linux-kernel - [PATCH v3 18/57] sched: Simplify sched_rr_get

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Message-ID: <20230612093538.792690687@infradead.org>
Date:   Mon, 12 Jun 2023 11:07:31 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     torvalds@...ux-foundation.org, keescook@...omium.org,
        gregkh@...uxfoundation.org, pbonzini@...hat.com
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Subject: [PATCH v3 18/57] sched: Simplify sched_rr_get_interval()

Use guards to reduce gotos and simplify control flow.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/sched/core.c |   40 ++++++++++++++++------------------------
 1 file changed, 16 insertions(+), 24 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8941,38 +8941,30 @@ SYSCALL_DEFINE1(sched_get_priority_min,
 
 static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
 {
-	struct task_struct *p;
-	unsigned int time_slice;
-	struct rq_flags rf;
-	struct rq *rq;
+	unsigned int time_slice = 0;
 	int retval;
 
 	if (pid < 0)
 		return -EINVAL;
 
-	retval = -ESRCH;
-	rcu_read_lock();
-	p = find_process_by_pid(pid);
-	if (!p)
-		goto out_unlock;
-
-	retval = security_task_getscheduler(p);
-	if (retval)
-		goto out_unlock;
-
-	rq = task_rq_lock(p, &rf);
-	time_slice = 0;
-	if (p->sched_class->get_rr_interval)
-		time_slice = p->sched_class->get_rr_interval(rq, p);
-	task_rq_unlock(rq, p, &rf);
+	scoped_guard (rcu) {
+		struct task_struct *p = find_process_by_pid(pid);
+		if (!p)
+			return -ESRCH;
+
+		retval = security_task_getscheduler(p);
+		if (retval)
+			return retval;
+
+		scoped_guard (task_rq_lock, p) {
+			struct rq *rq = scope.rq;
+			if (p->sched_class->get_rr_interval)
+				time_slice = p->sched_class->get_rr_interval(rq, p);
+		}
+	}
 
-	rcu_read_unlock();
 	jiffies_to_timespec64(time_slice, t);
 	return 0;
-
-out_unlock:
-	rcu_read_unlock();
-	return retval;
 }
 
 /**