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 <dongml2@xxxxxxxxxxxxxxx>
---
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_notrace(void)
preempt_enable_notrace();
}
+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.
--
2.50.1
