Re: [PATCH 18/33] cpuset: Propagate cpuset isolation update to workqueue through housekeeping

[Waiman Long <llong@redhat.com>]

On 12/24/25 8:45 AM, Frederic Weisbecker wrote:
> Until now, cpuset would propagate isolated partition changes to
> workqueues so that unbound workers get properly reaffined.
>
> Since housekeeping now centralizes, synchronize and propagates isolation
> cpumask changes, perform the work from that subsystem for consolidation
> and consistency purposes.
>
> For simplification purpose, the target function is adapted to take the
> new housekeeping mask instead of the isolated mask.
>
> Suggested-by: Tejun Heo <tj@kernel.org>
> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
> ---
>   include/linux/workqueue.h |  2 +-
>   init/Kconfig              |  1 +
>   kernel/cgroup/cpuset.c    |  9 +++------
>   kernel/sched/isolation.c  |  4 +++-
>   kernel/workqueue.c        | 17 ++++++++++-------
>   5 files changed, 18 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
> index dabc351cc127..a4749f56398f 100644
> --- a/include/linux/workqueue.h
> +++ b/include/linux/workqueue.h
> @@ -588,7 +588,7 @@ struct workqueue_attrs *alloc_workqueue_attrs_noprof(void);
>   void free_workqueue_attrs(struct workqueue_attrs *attrs);
>   int apply_workqueue_attrs(struct workqueue_struct *wq,
>   			  const struct workqueue_attrs *attrs);
> -extern int workqueue_unbound_exclude_cpumask(cpumask_var_t cpumask);
> +extern int workqueue_unbound_housekeeping_update(const struct cpumask *hk);
>   
>   extern bool queue_work_on(int cpu, struct workqueue_struct *wq,
>   			struct work_struct *work);
> diff --git a/init/Kconfig b/init/Kconfig
> index fa79feb8fe57..518830fb812f 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1254,6 +1254,7 @@ config CPUSETS
>   	bool "Cpuset controller"
>   	depends on SMP
>   	select UNION_FIND
> +	select CPU_ISOLATION
>   	help
>   	  This option will let you create and manage CPUSETs which
>   	  allow dynamically partitioning a system into sets of CPUs and
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index e13e32491ebf..a492d23dd622 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1484,15 +1484,12 @@ static void update_isolation_cpumasks(void)
>   
>   	lockdep_assert_cpus_held();
>   
> -	ret = workqueue_unbound_exclude_cpumask(isolated_cpus);
> -	WARN_ON_ONCE(ret < 0);
> -
> -	ret = tmigr_isolated_exclude_cpumask(isolated_cpus);
> -	WARN_ON_ONCE(ret < 0);
> -
>   	ret = housekeeping_update(isolated_cpus, HK_TYPE_DOMAIN);
>   	WARN_ON_ONCE(ret < 0);
>   
> +	ret = tmigr_isolated_exclude_cpumask(isolated_cpus);
> +	WARN_ON_ONCE(ret < 0);
> +
>   	isolated_cpus_updating = false;
>   }
>   
> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
> index 7dbe037ea8df..d224bca299ed 100644
> --- a/kernel/sched/isolation.c
> +++ b/kernel/sched/isolation.c
> @@ -121,6 +121,7 @@ EXPORT_SYMBOL_GPL(housekeeping_test_cpu);
>   int housekeeping_update(struct cpumask *isol_mask, enum hk_type type)
>   {
>   	struct cpumask *trial, *old = NULL;
> +	int err;
>   
>   	if (type != HK_TYPE_DOMAIN)
>   		return -ENOTSUPP;
> @@ -149,10 +150,11 @@ int housekeeping_update(struct cpumask *isol_mask, enum hk_type type)
>   	pci_probe_flush_workqueue();
>   	mem_cgroup_flush_workqueue();
>   	vmstat_flush_workqueue();
> +	err = workqueue_unbound_housekeeping_update(housekeeping_cpumask(type));
>   
>   	kfree(old);
>   
> -	return 0;
> +	return err;
>   }
>   
>   void __init housekeeping_init(void)
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 253311af47c6..eb5660013222 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -6959,13 +6959,16 @@ static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)
>   }
>   
>   /**
> - * workqueue_unbound_exclude_cpumask - Exclude given CPUs from unbound cpumask
> - * @exclude_cpumask: the cpumask to be excluded from wq_unbound_cpumask
> + * workqueue_unbound_housekeeping_update - Propagate housekeeping cpumask update
> + * @hk: the new housekeeping cpumask
>    *
> - * This function can be called from cpuset code to provide a set of isolated
> - * CPUs that should be excluded from wq_unbound_cpumask.
> + * Update the unbound workqueue cpumask on top of the new housekeeping cpumask such
> + * that the effective unbound affinity is the intersection of the new housekeeping
> + * with the requested affinity set via nohz_full=/isolcpus= or sysfs.
> + *
> + * Return: 0 on success and -errno on failure.
>    */
> -int workqueue_unbound_exclude_cpumask(cpumask_var_t exclude_cpumask)
> +int workqueue_unbound_housekeeping_update(const struct cpumask *hk)
>   {
>   	cpumask_var_t cpumask;
>   	int ret = 0;
> @@ -6981,14 +6984,14 @@ int workqueue_unbound_exclude_cpumask(cpumask_var_t exclude_cpumask)
>   	 * (HK_TYPE_WQ ∩ HK_TYPE_DOMAIN) house keeping mask and rewritten
>   	 * by any subsequent write to workqueue/cpumask sysfs file.
>   	 */
> -	if (!cpumask_andnot(cpumask, wq_requested_unbound_cpumask, exclude_cpumask))
> +	if (!cpumask_and(cpumask, wq_requested_unbound_cpumask, hk))
>   		cpumask_copy(cpumask, wq_requested_unbound_cpumask);
>   	if (!cpumask_equal(cpumask, wq_unbound_cpumask))
>   		ret = workqueue_apply_unbound_cpumask(cpumask);
>   
>   	/* Save the current isolated cpumask & export it via sysfs */
>   	if (!ret)
> -		cpumask_copy(wq_isolated_cpumask, exclude_cpumask);
> +		cpumask_andnot(wq_isolated_cpumask, cpu_possible_mask, hk);
>   
>   	mutex_unlock(&wq_pool_mutex);
>   	free_cpumask_var(cpumask);
Reviewed-by: Waiman Long <longman@redhat.com>