kernel/workqueue: Let rescuers follow unbound wq cpumask changes

When workqueue cpumask changes are committed the associated rescuer (if
one exists) affinity is not touched and this might be a problem down the
line for isolated setups.

Make sure rescuers affinity is updated every time a workqueue cpumask
changes, so that rescuers can't break isolation.

 [longman: set_cpus_allowed_ptr() will block until the designated task
  is enqueued on an allowed CPU, no wake_up_process() needed. Also use
  the unbound_effective_cpumask() helper as suggested by Tejun.]

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index da124859a691be0035c31556373de227afe21ffb..a24c7cfb80b4e5a64ae6f5887e1d30fbbb02ba11 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5051,6 +5051,11 @@ static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
        /* update node_nr_active->max */
        wq_update_node_max_active(ctx->wq, -1);
 
+       /* rescuer needs to respect wq cpumask changes */
+       if (ctx->wq->rescuer)
+               set_cpus_allowed_ptr(ctx->wq->rescuer->task,
+                                    unbound_effective_cpumask(ctx->wq));
+
        mutex_unlock(&ctx->wq->mutex);
 }