rcu: Disable interrupts directly in rcu_gp_init()

Interrupts are enabled in rcu_gp_init(), so this commit switches from
local_irq_save() and local_irq_restore() to local_irq_disable() and
local_irq_enable().

Link: https://lore.kernel.org/all/febb13ab-a4bb-48b4-8e97-7e9f7749e6da@moroto.mountain/Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

kernel/rcu/tree.c

@@ -1832,7 +1832,7 @@ static noinline_for_stack bool rcu_gp_init(void)
 	WRITE_ONCE(rcu_state.gp_state, RCU_GP_ONOFF);
 	/* Exclude CPU hotplug operations. */
 	rcu_for_each_leaf_node(rnp) {
-		local_irq_save(flags);
+		local_irq_disable();
 		arch_spin_lock(&rcu_state.ofl_lock);
 		raw_spin_lock_rcu_node(rnp);
 		if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
@@ -1840,7 +1840,7 @@ static noinline_for_stack bool rcu_gp_init(void)
 			/* Nothing to do on this leaf rcu_node structure. */
 			raw_spin_unlock_rcu_node(rnp);
 			arch_spin_unlock(&rcu_state.ofl_lock);
-			local_irq_restore(flags);
+			local_irq_enable();
 			continue;
 		}
 
@@ -1877,7 +1877,7 @@ static noinline_for_stack bool rcu_gp_init(void)
 
 		raw_spin_unlock_rcu_node(rnp);
 		arch_spin_unlock(&rcu_state.ofl_lock);
-		local_irq_restore(flags);
+		local_irq_enable();
 	}
 	rcu_gp_slow(gp_preinit_delay); /* Races with CPU hotplug. */