[PATCH 1/5] cgroup/cpuset: Skip task update if hotplug doesn't affect current cpuset

From: Waiman Long
Date: Mon Mar 06 2023 - 15:11:03 EST


If a hotplug event doesn't affect the current cpuset, there is no point
to call hotplug_update_tasks() or hotplug_update_tasks_legacy(). So
just skip it.

Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
kernel/cgroup/cpuset.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 636f1c682ac0..a801abad3bac 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3508,6 +3508,8 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
update_tasks:
cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);
mems_updated = !nodes_equal(new_mems, cs->effective_mems);
+ if (!cpus_updated && !mems_updated)
+ goto unlock; /* Hotplug doesn't affect this cpuset */

if (mems_updated)
check_insane_mems_config(&new_mems);
@@ -3519,6 +3521,7 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
hotplug_update_tasks_legacy(cs, &new_cpus, &new_mems,
cpus_updated, mems_updated);

+unlock:
percpu_up_write(&cpuset_rwsem);
}

--
2.31.1