Re: [lttng-dev] [PATCH lttng-tools] Fix: test code assumes that child process is schedule to run before parent

[Mathieu Desnoyers via lttng-dev <lttng-dev@lists.lttng.org>]

----- On Apr 1, 2021, at 12:19 PM, lttng-dev lttng-dev@lists.lttng.org wrote:

> ----- On Mar 31, 2021, at 2:56 PM, lttng-dev lttng-dev@lists.lttng.org wrote:
> 
>> the following tests fails on arm64
>> - test_event_vpid_tracker ust 0 "${EVENT_NAME}"
>> - test_event_vpid_track_untrack ust 0 "${EVENT_NAME}"
>> - test_event_pid_tracker ust 0 "${EVENT_NAME}"
>> - test_event_pid_track_untrack ust 0 "${EVENT_NAME}"
>> 
>> Signed-off-by: Anders Wallin <wallinux@gmail.com>
>> ---
>> tests/regression/tools/tracker/test_event_tracker | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>> 
>> diff --git a/tests/regression/tools/tracker/test_event_tracker
>> b/tests/regression/tools/tracker/test_event_tracker
>> index 711690af..649c7e61 100755
>> --- a/tests/regression/tools/tracker/test_event_tracker
>> +++ b/tests/regression/tools/tracker/test_event_tracker
>> @@ -5,7 +5,7 @@
>> #
>> # SPDX-License-Identifier: GPL-2.0-only
>> 
>> -TEST_DESC="LTTng - Event traker test"
>> +TEST_DESC="LTTng - Event tracker test"
>> 
>> CURDIR=$(dirname "$0")/
>> TESTDIR="$CURDIR/../../.."
>> @@ -42,6 +42,8 @@ function prepare_ust_app
>> 
>> 	$TESTAPP_BIN -i $NR_ITER -w $NR_USEC_WAIT -a "$AFTER_FIRST_PATH" -b
>> 	"$BEFORE_LAST_PATH" &
>> 	CHILD_PID=$!
>> +	# voluntary context switch to start $TESTAPP_BIN
>> +	sleep 0.1
> 
> No, we have been bitten again and again by test issues hidden by sleeps in the
> test code. Using sleeps for synchronization is flaky.
> 
> I don't know if we documented it, but we as maintainers are strongly against
> anything that looks like a delay-based approach to fixing a race in the tests.
> This typically just bury the race under the carpet and it shows up only in
> specific conditions on the CI workers.
> 
> We need to add proper rendez-vous based synchronization to the test if some
> is missing.
> 
> Adding Jérémie in CC.

And then I read on the rest of the email thread... so it's being taken care of, good! :)

Thanks,

Mathieu

> 
> Thanks,
> 
> Mathieu
> 
> 
>> }
>> 
>> function trace_ust_app
>> --
>> 2.31.1
>> 
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> 
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
> _______________________________________________
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> lttng-dev@lists.lttng.org
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-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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