linux-kernel - [PATCH] rcu: per-cpu rcuc kthread are created only when rcutree.use

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Date:   Wed, 29 Dec 2021 00:05:10 +0800
From:   Zqiang <qiang1.zhang@...el.com>
To:     paulmck@...nel.org, frederic@...nel.org
Cc:     linux-kernel@...r.kernel.org, qiang1.zhang@...el.com
Subject: [PATCH] rcu: per-cpu rcuc kthread are created only when rcutree.use_softirq=0

In non-RT kernel, if the RCU_BOOST is enabled, the per-cpu rcuc
kthread will be created, however under the rcutree.use_softirq=1,
the RCU core processing only in softirq context, the rcuc kthread
doesn't do anything, so remove RCU_BOOST interference.

Signed-off-by: Zqiang <qiang1.zhang@...el.com>
---
 kernel/rcu/tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 9b58bae0527a..ed64b4fcb8a0 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2902,7 +2902,7 @@ static int __init rcu_spawn_core_kthreads(void)
 
 	for_each_possible_cpu(cpu)
 		per_cpu(rcu_data.rcu_cpu_has_work, cpu) = 0;
-	if (!IS_ENABLED(CONFIG_RCU_BOOST) && use_softirq)
+	if (use_softirq)
 		return 0;
 	WARN_ONCE(smpboot_register_percpu_thread(&rcu_cpu_thread_spec),
 		  "%s: Could not start rcuc kthread, OOM is now expected behavior\n", __func__);
-- 
2.25.1