workqueue: Minor follow-ups to the rescuer destruction change

* Now that wq->rescuer may be cleared while rescuer is still there,
  switch show_pwq() debug printout to test worker->rescue_wq to
  identify rescuers intead of testing wq->rescuer.

* Update comment on ->rescuer locking.

Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Lai Jiangshan <jiangshanlai@gmail.com>

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 3f067f1d72e3055b538429a6248af3971678564f..7f7aa45dac3777b67570d7c54b0b7fc41134def9 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -248,7 +248,7 @@ struct workqueue_struct {
        struct list_head        flusher_overflow; /* WQ: flush overflow list */
 
        struct list_head        maydays;        /* MD: pwqs requesting rescue */
-       struct worker           *rescuer;       /* I: rescue worker */
+       struct worker           *rescuer;       /* MD: rescue worker */
 
        int                     nr_drainers;    /* WQ: drain in progress */
        int                     saved_max_active; /* WQ: saved pwq max_active */
@@ -4672,7 +4672,7 @@ static void show_pwq(struct pool_workqueue *pwq)
 
                        pr_cont("%s %d%s:%ps", comma ? "," : "",
                                task_pid_nr(worker->task),
-                               worker == pwq->wq->rescuer ? "(RESCUER)" : "",
+                               worker->rescue_wq ? "(RESCUER)" : "",
                                worker->current_func);
                        list_for_each_entry(work, &worker->scheduled, entry)
                                pr_cont_work(false, work);