From: Frederic Weisbecker <frederic@kernel.org>
Date: Mon, 2 Jun 2025 10:32:32 +0000 (+0200)
Subject: sched/isolation: Remove HK_TYPE_TICK test from cpu_is_isolated()
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1c3329df409b9b50517bf4a1399ed793d277a20c;p=thirdparty%2Flinux.git

sched/isolation: Remove HK_TYPE_TICK test from cpu_is_isolated()

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_DOMAIN should always be a subset of
HK_TYPE_KERNEL_NOISE (of which HK_TYPE_TICK is only an alias).

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>
Acked-by: Waiman Long <longman@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Marco Crivellari <marco.crivellari@suse.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Waiman Long <longman@redhat.com>
---

diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index d0fb0f6473186..dc3975ff1b2e1 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -82,8 +82,7 @@ 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 */