From: Waiman Long <longman@redhat.com>
Date: Fri, 17 Mar 2023 15:15:06 +0000 (-0400)
Subject: cgroup/cpuset: Skip task update if hotplug doesn't affect current cpuset
X-Git-Tag: v6.6.7~2953^2~3
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=df59b72cd8fb8ca00301f47e65853efed195d23f;p=platform%2Fkernel%2Flinux-starfive.git

cgroup/cpuset: Skip task update if hotplug doesn't affect current cpuset

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@redhat.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
---

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 8472c71..a05bc93 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3516,6 +3516,8 @@ retry:
 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);
@@ -3527,6 +3529,7 @@ update_tasks:
 		hotplug_update_tasks_legacy(cs, &new_cpus, &new_mems,
 					    cpus_updated, mems_updated);
 
+unlock:
 	percpu_up_write(&cpuset_rwsem);
 }