From nobody Sun Apr 5 16:29:00 2026 Received: from CO1PR03CU002.outbound.protection.outlook.com (mail-westus2azon11010030.outbound.protection.outlook.com [52.101.46.30]) (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 75BF52940D; Tue, 24 Mar 2026 00:14:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.46.30 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774311282; cv=fail; b=oojYdyM+hsG8EitdI2rmb4/psQGN+e+V774FG2XjBx8XnXXkUYqm4xdC1yPw3pPXynIynDcHUR7X6elVWiuPFkzVpXYxIznptgLPPdqvB5PnjA37WkgmVXFqy0TE/fvQCZxJC9+meaCqrtOzfdP4agwpRkt2l5eZhpncMXR/r0Y= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774311282; c=relaxed/simple; bh=1hDOyodo+9eFYTqwLnDGYeKhueF2uPcDT8dZ0F4+7W4=; h=From:To:Cc:Subject:Date:Message-Id:Content-Type:MIME-Version; b=loAhfOm/eXTgY7OAxSuJ74MRtXNC7gMtzRf02z0N71M3bDI7bb9UQF2AFS+DTiPCEx8EAR3hsGVB5+9Wp3QcArOaLN2KlVe0bqYwKS/UL4kpyxDNG9bduBZrSQBKpa88waUrgqgJpaB2wuGRYt63Yjx2Qu4qZgCtee+dJLDbYkM= 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=WnqsRCFT; arc=fail smtp.client-ip=52.101.46.30 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="WnqsRCFT" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=xnIBa7CuS/oxJibOYVg8S3Ze8nm5FQLUKRH/8/+DHuBKOU+Xy+uxLVVUDFTfuaEPsnVt0ouWVT8+oY07GhcODpHHjcDb7/dSvQFZ+ahdOWsrGBp5uQ2Bx5Z030YLOkOr/54PnTRhSsBzMcNv6tulfxvVFNlEufjLY07/HXmlWA1AfBwuqq8tur/z4eA4/9PJeUFQTXyWL6W8P4XOhE4gpqGhphxqn1ujwOF7SYo1KuHfEe4YkHC4dy9ju7fzWIK4KaOudHC+yCKZfim7O9xfD8eQ5HXI9wFJwBwKycKCF6Iq3ZbZjDOS05LlaKLwBBh1VXX6j71p0OyA7xJxDYN3qw== 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=U3K0zxHkNFmZVnUY1uw/twkJQU6LMa6O2SV09kxYGsQ=; b=OzaDv981+DCg7ooTseTV2YXQplkPFGFF+vbRhtz/ngZG+DYOc3QuR6uyUQdiqS4leEkEm5Dn9SRtuQhzTrVCD+N9hSwojErvrg1itHEih7c9bZU+es/6GPbm85Ld9DPWKQPpWcq/B6kmBgq8oP4W9NDahOUa/Gbd4w6v4IQQBVmH3E53cj86mFlqKANr0eVZLYU04HC3UbHAEjm0Pw7bpGcSqrh5icGTzJUXYEwEe/kqS/j1EQyVjpRfD32imMfN58fGqjCI1MTgvQ4t2KsGYg5+luY6pdoLKgK0UUtOTAwUcJTP4NWRcCg83Ui7sVfE1E/eW2vfXBBgeDgJIw4UoA== 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=U3K0zxHkNFmZVnUY1uw/twkJQU6LMa6O2SV09kxYGsQ=; b=WnqsRCFTr/jocCeCjiuyZvqAi4MNsZ3XiYSvOub5cutvda9A1OK/Ca4b/vVVzfKXwr2qkzZXZSIk1JJ/2y5xTJQH6sHTaxRf8V9By4bgvAgrgqmSB2HjU98bNuy7/r0QmsNsmEwSLMX4fS3p/8WzFMEVqfPhpdX627htwn3L9DKDriXs6q8gGxsqdDR9pKZsN/TbNNqcSzn2U4NuuuHz7pbfo7K58wfzjBrxWWSsOeFuwk3rfOVh6IVEcDcGswarkgyGSwdjulP+x9jEv2vAt/hrmI4KsLgdyMWTW9bcdhUtrxBNpt0Eqr1XuGTKBVFjavMkNq7OLvlZkjs7Flq/RQ== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from DS0PR12MB6486.namprd12.prod.outlook.com (2603:10b6:8:c5::21) by SJ2PR12MB8782.namprd12.prod.outlook.com (2603:10b6:a03:4d0::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9745.12; Tue, 24 Mar 2026 00:14:38 +0000 Received: from DS0PR12MB6486.namprd12.prod.outlook.com ([fe80::88a9:f314:c95f:8b33]) by DS0PR12MB6486.namprd12.prod.outlook.com ([fe80::88a9:f314:c95f:8b33%4]) with mapi id 15.20.9745.019; Tue, 24 Mar 2026 00:14:38 +0000 From: Joel Fernandes To: "Paul E . McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki Cc: Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , rcu@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] srcu: Use irq_work to start GP in tiny SRCU Date: Mon, 23 Mar 2026 20:14:18 -0400 Message-Id: <20260324001418.89363-1-joelagnelf@nvidia.com> X-Mailer: git-send-email 2.34.1 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: BL1PR13CA0142.namprd13.prod.outlook.com (2603:10b6:208:2bb::27) To DS0PR12MB6486.namprd12.prod.outlook.com (2603:10b6:8:c5::21) 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: DS0PR12MB6486:EE_|SJ2PR12MB8782:EE_ X-MS-Office365-Filtering-Correlation-Id: e8dc5536-ba20-4f00-2268-08de893a565c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|1800799024|366016|18002099003|56012099003; X-Microsoft-Antispam-Message-Info: rtijPDGkT5qROkWPacPnMw9SF2LxDKKb/o0+YJvRZg0k9o9eBt7oBf/bhJrnin35rMqhKilox/cnzyK97wX51n7IC0luKdPsJCZZkHqlt0ihFQyT+8NDRwj/LIv76pNxBxnWik3+wQXgKIB3FpkfcrgKxGIvbz2+XuiAQvK3SQhkMa2lo7cV1WySkZpK11EoryXDsafM6+3b408/OEdPFF1/YItq3cCeww6mmimz5wOsXRgY6Lp4lzRqb4P1EQ4WVbYubXFnShTu5P0ParpGuaVtJn4OEj3Z/zjb7IULzMHF6ljEVazHXV7rSSbSvQ0pNmffRdT3Mbop6k7Dtit+p/X2BA8vaZaehU9Yiq2GIQm9pmYRsBErW7tOVwBx/1YQU+9rr2o3FVNHvrDX8KOU0rTU6w3vUWglLC8mkL/wTjBWT/uyu6wT2+UFZS/KaXNgaljP3Eo/xucKkKHaKliwQ9YtwrByz059extA7SORc4nV3JTtqy+cbzFO6kKADJ4W8lOpolgSz6xWRcrfHQGJpXB9JeVDVuQLUdET7iKY4LmA7n8YOeZZV98KLhGfnPd1YlWW14e56KcK1KAVOqOHQk0A48mIvGu4FOcykM149KN6/6epq8VWG+uFbEord3Rx6wctYvYNNx52PnDQKnelYxiLUAi8RB+h1qoBvNxlPaSum9I0/CJML+I8S4gWM3r+oHwfsdrafSpAAQiK/VGXS7g2HWGLon/Fi+/qgEoE540= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS0PR12MB6486.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(7416014)(376014)(1800799024)(366016)(18002099003)(56012099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?ndQpFtKn94b2Hv9QyEW6Htsft3kJgvmsmgTobzhFuXBsfBhZ4T0mOnHI4gdT?= =?us-ascii?Q?/PYk3kaApv5xBcP5pb9pa2g0HIYJ5Le2uLltBoZ9RVHFl0Vn+zPov9e4FHqb?= =?us-ascii?Q?e7CnyiqfuBcdFcgQ83Ip3/EV1wQLVl/pWaPAgvOhQhGHTBe4dLLAQJZJgdGR?= =?us-ascii?Q?hAxRxUtH+CUl7Cr9j0/ag+G/3+/fp3smSA5YMiGrDa94360HhB3u68JVjSg+?= =?us-ascii?Q?w9QEeCca3LL+2a7XDejBXmY4p6Xp0sJY0GxcXu+KnJKxa0rEzseI4gAikhMo?= =?us-ascii?Q?W7GgAQqd/HVPGkglkerG2OYBE+yQW4fIAjslhQHh04kbivL5dAsTdYuZuuay?= =?us-ascii?Q?j+lIZr1Dzq9c70tLYzPDfmCoLySp01ZA8VnZ62M5Hx7gWpqYKOXhWC6TNomf?= =?us-ascii?Q?6XFaEgBxERsrciMBFqpGctkqDCT9mgjvmh0OdAshzJnAegj9vQqKJJxB+lGv?= =?us-ascii?Q?VM4ooQUk7ejwMJkRPE9Gb3hLiPSXafs1+MdPDccxiHhRwinFqbFpml4DSdNP?= =?us-ascii?Q?OrLBOMz9nCmEo+h4KM0Z+Z31C176Zs95nKMhVnC0YlXt9y8znOIkOAoLtn6R?= =?us-ascii?Q?xI8e8J+iNR15GkCL+i7fDaCknIhUL0xyfemmqQn8lOf4yvCMWN+M3e00AHYq?= =?us-ascii?Q?te4YKOvTtrH9FPtrI/cazQlimM6smgXWuH1a5gBsTny5+GNhnkmRe/VBaikU?= =?us-ascii?Q?atE5IDhNNIud5SrnR/iRhoQXcZRVs9CZUXlngk+pY3YhFJnO9RNtBJiOudWX?= =?us-ascii?Q?ivyqZK7kXTgF37Q/78i9+MsvDiwYR9iHsGPid8zfMw+WfCHjqVE9DMZYeDEV?= =?us-ascii?Q?a5zqk/GSIGifzxnFb/6IawU0jc7A0Jm2kFNsx7lPRSeQt+5aNSKsQtf6HX+z?= =?us-ascii?Q?FpRJO0mxcipi19m+LJqg7bUpx4QTm7M/nox20H9itdV615cuKV+Y4UZW5JYM?= =?us-ascii?Q?8Rpmb8K4qO5p1dUoK97TlHNBu/JWWF6syqiz3wuMfaNTgEwoKL+g2J2D2yAV?= =?us-ascii?Q?yXFFYJhLEInjo+p8VIA+e9s+HotiRPqnXH1/n+JdqZgHna37tmLYfscxpxex?= =?us-ascii?Q?hGnu4A2J9Dy03lryC6EyHv5jpxJf+VkgZo+Y3zQMWBdklmsGnwkAHRsQ+9ki?= =?us-ascii?Q?69o2GdjC/+o9lF87E85ssY7IGrbWlsa4L/dHe/CuEsOeTDhHlabwV3/+gG52?= =?us-ascii?Q?m+BpAOgs/5c45EPaF+BpvqWVk4tRz9aclmxpCem3vy1rQ+pOMj05bC8Kp8vE?= =?us-ascii?Q?IF9GYNiZOwJTUUa5dIgOD0mZNZ2WdUOg3Q6EQfRhLrP2B2QCGGIHU3skLwbl?= =?us-ascii?Q?sjCMtkK70Z74/tuHfGI4u19B8+EfjvuRLS69YhYC1HqNIwMKiFIPEBNl4cm9?= =?us-ascii?Q?yvdlKbvrW0j5RLDhiGNQqVWO2JqxdshDEyCrUIL5w3tgAmEaMNc74MqGjf2F?= =?us-ascii?Q?4ARn87Ji4m0wSw0YAmlqb9BfG+Xhi4MeAh/xvwjbd/EVVUlJsKJ+FEBBR+Md?= =?us-ascii?Q?prH8dv04o63DN8rWq1yN7T/BETJXAxK8hE31PAU37rJCQLUAYBgUA+ckcjEA?= =?us-ascii?Q?o/8LMXwZKPqmkiVccCxf1Ig6/TlvVSdX1GI65GWt8LTiY8qtmDmgxabvAUkX?= =?us-ascii?Q?DKpLh1h0DcCVPDTLtOFzkYT831nGY1+b1JZuOEg8ZfeZyt3AaoM82sHaS744?= =?us-ascii?Q?WikjcrvJf0hnVZizNjg+O+zwKuf9P1DNngquHNfudr+JnyD9KfulV69tGocs?= =?us-ascii?Q?ZTeSK77zwQ=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: e8dc5536-ba20-4f00-2268-08de893a565c X-MS-Exchange-CrossTenant-AuthSource: DS0PR12MB6486.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Mar 2026 00:14:38.4237 (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: 5yW5nUeDQGq2uSNi+mkJBSmaTOfVLo6WIVzlJ+ZhxGJFiZohEua/OSnAY9cWNW2GVckGNKSmSzC2z9zcv13W0A== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ2PR12MB8782 Content-Type: text/plain; charset="utf-8" Tiny SRCU's srcu_gp_start_if_needed() directly calls schedule_work(), which acquires the workqueue pool->lock. This causes a lockdep splat when call_srcu() is called with a scheduler lock held, due to: call_srcu() [holding pi_lock] srcu_gp_start_if_needed() schedule_work() -> pool->lock workqueue_init() / create_worker() [holding pool->lock] wake_up_process() -> try_to_wake_up() -> pi_lock Also add irq_work_sync() to cleanup_srcu_struct() to prevent a use-after-free if a queued irq_work fires after cleanup begins. Tested with rcutorture SRCU-T and no lockdep warnings. [ Thanks to Boqun for similar fix in patch "rcu: Use an intermediate irq_wo= rk to start process_srcu()" ] Signed-off-by: Joel Fernandes --- include/linux/srcutiny.h | 4 ++++ kernel/rcu/srcutiny.c | 19 ++++++++++++++++++- 2 files changed, 22 insertions(+), 1 deletion(-) diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h index dec7cbe015aa..905b629e8fa3 100644 --- a/include/linux/srcutiny.h +++ b/include/linux/srcutiny.h @@ -11,6 +11,7 @@ #ifndef _LINUX_SRCU_TINY_H #define _LINUX_SRCU_TINY_H =20 +#include #include =20 struct srcu_struct { @@ -24,18 +25,21 @@ struct srcu_struct { struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */ struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */ struct work_struct srcu_work; /* For driving grace periods. */ + struct irq_work srcu_irq_work; /* Defer schedule_work() to irq work. */ #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ }; =20 void srcu_drive_gp(struct work_struct *wp); +void srcu_tiny_irq_work(struct irq_work *irq_work); =20 #define __SRCU_STRUCT_INIT(name, __ignored, ___ignored, ____ignored) \ { \ .srcu_wq =3D __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \ .srcu_cb_tail =3D &name.srcu_cb_head, \ .srcu_work =3D __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \ + .srcu_irq_work =3D { .func =3D srcu_tiny_irq_work }, \ __SRCU_DEP_MAP_INIT(name) \ } =20 diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c index 3450c3751ef7..a2e2d516e51b 100644 --- a/kernel/rcu/srcutiny.c +++ b/kernel/rcu/srcutiny.c @@ -9,6 +9,7 @@ */ =20 #include +#include #include #include #include @@ -41,6 +42,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ss= p) ssp->srcu_idx_max =3D 0; INIT_WORK(&ssp->srcu_work, srcu_drive_gp); INIT_LIST_HEAD(&ssp->srcu_work.entry); + init_irq_work(&ssp->srcu_irq_work, srcu_tiny_irq_work); return 0; } =20 @@ -84,6 +86,7 @@ EXPORT_SYMBOL_GPL(init_srcu_struct); void cleanup_srcu_struct(struct srcu_struct *ssp) { WARN_ON(ssp->srcu_lock_nesting[0] || ssp->srcu_lock_nesting[1]); + irq_work_sync(&ssp->srcu_irq_work); flush_work(&ssp->srcu_work); WARN_ON(ssp->srcu_gp_running); WARN_ON(ssp->srcu_gp_waiting); @@ -177,6 +180,20 @@ void srcu_drive_gp(struct work_struct *wp) } EXPORT_SYMBOL_GPL(srcu_drive_gp); =20 +/* + * Use an irq_work to defer schedule_work() to avoid acquiring the workque= ue + * pool->lock while the caller might hold scheduler locks, causing lockdep + * splats due to workqueue_init() doing a wakeup. + */ +void srcu_tiny_irq_work(struct irq_work *irq_work) +{ + struct srcu_struct *ssp; + + ssp =3D container_of(irq_work, struct srcu_struct, srcu_irq_work); + schedule_work(&ssp->srcu_work); +} +EXPORT_SYMBOL_GPL(srcu_tiny_irq_work); + static void srcu_gp_start_if_needed(struct srcu_struct *ssp) { unsigned long cookie; @@ -189,7 +206,7 @@ static void srcu_gp_start_if_needed(struct srcu_struct = *ssp) WRITE_ONCE(ssp->srcu_idx_max, cookie); if (!READ_ONCE(ssp->srcu_gp_running)) { if (likely(srcu_init_done)) - schedule_work(&ssp->srcu_work); + irq_work_queue(&ssp->srcu_irq_work); else if (list_empty(&ssp->srcu_work.entry)) list_add(&ssp->srcu_work.entry, &srcu_boot_list); } --=20 2.34.1