[PATCH 5/8] sched: Simplify sched_rr_get_interval()

From: Peter Zijlstra
Date: Wed Aug 09 2023 - 16:43:56 EST


Use guards to reduce gotos and simplify control flow.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
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;
}

/**