Re: [PATCH 19/23] cgroup/cpuset: Improve check for calling housekeeping_update()

[Waiman Long]

On 4/22/26 9:10 PM, Chen Ridong wrote:

On 2026/4/21 11:03, Waiman Long wrote:

By making sure that isolated_hk_cpus matches isolated_cpus at boot time,
we can more accurately determine if calling housekeeping_update()
is needed by comparing if the two cpumasks are equal. The
update_housekeeping flag still have a use in cpuset_handle_hotplug()
to determine if a work function should be queued to invoke
cpuset_update_sd_hk_unlock() as it is not supposed to look at
isolated_hk_cpus without holding cpuset_top_mutex.

Currently, isolated_hk_cpus is updated within the cpuset_mutex critical section
(before mutex_unlock(&cpuset_mutex)) in cpuset_update_sd_hk_unlock. Therefore, I
think update_housekeeping can now be removed.

That is true. I will remove in the next version.

Thanks,
Longman

Signed-off-by: Waiman Long <long...@redhat.com>
---
  kernel/cgroup/cpuset.c | 36 ++++++++++++++++++++----------------
  1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index a4eccb0ec0d1..1b0c50b46a49 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1339,26 +1339,29 @@ static void cpuset_update_sd_hk_unlock(void)
        __releases(&cpuset_mutex)
        __releases(&cpuset_top_mutex)
  {
+       update_housekeeping = false;
+
        /* force_sd_rebuild will be cleared in rebuild_sched_domains_locked() */
        if (force_sd_rebuild)
                rebuild_sched_domains_locked();

- if (update_housekeeping) {

-               update_housekeeping = false;
-               cpumask_copy(isolated_hk_cpus, isolated_cpus);
-
-               /*
-                * housekeeping_update() is now called without holding
-                * cpus_read_lock and cpuset_mutex. Only cpuset_top_mutex
-                * is still being held for mutual exclusion.
-                */
-               mutex_unlock(&cpuset_mutex);
-               cpus_read_unlock();
-               WARN_ON_ONCE(housekeeping_update(isolated_hk_cpus, 
BIT(HK_TYPE_DOMAIN)));
-               mutex_unlock(&cpuset_top_mutex);
-       } else {
+       if (cpumask_equal(isolated_hk_cpus, isolated_cpus)) {
+               /* No housekeeping cpumask update needed */
                cpuset_full_unlock();
+               return;
        }
+
+       cpumask_copy(isolated_hk_cpus, isolated_cpus);
+
+       /*
+        * housekeeping_update() is now called without holding
+        * cpus_read_lock and cpuset_mutex. Only cpuset_top_mutex
+        * is still being held for mutual exclusion.
+        */
+       mutex_unlock(&cpuset_mutex);
+       cpus_read_unlock();
+       WARN_ON_ONCE(housekeeping_update(isolated_hk_cpus, 
BIT(HK_TYPE_DOMAIN)));
+       mutex_unlock(&cpuset_top_mutex);
  }

/*

@@ -3692,10 +3695,11 @@ int __init cpuset_init(void)

BUG_ON(!alloc_cpumask_var(&cpus_attach, GFP_KERNEL)); - if (housekeeping_enabled(HK_TYPE_DOMAIN_BOOT))

+       if (housekeeping_enabled(HK_TYPE_DOMAIN_BOOT)) {
                cpumask_andnot(isolated_cpus, cpu_possible_mask,
                               housekeeping_cpumask(HK_TYPE_DOMAIN_BOOT));
-
+               cpumask_copy(isolated_hk_cpus, isolated_cpus);
+       }
        return 0;
  }