linux-kernel - [tip: sched/core] sched: Simplify sched_tick

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Date:   Mon, 14 Aug 2023 15:08:04 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Valentin Schneider <vschneid@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched: Simplify sched_tick_remote()

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

Commit-ID:     6dafc713e3b0d8ffbd696d200d8c9dd212ddcdfc
Gitweb:        https://git.kernel.org/tip/6dafc713e3b0d8ffbd696d200d8c9dd212ddcdfc
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Tue, 01 Aug 2023 22:41:28 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 14 Aug 2023 17:01:26 +02:00

sched: Simplify sched_tick_remote()

Use guards to reduce gotos and simplify control flow.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Valentin Schneider <vschneid@...hat.com>
Link: https://lore.kernel.org/r/20230801211812.236247952@infradead.org
---
 kernel/sched/core.c | 39 ++++++++++++++++-----------------------
 1 file changed, 16 insertions(+), 23 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index cd7f2ed..1b2fa91 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5721,9 +5721,6 @@ static void sched_tick_remote(struct work_struct *work)
 	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;
 
 	/*
@@ -5733,30 +5730,26 @@ static void sched_tick_remote(struct work_struct *work)
 	 * 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;
 
-	rq_lock_irq(rq, &rf);
-	curr = rq->curr;
-	if (cpu_is_offline(cpu))
-		goto out_unlock;
+		if (cpu_online(cpu)) {
+			update_rq_clock(rq);
 
-	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);
 
-	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