linux-kernel - [PATCH v3 08/57] sched: Simplify wake_up_if

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Message-ID: <20230612093537.977924652@infradead.org>
Date:   Mon, 12 Jun 2023 11:07:21 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     torvalds@...ux-foundation.org, keescook@...omium.org,
        gregkh@...uxfoundation.org, pbonzini@...hat.com
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Subject: [PATCH v3 08/57] sched: Simplify wake_up_if_idle()

Use guards to reduce gotos and simplify control flow.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/sched/core.c  |   20 ++++++--------------
 kernel/sched/sched.h |   15 +++++++++++++++
 2 files changed, 21 insertions(+), 14 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3872,21 +3872,13 @@ static void __ttwu_queue_wakelist(struct
 void wake_up_if_idle(int cpu)
 {
 	struct rq *rq = cpu_rq(cpu);
-	struct rq_flags rf;
 
-	rcu_read_lock();
-
-	if (!is_idle_task(rcu_dereference(rq->curr)))
-		goto out;
-
-	rq_lock_irqsave(rq, &rf);
-	if (is_idle_task(rq->curr))
-		resched_curr(rq);
-	/* Else CPU is not idle, do nothing here: */
-	rq_unlock_irqrestore(rq, &rf);
-
-out:
-	rcu_read_unlock();
+	guard(rcu)();
+	if (is_idle_task(rcu_dereference(rq->curr))) {
+		guard(rq_lock)(rq);
+		if (is_idle_task(rq->curr))
+			resched_curr(rq);
+	}
 }
 
 bool cpus_share_cache(int this_cpu, int that_cpu)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1678,6 +1678,21 @@ rq_unlock(struct rq *rq, struct rq_flags
 	raw_spin_rq_unlock(rq);
 }
 
+DEFINE_LOCK_GUARD_1(rq_lock, struct rq,
+		    rq_lock(_T->lock, &_T->rf),
+		    rq_unlock(_T->lock, &_T->rf),
+		    struct rq_flags rf)
+
+DEFINE_LOCK_GUARD_1(rq_lock_irq, struct rq,
+		    rq_lock_irq(_T->lock, &_T->rf),
+		    rq_unlock_irq(_T->lock, &_T->rf),
+		    struct rq_flags rf)
+
+DEFINE_LOCK_GUARD_1(rq_lock_irqsave, struct rq,
+		    rq_lock_irqsave(_T->lock, &_T->rf),
+		    rq_unlock_irqrestore(_T->lock, &_T->rf),
+		    struct rq_flags rf)
+
 static inline struct rq *
 this_rq_lock_irq(struct rq_flags *rf)
 	__acquires(rq->lock)