clocksource/wdtest: Print time values for short udelay(1)

When a pair of clocksource reads separated by a udelay(1) claim less than a
full microsecond of elapsed time, print the measured delay as part of the
splat.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/717a2ddf-a80f-490b-aa3a-4e4b74fa56ca@paulmck-laptop

diff --git a/kernel/time/clocksource-wdtest.c b/kernel/time/clocksource-wdtest.c
index 62e73444ffe45ad42511ccb0e5b9a7aeaeeaa415..38dae590b29f57fbc1e2333866eac2c811b99655 100644 (file)
--- a/kernel/time/clocksource-wdtest.c
+++ b/kernel/time/clocksource-wdtest.c
@@ -137,7 +137,8 @@ static int wdtest_func(void *arg)
        udelay(1);
        j2 = clocksource_wdtest_ktime.read(&clocksource_wdtest_ktime);
        pr_info("--- tsc-like times: %lu - %lu = %lu.\n", j2, j1, j2 - j1);
-       WARN_ON_ONCE(time_before(j2, j1 + NSEC_PER_USEC));
+       WARN_ONCE(time_before(j2, j1 + NSEC_PER_USEC),
+                 "Expected at least 1000ns, got %lu.\n", j2 - j1);
 
        /* Verify tsc-like stability with various numbers of errors injected. */
        max_retries = clocksource_get_max_watchdog_retry();