From: Lai Jiangshan <jiangshan.ljs@antgroup.com>

Simplify the rescuer work by looping directly in the rescuer rather than
adding the pwq back to the maydays list. This also helps when
max_requests is 1 or small but pwq->inactive_works has a large number of
pending work items.

This might hurt fairness among PWQs and the rescuer could end up being
stuck on one PWQ indefinitely, but the rescuer's objective is to make
forward progress rather than ensure fairness.

Fairness can be further improved in future by assigning work items to
the rescuer one by one and this is a temporary change to ease the
transition.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
---
 kernel/workqueue.c | 24 +-----------------------
 1 file changed, 1 insertion(+), 23 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 2654fbd481a1..02386e6eb409 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3520,31 +3520,9 @@ static int rescuer_thread(void *__rescuer)
 
 		WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
 
-		if (assign_rescuer_work(pwq, rescuer)) {
+		while (assign_rescuer_work(pwq, rescuer))
 			process_scheduled_works(rescuer);
 
-			/*
-			 * The above execution of rescued work items could
-			 * have created more to rescue through
-			 * pwq_activate_first_inactive() or chained
-			 * queueing.  Let's put @pwq back on mayday list so
-			 * that such back-to-back work items, which may be
-			 * being used to relieve memory pressure, don't
-			 * incur MAYDAY_INTERVAL delay inbetween.
-			 */
-			if (pwq->nr_active && need_to_create_worker(pool)) {
-				raw_spin_lock(&wq_mayday_lock);
-				/*
-				 * Queue iff somebody else hasn't queued it already.
-				 */
-				if (list_empty(&pwq->mayday_node)) {
-					get_pwq(pwq);
-					list_add_tail(&pwq->mayday_node, &wq->maydays);
-				}
-				raw_spin_unlock(&wq_mayday_lock);
-			}
-		}
-
 		/*
 		 * Leave this pool. Notify regular workers; otherwise, we end up
 		 * with 0 concurrency and stalling the execution.
-- 
2.19.1.6.gb485710b

On Tue, Nov 25, 2025 at 02:36:14PM +0800, Lai Jiangshan wrote:
> From: Lai Jiangshan <jiangshan.ljs@antgroup.com>
> 
> Simplify the rescuer work by looping directly in the rescuer rather than
> adding the pwq back to the maydays list. This also helps when
> max_requests is 1 or small but pwq->inactive_works has a large number of
> pending work items.
> 
> This might hurt fairness among PWQs and the rescuer could end up being
> stuck on one PWQ indefinitely, but the rescuer's objective is to make
> forward progress rather than ensure fairness.
> 
> Fairness can be further improved in future by assigning work items to
> the rescuer one by one and this is a temporary change to ease the
> transition.

Again, I'd just note that this is temporary removal rather than trying
justify that fairness doesn't matter because I think it does (not in terms
of theoretical correctness but in the practical approach of avoiding
unnecessary surprises) and the behavior is restored by a later patch.

Thanks.

-- 
tejun