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Subject: Re: [PATCH v2 3/3] Documentation: dyndbg: Improve cli param examples
To:     Andrew Halaney <ahalaney@redhat.com>, jim.cromie@gmail.com
Cc:     Jonathan Corbet <corbet@lwn.net>,
        Linux Documentation List <linux-doc@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
References: <20210913222440.731329-1-ahalaney@redhat.com>
 <20210913222440.731329-4-ahalaney@redhat.com>
 <ff05cae4-8fa7-d1b6-795e-3bd85316774d@akamai.com>
 <CAJfuBxzrJwr17-RWZzhw90pKXZ1hL5kepuzvt1Di=JyekMJf4A@mail.gmail.com>
 <20210917205341.5bayndskygan6qrd@halaneylaptop>
From:   Jason Baron <jbaron@akamai.com>
Message-ID: <088053f9-3113-66ce-9717-8afd84c48e53@akamai.com>
Date:   Fri, 17 Sep 2021 17:54:35 -0400
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On 9/17/21 4:53 PM, Andrew Halaney wrote:
> On Fri, Sep 17, 2021 at 02:30:09PM -0600, jim.cromie@gmail.com wrote:
>> On Fri, Sep 17, 2021 at 1:50 PM Jason Baron <jbaron@akamai.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@redhat.com>
>>>> Suggested-by: Jim Cromie <jim.cromie@gmail.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.

Fine with me.

Thanks,

-Jason

>
> 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"