Re: [PATCH RFC 0/3] workqueue: Take the pwq backend from the attrs

[Marco Crivellari]

Hello,

On Fri, Sep 18, 2026 at 4:25 PM Breno Leitao <leitao@xxxxxxxxxx> wrote:
> [...]
> Not done: the switching itself. concurrency_managed is fixed when the
> workqueue is created and is not exported through sysfs, so nothing takes a
> workqueue onto the backend or off it yet. WQ_BH is still its own path
> rather than a third backend, the static per-cpu pools are still looked up
> outside unbound_pool_hash, and callers still pass WQ_PERCPU rather than
> asking for the attrs they want.

I personally think it is better that way indeed, with WQ_PERCPU present.

I started an RFC about WQ_PREFER_PERCPU, still not published: the idea
would be an unbound workqueue that can be per-CPU (using affinities)
but without CM; so when CPUs are isolated, these WQ_PREFER_PERCPU WQs
can act as unbound. So the CM flag you added makes sense to me.

I tested my code a bit on the wq/for-7.4 branch, and it seems to be
working, but I will wait to see what happens with this series, before
sending mine.

Let's hear Tejun opinion about all of this; I'm also interested
regarding my series, so I can change if I'm not heading in the right
direction.

Thanks!
-- 

Marco Crivellari

SUSE Labs