linux-kernel - [RFC][PATCH] selftest: timers: Tweak raw_skew to SKIP when ADJ

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Date:   Tue,  3 Jul 2018 12:36:27 -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] selftest: timers: Tweak raw_skew to SKIP when ADJ_OFFSET is 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 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>
---
 tools/testing/selftests/timers/raw_skew.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/timers/raw_skew.c b/tools/testing/selftests/timers/raw_skew.c
index ca6cd14..d3fc453 100644
--- a/tools/testing/selftests/timers/raw_skew.c
+++ b/tools/testing/selftests/timers/raw_skew.c
@@ -94,6 +94,7 @@ int main(int argv, char **argc)
 	struct timespec mon, raw, start, end;
 	long long delta1, delta2, interval, eppm, ppm;
 	struct timex tx1, tx2;
+	int adj_offset_bad = 0;
 
 	setbuf(stdout, NULL);
 
@@ -108,8 +109,10 @@ int main(int argv, char **argc)
 	start = mon;
 	delta1 = diff_timespec(mon, raw);
 
-	if (tx1.offset)
+	if (tx1.offset) {
 		printf("WARNING: ADJ_OFFSET in progress, this will cause inaccurate results\n");
+		adj_offset_bad = 1;
+	}
 
 	printf("Estimating clock drift: ");
 	sleep(120);
@@ -134,6 +137,10 @@ int main(int argv, char **argc)
 	printf(" %lld.%i(act)", ppm/1000, abs((int)(ppm%1000)));
 
 	if (llabs(eppm - ppm) > 1000) {
+		if (adj_offset_bad) {
+			printf("	[SKIP]\n");
+			return ksft_exit_skip("ADJ_OFFSET in progress. Shutdown NTPd or other time steering daemons\n");
+		}
 		printf("	[FAILED]\n");
 		return ksft_exit_fail();
 	}
-- 
2.7.4