linux-kernel - Re: [PATCH v2 3/3] Documentation: dyndbg: Improve cli param examples

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Date:   Fri, 17 Sep 2021 14:30:09 -0600
From:   jim.cromie@...il.com
To:     Jason Baron <jbaron@...mai.com>
Cc:     Andrew Halaney <ahalaney@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Linux Documentation List <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] Documentation: dyndbg: Improve cli param examples

On Fri, Sep 17, 2021 at 1:50 PM Jason Baron <jbaron@...mai.com> wrote:
>
>
>
> On 9/13/21 6:24 PM, Andrew Halaney wrote:
> > Jim pointed out that using $module.dyndbg= is always a more flexible
> > choice for using dynamic debug on the command line. The $module.dyndbg
> > style is checked at boot and handles if $module is a builtin. If it is
> > actually a loadable module, it is handled again later when the module is
> > loaded.
> >
> > If you just use dyndbg="module $module +p" dynamic debug is only enabled
> > when $module is a builtin.
> >
> > It was recommended to illustrate wildcard usage as well.
> >
> > Signed-off-by: Andrew Halaney <ahalaney@...hat.com>
> > Suggested-by: Jim Cromie <jim.cromie@...il.com>
> > ---
> >   Documentation/admin-guide/dynamic-debug-howto.rst | 7 +++++--
> >   1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst
> > index d0911e7cc271..4bfb23ed64ec 100644
> > --- a/Documentation/admin-guide/dynamic-debug-howto.rst
> > +++ b/Documentation/admin-guide/dynamic-debug-howto.rst
> > @@ -357,7 +357,10 @@ Examples
> >     Kernel command line: ...
> >       // see whats going on in dyndbg=value processing
> >       dynamic_debug.verbose=1
> > -    // enable pr_debugs in 2 builtins, #cmt is stripped
> > -    dyndbg="module params +p #cmt ; module sys +p"
> > +    // Enable pr_debugs in the params builtin
> > +    params.dyndbg="+p"
>
> If we are going out of our way to change this to indicate that it works
> for builtin and modules, it seems like the comment above should reflect
> that? IE, something like this?
>
> '// Enable pr_debugs in the params module or if params is builtin.
>

I dont think params can be a loadable module, so its not a great
example of this.
it should be one that "everyone" knows is usually loaded.

conversely, bare dyndbg example should have only builtin modules,
then the contrast between 2 forms is most evident.


> The first two patches look fine to me, so if you agree maybe just
> re-spin this one?
>
> Thanks,
>
> -Jason
>
> > +    // enable pr_debugs in all files under init/
> > +    // and the function pc87360_init_device, #cmt is stripped
> > +    dyndbg="file init/* +p #cmt ; func pc87360_init_device +p"
> >       // enable pr_debugs in 2 functions in a module loaded later
> >       pc87360.dyndbg="func pc87360_init_device +p; func pc87360_find +p"
>