Re: [PATCH v3 20/21] dyndbg: add user-flag, negating-flags, and filtering on flags

Petr Mladek
2020-06-19T07:46:01Z

On Thu 2020-06-18 13:11:05, jim.cromie@gmail.com wrote:
> On Thu, Jun 18, 2020 at 12:17 PM Jason Baron <jbaron@akamai.com> wrote:
> > Yes, I'm wondering as well if people are really going to use the
> > new flags and filter flags - I mentioned that here:
> > https://lkml.org/lkml/2020/6/12/732
>
> yes, I saw, and replied there.

No, the repply only explains how the interface might be used. There is
no prove that people would actually use it.

> but since that was v1, and we're on v3, we should refresh.
>
> the central use-case is above, 1-liner version summarized here:
>
> 1- enable sites as you chase a problem with +up
> 2- examine them with grep =pu
> 3- change the set to suit, either by adding or subtracting callsites.
> 4- continue debugging, and changing callsites to suit
> 5- grep =pu control > ~/debugging-session-task1-callsites
> 6- echo up-p >control # disable for now, leave u-set for later
> 7- do other stuff
> 8 echo uP+p >control # reactivate useful debug-state and resume

In short, this feature allows repeatedly enable/disable some
slowly growing maze of debug messages. Who need this, please? !!!

If I am debugging then I add/remove debug messages. But I never
enable/disable all of them repeatedly.

Also this is far from the original problem. It was about debugging
a single driver (venus, drm). In this case, people need something
easy to use. The following is the easy way:

drm.debug = area_of_interest
venus.debug = level_of_interest

echo module=drm group=area_of_interest +p >control [*]
echo module=venus group=level_of_interes +p >control

Anyway, why filtering and 'u' flag would be necessary to debug these drivers?
Is anyone going to use it?

I would really like to hear the motivation for these features.
Has anyone asked for them?
Or are these just some "interesting" ideas from some brainstorming?

[*] Well, I wonder if the dyndbg interface would even be useful for drm
because it it is actually split into many modules. So it might require
creating/maintaining several filters.

Best Regards,
Petr

PS: This is probably my last mail in this thread. It goes in cycle.
You repeatedly explain how many possibilities the new features
allow. I repeatedly doubt that they are worth it.

I also proposed another solution for the original problem (venus)
but it has never been commented.

I just hope that these features will not get merged without
a clear interest in them.