linux-kernel - Re: [PATCH v14 clocksource 6/6] clocksource: Print deviation in nanoseconds for unstable case

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Date:   Tue, 11 May 2021 20:38:07 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Feng Tang <feng.tang@...el.com>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        john.stultz@...aro.org, sboyd@...nel.org, corbet@....net,
        Mark.Rutland@....com, maz@...nel.org, kernel-team@...com,
        neeraju@...eaurora.org, ak@...ux.intel.com, zhengjun.xing@...el.com
Subject: Re: [PATCH v14 clocksource 6/6] clocksource: Print deviation in
 nanoseconds for unstable case

On Wed, May 12, 2021 at 10:21:36AM +0800, Feng Tang wrote:
> On Tue, May 11, 2021 at 04:34:55PM -0700, Paul E. McKenney wrote:
> > From: Feng Tang <feng.tang@...el.com>
> > 
> > Currently when an unstable clocksource is detected, the raw counters
> > of that clocksource and watchdog will be printed, which can only be
> > understood after some math calculation.  So print the existing delta in
> > nanoseconds to make it easier for humans to check the results.
> > 
> > Signed-off-by: Feng Tang <feng.tang@...el.com>
> > Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> > ---
> >  kernel/time/clocksource.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
> > index bbe1bcf44ffa..9c45b98e60e2 100644
> > --- a/kernel/time/clocksource.c
> > +++ b/kernel/time/clocksource.c
> > @@ -406,10 +406,10 @@ static void clocksource_watchdog(struct timer_list *unused)
> >  		if (abs(cs_nsec - wd_nsec) > md) {
> >  			pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n",
> >  				smp_processor_id(), cs->name);
> > -			pr_warn("                      '%s' wd_now: %llx wd_last: %llx mask: %llx\n",
> > -				watchdog->name, wdnow, wdlast, watchdog->mask);
> > -			pr_warn("                      '%s' cs_now: %llx cs_last: %llx mask: %llx\n",
> > -				cs->name, csnow, cslast, cs->mask);
> > +			pr_warn("                      '%s' wd_nesc: %lld wd_now: %llx wd_last: %llx mask: %llx\n",
> 
> There is a typo in the message, 'wd_nesc' should be 'wd_nsec' , 
> sorry for that.

No problem!  I already have you covered with bfa55d346b23 ("squash!
clocksource: Print deviation in nanoseconds for unstable case").

I will merge it on the next rebase.

							Thanx, Paul

> Thanks,
> Feng
> 
> 
> > +				watchdog->name, wd_nsec, wdnow, wdlast, watchdog->mask);
> > +			pr_warn("                      '%s' cs_nsec: %lld cs_now: %llx cs_last: %llx mask: %llx\n",
> > +				cs->name, cs_nsec, csnow, cslast, cs->mask);
> >  			if (curr_clocksource == cs)
> >  				pr_warn("                      '%s' is current clocksource.\n", cs->name);
> >  			else if (curr_clocksource)
> > -- 
> > 2.31.1.189.g2e36527f23