On Mon, Feb 02, 2026 at 03:11:43PM -0500, Waiman Long wrote:
> @@ -1310,14 +1321,34 @@ static bool prstate_housekeeping_conflict(int
> prstate, struct cpumask *new_cpus)
> */
> static void update_isolation_cpumasks(void)
> {
> - int ret;
> + static DECLARE_WORK(isolcpus_work, isolcpus_workfn);
>
> if (!isolated_cpus_updating)
> return;
>
> - ret = housekeeping_update(isolated_cpus);
> - WARN_ON_ONCE(ret < 0);
> + /*
> + * This function can be reached either directly from regular cpuset
> + * control file write or via CPU hotplug. In the latter case, it is
> + * the per-cpu kthread that calls cpuset_handle_hotplug() on behalf
> + * of the task that initiates CPU shutdown or bringup.
> + *
> + * To have better flexibility and prevent the possibility of deadlock
> + * when calling from CPU hotplug, we defer the housekeeping_update()
> + * call to after the current cpuset critical section has finished.
> + * This is done via workqueue.
> + */
> + if (current->flags & PF_KTHREAD) {
/* Serializes the static isolcpus_workfn. */
lockdep_assert_held(&cpuset_mutex);
> + /*
> + * We rely on WORK_STRUCT_PENDING_BIT to not requeue a work
> + * item that is still pending.
> + */
> + queue_work(system_unbound_wq, &isolcpus_work);
> + /* Also defer sched domains regeneration to the work function */
> + force_sd_rebuild = false;
> + return;
> + }
>
> + WARN_ON_ONCE(housekeeping_update(isolated_cpus) < 0);
> isolated_cpus_updating = false;
> }
