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

From: Jonathan Rajotte-Julien via lttng-dev <lttng-dev@lists.lttng.org>
To: Anders Wallin <wallinux@gmail.com>
Cc: lttng-dev <lttng-dev@lists.lttng.org>
Subject: Re: [lttng-dev] [PATCH lttng-tools] Fix: test code assumes that child process is schedule to run before parent
Date: Wed, 31 Mar 2021 15:25:09 -0400 (EDT)	[thread overview]
Message-ID: <592114658.48857.1617218709305.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <20210331185624.406960-1-wallinux@gmail.com>

> #
> # 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

A wait on the $AFTER_FIRST_PATH file would be probably more deterministic than a sleep here.

  while [ ! -f "${AFTER_FIRST_PATH}" ]; do
          sleep 0.1
  done

I would also expect something similar for the `prepare_kernel_app` function considering the same race is most probably present and simply not triggered by a chance of luck.
Seems like gen-kernel-test-events does not expose the same sync capabilities here, please use gen-ust-events as an example of how it is done.

Let us know how your testing goes.

Thanks
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