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McKenney" Cc: Kumar Kartikeya Dwivedi , Sebastian Andrzej Siewior , frederic@kernel.org, neeraj.iitr10@gmail.com, urezki@gmail.com, boqun.feng@gmail.com, rcu@vger.kernel.org, Tejun Heo , bpf@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrea Righi , Zqiang References: <2d9e7e42-8667-4880-9708-b81a82443809@nvidia.com> <20260320181400.15909-1-boqun@kernel.org> Content-Language: en-US From: Joel Fernandes In-Reply-To: <20260320181400.15909-1-boqun@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MN0PR03CA0026.namprd03.prod.outlook.com (2603:10b6:208:52f::23) To DS0PR12MB6486.namprd12.prod.outlook.com (2603:10b6:8:c5::21) Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS0PR12MB6486:EE_|PH7PR12MB9176:EE_ X-MS-Office365-Filtering-Correlation-Id: 9977c3bc-1a48-48da-1b74-08de86b589bc X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|1800799024|366016|18002099003|7053199007|56012099003|22082099003; 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However as BPF instrument can > happen basically everywhere (including where a scheduler lock is held), > call_srcu() now needs to avoid acquiring scheduler lock because > otherwise it could cause deadlock [1]. Fix this by following what the > previous RCU Tasks Trace did: using an irq_work to delay the queuing of > the work to start process_srcu(). > > [boqun: Apply Joel's feedback] > > Reported-by: Andrea Righi > Closes: https://lore.kernel.org/all/abjzvz_tL_siV17s@gpd4/ > Fixes: commit c27cea4416a3 ("rcu: Re-implement RCU Tasks Trace in terms of SRCU-fast") > Link: https://lore.kernel.org/rcu/3c4c5a29-24ea-492d-aeee-e0d9605b4183@nvidia.com/ [1] > Suggested-by: Zqiang > Signed-off-by: Boqun Feng > --- > @Zqiang, I put your name as Suggested-by because you proposed the same > idea, let me know if you rather not have it. > > @Joel, I did two updates (including your test feedback, other one is > call irq_work_sync() when we clean the srcu_struct), please give it a > try. Thanks Boqun, I applied it for testing further. It would be good if Andrea and Kumar can try this patch as well to confirm that the BPF issues are gone. thanks, -- Joel Fernandes