workqueue: Avoid a false warning in unbind_workers()

Doing set_cpus_allowed_ptr() with wq_unbound_cpumask can be possible fails and trigger the false warning. Use cpu_possible_mask instead when wq_unbound_cpumask has no active CPUs. It is very easy to trigger the warning: Set wq_unbound_cpumask to a small set of CPUs. Offline all the CPUs of wq_unbound_cpumask. Offline an extra CPU and trigger the warning.

Lai Jiangshan committed 4 years ago

Commit 46a4d671 parent 8bee9dd1 file · +4 −1Browse files

Showing the changes to kernel/workqueue.c (1 of 1 file). Show all

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kernel/workqueue.c+4−1

@@ -5001,7 +5001,10 @@ static void unbind_workers(int cpu) · 5000 unmodified lines
5001	5001
5002	5002	for_each_pool_worker(worker, pool) {
5003	5003	kthread_set_per_cpu(worker->task, -1);
5004		− WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, wq_unbound_cpumask) < 0);
	5004	+ if (cpumask_intersects(wq_unbound_cpumask, cpu_active_mask))
	5005	+ WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, wq_unbound_cpumask) < 0);
	5006	+ else
	5007	+ WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
5005	5008	}
5006	5009
5007	5010	mutex_unlock(&wq_pool_attach_mutex);