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

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Date:   Fri, 17 Sep 2021 15:53:41 -0500
From:   Andrew Halaney <ahalaney@...hat.com>
To:     jim.cromie@...il.com
Cc:     Jason Baron <jbaron@...mai.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 02:30:09PM -0600, jim.cromie@...il.com wrote:
> 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.
> 

Thank you both for the feedback, good points.

Does something like:

    // Enable pr_debugs in the btrfs module (can be builtin or loadable)
    btrfs.dyndbg="+p"
    // enable pr_debugs in all files under init/
    // and the function parse_one, #cmt is stripped
    dyndbg="file init/* +p #cmt ; func parse_one +p"

Work for you both? I think that makes the advantages of $module.dyndbg=
more clear and makes the usage of dyndbg= stick to strictly builtins.
If so I'll respin this patch in v3 of the series.

Thanks,
Andrew

> 
> > 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"
> >
>