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McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang Cc: rcu@vger.kernel.org Subject: [PATCH RFC v1 1/6] rcu: introduce rcu_defer_qs_clear() helper Date: Fri, 22 May 2026 10:23:35 -0400 Message-Id: <20260522142342.1536533-2-joelagnelf@nvidia.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260522142342.1536533-1-joelagnelf@nvidia.com> References: <20260522142342.1536533-1-joelagnelf@nvidia.com> Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: MN2PR01CA0051.prod.exchangelabs.com (2603:10b6:208:23f::20) 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_|DS4PR12MB9793:EE_ X-MS-Office365-Filtering-Correlation-Id: 9e61e10a-3a0f-4cae-eead-08deb80dc3e0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|366016|1800799024|921020|56012099003|22082099003|18002099003|11063799006; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?iS1fV2U4lNfsz7l5obGoQzMLaYnoSOFsFmxbHY9xgj8v/sAcSfIXqp+g6Aa3?= =?us-ascii?Q?wP6c1DIVVhONK//BtiNhsgFzVO4+2jALIgStk0vhq2Gf2NYKmYCHLIpuu/+U?= =?us-ascii?Q?QvCB7svxhVcPHpBnbzNNJX9w2bNpcQdV9QGYEXLSEQIemieBVKBe1cMH7hih?= =?us-ascii?Q?GjCge+We447H04gijcQFyklApEX2bVDNjbWXDBCOCJaA15HIj0rnLbYIzwJn?= =?us-ascii?Q?oij2TOWxSBXN0NSgbJJx/L1OObo+u7lYIKXlioA7Rd5CsZQrWH54GnUNwtn3?= =?us-ascii?Q?KaBPm2e1hWEuhVwNK2gEszUM9MJMNwYP2PBgOzQ5YIOTS7MT6cheDGXE7fnc?= =?us-ascii?Q?wnIRZ0XSdxMZ20edOEgGgwfPO/owgn0rPIWQDT+1lyJqJZjEWF1dbLroZCSY?= =?us-ascii?Q?FbtQrH/xdedb0I5XPD/01un59HP6Az8ro8SP5mYzwxz/ro7+ld4whCAaBBMn?= =?us-ascii?Q?kYYHIYhApVl+wFdXSlHx0hgzU0/6fkkMS3IJVpmDPnBRvymQwLhzKNqxnydX?= =?us-ascii?Q?UbptwC3GCG1yFZe6WPHJw3lysioHzqDfu0YCJ+ESaQ/Af20Zf0Lz4AX2q/Xi?= =?us-ascii?Q?FgqkHN52F22Q8R1Ajkf6U/R2HdPXe2wHfTeKvGwG4KoXRZGlRQq6YIwxnhKC?= =?us-ascii?Q?E6xvXL5+0Ko2LYWXXToil7NAfudkfpu7Yy14j5HirXjkIYWcPuknmSXYMaDB?= =?us-ascii?Q?JTgpMgoDwFuIvCfXJVSXkbj6gK5rMgaVAkDnhH3QrvtXOkYMn/AqhWLmIBgG?= =?us-ascii?Q?tOm6DexFKAoHmSbmzoLt9yI4yk6b9GZrZh0xMD7fgGdxcO71j/k4nI7Pew7z?= =?us-ascii?Q?cBACKSB5j8tFmWebhR31y0Ya3V69VIn4yL9O5nNXMU+0pc0M6aBluQcTxoyC?= =?us-ascii?Q?HS62cESR7lukqQ98Kqn5V+v0vIKoBs5tJJSEnWKZDycRfMf4UjkvfU5nSXxY?= =?us-ascii?Q?F4Q/+EgiZvsnrReh5l2AomppChaVAMEeFJ7vRpV5lfHSPlUop7NWiKxtp/fT?= =?us-ascii?Q?PJFBgqJgAw0JYcgOYQZ0e/bAOXbtPnGcUIPSuFpMG648csrX+SfACIwVdITo?= =?us-ascii?Q?dSUQTMt7GDqrlf08kkygMppv06NjDIvWXnqnJO+05Mct1kiS36PaI6aJe1dK?= =?us-ascii?Q?kJmuJwyGSEYVjFLsfzcVc/2z/8v4HEdkQ4WtVxC+fYbilvlH5GGM7WOb1dV/?= =?us-ascii?Q?EY8TzIcuCG3WJ0kf63wIRuN/0dTnZxRgmmnY+UrCVA2LFW6htnutQZo5nYXi?= =?us-ascii?Q?+ZRZZYnlfKvb5xNaKMKB5KeBywt4H/AuMWlzZ54dkdNjA3e5OfhWgptEiLyt?= =?us-ascii?Q?H6CtucDIcA0VeG2FaJqNWjkKAwdkXriJEcoD2YoDQVLPg0dP7DPdjB0/p9gW?= =?us-ascii?Q?MbOE1Dd2WTxF9iICixIHyDKbrDGTiFECc3tDlR+dLruf6ESOCN4m8era/jyq?= =?us-ascii?Q?PvLs0rStOhw9bw2n2lsiuNykaW/vph7P7ruF8f5qF4EDZbLyq2dopud/Qdpy?= =?us-ascii?Q?Ix5csxTCTXvFFvJL+wWXCzph/60kbuIp5+ny2jFEDIJIKUjv+3DQqJ1rrWAe?= =?us-ascii?Q?lg9roIEnQRCmukQogOL1NQGYj2OdHy1M8t2K0wnTsoQIbztDiRysjBAp44MP?= =?us-ascii?Q?KVEL6wlaRcpJesIbMZfX9bj3QMLkhLuNTpGS+YFfWRaZXgRV0SCXCoZNbdwO?= =?us-ascii?Q?JZYqxm9kee7s9wAPxEmDYP1QNhSnNmpQ9aOTG2lR1erredX90T487B37I6vT?= =?us-ascii?Q?ReAeenFsQw=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 9e61e10a-3a0f-4cae-eead-08deb80dc3e0 X-MS-Exchange-CrossTenant-AuthSource: DS0PR12MB6486.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 May 2026 14:23:59.5920 (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: Rwf0UeHqpwSlKbsICGAkhhnPPU/1icA7oo13judRuqjD1mqLA1+Q4518sAkXnVZlAtxOAQYRvA5Z9CRa3yvDbg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS4PR12MB9793 Currently rdp->defer_qs_pending transitions from DEFER_QS_PENDING to DEFER_QS_IDLE at two sites: rcu_preempt_deferred_qs_irqrestore() and rcu_preempt_deferred_qs_handler() (depth>0 reset). Both write the IDLE value directly. Introduce a single inline helper rcu_defer_qs_clear() in tree.h and route both sites through it. This becomes the single PENDING->IDLE transition point for upcoming work. Signed-off-by: Joel Fernandes --- kernel/rcu/tree.h | 5 +++++ kernel/rcu/tree_plugin.h | 4 ++-- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 7dfc57e9adb1..4069132f9d44 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -296,6 +296,11 @@ struct rcu_data { int cpu; }; +static inline void rcu_defer_qs_clear(struct rcu_data *rdp) +{ + WRITE_ONCE(rdp->defer_qs_pending, DEFER_QS_IDLE); +} + /* Values for nocb_defer_wakeup field in struct rcu_data. */ #define RCU_NOCB_WAKE_NOT 0 #define RCU_NOCB_WAKE_BYPASS 1 diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 95ad967adcf3..8637f405cb47 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -488,7 +488,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags) rdp = this_cpu_ptr(&rcu_data); if (rdp->defer_qs_pending == DEFER_QS_PENDING) - rdp->defer_qs_pending = DEFER_QS_IDLE; + rcu_defer_qs_clear(rdp); /* * If RCU core is waiting for this CPU to exit its critical section, @@ -645,7 +645,7 @@ static void rcu_preempt_deferred_qs_handler(struct irq_work *iwp) * 5. Deferred QS reporting does not happen. */ if (rcu_preempt_depth() > 0) - WRITE_ONCE(rdp->defer_qs_pending, DEFER_QS_IDLE); + rcu_defer_qs_clear(rdp); } /* -- 2.34.1