On 21/01/21 11:17, Peter Zijlstra wrote:
> @@ -4972,9 +4977,11 @@ static void rebind_workers(struct worker
> * of all workers first and then clear UNBOUND. As we're called
> * from CPU_ONLINE, the following shouldn't fail.
> */
> - for_each_pool_worker(worker, pool)
> + for_each_pool_worker(worker, pool) {
> + kthread_set_per_cpu(worker->task, pool->cpu);
> WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
> pool->attrs->cpumask) < 0);
At the end of this series, is_cpu_allowed() allows kthreads with
KTHREAD_IS_PER_CPU on any online CPU, even if it isn't the designated
kthread->cpu.
I thought there might be a race here, given this gives us a window where a
pcpu kworker has the flag but is still affined to cpus_possible_mask. Now,
given cpus_write_lock(), we can't have a CPU going up while another goes
down. So I think it's actually fine, and I've been chasing ghosts yet again.
> + }
>
> raw_spin_lock_irq(&pool->lock);
>
