On 14/12/20 15:54, Lai Jiangshan wrote:
> @@ -1848,11 +1848,11 @@ static void worker_attach_to_pool(struct worker
> *worker,
> {
> mutex_lock(&wq_pool_attach_mutex);
>
> - /*
> - * 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.
> - */
> - set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
> + /* Is there any cpu in pool->attrs->cpumask online? */
> + if (cpumask_any_and(pool->attrs->cpumask, wq_online_cpumask) <
> nr_cpu_ids)
if (cpumask_intersects(pool->attrs->cpumask, wq_online_cpumask))
> + WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
> pool->attrs->cpumask) < 0);
> + else
> + WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
> cpu_possible_mask) < 0);
So for that late-spawned per-CPU kworker case: the outgoing CPU should have
already been cleared from wq_online_cpumask, so it gets its affinity reset
to the possible mask and the subsequent wakeup will ensure it's put on an
active CPU.
Seems alright to me.
>
> /*
> * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
