Factor out migrate_enable_rcu/migrate_disable_rcu from
rcu_read_lock_dont_migrate/rcu_read_unlock_migrate.

These functions will be used in the following patches.

It's a little weird to define them in rcupdate.h. Maybe we should move
them to sched.h?

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
---
 include/linux/rcupdate.h | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index c5b30054cd01..43626ccc07e2 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -988,18 +988,32 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
 	preempt_enable_notrace();
 }
 
-static __always_inline void rcu_read_lock_dont_migrate(void)
+/* This can only be used with rcu_read_lock held */
+static inline void migrate_enable_rcu(void)
+{
+	WARN_ON_ONCE(!rcu_read_lock_held());
+	if (IS_ENABLED(CONFIG_PREEMPT_RCU))
+		migrate_enable();
+}
+
+/* This can only be used with rcu_read_lock held */
+static inline void migrate_disable_rcu(void)
 {
+	WARN_ON_ONCE(!rcu_read_lock_held());
 	if (IS_ENABLED(CONFIG_PREEMPT_RCU))
 		migrate_disable();
+}
+
+static __always_inline void rcu_read_lock_dont_migrate(void)
+{
 	rcu_read_lock();
+	migrate_disable_rcu();
 }
 
 static inline void rcu_read_unlock_migrate(void)
 {
+	migrate_enable_rcu();
 	rcu_read_unlock();
-	if (IS_ENABLED(CONFIG_PREEMPT_RCU))
-		migrate_enable();
 }
 
 /**
-- 
2.51.0

On Tue, Oct 14, 2025 at 4:27 AM Menglong Dong <menglong8.dong@gmail.com> wrote:
>
> Factor out migrate_enable_rcu/migrate_disable_rcu from
> rcu_read_lock_dont_migrate/rcu_read_unlock_migrate.
>
> These functions will be used in the following patches.
>
> It's a little weird to define them in rcupdate.h. Maybe we should move
> them to sched.h?
>
> Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
> ---
>  include/linux/rcupdate.h | 20 +++++++++++++++++---
>  1 file changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index c5b30054cd01..43626ccc07e2 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -988,18 +988,32 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
>         preempt_enable_notrace();
>  }
>
> -static __always_inline void rcu_read_lock_dont_migrate(void)
> +/* This can only be used with rcu_read_lock held */
> +static inline void migrate_enable_rcu(void)
> +{
> +       WARN_ON_ONCE(!rcu_read_lock_held());
> +       if (IS_ENABLED(CONFIG_PREEMPT_RCU))
> +               migrate_enable();
> +}
> +
> +/* This can only be used with rcu_read_lock held */
> +static inline void migrate_disable_rcu(void)
>  {
> +       WARN_ON_ONCE(!rcu_read_lock_held());
>         if (IS_ENABLED(CONFIG_PREEMPT_RCU))
>                 migrate_disable();
> +}
> +
> +static __always_inline void rcu_read_lock_dont_migrate(void)
> +{
>         rcu_read_lock();
> +       migrate_disable_rcu();
>  }
>
>  static inline void rcu_read_unlock_migrate(void)
>  {
> +       migrate_enable_rcu();
>         rcu_read_unlock();
> -       if (IS_ENABLED(CONFIG_PREEMPT_RCU))
> -               migrate_enable();
>  }

Sorry. I don't like any of it. It obfuscates the code
without adding any benefits.

pw-bot: cr