linux-kernel - [PATCH] rcu: Avoid boost task running on isolated cpus

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Date:   Mon, 15 Nov 2021 13:15:46 +0800
From:   Zqiang <qiang.zhang1211@...il.com>
To:     paulmck@...nel.org
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
        Zqiang <qiang.zhang1211@...il.com>
Subject: [PATCH] rcu: Avoid boost task running on isolated cpus

If the nohz_full is enabled, when the boost task be created,
the cpus_allowed_ptr be set housekeeping_cpumask(HK_FLAG_KTHREAD),
however when the rcu_boost_kthread_setaffinity() be called, the
original affinity will be changed, the isolated cpus should be
considered again.

Signed-off-by: Zqiang <qiang.zhang1211@...il.com>
---
 kernel/rcu/tree_plugin.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 5199559fbbf0..87e7ebbdb12e 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1204,8 +1204,9 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
 		if ((mask & leaf_node_cpu_bit(rnp, cpu)) &&
 		    cpu != outgoingcpu)
 			cpumask_set_cpu(cpu, cm);
+	cpumask_and(cm, cm, housekeeping_cpumask(HK_FLAG_RCU));
 	if (cpumask_weight(cm) == 0)
-		cpumask_setall(cm);
+		cpumask_copy(cm, housekeeping_cpumask(HK_FLAG_RCU));
 	set_cpus_allowed_ptr(t, cm);
 	free_cpumask_var(cm);
 }
-- 
2.17.1