Patch "workqueue: avoid hard lockups in show_workqueue_state()" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

workqueue: avoid hard lockups in show_workqueue_state()

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
workqueue-avoid-hard-lockups-in-show_workqueue_state.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Sergey Senozhatsky <[email protected]>
Date: Thu, 11 Jan 2018 09:53:35 +0900
Subject: workqueue: avoid hard lockups in show_workqueue_state()

From: Sergey Senozhatsky <[email protected]>

commit 62635ea8c18f0f62df4cc58379e4f1d33afd5801 upstream.

show_workqueue_state() can print out a lot of messages while being in atomic context, e.g. sysrq-t -> show_workqueue_state(). If the console device is slow it may end up triggering NMI hard lockup watchdog.

---
 kernel/workqueue.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

@@ -48,6 +48,7 @@
 #include <linux/nodemask.h>
 #include <linux/moduleparam.h>
 #include <linux/uaccess.h>
+#include <linux/nmi.h>
 
 #include "workqueue_internal.h"
 

@@ -4479,6 +4480,12 @@ void show_workqueue_state(void)
 			if (pwq->nr_active || !list_empty(&pwq->delayed_works))
 				show_pwq(pwq);
 			spin_unlock_irqrestore(&pwq->pool->lock, flags);
+			/*
+			 * We could be printing a lot from atomic context, e.g.
+			 * sysrq-t -> show_workqueue_state(). Avoid triggering
+			 * hard lockup.
+			 */
+			touch_nmi_watchdog();
 		}
 	}
 

@@ -4506,6 +4513,12 @@ void show_workqueue_state(void)
 		pr_cont("\n");
 	next_pool:
 		spin_unlock_irqrestore(&pool->lock, flags);
+		/*
+		 * We could be printing a lot from atomic context, e.g.
+		 * sysrq-t -> show_workqueue_state(). Avoid triggering
+		 * hard lockup.
+		 */
+		touch_nmi_watchdog();
 	}
 
 	rcu_read_unlock_sched();

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/workqueue-avoid-hard-lockups-in-show_workqueue_state.patch