Re: [PATCH] selftests/ftrace: Account for fprobe attachment at creation

Masami Hiramatsu
2026-04-08T00:49:23Z

On Tue, 7 Apr 2026 19:57:51 +0800
Cao Ruichuang <create0818@163.com> wrote:

> add_remove_fprobe.tc assumes that enabling an fprobe event is what adds
> its target function to enabled_functions.
>
> On the current kernel, the fprobe target already appears in
> enabled_functions as soon as the event is created, and enabling the
> event does not change that count again. That makes the test fail even
> though the event lifecycle itself works.
>
> Record the attachment baseline after creating the probe events and only
> check that enabling them keeps the expected functions attached. The
> cleanup checks still verify that removing the events returns
> enabled_functions to its original state.
>

Hmm, did you run this test with not clean environment?
It is not designed to do so.
(I think we should not check ocnt, or if there are any entries,
we should stop this test as unresolved.)

Thank you,

> Signed-off-by: Cao Ruichuang <create0818@163.com>
> ---
> .../test.d/dynevent/add_remove_fprobe.tc | 28 +++++++++++++------
> 1 file changed, 19 insertions(+), 9 deletions(-)
>
> diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe.tc b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe.tc
> index 47067a5e3..ff08bd1ac 100644
> --- a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe.tc
> +++ b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe.tc
> @@ -26,23 +26,29 @@ grep -q myevent2 dynamic_events
> grep -q myevent3 dynamic_events
> test -d events/fprobes/myevent1
> test -d events/fprobes/myevent2
> -
> -echo 1 > events/fprobes/myevent1/enable
> -# Make sure the event is attached.
> grep -q $PLACE enabled_functions
> +grep -q $PLACE2 enabled_functions
> cnt=`cat enabled_functions | wc -l`
> -if [ $cnt -eq $ocnt ]; then
> +if [ $cnt -le $ocnt ]; then
> + exit_fail
> +fi
> +
> +echo 1 > events/fprobes/myevent1/enable
> +cnt1=`cat enabled_functions | wc -l`
> +if [ $cnt1 -ne $cnt ]; then
> exit_fail
> fi
>
> echo 1 > events/fprobes/myevent2/enable
> cnt2=`cat enabled_functions | wc -l`
> +if [ $cnt2 -ne $cnt1 ]; then
> + exit_fail
> +fi
>
> echo 1 > events/fprobes/myevent3/enable
> -# If the function is different, the attached function should be increased
> grep -q $PLACE2 enabled_functions
> cnt=`cat enabled_functions | wc -l`
> -if [ $cnt -eq $cnt2 ]; then
> +if [ $cnt -ne $cnt2 ]; then
> exit_fail
> fi
>
> @@ -62,11 +68,15 @@ if [ $cnt -ne $ocnt ]; then
> fi
>
> echo "f:myevent4 $PLACE" >> dynamic_events
> +grep -q $PLACE enabled_functions
> +cnt=`cat enabled_functions | wc -l`
> +if [ $cnt -le $ocnt ]; then
> + exit_fail
> +fi
>
> echo 1 > events/fprobes/myevent4/enable
> -# Should only have one enabled
> -cnt=`cat enabled_functions | wc -l`
> -if [ $cnt -ne $((ocnt + 1)) ]; then
> +cnt2=`cat enabled_functions | wc -l`
> +if [ $cnt2 -ne $cnt ]; then
> exit_fail
> fi
>
> --
> 2.39.5 (Apple Git-154)
>

--
Masami Hiramatsu (Google) <mhiramat@kernel.org>