Re: [Jack-Devel] jackd-logging -- was jackd2+ardour3 - tracking down "JackActivationCount::Signal value = 0 ref = INT"

On 07/16/2011 03:09 PM, Stéphane Letz wrote:
[..]

>>>> It makes me wonder: Why are the Xrun messages exclusively in 
>>>> jack.log and the "JackActivationCount" messages exclusively in
>>>> the application log? Here the latter do not show up in
>>>> jack.log.
>>>> 
>> 
>> Maybe what all that those apps have in common is that they're
>> using 'jack_error_callback()'. So the jack-errors do not end up in
>> jackd's log any more but are handled by the application.
>> 
>> jack2 does no queue those messages but passes them directly to the 
>> configured log-callback:
>> 
>> jack_error() | jack_info() -> jack_format_and_log() ->
>> log_function() -> jack_error_callback() | jack_info_callback()
>> 
>> so if jack_error() is called from real-time context (e.g. 
>> JackActivationCount), also the jack_log_callback() of the 
>> client-application is invoked with realtime privileges! At least
>> with the current jackdmp implementation.
> 
> I'm a bit lost here.

JackActivationCount::Signal() is called with Sched-FIFO privileges and
it uses jack_error().

I was under the impression that jack_error() (e.g the
"JackActivationCount") would invoke the client's error-callback with RT
privileges - but this is not the case.

> RT threads are supposed to call "set_threaded_log_function" so that
> "JackMessageBufferAdd" is used for logging, thus no blocking logging
> functions are used in RT context. Otherwise non RT versions are
> used.

Good. I've missed that one!

jack_format_and_log() is actually calling JackMessageBufferAdd() instead
of directly calling the jack_log_function().

All OK.

Thanks for elaborating on this, your comments pushed me in the right
direction to improve my understanding of jackdmp's code.

> What is the exact problem? (beside the JackActivationCount be printed
> by "jack_error" and should be moved to "jack_log")

None anymore.

>>> This is in jackdbus right?
>> 
>> indeed.
>> 
>>> How the info/log/error message are handled can be configurated
>>> with the jack_set_error_function/jack_set_info_function from
>>> jack.h API. You should look in how jackdbus configure them.
>>> And/or ask Nedko...
>> 
>> dbus/jackdbus.c does not expose them, but hardcodes internal
>> handlers that simply append the messages to the log-file.
>> 
>> Oh well,
>> robin
> 
> Ask Nedko !!

Hey Nedko (CCed), could you please shed some light on jackdbus logging.
Is there some [planned] functionality for specifying the log level (e.g.
a quiet mode). Jack offers 3 levels: _error, _info, _log; "verbose mode"
only allows to switch on/off the latter.

Furthermore, changing the verbose mode with jack_control requires
re-starting the client(s) (or backend) in order for the change to take
effect.

Is it planned to dup messages? If a client sets a callback - i.e.
jack_set_error_function() -  messages do no longer end up in jackd's
log, but are only sent only to that client.

Cheers!
robin

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