[PATCH 5.10 090/289] watchdog: explicitly update timestamp when reporting softlockup

[Greg Kroah-Hartman]

From: Petr Mladek <pmladek@xxxxxxxx>

[ Upstream commit c9ad17c991492f4390f42598f6ab0531f87eed07 ]

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/20210311122130.6788-3-pmladek@xxxxxxxx
Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Laurence Oberman <loberman@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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));
-- 
2.30.2