linux-kernel - [RFC][PATCH v2] selftest: timers: Tweak raw_skew to SKIP when ADJ_OFFSET/other clock adjustments are in progress

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Date:   Thu,  5 Jul 2018 10:50:31 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     lkml <linux-kernel@...r.kernel.org>
Cc:     John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Miroslav Lichvar <mlichvar@...hat.com>,
        Richard Cochran <richardcochran@...il.com>,
        Prarit Bhargava <prarit@...hat.com>,
        Stephen Boyd <sboyd@...nel.org>, Shuah Khan <shuah@...nel.org>,
        linux-kselftest@...r.kernel.org
Subject: [RFC][PATCH v2] selftest: timers: Tweak raw_skew to SKIP when ADJ_OFFSET/other clock adjustments are in progress

In the past we've warned when ADJ_OFFSET was in progress, usually
caused by ntpd or some other time adjusting daemon running in non
steady sate, which can cause the skew calculations to be incorrect

Thus, this patch sets a flag which we check if the clock was being
adjusted when we fail so that we don't cause false negatives.

Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Miroslav Lichvar <mlichvar@...hat.com>
Cc: Richard Cochran <richardcochran@...il.com>
Cc: Prarit Bhargava <prarit@...hat.com>
Cc: Stephen Boyd <sboyd@...nel.org>
Cc: Shuah Khan <shuah@...nel.org>
Cc: linux-kselftest@...r.kernel.org
Suggested-by: Miroslav Lichvar <mlichvar@...hat.com>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
v2: Widened the checks to look for other clock adjustments that
    could happen, as suggested by Miroslav
---
 tools/testing/selftests/timers/raw_skew.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/testing/selftests/timers/raw_skew.c b/tools/testing/selftests/timers/raw_skew.c
index ca6cd14..dcf73c5 100644
--- a/tools/testing/selftests/timers/raw_skew.c
+++ b/tools/testing/selftests/timers/raw_skew.c
@@ -134,6 +134,11 @@ int main(int argv, char **argc)
 	printf(" %lld.%i(act)", ppm/1000, abs((int)(ppm%1000)));
 
 	if (llabs(eppm - ppm) > 1000) {
+		if (tx1.offset || tx2.offset ||
+		    tx1.freq != tx2.freq || tx1.tick != tx2.tick) {
+			printf("	[SKIP]\n");
+			return ksft_exit_skip("The clock was adjusted externally. Shutdown NTPd or other time sync daemons\n");
+		}
 		printf("	[FAILED]\n");
 		return ksft_exit_fail();
 	}
-- 
2.7.4