Re: [PATCH RFC v2 8/8] selftests/perf: Add kselftest for remove_on_exec

[Marco Elver]

On Tue, 23 Mar 2021 at 04:10, Ian Rogers <irogers@xxxxxxxxxx> wrote:
> On Mon, Mar 22, 2021 at 6:24 AM Marco Elver <elver@xxxxxxxxxx> wrote:
> > On Wed, Mar 10, 2021 at 11:41AM +0100, Marco Elver wrote:
> > > Add kselftest to test that remove_on_exec removes inherited events from
> > > child tasks.
> > >
> > > Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
> >
> > To make compatible with more recent libc, we'll need to fixup the tests
> > with the below.
> >
> > Also, I've seen that tools/perf/tests exists, however it seems to be
> > primarily about perf-tool related tests. Is this correct?
> >
> > I'd propose to keep these purely kernel ABI related tests separate, and
> > that way we can also make use of the kselftests framework which will
> > also integrate into various CI systems such as kernelci.org.
>
> Perhaps there is a way to have both? Having the perf tool spot an
> errant kernel feels like a feature. There are also
> tools/lib/perf/tests and Vince Weaver's tests [1]. It is possible to
> run standalone tests from within perf test by having them be executed
> by a shell test.

Thanks for the pointers. Sure, I'd support more additional tests.

But I had another look and it seems the tests in
tools/{perf,lib/perf}/tests do focus on perf-tool or the library
respectively, so adding kernel ABI tests there feels wrong. (If
perf-tool somehow finds use for sigtrap, or remove_on_exec, then
having a perf-tool specific test for those would make sense again.)

The tests at [1] do seem relevant, and its test strategy seems more
extensive, including testing older kernels. Unfortunately it is
out-of-tree, but that's probably because it was started before
kselftest came into existence. But there are probably things that [1]
contains that are not appropriate in-tree.

It's all a bit confusing.

Going forward, if you insist on tests being also added to [1], we can
perhaps mirror some of the kselftest tests there. There's also a
logistical problem with the tests added here, because the tests
require an up-to-date siginfo_t, and they use the kernel's
<asm/siginfo.h> with some trickery. Until libc's siginfo_t is updated,
it probably doesn't make sense to add these tests to [1].

The other question is, would it be possible to also copy some of the
tests in [1] and convert to kselftest, so that they live in-tree and
are tested regularly (CI, ...)?

Because I'd much prefer in-tree tests with little boilerplate, that
are structured with parsable output; in the kernel we have the
kselftest framework for tests with a user space component, and KUnit
for pure in-kernel tests.

Thanks,
-- Marco

> Thanks,
> Ian
>
> [1] https://github.com/deater/perf_event_tests
[...]