linux-kernel - Re: [FIX PATCH] selftests: tracing: Fix to unmount tracefs for recovering environment

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Date:   Mon, 11 Sep 2023 13:09:09 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc:     Shuah Khan <shuah@...nel.org>, Mark Brown <broonie@...nel.org>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [FIX PATCH] selftests: tracing: Fix to unmount tracefs for
 recovering environment

On Sat,  9 Sep 2023 18:36:39 +0900
"Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:

> From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 
> Fix to unmount the tracefs if the ftracetest mounted it for recovering
> system environment. If the tracefs is already mounted, this does nothing.
> 
> Suggested-by: Mark Brown <broonie@...nel.org>
> Link: https://lore.kernel.org/all/29fce076-746c-4650-8358-b4e0fa215cf7@sirena.org.uk/
> Fixes: cbd965bde74c ("ftrace/selftests: Return the skip code when tracing directory not configured in kernel")
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> ---
>  tools/testing/selftests/ftrace/ftracetest |    8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/tools/testing/selftests/ftrace/ftracetest b/tools/testing/selftests/ftrace/ftracetest
> index cb5f18c06593..89c212d82256 100755
> --- a/tools/testing/selftests/ftrace/ftracetest
> +++ b/tools/testing/selftests/ftrace/ftracetest
> @@ -31,6 +31,9 @@ err_ret=1
>  # kselftest skip code is 4
>  err_skip=4
>  
> +# umount required
> +UMOUNT_DIR=""
> +
>  # cgroup RT scheduling prevents chrt commands from succeeding, which
>  # induces failures in test wakeup tests.  Disable for the duration of
>  # the tests.
> @@ -45,6 +48,9 @@ setup() {
>  
>  cleanup() {
>    echo $sched_rt_runtime_orig > $sched_rt_runtime
> +  if [ "${UMOUNT_DIR}" ]; then

Shouldn't the above be:

     if [ ! -z "${UNMOUNT_DIR}" ]; then

?

-- Steve

> +    umount ${UMOUNT_DIR} ||:
> +  fi
>  }
>  
>  errexit() { # message
> @@ -160,11 +166,13 @@ if [ -z "$TRACING_DIR" ]; then
>  	    mount -t tracefs nodev /sys/kernel/tracing ||
>  	      errexit "Failed to mount /sys/kernel/tracing"
>  	    TRACING_DIR="/sys/kernel/tracing"
> +	    UMOUNT_DIR=${TRACING_DIR}
>  	# If debugfs exists, then so does /sys/kernel/debug
>  	elif [ -d "/sys/kernel/debug" ]; then
>  	    mount -t debugfs nodev /sys/kernel/debug ||
>  	      errexit "Failed to mount /sys/kernel/debug"
>  	    TRACING_DIR="/sys/kernel/debug/tracing"
> +	    UMOUNT_DIR=${TRACING_DIR}
>  	else
>  	    err_ret=$err_skip
>  	    errexit "debugfs and tracefs are not configured in this kernel"