[023/178] watchdog: explicitly update timestamp when reporting softlockup

Commit Message

Andrew Morton April 30, 2021, 5:54 a.m. UTC

From: Petr Mladek <[e-mail]>
Subject: watchdog: explicitly update timestamp when reporting softlockup

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.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Petr Mladek <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Laurence Oberman <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Vincent Whitchurch <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 kernel/watchdog.c |    3 +++
 1 file changed, 3 insertions(+)

Patch

--- a/kernel/watchdog.c~watchdog-explicitly-update-timestamp-when-reporting-softlockup
+++ a/kernel/watchdog.c
@@ -410,6 +410,9 @@  static enum hrtimer_restart watchdog_tim
 			}
 		}
 
+		/* 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));