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Thu, 21 Aug 2025 02:06:27 -0700 (PDT) Received: from 7940hx ([43.129.244.20]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-76ea0c16351sm1708937b3a.14.2025.08.21.02.06.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Aug 2025 02:06:27 -0700 (PDT) From: Menglong Dong X-Google-Original-From: Menglong Dong To: ast@kernel.org, paulmck@kernel.org Cc: frederic@kernel.org, neeraj.upadhyay@kernel.org, joelagnelf@nvidia.com, josh@joshtriplett.org, boqun.feng@gmail.com, urezki@gmail.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang.zhang@linux.dev, daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org Subject: [PATCH bpf-next v3 1/7] rcu: add rcu_read_lock_dont_migrate() Date: Thu, 21 Aug 2025 17:06:03 +0800 Message-ID: <20250821090609.42508-2-dongml2@chinatelecom.cn> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250821090609.42508-1-dongml2@chinatelecom.cn> References: <20250821090609.42508-1-dongml2@chinatelecom.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" migrate_disable() is called to disable migration in the kernel, and it is often used together with rcu_read_lock(). However, with PREEMPT_RCU disabled, it's unnecessary, as rcu_read_lock() will always disable preemption, which will also disable migration. Introduce rcu_read_lock_dont_migrate() and rcu_read_unlock_migrate(), which will do the migration enable and disable only when PREEMPT_RCU. Signed-off-by: Menglong Dong Reviewed-by: Paul E. McKenney --- v3: - make rcu_read_lock_dont_migrate() more compact v2: - introduce rcu_read_lock_dont_migrate() instead of rcu_migrate_disable() --- include/linux/rcupdate.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 120536f4c6eb..9691ca380a4f 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -962,6 +962,20 @@ static inline notrace void rcu_read_unlock_sched_notra= ce(void) preempt_enable_notrace(); } =20 +static __always_inline void rcu_read_lock_dont_migrate(void) +{ + if (IS_ENABLED(CONFIG_PREEMPT_RCU)) + migrate_disable(); + rcu_read_lock(); +} + +static inline void rcu_read_unlock_migrate(void) +{ + rcu_read_unlock(); + if (IS_ENABLED(CONFIG_PREEMPT_RCU)) + migrate_enable(); +} + /** * RCU_INIT_POINTER() - initialize an RCU protected pointer * @p: The pointer to be initialized. --=20 2.50.1