rcu: in_irq() cleanup

This commit replaces the obsolete and ambiguous macro in_irq() with its
shiny new in_hardirq() equivalent.

Signed-off-by: Changbin Du <changbin.du@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

include/linux/rcutiny.h

@@ -85,7 +85,7 @@ static inline void rcu_irq_enter_irqson(void) { }
 static inline void rcu_irq_exit(void) { }
 static inline void rcu_irq_exit_check_preempt(void) { }
 #define rcu_is_idle_cpu(cpu) \
-	(is_idle_task(current) && !in_nmi() && !in_irq() && !in_serving_softirq())
+	(is_idle_task(current) && !in_nmi() && !in_hardirq() && !in_serving_softirq())
 static inline void exit_rcu(void) { }
 static inline bool rcu_preempt_need_deferred_qs(struct task_struct *t)
 {

kernel/rcu/tree.c

@@ -1467,7 +1467,7 @@ static void rcu_gp_kthread_wake(void)
 {
 	struct task_struct *t = READ_ONCE(rcu_state.gp_kthread);
 
-	if ((current == t && !in_irq() && !in_serving_softirq()) ||
+	if ((current == t && !in_hardirq() && !in_serving_softirq()) ||
 	    !READ_ONCE(rcu_state.gp_flags) || !t)
 		return;
 	WRITE_ONCE(rcu_state.gp_wake_time, jiffies);

kernel/rcu/tree_plugin.h

@@ -642,7 +642,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
 			   (IS_ENABLED(CONFIG_RCU_BOOST) && irqs_were_disabled &&
 			    t->rcu_blocked_node);
 		// Need to defer quiescent state until everything is enabled.
-		if (use_softirq && (in_irq() || (expboost && !irqs_were_disabled))) {
+		if (use_softirq && (in_hardirq() || (expboost && !irqs_were_disabled))) {
 			// Using softirq, safe to awaken, and either the
 			// wakeup is free or there is either an expedited
 			// GP in flight or a potential need to deboost.