sched: Simplify wake_up_if_idle()

Use guards to reduce gotos and simplify control flow.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lore.kernel.org/r/20230801211812.032678917@infradead.org

kernel/sched/core.c

@@ -3939,21 +3939,13 @@ static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags
 void wake_up_if_idle(int cpu)
 {
 	struct rq *rq = cpu_rq(cpu);
-	struct rq_flags rf;
-
-	rcu_read_lock();
 
-	if (!is_idle_task(rcu_dereference(rq->curr)))
-		goto out;
-
-	rq_lock_irqsave(rq, &rf);
-	if (is_idle_task(rq->curr))
-		resched_curr(rq);
-	/* Else CPU is not idle, do nothing here: */
-	rq_unlock_irqrestore(rq, &rf);
-
-out:
-	rcu_read_unlock();
+	guard(rcu)();
+	if (is_idle_task(rcu_dereference(rq->curr))) {
+		guard(rq_lock_irqsave)(rq);
+		if (is_idle_task(rq->curr))
+			resched_curr(rq);
+	}
 }
 
 bool cpus_share_cache(int this_cpu, int that_cpu)

kernel/sched/sched.h

@@ -1705,6 +1705,21 @@ rq_unlock(struct rq *rq, struct rq_flags *rf)
 	raw_spin_rq_unlock(rq);
 }
 
+DEFINE_LOCK_GUARD_1(rq_lock, struct rq,
+		    rq_lock(_T->lock, &_T->rf),
+		    rq_unlock(_T->lock, &_T->rf),
+		    struct rq_flags rf)
+
+DEFINE_LOCK_GUARD_1(rq_lock_irq, struct rq,
+		    rq_lock_irq(_T->lock, &_T->rf),
+		    rq_unlock_irq(_T->lock, &_T->rf),
+		    struct rq_flags rf)
+
+DEFINE_LOCK_GUARD_1(rq_lock_irqsave, struct rq,
+		    rq_lock_irqsave(_T->lock, &_T->rf),
+		    rq_unlock_irqrestore(_T->lock, &_T->rf),
+		    struct rq_flags rf)
+
 static inline struct rq *
 this_rq_lock_irq(struct rq_flags *rf)
 	__acquires(rq->lock)