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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 <qiang.zhang1211@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Zqiang 2021-11-15 13:15:46 +08:00 committed by Paul E. McKenney
parent 17ea371882
commit c2cf0767e9
1 changed files with 2 additions and 1 deletions
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3
kernel/rcu/tree_plugin.h
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@ -1203,8 +1203,9 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
if ((mask & leaf_node_cpu_bit(rnp, cpu)) && if ((mask & leaf_node_cpu_bit(rnp, cpu)) &&
cpu != outgoingcpu) cpu != outgoingcpu)
cpumask_set_cpu(cpu, cm); cpumask_set_cpu(cpu, cm);
cpumask_and(cm, cm, housekeeping_cpumask(HK_FLAG_RCU));
if (cpumask_weight(cm) == 0) if (cpumask_weight(cm) == 0)
cpumask_setall(cm); cpumask_copy(cm, housekeeping_cpumask(HK_FLAG_RCU));
set_cpus_allowed_ptr(t, cm); set_cpus_allowed_ptr(t, cm);
free_cpumask_var(cm); free_cpumask_var(cm);
} }