From c2cf0767e98eb4487444e5c7ebba491a866811ce Mon Sep 17 00:00:00 2001 From: Zqiang Date: Mon, 15 Nov 2021 13:15:46 +0800 Subject: [PATCH] rcu: Avoid running boost kthreads on isolated CPUs When the boost kthreads are created on systems with nohz_full CPUs, the cpus_allowed_ptr is set to housekeeping_cpumask(HK_FLAG_KTHREAD). However, when the rcu_boost_kthread_setaffinity() is called, the original affinity will be changed and these kthreads can subsequently run on nohz_full CPUs. This commit makes rcu_boost_kthread_setaffinity() restrict these boost kthreads to housekeeping CPUs. Signed-off-by: Zqiang Signed-off-by: Paul E. McKenney --- 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 f44580276fbdc..87fc4609b7563 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1203,8 +1203,9 @@ 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); }