linux-kernel - [PATCH] sched: simplify is_cpu

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Date:   Tue, 18 May 2021 20:54:46 +0800
From:   Yejune Deng <yejune.deng@...il.com>
To:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com
Cc:     linux-kernel@...r.kernel.org, Yejune Deng <yejunedeng@...il.com>
Subject: [PATCH] sched: simplify is_cpu_allowed() code

Combine multiple if statements that return the same value.

Signed-off-by: Yejune Deng <yejunedeng@...il.com>
---
 kernel/sched/core.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3ab28de..b9b4452 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2153,26 +2153,18 @@ static inline bool rq_has_pinned_tasks(struct rq *rq)
  */
 static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
 {
-	/* When not in the task's cpumask, no point in looking further. */
-	if (!cpumask_test_cpu(cpu, p->cpus_ptr))
+	/*
+	 * When not in the task's cpumask, no point in looking further.
+	 * Regular kernel threads don't get to stay during offline.
+	 *
+	 */
+	if (!cpumask_test_cpu(cpu, p->cpus_ptr) || cpu_dying(cpu))
 		return false;
 
-	/* migrate_disabled() must be allowed to finish. */
-	if (is_migration_disabled(p))
-		return cpu_online(cpu);
-
 	/* Non kernel threads are not allowed during either online or offline. */
 	if (!(p->flags & PF_KTHREAD))
 		return cpu_active(cpu);
 
-	/* KTHREAD_IS_PER_CPU is always allowed. */
-	if (kthread_is_per_cpu(p))
-		return cpu_online(cpu);
-
-	/* Regular kernel threads don't get to stay during offline. */
-	if (cpu_dying(cpu))
-		return false;
-
 	/* But are allowed during online. */
 	return cpu_online(cpu);
 }
-- 
2.7.4