linux-kernel - [RFC PATCH 2/2] selftests/timers: Improve skew_consistency by testing with other clockids

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Message-ID: <20250315003800.3054684-2-jstultz@google.com>
Date: Fri, 14 Mar 2025 17:37:42 -0700
From: John Stultz <jstultz@...gle.com>
To: LKML <linux-kernel@...r.kernel.org>
Cc: John Stultz <jstultz@...gle.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Stephen Boyd <sboyd@...nel.org>, Anna-Maria Behnsen <anna-maria@...utronix.de>, 
	Frederic Weisbecker <frederic@...nel.org>, Shuah Khan <shuah@...nel.org>, 
	Miroslav Lichvar <mlichvar@...hat.com>, linux-kselftest@...r.kernel.org, 
	kernel-team@...roid.com, Lei Chen <lei.chen@...rtx.com>
Subject: [RFC PATCH 2/2] selftests/timers: Improve skew_consistency by testing
 with other clockids

Lei Chen reported a bug with CLOCK_MONOTONIC_COARSE having
inconsistencies when NTP is adjusting the clock frequency.

This has gone seemingly undetected for ~15 years, illustrating a
clear gap in our testing.

The skew_consistency test is intended to catch this sort of
problem, but was focused on only evaluating CLOCK_MONOTONIC, and
thus missed the problem on CLOCK_MONOTONIC_COARSE.

So adjust the test to run with all clockids for 60 seconds each
instead of 10 minutes with just CLOCK_MONOTONIC.

Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Stephen Boyd <sboyd@...nel.org>
Cc: Anna-Maria Behnsen <anna-maria@...utronix.de>
Cc: Frederic Weisbecker <frederic@...nel.org>
Cc: Shuah Khan <shuah@...nel.org>
Cc: Miroslav Lichvar <mlichvar@...hat.com>
Cc: linux-kselftest@...r.kernel.org
Cc: kernel-team@...roid.com
Cc: Lei Chen <lei.chen@...rtx.com>
Reported-by: Lei Chen <lei.chen@...rtx.com>
Closes: https://lore.kernel.org/lkml/20250310030004.3705801-1-lei.chen@smartx.com/
Signed-off-by: John Stultz <jstultz@...gle.com>
---
 tools/testing/selftests/timers/skew_consistency.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/timers/skew_consistency.c b/tools/testing/selftests/timers/skew_consistency.c
index 83450145fe657..46c391d7f45dc 100644
--- a/tools/testing/selftests/timers/skew_consistency.c
+++ b/tools/testing/selftests/timers/skew_consistency.c
@@ -47,7 +47,7 @@ int main(int argc, char **argv)
 
 	pid = fork();
 	if (!pid)
-		return system("./inconsistency-check -c 1 -t 600");
+		return system("./inconsistency-check -t 60");
 
 	ppm = 500;
 	ret = 0;
-- 
2.49.0.rc1.451.g8f38331e32-goog