linux-kernel - Re: [PATCH -kselftest/kunit] kcsan: test: use new suite

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Date:   Wed, 4 May 2022 15:47:26 +0200
From:   Marco Elver <elver@...gle.com>
To:     David Gow <davidgow@...gle.com>
Cc:     kasan-dev <kasan-dev@...glegroups.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Daniel Latypov <dlatypov@...gle.com>,
        Brendan Higgins <brendanhiggins@...gle.com>
Subject: Re: [PATCH -kselftest/kunit] kcsan: test: use new suite_{init,exit} support

On Wed, 4 May 2022 at 15:43, David Gow <davidgow@...gle.com> wrote:
>
> On Wed, May 4, 2022 at 3:09 PM Marco Elver <elver@...gle.com> wrote:
> >
> > Use the newly added suite_{init,exit} support for suite-wide init and
> > cleanup. This avoids the unsupported method by which the test used to do
> > suite-wide init and cleanup (avoiding issues such as missing TAP
> > headers, and possible future conflicts).
> >
> > Signed-off-by: Marco Elver <elver@...gle.com>
> > ---
> > This patch should go on the -kselftest/kunit branch, where this new
> > support currently lives, including a similar change to the KFENCE test.
> > ---
>
> Thanks! This is working for me. I ran it as a builtin using kunit_tool
> under (I had to add an x86_64-smp architecture), then use:
> ./tools/testing/kunit/kunit.py run --arch=x86_64-smp
> --kconfig_add=CONFIG_KCSAN=y --kconfig_add=CONFIG_DEBUG_KERNEL=y
> --timeout 900 'kcsan'
>
> To add the x86_64 smp architecture, I added a file
> ./tools/testing/kunit/qemu_configs/x86_64-smp.py, which was a copy of
> x86_64.py but with 'CONFIG_SMP=y' added to XXXX and '-smp 16' added to
> YYYY.
> It took about 10 minutes on my system, so the default 5 minute timeout
> definitely wasn't enough.

The trick to reduce the KCSAN test time is to set
CONFIG_KCSAN_REPORT_ONCE_IN_MS=100 or lower. So should you consider a
special KUnit config, I'd add that.

> (It's maybe worth noting that kunit_tool's output is pretty ugly when
> this isn't running on an SMP system, as the skipped subtests -- plus
> the "no tests run" errors -- take up a lot of space on the screen.
> That's possibly something we should consider when we look further into
> how the kunit_tool NO_TEST result works. Not really related to this
> change (or even this test) though.)
>
> No complaints about the patch: I'm just really glad to see things
> migrate off custom init/exit code!
>
> Reviewed-by: David Gow <davidgow@...gle.com>

Thank you!

> -- David
>
> >  kernel/kcsan/kcsan_test.c | 31 +++++++++++++------------------
> >  1 file changed, 13 insertions(+), 18 deletions(-)
> >
> > diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c
> > index a36fca063a73..59560b5e1d9c 100644
> > --- a/kernel/kcsan/kcsan_test.c
> > +++ b/kernel/kcsan/kcsan_test.c
> > @@ -1565,14 +1565,6 @@ static void test_exit(struct kunit *test)
> >         torture_cleanup_end();
> >  }
> >
> > -static struct kunit_suite kcsan_test_suite = {
> > -       .name = "kcsan",
> > -       .test_cases = kcsan_test_cases,
> > -       .init = test_init,
> > -       .exit = test_exit,
> > -};
> > -static struct kunit_suite *kcsan_test_suites[] = { &kcsan_test_suite, NULL };
> > -
> >  __no_kcsan
> >  static void register_tracepoints(struct tracepoint *tp, void *ignore)
> >  {
> > @@ -1588,11 +1580,7 @@ static void unregister_tracepoints(struct tracepoint *tp, void *ignore)
> >                 tracepoint_probe_unregister(tp, probe_console, NULL);
> >  }
> >
> > -/*
> > - * We only want to do tracepoints setup and teardown once, therefore we have to
> > - * customize the init and exit functions and cannot rely on kunit_test_suite().
> > - */
> > -static int __init kcsan_test_init(void)
> > +static int kcsan_suite_init(struct kunit_suite *suite)
> >  {
> >         /*
> >          * Because we want to be able to build the test as a module, we need to
> > @@ -1600,18 +1588,25 @@ static int __init kcsan_test_init(void)
> >          * won't work here.
> >          */
> >         for_each_kernel_tracepoint(register_tracepoints, NULL);
> > -       return __kunit_test_suites_init(kcsan_test_suites);
> > +       return 0;
> >  }
> >
> > -static void kcsan_test_exit(void)
> > +static void kcsan_suite_exit(struct kunit_suite *suite)
> >  {
> > -       __kunit_test_suites_exit(kcsan_test_suites);
> >         for_each_kernel_tracepoint(unregister_tracepoints, NULL);
> >         tracepoint_synchronize_unregister();
> >  }
> >
> > -late_initcall_sync(kcsan_test_init);
> > -module_exit(kcsan_test_exit);
> > +static struct kunit_suite kcsan_test_suite = {
> > +       .name = "kcsan",
> > +       .test_cases = kcsan_test_cases,
> > +       .init = test_init,
> > +       .exit = test_exit,
> > +       .suite_init = kcsan_suite_init,
> > +       .suite_exit = kcsan_suite_exit,
> > +};
> > +
> > +kunit_test_suites(&kcsan_test_suite);
> >
> >  MODULE_LICENSE("GPL v2");
> >  MODULE_AUTHOR("Marco Elver <elver@...gle.com>");
> > --
> > 2.36.0.464.gb9c8b46e94-goog
> >