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 <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Fixes: c0f08d6 ("srcu: Add srcu_read_lock_lite() and srcu_read_unlock_lite()")
Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Reviewed-by: Neeraj Upadhyay <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>

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);
 }
 
 /**