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 4.9-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-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 62635ea8c18f0f62df4cc58379e4f1d33afd5801 Mon Sep 17 00:00:00 2001
From: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
Date: Thu, 11 Jan 2018 09:53:35 +0900
Subject: workqueue: avoid hard lockups in show_workqueue_state()
From: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
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@xxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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"
@@ -4424,6 +4425,12 @@ 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();
}
}
@@ -4451,6 +4458,12 @@ 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@xxxxxxxxx are
queue-4.9/workqueue-avoid-hard-lockups-in-show_workqueue_state.patch