[SRU,B] selftest: timers: Tweak raw_skew to SKIP when ADJ_OFFSET/other clock adjustments are in progress

Message ID 20190201174526.16454-1-dan.streetman@canonical.com
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  • [SRU,B] selftest: timers: Tweak raw_skew to SKIP when ADJ_OFFSET/other clock adjustments are in progress
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Commit Message

Dan Streetman Feb. 1, 2019, 5:45 p.m.
From: John Stultz <john.stultz@linaro.org>

BugLink: https://bugs.launchpad.net/bugs/1811194

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 checks to see if the clock was being adjusted
when we fail so that we don't cause false negatives.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
Suggested-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
v2: Widened the checks to look for other clock adjustments that
    could happen, as suggested by Miroslav
v3: Fixed up commit message

Signed-off-by: Dan Streetman <ddstreet@canonical.com>
(cherry-picked from upstream 1416270f4a1ae83ea84156ceba19a66a8f88be1f)
---
 tools/testing/selftests/timers/raw_skew.c | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Stefan Bader Feb. 7, 2019, 8:18 a.m. | #1
On 01.02.19 18:45, Dan Streetman wrote:
> From: John Stultz <john.stultz@linaro.org>
> 
> BugLink: https://bugs.launchpad.net/bugs/1811194
> 
> 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 checks to see if the clock was being adjusted
> when we fail so that we don't cause false negatives.
> 
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Miroslav Lichvar <mlichvar@redhat.com>
> Cc: Richard Cochran <richardcochran@gmail.com>
> Cc: Prarit Bhargava <prarit@redhat.com>
> Cc: Stephen Boyd <sboyd@kernel.org>
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: linux-kselftest@vger.kernel.org
> Suggested-by: Miroslav Lichvar <mlichvar@redhat.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> v2: Widened the checks to look for other clock adjustments that
>     could happen, as suggested by Miroslav
> v3: Fixed up commit message
> 
> Signed-off-by: Dan Streetman <ddstreet@canonical.com>
> (cherry-picked from upstream 1416270f4a1ae83ea84156ceba19a66a8f88be1f)
Acked-by: Stefan Bader <stefan.bader@canonical.com>
> ---
>  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 ca6cd146aafe..dcf73c5dab6e 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();
>  	}
>
Kleber Souza Feb. 28, 2019, 1:01 p.m. | #2
On 2/1/19 6:45 PM, Dan Streetman wrote:
> From: John Stultz <john.stultz@linaro.org>
>
> BugLink: https://bugs.launchpad.net/bugs/1811194
>
> 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 checks to see if the clock was being adjusted
> when we fail so that we don't cause false negatives.
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Miroslav Lichvar <mlichvar@redhat.com>
> Cc: Richard Cochran <richardcochran@gmail.com>
> Cc: Prarit Bhargava <prarit@redhat.com>
> Cc: Stephen Boyd <sboyd@kernel.org>
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: linux-kselftest@vger.kernel.org
> Suggested-by: Miroslav Lichvar <mlichvar@redhat.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> v2: Widened the checks to look for other clock adjustments that
>     could happen, as suggested by Miroslav
> v3: Fixed up commit message
>
> Signed-off-by: Dan Streetman <ddstreet@canonical.com>
> (cherry-picked from upstream 1416270f4a1ae83ea84156ceba19a66a8f88be1f)


Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>


> ---
>  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 ca6cd146aafe..dcf73c5dab6e 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();
>  	}
Khaled Elmously March 4, 2019, 5:13 a.m. | #3
On 2019-02-01 12:45:26 , Dan Streetman wrote:
> From: John Stultz <john.stultz@linaro.org>
> 
> BugLink: https://bugs.launchpad.net/bugs/1811194
> 
> 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 checks to see if the clock was being adjusted
> when we fail so that we don't cause false negatives.
> 
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Miroslav Lichvar <mlichvar@redhat.com>
> Cc: Richard Cochran <richardcochran@gmail.com>
> Cc: Prarit Bhargava <prarit@redhat.com>
> Cc: Stephen Boyd <sboyd@kernel.org>
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: linux-kselftest@vger.kernel.org
> Suggested-by: Miroslav Lichvar <mlichvar@redhat.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> v2: Widened the checks to look for other clock adjustments that
>     could happen, as suggested by Miroslav
> v3: Fixed up commit message
> 
> Signed-off-by: Dan Streetman <ddstreet@canonical.com>
> (cherry-picked from upstream 1416270f4a1ae83ea84156ceba19a66a8f88be1f)
> ---

Dan, the way you're adding your "cherry picked from" and Signed-off-by lines means they won't actually show up in the commit message.

The "cherry picked from" line and your Signed-off-by should immediately follow the provenance of the patch.
Also, the syntax is "cherry picked from commit X" (no hyphen, and "commit" instead of "upstream")

So in this case your commit message should look like:


selftest: timers: Tweak raw_skew to SKIP when ADJ_OFFSET/other clock adjustments are in progress
  
BugLink: https://bugs.launchpad.net/bugs/1811194

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 checks to see if the clock was being adjusted
when we fail so that we don't cause false negatives.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
Suggested-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
(cherry picked from 1416270f4a1ae83ea84156ceba19a66a8f88be1f)
Signed-off-by: Dan Streetman <ddstreet@canonical.com>










>  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 ca6cd146aafe..dcf73c5dab6e 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();
>  	}
> -- 
> 2.19.1
> 
> 
> -- 
> kernel-team mailing list
> kernel-team@lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team
Khaled Elmously March 4, 2019, 5:15 a.m. | #4
Applied after fixing the commit message 


On 2019-02-01 12:45:26 , Dan Streetman wrote:
> From: John Stultz <john.stultz@linaro.org>
> 
> BugLink: https://bugs.launchpad.net/bugs/1811194
> 
> 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 checks to see if the clock was being adjusted
> when we fail so that we don't cause false negatives.
> 
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Miroslav Lichvar <mlichvar@redhat.com>
> Cc: Richard Cochran <richardcochran@gmail.com>
> Cc: Prarit Bhargava <prarit@redhat.com>
> Cc: Stephen Boyd <sboyd@kernel.org>
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: linux-kselftest@vger.kernel.org
> Suggested-by: Miroslav Lichvar <mlichvar@redhat.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> v2: Widened the checks to look for other clock adjustments that
>     could happen, as suggested by Miroslav
> v3: Fixed up commit message
> 
> Signed-off-by: Dan Streetman <ddstreet@canonical.com>
> (cherry-picked from upstream 1416270f4a1ae83ea84156ceba19a66a8f88be1f)
> ---
>  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 ca6cd146aafe..dcf73c5dab6e 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();
>  	}
> -- 
> 2.19.1
> 
> 
> -- 
> kernel-team mailing list
> kernel-team@lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team
Dan Streetman March 4, 2019, 12:12 p.m. | #5
On Mon, Mar 4, 2019 at 12:13 AM Khaled Elmously
<khalid.elmously@canonical.com> wrote:
>
> On 2019-02-01 12:45:26 , Dan Streetman wrote:
> > From: John Stultz <john.stultz@linaro.org>
> >
> > BugLink: https://bugs.launchpad.net/bugs/1811194
> >
> > 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 checks to see if the clock was being adjusted
> > when we fail so that we don't cause false negatives.
> >
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Ingo Molnar <mingo@kernel.org>
> > Cc: Miroslav Lichvar <mlichvar@redhat.com>
> > Cc: Richard Cochran <richardcochran@gmail.com>
> > Cc: Prarit Bhargava <prarit@redhat.com>
> > Cc: Stephen Boyd <sboyd@kernel.org>
> > Cc: Shuah Khan <shuah@kernel.org>
> > Cc: linux-kselftest@vger.kernel.org
> > Suggested-by: Miroslav Lichvar <mlichvar@redhat.com>
> > Signed-off-by: John Stultz <john.stultz@linaro.org>
> > ---
> > v2: Widened the checks to look for other clock adjustments that
> >     could happen, as suggested by Miroslav
> > v3: Fixed up commit message
> >
> > Signed-off-by: Dan Streetman <ddstreet@canonical.com>
> > (cherry-picked from upstream 1416270f4a1ae83ea84156ceba19a66a8f88be1f)
> > ---
>
> Dan, the way you're adding your "cherry picked from" and Signed-off-by lines means they won't actually show up in the commit message.
>
> The "cherry picked from" line and your Signed-off-by should immediately follow the provenance of the patch.
> Also, the syntax is "cherry picked from commit X" (no hyphen, and "commit" instead of "upstream")

thanks - can I send a sauce patch adding checks to checkpatch for
Ubuntu-specific formatting like this?

>
> So in this case your commit message should look like:
>
>
> selftest: timers: Tweak raw_skew to SKIP when ADJ_OFFSET/other clock adjustments are in progress
>
> BugLink: https://bugs.launchpad.net/bugs/1811194
>
> 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 checks to see if the clock was being adjusted
> when we fail so that we don't cause false negatives.
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Miroslav Lichvar <mlichvar@redhat.com>
> Cc: Richard Cochran <richardcochran@gmail.com>
> Cc: Prarit Bhargava <prarit@redhat.com>
> Cc: Stephen Boyd <sboyd@kernel.org>
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: linux-kselftest@vger.kernel.org
> Suggested-by: Miroslav Lichvar <mlichvar@redhat.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> (cherry picked from 1416270f4a1ae83ea84156ceba19a66a8f88be1f)
> Signed-off-by: Dan Streetman <ddstreet@canonical.com>
>
>
>
>
>
>
>
>
>
>
> >  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 ca6cd146aafe..dcf73c5dab6e 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();
> >       }
> > --
> > 2.19.1
> >
> >
> > --
> > kernel-team mailing list
> > kernel-team@lists.ubuntu.com
> > https://lists.ubuntu.com/mailman/listinfo/kernel-team
Kleber Souza March 7, 2019, 2:52 p.m. | #6
On 3/4/19 1:12 PM, Dan Streetman wrote:
> On Mon, Mar 4, 2019 at 12:13 AM Khaled Elmously
> <khalid.elmously@canonical.com> wrote:
>>
>> On 2019-02-01 12:45:26 , Dan Streetman wrote:
>>> From: John Stultz <john.stultz@linaro.org>
>>>
>>> BugLink: https://bugs.launchpad.net/bugs/1811194
>>>
>>> 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 checks to see if the clock was being adjusted
>>> when we fail so that we don't cause false negatives.
>>>
>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>> Cc: Ingo Molnar <mingo@kernel.org>
>>> Cc: Miroslav Lichvar <mlichvar@redhat.com>
>>> Cc: Richard Cochran <richardcochran@gmail.com>
>>> Cc: Prarit Bhargava <prarit@redhat.com>
>>> Cc: Stephen Boyd <sboyd@kernel.org>
>>> Cc: Shuah Khan <shuah@kernel.org>
>>> Cc: linux-kselftest@vger.kernel.org
>>> Suggested-by: Miroslav Lichvar <mlichvar@redhat.com>
>>> Signed-off-by: John Stultz <john.stultz@linaro.org>
>>> ---
>>> v2: Widened the checks to look for other clock adjustments that
>>>     could happen, as suggested by Miroslav
>>> v3: Fixed up commit message
>>>
>>> Signed-off-by: Dan Streetman <ddstreet@canonical.com>
>>> (cherry-picked from upstream 1416270f4a1ae83ea84156ceba19a66a8f88be1f)
>>> ---
>>
>> Dan, the way you're adding your "cherry picked from" and Signed-off-by lines means they won't actually show up in the commit message.
>>
>> The "cherry picked from" line and your Signed-off-by should immediately follow the provenance of the patch.
>> Also, the syntax is "cherry picked from commit X" (no hyphen, and "commit" instead of "upstream")
> 
> thanks - can I send a sauce patch adding checks to checkpatch for
> Ubuntu-specific formatting like this?

Hi Dan,

We already have plans to write a tool in the style of checkpatch to check all
the info and formatting we request for our patches. We'll let people known
once we have something that can be used.

Thanks!
Kleber


> 
>>
>> So in this case your commit message should look like:
>>
>>
>> selftest: timers: Tweak raw_skew to SKIP when ADJ_OFFSET/other clock adjustments are in progress
>>
>> BugLink: https://bugs.launchpad.net/bugs/1811194
>>
>> 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 checks to see if the clock was being adjusted
>> when we fail so that we don't cause false negatives.
>>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Ingo Molnar <mingo@kernel.org>
>> Cc: Miroslav Lichvar <mlichvar@redhat.com>
>> Cc: Richard Cochran <richardcochran@gmail.com>
>> Cc: Prarit Bhargava <prarit@redhat.com>
>> Cc: Stephen Boyd <sboyd@kernel.org>
>> Cc: Shuah Khan <shuah@kernel.org>
>> Cc: linux-kselftest@vger.kernel.org
>> Suggested-by: Miroslav Lichvar <mlichvar@redhat.com>
>> Signed-off-by: John Stultz <john.stultz@linaro.org>
>> (cherry picked from 1416270f4a1ae83ea84156ceba19a66a8f88be1f)
>> Signed-off-by: Dan Streetman <ddstreet@canonical.com>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>>  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 ca6cd146aafe..dcf73c5dab6e 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();
>>>       }
>>> --
>>> 2.19.1
>>>
>>>
>>> --
>>> kernel-team mailing list
>>> kernel-team@lists.ubuntu.com
>>> https://lists.ubuntu.com/mailman/listinfo/kernel-team
>

Patch

diff --git a/tools/testing/selftests/timers/raw_skew.c b/tools/testing/selftests/timers/raw_skew.c
index ca6cd146aafe..dcf73c5dab6e 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();
 	}