[PATCH 3/6] workqueue: make destroy_worker() atomically

destroy_worker() doesn't need to wait for worker's task exit. There is no essential things to do after kthread_stop(). So we remove kthread_stop(). put_unbound_pool() needs to wait for workers' tasks exit. we add a new completion to handle it. The purpose of this patch is not making the slowpath

[PATCH 3/6] workqueue: make destroy_worker() atomically

destroy_worker() doesn't need to wait for worker's task exit. There is no essential things to do after kthread_stop(). So we remove kthread_stop(). put_unbound_pool() needs to wait for workers' tasks exit. we add a new completion to handle it. The purpose of this patch is not making the slowpath