Commit 640f17c8 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

workqueue: Restrict affinity change to rescuer 



create_worker() will already set the right affinity using
kthread_bind_mask(), this means only the rescuer will need to change
it's affinity.

Howveer, while in cpu-hot-unplug a regular task is not allowed to run
on online&&!active as it would be pushed away quite agressively. We
need KTHREAD_IS_PER_CPU to survive in that environment.

Therefore set the affinity after getting that magic flag.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Tested-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210121103506.826629830@infradead.org
parent 5c25b5ff

kernel/workqueue.c

+3 −6
Original line number Diff line number Diff line
@@ -1848,12 +1848,6 @@ 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);



	/*

	 * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains

	 * stable across this function.  See the comments above the flag
@@ -1864,6 +1858,9 @@ static void worker_attach_to_pool(struct worker *worker, 
	else

		kthread_set_per_cpu(worker->task, pool->cpu);



	if (worker->rescue_wq)

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



	list_add_tail(&worker->node, &pool->workers);

	worker->pool = pool;