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

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Date:   Tue, 12 Sep 2023 10:28:57 -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>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched: Simplify tg_set_cfs_bandwidth()

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

Commit-ID:     f838a17459e09ec1d573d71f1575aea8c85cccd5
Gitweb:        https://git.kernel.org/tip/f838a17459e09ec1d573d71f1575aea8c85cccd5
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Fri, 09 Jun 2023 20:45:16 +02:00
Committer:     root <root@...sy.programming.kicks-ass.net>
CommitterDate: Sat, 09 Sep 2023 15:10:17 +02:00

sched: Simplify tg_set_cfs_bandwidth()

Use guards to reduce gotos and simplify control flow.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 include/linux/cpu.h |  2 ++
 kernel/sched/core.c | 38 +++++++++++++++++++-------------------
 2 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 6e6e57e..3520613 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -148,6 +148,8 @@ static inline int remove_cpu(unsigned int cpu) { return -EPERM; }
 static inline void smp_shutdown_nonboot_cpus(unsigned int primary_cpu) { }
 #endif	/* !CONFIG_HOTPLUG_CPU */
 
+DEFINE_LOCK_GUARD_0(cpus_read_lock, cpus_read_lock(), cpus_read_unlock())
+
 #ifdef CONFIG_PM_SLEEP_SMP
 extern int freeze_secondary_cpus(int primary);
 extern void thaw_secondary_cpus(void);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index bcae6e3..081a249 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10803,11 +10803,12 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
 	 * Prevent race between setting of cfs_rq->runtime_enabled and
 	 * unthrottle_offline_cfs_rqs().
 	 */
-	cpus_read_lock();
-	mutex_lock(&cfs_constraints_mutex);
+	guard(cpus_read_lock)();
+	guard(mutex)(&cfs_constraints_mutex);
+
 	ret = __cfs_schedulable(tg, period, quota);
 	if (ret)
-		goto out_unlock;
+		return ret;
 
 	runtime_enabled = quota != RUNTIME_INF;
 	runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
@@ -10817,39 +10818,38 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
 	 */
 	if (runtime_enabled && !runtime_was_enabled)
 		cfs_bandwidth_usage_inc();
-	raw_spin_lock_irq(&cfs_b->lock);
-	cfs_b->period = ns_to_ktime(period);
-	cfs_b->quota = quota;
-	cfs_b->burst = burst;
 
-	__refill_cfs_bandwidth_runtime(cfs_b);
+	scoped_guard (raw_spinlock_irq, &cfs_b->lock) {
+		cfs_b->period = ns_to_ktime(period);
+		cfs_b->quota = quota;
+		cfs_b->burst = burst;
 
-	/* Restart the period timer (if active) to handle new period expiry: */
-	if (runtime_enabled)
-		start_cfs_bandwidth(cfs_b);
+		__refill_cfs_bandwidth_runtime(cfs_b);
 
-	raw_spin_unlock_irq(&cfs_b->lock);
+		/*
+		 * Restart the period timer (if active) to handle new
+		 * period expiry:
+		 */
+		if (runtime_enabled)
+			start_cfs_bandwidth(cfs_b);
+	}
 
 	for_each_online_cpu(i) {
 		struct cfs_rq *cfs_rq = tg->cfs_rq[i];
 		struct rq *rq = cfs_rq->rq;
-		struct rq_flags rf;
 
-		rq_lock_irq(rq, &rf);
+		guard(rq_lock_irq)(rq);
 		cfs_rq->runtime_enabled = runtime_enabled;
 		cfs_rq->runtime_remaining = 0;
 
 		if (cfs_rq->throttled)
 			unthrottle_cfs_rq(cfs_rq);
-		rq_unlock_irq(rq, &rf);
 	}
+
 	if (runtime_was_enabled && !runtime_enabled)
 		cfs_bandwidth_usage_dec();
-out_unlock:
-	mutex_unlock(&cfs_constraints_mutex);
-	cpus_read_unlock();
 
-	return ret;
+	return 0;
 }
 
 static int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)