8kL/Z+?= =?us-ascii?Q?bvBTl5PUGlhgul3qqe5lLKx1FxPhqZcoAspFldm5Ycmjbe1FLqHULWgYk5n7?= =?us-ascii?Q?arwImGiPW6R5LOysLh8/6rlUuPUq5O83YhOulJBVNlPVqC8H0gip5ZVVUgoE?= =?us-ascii?Q?WZE3tg12DfAenuj9r8MOAxCzrpZkWH3eQb84tSugWdYdiyR1F8MGIdej/f1O?= =?us-ascii?Q?rJ05+IAtaHAPS7qqIEMuJSz+L6Omz6Ps3UgBaBCpceaioZu/ZHAXqGu6yEIa?= =?us-ascii?Q?YpIL6ZsA0Te1nrtKkIBBj9oBrjzKemVlnUMYHiT4UlICdr2ko8VdoC2EQCL7?= =?us-ascii?Q?9LxKEI4UyDm4Iq2zB6YMWujRld4zOwFm3TPrTHW0apoXRmv9xSqCyan/3e+K?= =?us-ascii?Q?6d27y0zTtAhSeKe/myTlPQr7n6uhToqnq4xR00SX0jvjGudM3+c+EULToEsF?= =?us-ascii?Q?AVCRBZzaXhXiGTwG/CTI7Bt2d+E8CXGxXbWGUrDDYeaOCR4V555wtz5DlZKv?= =?us-ascii?Q?qDm2/iOLJfx9dr48HNbn0d3GTEj8uppxZQRiOpwiyqf1S2bytHsW9MdIulMn?= =?us-ascii?Q?xj/0JetIfMuQrvJggPFdcXAU+rpnd299i4keZedHP2+K/dvqmq3cmiT2ECPy?= =?us-ascii?Q?xRvGc98o5MzynTsKBJV1NmKTZR5T9qAHBx3sfoSZb+k6rUoPPQP2iBL2RXzg?= =?us-ascii?Q?DuS6mFrfVZC2Gv42HUcUcyIesIoY2OMjyN3ANN3qwNCC5A4BFfDeEb2xSWjZ?= =?us-ascii?Q?Cpc1DiLtgG5fheK6P8N/SkOLsVombWmO3sb6Ah/nslCD2Z7uaN9b0FmCCWLm?= =?us-ascii?Q?rdKIvqkURg0SKgSpHZUWEzuEtHv/PIIN2bgKLuw9AK+MR3wIzXePya37PXOW?= =?us-ascii?Q?xdDkOhPz2lL9esqBntd/8fLvHmBvtq2hDAKS9g9VCC8a0600lmQBAYmAjMNr?= =?us-ascii?Q?H12QOzw6L/fzBljbGEnt9jm0IiNxZx6SbixqVzhum885Pa9vNnhQdbQAwG5A?= =?us-ascii?Q?Rfm6zTNUNDE5C22i7yiaYBIz9NKm3DfD8jA3JWxq3EeKu8gx0SXFzVlhwJhU?= =?us-ascii?Q?5G2ejVfuuMl53Mpsck4z+7gnZIgGQTMpMys1Y3Xuk9/xEneoAUJYm2XU+VvP?= =?us-ascii?Q?JGKae0EAPGV7SeO/rCkdwgKtp+oji2rLoHLuUr+eLDArP6xhV8vb0qlRatz8?= =?us-ascii?Q?13n8Dv62k8hyyCecJ+dqxcC+dGeVvKvndr6fC/qNVGMlztZChvvpZQe6+WXp?= =?us-ascii?Q?XAcFLpYT5NZsj4aKBHZoNe9+8hQknr+2HJ+6FROo+aBplXKvBLEPdo7hGatw?= =?us-ascii?Q?f7Ow2awXTE29/lwJ85+Cr4OLSNsZo29RaKWRvYqtdqr2h5qaBRde6QGbiKUg?= =?us-ascii?Q?acW+nHSR5FWJWXgSUqnplgItsa7eh5BrXYFZjxGn61oTG7oVZI9xQ97Ti1Kp?= =?us-ascii?Q?1SVCI24pdHxV7NpYRdaXh677qqUvLK+KRp5j87OM+zAjfDytokW6vlivZ5jj?= =?us-ascii?Q?o52vd41NSw=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 2869a382-d6cf-4b0b-eb0f-08de4a5e5fd4 X-MS-Exchange-CrossTenant-AuthSource: SN7PR12MB8059.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Jan 2026 00:23:52.8935 (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: H7pgCF5kee7ldy1ptrVtVO0xOe8W12FNwuZMe9KLZgATQQBbiWWHiGmNCh53RDmJQ7rvjG+qmLThL8XoV/5U/Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CYYPR12MB8872 Content-Type: text/plain; charset="utf-8" If a task is on the rcu_node_entry list, its blocked flag should already be set (it's set before adding to any list in rcu_note_context_switch()). The current code silently re-sets it, which could mask bugs. Add a WARN_ON_ONCE to detect this invariant violation. If this warning ever fires, it indicates a bug where a task was added to a blocked list without properly setting the blocked flag first. Signed-off-by: Joel Fernandes --- kernel/rcu/tree_plugin.h | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index dbe2d02be824..73ba5f4a968d 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -846,6 +846,7 @@ void exit_rcu(void) if (unlikely(!list_empty(¤t->rcu_node_entry))) { rcu_preempt_depth_set(1); barrier(); + WARN_ON_ONCE(!t->rcu_read_unlock_special.b.blocked); WRITE_ONCE(t->rcu_read_unlock_special.b.blocked, true); } else if (unlikely(rcu_preempt_depth())) { rcu_preempt_depth_set(1); --=20 2.34.1