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rcu: add rcu_read_lock_dont_migrate()

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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 <[email protected]>
Reviewed-by: Paul E. McKenney <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>
This commit is contained in:
Menglong Dong authored and Alexei Starovoitov committed 2025-08-25 18:52:16 -07:00
1 parent 4223bf833c
commit 1b93c03fb3
1 file changed
+14
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include/linux/rcupdate.h
+14
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@@ -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.