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workqueue: avoid hard lockups in show_workqueue_state()

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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+
This commit is contained in:
Sergey Senozhatsky 2018-01-11 09:53:35 +09:00 committed by Tejun Heo
parent 01dfee9582
commit 62635ea8c1
1 changed files with 13 additions and 0 deletions
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13
kernel/workqueue.c
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@ -48,6 +48,7 @@
#include <linux/moduleparam.h>
#include <linux/uaccess.h>
#include <linux/sched/isolation.h>
#include <linux/nmi.h>
#include "workqueue_internal.h"
@ -4463,6 +4464,12 @@ 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();
}
}
@ -4490,6 +4497,12 @@ 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();