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From:   Eric Dumazet <edumazet@google.com>
Date:   Wed, 15 Dec 2021 02:23:46 -0800
Message-ID: <CANn89iJ-uGzpbAhNjT=fGfDYTjpxo335yhKbqUKwSUPOwPZqWw@mail.gmail.com>
Subject: Re: [PATCH -next] lib: TEST_REF_TRACKER should depend on REF_TRACKER
 instead of selecting it
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Jakub Kicinski <kuba@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        netdev <netdev@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, Dec 15, 2021 at 2:10 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Eric,
>
> On Wed, Dec 15, 2021 at 10:51 AM Eric Dumazet <edumazet@google.com> wrote:
> > On Wed, Dec 15, 2021 at 1:36 AM Geert Uytterhoeven
> > <geert+renesas@glider.be> wrote:
> > > TEST_REF_TRACKER selects REF_TRACKER, thus enabling an optional feature
> > > the user may not want to have enabled.  Fix this by making the test
> > > depend on REF_TRACKER instead.
> >
> > I do not understand this.
>
> The issue is that merely enabling tests should not enable optional
> features, to prevent unwanted features sneaking into a product.

if you do not want the feature, just say no ?

# CONFIG_TEST_REF_TRACKER is not set
# CONFIG_NET_DEV_REFCNT_TRACKER is not set
# CONFIG_NET_NS_REFCNT_TRACKER is not set


> If tests depend on features, all tests for features that are enabled can
> still be enabled (e.g. made modular, so they can be loaded when needed).
>
> > How can I test this infra alone, without any ref_tracker being selected ?
> >
> > I have in my configs
> >
> > CONFIG_TEST_REF_TRACKER=m
> > # CONFIG_NET_DEV_REFCNT_TRACKER is not set
> > # CONFIG_NET_NS_REFCNT_TRACKER is not set
> >
> > This should work.
>
> So you want to test the reference tracker, without having any actual
> users of the reference tracker enabled?

Yes, I fail to see the problem you have with this.

lib/ref_tracker.c is not adding intrusive features like KASAN.

>
> Perhaps REF_TRACKER should become visible, cfr. CRC32 and
> the related CRC32_SELFTEST?

I can not speak for CRC32.

My point is that I sent a series, I wanted this series to be bisectable.

When the test was added, I wanted to be able to use it right away.
(like compile it, and run it)

>
> > I would not have sent patches built around ref_tracker if I had no
> > ways of testing the base infrastructure.
>
> > > --- a/lib/Kconfig.debug
> > > +++ b/lib/Kconfig.debug
> > > @@ -2114,8 +2114,7 @@ config BACKTRACE_SELF_TEST
> > >
> > >  config TEST_REF_TRACKER
> > >         tristate "Self test for reference tracker"
> > > -       depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
> > > -       select REF_TRACKER
> > > +       depends on DEBUG_KERNEL && STACKTRACE_SUPPORT && REF_TRACKER
> > >         help
> > >           This option provides a kernel module performing tests
> > >           using reference tracker infrastructure.
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds