netdev - Re: [PATCH bpf-next 6/9] selftests/bpf: abstract away test log output

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Message-ID: <20190727003408.5hgu5prcz2mwqv22@ast-mbp.dhcp.thefacebook.com>
Date:   Fri, 26 Jul 2019 17:34:09 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Stanislav Fomichev <sdf@...ichev.me>
Cc:     Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next 6/9] selftests/bpf: abstract away test log output

On Fri, Jul 26, 2019 at 03:26:52PM -0700, Stanislav Fomichev wrote:
> On 07/26, Andrii Nakryiko wrote:
> > On Fri, Jul 26, 2019 at 2:31 PM Stanislav Fomichev <sdf@...ichev.me> wrote:
> > >
> > > On 07/26, Andrii Nakryiko wrote:
> > > > This patch changes how test output is printed out. By default, if test
> > > > had no errors, the only output will be a single line with test number,
> > > > name, and verdict at the end, e.g.:
> > > >
> > > >   #31 xdp:OK
> > > >
> > > > If test had any errors, all log output captured during test execution
> > > > will be output after test completes.
> > > >
> > > > It's possible to force output of log with `-v` (`--verbose`) option, in
> > > > which case output won't be buffered and will be output immediately.
> > > >
> > > > To support this, individual tests are required to use helper methods for
> > > > logging: `test__printf()` and `test__vprintf()`.
> > > >
> > > > Signed-off-by: Andrii Nakryiko <andriin@...com>
> > > > ---
> > > >  .../selftests/bpf/prog_tests/bpf_obj_id.c     |   6 +-
> > > >  .../bpf/prog_tests/bpf_verif_scale.c          |  31 ++--
> > > >  .../bpf/prog_tests/get_stack_raw_tp.c         |   4 +-
> > > >  .../selftests/bpf/prog_tests/l4lb_all.c       |   2 +-
> > > >  .../selftests/bpf/prog_tests/map_lock.c       |  10 +-
> > > >  .../selftests/bpf/prog_tests/send_signal.c    |   8 +-
> > > >  .../selftests/bpf/prog_tests/spinlock.c       |   2 +-
> > > >  .../bpf/prog_tests/stacktrace_build_id.c      |   4 +-
> > > >  .../bpf/prog_tests/stacktrace_build_id_nmi.c  |   4 +-
> > > >  .../selftests/bpf/prog_tests/xdp_noinline.c   |   3 +-
> > > >  tools/testing/selftests/bpf/test_progs.c      | 135 +++++++++++++-----
> > > >  tools/testing/selftests/bpf/test_progs.h      |  37 ++++-
> > > >  12 files changed, 173 insertions(+), 73 deletions(-)
> > > >
> > 
> > [...]
> > 
> > > >               error_cnt++;
> > > > -             printf("test_l4lb:FAIL:stats %lld %lld\n", bytes, pkts);
> > > > +             test__printf("test_l4lb:FAIL:stats %lld %lld\n", bytes, pkts);
> > > #define printf(...) test__printf(...) in tests.h?
> > >
> > > A bit ugly, but no need to retrain everyone to use new printf wrappers.
> > 
> > I try to reduce amount of magic and surprising things, not add new
> > ones :) I also led by example and converted all current instances of
> > printf usage to test__printf, so anyone new will just copy/paste good
> > example, hopefully. Even if not, this non-buffered output will be
> > immediately obvious to anyone who just runs `sudo ./test_progs`.
> 
> [..]
> > And
> > author of new test with this problem should hopefully be the first and
> > the only one to catch and fix this.
> Yeah, that is my only concern, that regular printfs will eventually
> creep in. It's already confusing to go to/from printf/printk.
> 
> 2c:
> 
> I'm coming from a perspective of tools/testing/selftests/kselftest.h
> which is supposed to be a generic framework with custom
> printf variants (ksft_print_msg), but I still see a bunch of tests
> calling printf :-/
> 
> 	grep -ril ksft_exit_fail_msg selftests/ | xargs -n1 grep -w printf
> 
> Since we don't expect regular buffered io from the tests anyway
> it might be easier just to add a bit of magic and call it a day.

I think #define printf()
is not a good style in general.
glibc functions should never be #define-d.