sched: Simplify ttwu()

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/20230801211812.101069260@infradead.org

kernel/sched/core.c

@@ -3733,14 +3733,14 @@ ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
 		struct sched_domain *sd;
 
 		__schedstat_inc(p->stats.nr_wakeups_remote);
-		rcu_read_lock();
+
+		guard(rcu)();
 		for_each_domain(rq->cpu, sd) {
 			if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
 				__schedstat_inc(sd->ttwu_wake_remote);
 				break;
 			}
 		}
-		rcu_read_unlock();
 	}
 
 	if (wake_flags & WF_MIGRATED)
@@ -4199,10 +4199,9 @@ bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success)
 static int
 try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 {
-	unsigned long flags;
+	guard(preempt)();
 	int cpu, success = 0;
 
-	preempt_disable();
 	if (p == current) {
 		/*
 		 * We're waking current, this means 'p->on_rq' and 'task_cpu(p)
@@ -4229,10 +4228,10 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 	 * reordered with p->state check below. This pairs with smp_store_mb()
 	 * in set_current_state() that the waiting thread does.
 	 */
-	raw_spin_lock_irqsave(&p->pi_lock, flags);
+	scoped_guard (raw_spinlock_irqsave, &p->pi_lock) {
 		smp_mb__after_spinlock();
 		if (!ttwu_state_match(p, state, &success))
-		goto unlock;
+			break;
 
 		trace_sched_waking(p);
 
@@ -4260,7 +4259,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 		 */
 		smp_rmb();
 		if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags))
-		goto unlock;
+			break;
 
 #ifdef CONFIG_SMP
 		/*
@@ -4317,7 +4316,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 		 */
 		if (smp_load_acquire(&p->on_cpu) &&
 		    ttwu_queue_wakelist(p, task_cpu(p), wake_flags))
-		goto unlock;
+			break;
 
 		/*
 		 * If the owning (remote) CPU is still in the middle of schedule() with
@@ -4346,12 +4345,10 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 #endif /* CONFIG_SMP */
 
 		ttwu_queue(p, cpu, wake_flags);
-unlock:
-	raw_spin_unlock_irqrestore(&p->pi_lock, flags);
+	}
 out:
 	if (success)
 		ttwu_stat(p, task_cpu(p), wake_flags);
-	preempt_enable();
 
 	return success;
 }