Re: [PATCH-cgroup 1/4] workqueue: Add workqueue_unbound_exclude_cpumask() to exclude CPUs from wq_unbound_cpumask

[Waiman Long <longman@redhat.com>]

On 10/23/23 23:28, Tejun Heo wrote:
> Hello,
>
> On Wed, Oct 18, 2023 at 03:18:52PM -0400, Waiman Long wrote:
>> I have a second thought after taking a further look at that. First of all,
>> cpuset_allowed_mask isn't relevant here and the mask can certainly contain
>> offline CPUs. So cpu_possible_mask is the proper fallback.
>>
>> With the current patch, wq_user_unbound_cpumask is set up initially as
>> (HK_TYPE_WQ ∩ HK_TYPE_DOMAIN) house keeping mask and rewritten by any
>> subsequent write to workqueue/cpumask sysfs file. So using
> The current behavior is not something which is carefully planned. It's more
> accidental than anything. If we can come up with a more intutive and
> consistent behavior, that should be fine.
>
>> wq_user_unbound_cpumask has the implied precedence of user-sysfs written
>> mask, command line isolcpus or nohz_full option mask and cpu_possible_mask.
>> I think just fall back to wq_user_unbound_cpumask if the operation fails
>> should be enough.
> But yeah, that sounds acceptable.

I have implemented the fallback to the user requested cpumask in the 
failure case.

Cheers,
Longman