From 4c0736a76a186e5df2cd2afda3e7a04d2a427d1b Mon Sep 17 00:00:00 2001
From: Petr Mladek <pmladek@suse.com>
Date: Tue, 7 Mar 2023 13:53:34 +0100
Subject: [PATCH] workqueue: Warn when a rescuer could not be created
Git-commit: 4c0736a76a186e5df2cd2afda3e7a04d2a427d1b
Patch-mainline: v6.4-rc1
References: bsc#1211044

Rescuers are created when a workqueue with WQ_MEM_RECLAIM is allocated.
It typically happens during the system boot.

systemd switches the root filesystem from initrd to the booted system
during boot. It kills processes that block the switch for too long.
One of the process might be modprobe that tries to create a workqueue.

These problems are hard to reproduce. Also alloc_workqueue() does not
pass the error code. Make the debugging easier by printing an error,
similar to create_worker().

Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

---
 kernel/workqueue.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4074,13 +4074,18 @@ struct workqueue_struct *__alloc_workque
 		struct worker *rescuer;
 
 		rescuer = alloc_worker(NUMA_NO_NODE);
-		if (!rescuer)
+		if (!rescuer) {
+			pr_err("workqueue: Failed to allocate a rescuer for wq \"%s\"\n",
+			       wq->name);
 			goto err_destroy;
+		}
 
 		rescuer->rescue_wq = wq;
 		rescuer->task = kthread_create(rescuer_thread, rescuer, "%s",
 					       wq->name);
 		if (IS_ERR(rescuer->task)) {
+			pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %ld",
+			       wq->name, PTR_ERR(rescuer->task));
 			kfree(rescuer);
 			goto err_destroy;
 		}