Re: [PATCHv3 3/3] dynamic_debug: Add a flag for dynamic event tracing

Jason Baron
2021-11-09T22:15:23Z

On 11/9/21 4:51 PM, Steven Rostedt wrote:
> On Tue, 9 Nov 2021 16:42:48 -0500
> Jason Baron <jbaron@akamai.com> wrote:
>
>> Yeah there is a 'parallel' thread about adding the tracing ring buffer as
>> a 'back end' to the dynamic debug stuff over here:
>> https://urldefense.com/v3/__https://lore.kernel.org/lkml/20211105192637.2370737-9-jim.cromie@gmail.com/__;!!GjvTz_vk!GdVm3olk4hfEx6PjfDDPg4cIbtY60aeqP0IOwu1-S0qJRBZ-OuvC5I_stkqniA$
>
> As the maintainer of tracefs, why am I not Cc'd on that thread :-(
>
> I'll have to look at that thread later (no time now).
Agreed - that's my bad. I meant to add you earlier in the discussion...

>
>>
>> The attempt there is more generic but I realize now that it is adding the
>> tracing to an 'instance' which is specific to dynamic debug which is
>> being created via: trace_array_get_by_name(). I would prefer to just have
>> it print to the 'main' trace buffer such that it's easier to read,
>> although I guess they could still be consolidated via timestamps.
>> Hmmm...I think there was a previous proposal to just add a single
>> tracepoint (that takes a string) to the dynamic debug layer that could be
>> called if a dynamic debug site is enabled for trace buffer output. Would
>> that satisfy the ftrace level filtering requirements that you are looking
>> for?
>
> What we are looking at there is to pass the dynamic debug descriptor to the
> trace event filtering logic, where you could filter on information passed
> to it. For example, on a specific file if a trace event is called by
> several different files or modules.
>
> -- Steve

Ok, Could this be done at the dynamic debug level as it can already match on specific files and line numbers currently?

Thanks,

-Jason