Messages in this thread | | | Date | Wed, 2 Nov 2022 22:23:25 -0400 | Subject | Re: [PATCH clocksource 1/2] clocksource: Add comments to classify bogus measurements | From | Waiman Long <> |
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On 11/2/22 14:40, Paul E. McKenney wrote: > 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; > }
Looks good.
Reviewed-by: Waiman Long <longman@redhat.com>
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