[PATCH 24/33] kthread: Rely on HK_TYPE_DOMAIN for preferred affinity management

Frederic Weisbecker
2025-10-13T20:35:04Z

Unbound kthreads want to run neither on nohz_full CPUs nor on domain
isolated CPUs. And since nohz_full implies domain isolation, checking
the latter is enough to verify both.

Therefore exclude kthreads from domain isolation.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
kernel/kthread.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index cb0be05d6091..8d0c8c4c7e46 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -362,18 +362,20 @@ static void kthread_fetch_affinity(struct kthread *kthread, struct cpumask *cpum
{
const struct cpumask *pref;

+ guard(rcu)();
+
if (kthread->preferred_affinity) {
pref = kthread->preferred_affinity;
} else {
if (kthread->node == NUMA_NO_NODE)
- pref = housekeeping_cpumask(HK_TYPE_KTHREAD);
+ pref = housekeeping_cpumask(HK_TYPE_DOMAIN);
else
pref = cpumask_of_node(kthread->node);
}

- cpumask_and(cpumask, pref, housekeeping_cpumask(HK_TYPE_KTHREAD));
+ cpumask_and(cpumask, pref, housekeeping_cpumask(HK_TYPE_DOMAIN));
if (cpumask_empty(cpumask))
- cpumask_copy(cpumask, housekeeping_cpumask(HK_TYPE_KTHREAD));
+ cpumask_copy(cpumask, housekeeping_cpumask(HK_TYPE_DOMAIN));
}

static void kthread_affine_node(void)
--
2.51.0