[PATCH 7/9] sched: Simplify sched_tick_remote()

From: Peter Zijlstra
Date: Tue Aug 01 2023 - 17:25:20 EST


Use guards to reduce gotos and simplify control flow.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
kernel/sched/core.c | 43 ++++++++++++++++++-------------------------
1 file changed, 18 insertions(+), 25 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5651,9 +5651,6 @@ static void sched_tick_remote(struct wor
struct tick_work *twork = container_of(dwork, struct tick_work, work);
int cpu = twork->cpu;
struct rq *rq = cpu_rq(cpu);
- struct task_struct *curr;
- struct rq_flags rf;
- u64 delta;
int os;

/*
@@ -5663,30 +5660,26 @@ static void sched_tick_remote(struct wor
* statistics and checks timeslices in a time-independent way, regardless
* of when exactly it is running.
*/
- if (!tick_nohz_tick_stopped_cpu(cpu))
- goto out_requeue;
+ if (tick_nohz_tick_stopped_cpu(cpu)) {
+ guard(rq_lock_irq)(rq);
+ struct task_struct *curr = rq->curr;
+
+ if (cpu_online(cpu)) {
+ update_rq_clock(rq);
+
+ if (!is_idle_task(curr)) {
+ /*
+ * Make sure the next tick runs within a
+ * reasonable amount of time.
+ */
+ u64 delta = rq_clock_task(rq) - curr->se.exec_start;
+ WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
+ }
+ curr->sched_class->task_tick(rq, curr, 0);

- rq_lock_irq(rq, &rf);
- curr = rq->curr;
- if (cpu_is_offline(cpu))
- goto out_unlock;
-
- update_rq_clock(rq);
-
- if (!is_idle_task(curr)) {
- /*
- * Make sure the next tick runs within a reasonable
- * amount of time.
- */
- delta = rq_clock_task(rq) - curr->se.exec_start;
- WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
+ calc_load_nohz_remote(rq);
+ }
}
- curr->sched_class->task_tick(rq, curr, 0);
-
- calc_load_nohz_remote(rq);
-out_unlock:
- rq_unlock_irq(rq, &rf);
-out_requeue:

/*
* Run the remote tick once per second (1Hz). This arbitrary