Re: [RFC PATCH 1/8] workqueue: Unconditionally set cpumask in worker_attach_to_pool()

[Lai Jiangshan]

On Wed, Aug 17, 2022 at 5:18 AM Tejun Heo <tj@xxxxxxxxxx> wrote:
>
> cc'ing Waiman.
>
> On Thu, Aug 04, 2022 at 04:41:28PM +0800, Lai Jiangshan wrote:
> > From: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
> >
> > If a worker is spuriously woken up after kthread_bind_mask() but before
> > worker_attach_to_pool(), and there are some cpu-hot-[un]plug happening
> > during the same interval, the worker task might be pushed away from its
> > bound CPU with its affinity changed by the scheduler and worker_attach_to_pool()
> > doesn't rebind it properly.
> >
> > Do unconditionally affinity binding in worker_attach_to_pool() to fix
> > the problem.
> >
> > Prepare for moving worker_attach_to_pool() from create_worker() to the
> > starting of worker_thread() which will really cause the said interval
> > even without spurious wakeup.
>
> So, this looks fine but I think the whole thing can be simplified if we
> integrate this with the persistent user cpumask change that Waiman is
> working on. We can just set the cpumask once during init and let the
> scheduler core figure out what the current effective mask is as CPU
> availability changes.
>
>  http://lkml.kernel.org/r/20220816192734.67115-4-longman@xxxxxxxxxx
>

I like this approach.