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

[Anders Wallin via lttng-dev <lttng-dev@lists.lttng.org>]

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I agree, new version on the way w/o sleep!
Anders Wallin


On Thu, Apr 1, 2021 at 6:19 PM Mathieu Desnoyers <
mathieu.desnoyers@efficios.com> 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.
>
> Thanks,
>
> Mathieu
>
>
> > }
> >
> > function trace_ust_app
> > --
> > 2.31.1
> >
> > _______________________________________________
> > lttng-dev mailing list
> > lttng-dev@lists.lttng.org
> > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
>

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