[tip: timers/core] clocksource: Improve read-back-delay message

[tip-bot2 for Paul E. McKenney]

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     f092eb34b33043152bfb8a4ca01db9a06728261d
Gitweb:        https://git.kernel.org/tip/f092eb34b33043152bfb8a4ca01db9a06728261d
Author:        Paul E. McKenney <paulmck@xxxxxxxxxx>
AuthorDate:    Tue, 13 Dec 2022 13:57:28 -08:00
Committer:     Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Tue, 03 Jan 2023 20:43:45 -08:00

clocksource: Improve read-back-delay message

When cs_watchdog_read() is unable to get a qualifying clocksource read
within the limit set by max_cswd_read_retries, it prints a message
and marks the clocksource under test as unstable.  But that message is
unclear to anyone unfamiliar with the code:

clocksource: timekeeping watchdog on CPU13: wd-tsc-wd read-back delay 1000614ns, attempt 3, marking unstable

Therefore, add some context so that the message appears as follows:

clocksource: timekeeping watchdog on CPU13: wd-tsc-wd excessive read-back delay of 1000614ns vs. limit of 125000ns, wd-wd read-back delay only 27ns, attempt 3, marking tsc unstable

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: John Stultz <jstultz@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Stephen Boyd <sboyd@xxxxxxxxxx>
Cc: Feng Tang <feng.tang@xxxxxxxxx>
---
 kernel/time/clocksource.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index a3d19f6..b599149 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -260,8 +260,8 @@ static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow, 
 			goto skip_test;
 	}
 
-	pr_warn("timekeeping watchdog on CPU%d: wd-%s-wd read-back delay of %lldns, attempt %d, marking unstable\n",
-		smp_processor_id(), cs->name, wd_delay, nretries);
+	pr_warn("timekeeping watchdog on CPU%d: wd-%s-wd excessive read-back delay of %lldns vs. limit of %ldns, wd-wd read-back delay only %lldns, attempt %d, marking %s unstable\n",
+		smp_processor_id(), cs->name, wd_delay, WATCHDOG_MAX_SKEW, wd_seq_delay, nretries, cs->name);
 	return WD_READ_UNSTABLE;
 
 skip_test: