lkml.org 
[lkml]   [2022]   [Nov]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH clocksource 1/2] clocksource: Add comments to classify bogus measurements
Date
An extremely busy system can delay the clocksource watchdog, so that
the corresponding too-long bogus-measurement error does not necessarily
imply an error in the system. However, a too-short bogus-measurement
error likely indicates a bug in hardware, firmware or software.

Therefore, add comments clarifying these bogus-measurement pr_warn()s.

Reported-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: John Stultz <jstultz@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Waiman Long <longman@redhat.com>
---
kernel/time/clocksource.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index dcaf38c062161..3f5317faf891f 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -443,10 +443,12 @@ static void clocksource_watchdog(struct timer_list *unused)
/* Check for bogus measurements. */
wdi = jiffies_to_nsecs(WATCHDOG_INTERVAL);
if (wd_nsec < (wdi >> 2)) {
+ /* This usually indicates broken timer code or hardware. */
pr_warn("timekeeping watchdog on CPU%d: Watchdog clocksource '%s' advanced only %lld ns during %d-jiffy time interval, skipping watchdog check.\n", smp_processor_id(), watchdog->name, wd_nsec, WATCHDOG_INTERVAL);
continue;
}
if (wd_nsec > (wdi << 2)) {
+ /* This can happen on busy systems, which can delay the watchdog. */
pr_warn("timekeeping watchdog on CPU%d: Watchdog clocksource '%s' advanced an excessive %lld ns during %d-jiffy time interval, probable CPU overutilization, skipping watchdog check.\n", smp_processor_id(), watchdog->name, wd_nsec, WATCHDOG_INTERVAL);
continue;
}
--
2.31.1.189.g2e36527f23
\
 
 \ /
  Last update: 2022-11-02 19:40    [W:0.071 / U:0.556 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site