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%3Ba=su...

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 stable@vger.kernel.org know about it.

From 62635ea8c18f0f62df4cc58379e4f1d33afd5801 Mon Sep 17 00:00:00 2001

From: Sergey Senozhatsky sergey.senozhatsky.work@gmail.com Date: Thu, 11 Jan 2018 09:53:35 +0900 Subject: workqueue: avoid hard lockups in show_workqueue_state()

From: Sergey Senozhatsky sergey.senozhatsky.work@gmail.com

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.

Signed-off-by: Sergey Senozhatsky sergey.senozhatsky@gmail.com Signed-off-by: Tejun Heo tj@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

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

--- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -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 sergey.senozhatsky.work@gmail.com are

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