[PATCH 19/33] sched/isolation: Remove HK_TYPE_TICK test from cpu_is_isolated()

Frederic Weisbecker
2025-10-13T20:34:29Z

It doesn't make sense to use nohz_full without also isolating the
related CPUs from the domain topology, either through the use of
isolcpus= or cpuset isolated partitions.

And now HK_TYPE_DOMAIN includes all kinds of domain isolated CPUs.

This means that HK_TYPE_KERNEL_NOISE (of which HK_TYPE_TICK is only an
alias) should always be a subset of HK_TYPE_DOMAIN.

Therefore if a CPU is not HK_TYPE_DOMAIN, it shouldn't be
HK_TYPE_KERNEL_NOISE either. Testing the former is then enough.

Simplify cpu_is_isolated() accordingly.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
include/linux/sched/isolation.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index 0f50c152cf68..eef539820de2 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -75,8 +75,7 @@ static inline bool housekeeping_cpu(int cpu, enum hk_type type)

static inline bool cpu_is_isolated(int cpu)
{
- return !housekeeping_test_cpu(cpu, HK_TYPE_DOMAIN) ||
- !housekeeping_test_cpu(cpu, HK_TYPE_TICK);
+ return !housekeeping_test_cpu(cpu, HK_TYPE_DOMAIN);
}

#endif /* _LINUX_SCHED_ISOLATION_H */
--
2.51.0