[tip: sched/core] sched: Simplify sched_rr_get_interval()

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     dc163158330c1bd1be33e54d37b09f10c0a8db07
Gitweb:        https://git.kernel.org/tip/dc163158330c1bd1be33e54d37b09f10c0a8db07
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Fri, 09 Jun 2023 16:59:05 +02:00
Committer:     root <root@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
CommitterDate: Sat, 09 Sep 2023 15:10:16 +02:00

sched: Simplify sched_rr_get_interval()

Use guards to reduce gotos and simplify control flow.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 kernel/sched/core.c | 36 ++++++++++++++----------------------
 1 file changed, 14 insertions(+), 22 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e825839..acaab2d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9031,38 +9031,30 @@ SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
 
 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;
+	scoped_guard (rcu) {
+		struct task_struct *p = find_process_by_pid(pid);
+		if (!p)
+			return -ESRCH;
 
-	retval = security_task_getscheduler(p);
-	if (retval)
-		goto out_unlock;
+		retval = security_task_getscheduler(p);
+		if (retval)
+			return retval;
 
-	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 (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;
 }
 
 /**