Re: [PATCH 2/2] workqueue: Fix affinity of kworkers attached during late hotplug

[Peter Zijlstra]

On Fri, Dec 11, 2020 at 11:39:21AM +0000, Vincent Donnefort wrote:
> On Thu, Dec 10, 2020 at 04:38:30PM +0000, Valentin Schneider wrote:
> > +	if (pool->flags & POOL_DISASSOCIATED) {
> >  		worker->flags |= WORKER_UNBOUND;
> > +		set_cpus_allowed_ptr(worker->task, cpu_active_mask);
> > +	} else {
> > +		/*
> > +		 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
> > +		 * online CPUs. It'll be re-applied when any of the CPUs come up.
> > +		 */
> 
> Does this comment still stand ? IIUC, we should always be in the
> POOL_DISASSOCIATED case if the CPU from cpumask is offline. Unless a
> pool->attrs->cpumask can have several CPUs. In that case maybe we should check
> for the cpu_active_mask here too ?

IIUC it can be a numa mask, and would still be valid in that case.

> > +		set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
> > +	}