[PATCH 03/10] workqueue: Manually break affinity on pool detachment

[Lai Jiangshan]

From: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx>

Don't rely on the scheduler to force break affinity for us -- it will
stop doing that for per-cpu-kthreads.

Fixes: 06249738a41a ("workqueue: Manually break affinity on hotplug")
Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx>
---
 kernel/workqueue.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 1f5b8385c0cf..1f6cb83e0bc5 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1885,6 +1885,16 @@ static void worker_detach_from_pool(struct worker *worker)
 
 	if (list_empty(&pool->workers))
 		detach_completion = pool->detach_completion;
+
+	/*
+	 * The cpus of pool->attrs->cpumask might all go offline after
+	 * detachment, and the scheduler may not force break affinity
+	 * for us, so we do it on our own and unbind this worker which
+	 * can't be unbound by workqueue_offline_cpu() since it doesn't
+	 * belong to any pool after it.
+	 */
+	set_cpus_allowed_ptr(worker->task, cpu_possible_mask);
+
 	mutex_unlock(&wq_pool_attach_mutex);
 
 	/* clear leftover flags without pool->lock after it is detached */
-- 
2.19.1.6.gb485710b