On Fri, 2008-11-07 at 16:48 -0800, Fernando Lopez-Lezcano wrote: > On Fri, 2008-11-07 at 15:12 -0800, Fernando Lopez-Lezcano wrote: > > On Fri, 2008-11-07 at 10:12 -0800, Fernando Lopez-Lezcano wrote: > > > On Fri, 2008-11-07 at 10:12 +0100, Clemens Ladisch wrote: > > > > Fernando Lopez-Lezcano wrote: > > > > > I'm seeing a realtime patch related hard hang in the kernel alsa > > > > > subsystem (MIDI input/output). In a nutshell: > > > > > > > > > > - alsa rawmidi works (ie: "rawmidi -v -i hw:0" outputs a stream of > > > > > messages when pointed to a midi capable card that has an external > > > > > keyboard connected). > > > > > > > > > > - the alsa sequencer interface works (ie: aplaymidi connected to > > > > > aseqdump transfers data just fine). > > > > > > > > > > - BOTH combined do NOT work (ie: use aconnect to connect the port that > > > > > corresponds to the external midi interface to aseqdump: aseqdump hangs > > > > > forever after transferring the first message and the only way out is a > > > > > reboot). > > > > > > > > Please try the snd-virmidi driver, then we'd have a test case that does > > > > not require MIDI hardware. > > > > > > > > > ... including the output of a "echo t >/proc/sysrq-trigger" that > > > > > should show where aseqdump currently hangs (or so I think). > > > > > > > > It hangs in tasklet_kill(), which gets called while it tries to close > > > > the rawmidi port. > > > > > > > > The rawmidi framework uses this tasklet to notify the sequencer that new > > > > MIDI data is available. The handler function is > > > > snd_rawmidi_input_event_tasklet() in sound/core/rawmidi.c; the sequencer > > > > callback that gets called from there is snd_midi_input_event() in > > > > core/seq/seq_midi.c. > > > > > > > > You say that the first event gets delivered, so it might be possible > > > > that the tasklet never finishes executing. Please check whether the > > > > call to snd_seq_kernel_client_dispatch() in snd_midi_input_event() > > > > ever returns. > > > > > > I added a printk before and after the call, it looks like it gets called > > > and it returns (but only _once_... aseqdump hangs in an unkillable state > > > as before). > > > > Just in case, the tasklet keeps getting called as long as midi bytes are > > received. So the tasklet runs once, snd_midi_input_event gets called > > once and the tasklet keeps running again and again, but nobody runs > > snd_midi_input_event. Who should? > > I normally use rtirq to tune realtime priorities for realtime kernel > processes, as I looked around and noticed tasklets seem to be related to > (or are) software interrupts and those have priorities, so I disabled > rtirq and rebooted (which leaves the default priority of 50 for all > realtime kernel processes). > > Now I get __two__ midi bytes instead of one (active sensing messages > from the keyboard) and the whole thing stalls as before. This is repeatable. > ?? > So is this a priority inversion problem? And for that matter, what _should_ be the priority order of all the realtime little tasks of rt kernels?? Names have changed and there's a lot more of those... (I can readily hang the whole machine if I change the wrong one to a higher priority!) Any help appreciated... -- Fernando _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
