srcu: Remove smp_mb() from srcu_read_unlock_lite()

The srcu_read_unlock_lite() function invokes __srcu_read_unlock() instead
of __srcu_read_unlock_lite(), which means that it is doing an unnecessary
smp_mb().  This is harmless other than the performance degradation.

This commit therefore switches to __srcu_read_unlock_lite().

Reported-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Closes: https://lore.kernel.org/all/d07e8f4a-d5ff-4c8e-8e61-50db285c57e9@amd.com/
Fixes: c0f08d6 ("srcu: Add srcu_read_lock_lite() and srcu_read_unlock_lite()")
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

Author: paulmckrcu

include/linux/srcu.h

@@ -372,7 +372,7 @@ static inline void srcu_read_unlock_lite(struct srcu_struct *ssp, int idx)
 	WARN_ON_ONCE(idx & ~0x1);
 	srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_LITE);
 	srcu_lock_release(&ssp->dep_map);
-	__srcu_read_unlock(ssp, idx);
+	__srcu_read_unlock_lite(ssp, idx);
 }
 
 /**