Re: [Denemo-devel] portaudio + fluidsynth

[Dominic Sacré]

Hi Jeremiah, hi Richard,

Sorry for not getting back to you earlier. A couple of things have come 
up lately that left virtually no time to really follow this list or the 
changes in git, and it looks like I have quite a lot of catching up to 
do...

On Thursday 16 February 2012 21:47:20 Jeremiah Benham wrote:
> I don't know if there is a need. It seems to crash all the time no
> matter what file. I am using the portaudio backend and alsa midi
> backend. For some reason with the portmidi backend it does not seem
> to crash as easily. I am also getting many underruns but denemo is
> not crashing on them. Here is the bt full: No symbol table info
> available.
> #10 0x080dba9a in set_playbutton (pause=0) at view.c:8522
> No locals.
> #11 0x0812465e in stop_playing () at midi.c:114
> No locals.
> #12 0x08128688 in midi_stop () at audiointerface.c:447
> No locals.
> #13 0x08128199 in read_event_from_queue (backend=MIDI_BACKEND,
>     event_buffer=0xb7c6c171 "\220\"\177\n", event_length=0xb7c6c160,
>     event_time=0xb7c6c128, until_time=8.0942570018768318)
>     at audiointerface.c:308
>         playback_time = 8.0053333333333327
> #14 0x0812b3d6 in process_thread_func (data=0x0) at alsabackend.c:92
>         pev = 0x0
>         tv = {tv_sec = 1329423635, tv_usec = 636145}
>         playback_time = 8.0892570018768311
>         event_time = 7.5010199999999996
>         until_time = 8.0942570018768318
>         timeval = {tv_sec = 1329423635, tv_usec = 635971}
>         now = 1329423635.6361451
>         event_data = "\220\"\177"
>         event_length = 3
>         mutex = 0x86a1e50

So far I only took a quick glance at the current state of the master 
branch, but it looks like this crash is caused by calling GTK code from 
the ALSA backend's own thread. At the very least these calls would need 
to be protected by gtk_threads_enter(), but since the same code is also 
used by the JACK backend, g_idle_add() should be the way to go.

The different backends share a lot of common code, and the general rule 
is that code called from any of the backends' threads must be realtime-
safe, simply because it'll also be called from the JACK process thread.
So, even with proper synchronization in place, calling GUI code directly 
from the backend is strictly verboten :)


Dominic