From: Petr Mladek <pmladek@suse.com>
To: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Cc: Laurence Oberman <loberman@redhat.com>,
Vincent Whitchurch <vincent.whitchurch@axis.com>,
Michal Hocko <mhocko@suse.com>,
linux-kernel@vger.kernel.org, Petr Mladek <pmladek@suse.com>
Subject: [PATCH v2 2/7] watchdog: Explicitly update timestamp when reporting softlockup
Date: Thu, 10 Dec 2020 17:00:33 +0100 [thread overview]
Message-ID: <20201210160038.31441-3-pmladek@suse.com> (raw)
In-Reply-To: <20201210160038.31441-1-pmladek@suse.com>
The softlockup situation might stay for a long time or even forever.
When it happens, the softlockup debug messages are printed in regular
intervals defined by get_softlockup_thresh().
There is a mystery. The repeated message is printed after the full interval
that is defined by get_softlockup_thresh(). But the timer callback is called
more often as defined by sample_period. The code looks like the soflockup
should get reported in every sample_period when it was once behind the thresh.
It works only by chance. The watchdog is touched when printing the stall
report, for example, in printk_stack_address().
Make the behavior clear and predictable by explicitly updating
the timestamp in watchdog_timer_fn() when the report gets printed.
Signed-off-by: Petr Mladek <pmladek@suse.com>
---
kernel/watchdog.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index c58244064de8..7776d53a015c 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -409,6 +409,9 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
}
}
+ /* Start period for the next softlockup warning. */
+ update_touch_ts();
+
pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
smp_processor_id(), duration,
current->comm, task_pid_nr(current));
--
2.26.2
next prev parent reply other threads:[~2020-12-10 16:41 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-10 16:00 [PATCH v2 0/7] watchdog/softlockup: Report overall time and some cleanup Petr Mladek
2020-12-10 16:00 ` [PATCH v2 1/7] watchdog: Rename __touch_watchdog() to a better descriptive name Petr Mladek
2020-12-10 16:00 ` Petr Mladek [this message]
2020-12-10 16:00 ` [PATCH v2 3/7] watchdog/softlockup: Report the overall time of softlockups Petr Mladek
2020-12-10 16:00 ` [PATCH v2 4/7] watchdog/softlockup: Remove logic that tried to prevent repeated reports Petr Mladek
2020-12-10 16:00 ` [PATCH v2 5/7] watchdog: Fix barriers when printing backtraces from all CPUs Petr Mladek
2020-12-10 16:00 ` [PATCH v2 6/7] watchdog: Cleanup handling of false positives Petr Mladek
2020-12-10 16:00 ` [PATCH v2 7/7] Test softlockup Petr Mladek
2021-01-03 15:03 ` 3cc3ef45b2: RIP:version_proc_show kernel test robot
2021-01-05 9:37 ` Petr Mladek
2021-03-11 12:21 [PATCH v2 0/7] watchdog/softlockup: Report overall time and some cleanup Petr Mladek
2021-03-11 12:21 ` [PATCH v2 2/7] watchdog: Explicitly update timestamp when reporting softlockup Petr Mladek
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