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: [PATCH] workqueue: avoid hard lockups in show_workqueue_state()
References: bsc#1085474
Patch-mainline: v4.15-rc9
Git-commit: 62635ea8c18f0f62df4cc58379e4f1d33afd5801
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>
Cc: stable@vger.kernel.org # v4.5+
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
kernel/workqueue.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index f48983413342..a52543506037 100644
--- 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"
@@ -4439,6 +4440,12 @@ 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();
}
}
@@ -4466,6 +4473,12 @@ 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();
--
2.13.6