Since commit 041ee6f3727a ("kthread: Rely on HK_TYPE_DOMAIN for preferred
affinity management"), kthreads default to use the HK_TYPE_DOMAIN
cpumask. IOW, it is no longer affected by the setting of the nohz_full
boot kernel parameter.

That means HK_TYPE_KTHREAD should now be an alias of HK_TYPE_DOMAIN
instead of HK_TYPE_KERNEL_NOISE to correctly reflect the current kthread
behavior. Make the change as HK_TYPE_KTHREAD is still being used in
some networking code.

Fixes: 041ee6f3727a ("kthread: Rely on HK_TYPE_DOMAIN for preferred affinity management")
Signed-off-by: Waiman Long <longman@redhat.com>
---
 include/linux/sched/isolation.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index dc3975ff1b2e..cf0fd03dd7a2 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -20,6 +20,11 @@ enum hk_type {
 	HK_TYPE_KERNEL_NOISE,
 	HK_TYPE_MAX,
 
+	/*
+	 * HK_TYPE_KTHREAD is now an alias of HK_TYPE_DOMAIN
+	 */
+	HK_TYPE_KTHREAD = HK_TYPE_DOMAIN,
+
 	/*
 	 * The following housekeeping types are only set by the nohz_full
 	 * boot commandline option. So they can share the same value.
@@ -29,7 +34,6 @@ enum hk_type {
 	HK_TYPE_RCU     = HK_TYPE_KERNEL_NOISE,
 	HK_TYPE_MISC    = HK_TYPE_KERNEL_NOISE,
 	HK_TYPE_WQ      = HK_TYPE_KERNEL_NOISE,
-	HK_TYPE_KTHREAD = HK_TYPE_KERNEL_NOISE
 };
 
 #ifdef CONFIG_CPU_ISOLATION
-- 
2.53.0

I went through the series.

Patch 1 correctly updates HK_TYPE_KTHREAD to reflect the post-041ee6f3727a
behavior where kthreads follow HK_TYPE_DOMAIN. Keeping it mapped to
HK_TYPE_KERNEL_NOISE is no longer accurate, so the alias is the right fix.

Patch 2 properly introduces RCU protection for accessing the
HK_TYPE_KTHREAD/HK_TYPE_DOMAIN cpumask in IPVS. Since the mask can now
change at runtime, guarding against potential UAF is required. The
changes are minimal and the helper wrappers keep call sites clean.

Reviewed-by: David Dull <monderasdor@gmail.com>