I also noticed when starting jack:Apr 10 11:46:50 cubase pulseaudio[23745]: [pulseaudio] module-jack-sink.c: JACK error >Cannot use real-time scheduling (RR/5)(1: Operation not permitted)<
Apr 10 11:46:50 cubase pulseaudio[23745]: [pulseaudio] module-jack-sink.c: JACK error >JackClient::AcquireSelfRealTime error<
Although qjackctl reports that jackd *does* run with realtime scheduling. Confusing.
Anyway, reproduced the problem. Every so often, I get more of those "cannot get freq" messages and the sound locks up for a few seconds, but then comes back. Then, I got an much longer stream of them (maybe a minute's worth), but the sound and responsiveness of Ardour still came back. Right now, it happened when I was watching YouTube on Chrome via the Pulseaudio Jack sink.
At the time of the messages, qjackctl was suddenly using 25% of my decent i5 CPU.When I checked the log, it was full of messages like:
Tue Apr 11 16:28:09 2017: Jack: ALSA XRun wait_status = 0
Tue Apr 11 16:28:09 2017: Jack: JackSocketServerChannel::Execute : fPollTable i = 1 fd = 12
Tue Apr 11 16:28:09 2017: Jack: JackRequest::Notification
Tue Apr 11 16:28:09 2017: Jack: JackEngine::ClientNotify: no callback for notification = 3
Tue Apr 11 16:28:09 2017: Jack: JackEngine::ClientNotify: no callback for notification = 3
Tue Apr 11 16:28:09 2017: Jack: JackClient::ClientNotify ref = 2 name = dbusapi notify = 3
Tue Apr 11 16:28:09 2017: Jack: JackClient::kXRunCallback
Tue Apr 11 16:28:09 2017: Jack: JackEngine::ClientNotify: no callback for notification = 3
Tue Apr 11 16:28:09 2017: Jack: JackEngine::ClientNotify: no callback for notification = 3
Tue Apr 11 16:28:09 2017: Jack: JackExternalClient::ClientNotify ref = 5 client = qjackctl name = qjackctl notify = 3
Tue Apr 11 16:28:09 2017: Jack: JackEngine::ClientNotify: no callback for notification = 3
Tue Apr 11 16:28:09 2017: Jack: JackSocketServerChannel::Execute : fPollTable i = 2 fd = 14
Tue Apr 11 16:28:09 2017: Jack: JackSocketServerChannel::Execute : fPollTable i = 3 fd = 17
Tue Apr 11 16:28:09 2017: Jack: JackSocketServerChannel::Execute : fPollTable i = 4 fd = 20
Tue Apr 11 16:28:09 2017: Jack: JackSocketServerChannel::Execute : fPollTable i = 5 fd = 23
Tue Apr 11 16:28:09 2017: Jack: ALSA XRun wait_status = 0
Tue Apr 11 16:28:09 2017: Jack: JackSocketServerChannel::Execute : fPollTable i = 1 fd = 12
Tue Apr 11 16:28:09 2017: Jack: JackRequest::Notification
Tue Apr 11 16:28:09 2017: Jack: JackEngine::ClientNotify: no callback for notification = 3
Tue Apr 11 16:28:09 2017: Jack: JackEngine::ClientNotify: no callback for notification = 3
Tue Apr 11 16:28:09 2017: Jack: JackClient::ClientNotify ref = 2 name = dbusapi notify = 3
Tue Apr 11 16:28:09 2017: Jack: JackClient::kXRunCallback
This seems to happen at the same time as the syslog lines from my OP.
Apr 11 16:28:09 cubase kernel: [108661.803326] usb 3-3: 1:2: cannot get freq at ep 0x1
Apr 11 16:28:09 cubase kernel: [108661.805662] usb 3-3: 2:2: cannot get freq at ep 0x82
By the time I'd gathered enough log information to paste above, the hang was over, so I haven't yet had a chance to try Clemens' suggestion (If you kill Jack and PulseAudio, do aplay/arecord work?).
Anecdotally, from grepping logs, I do believe that "cannot get freq" lines in the syslog happen even when I'm not using jackd, but perhaps with jackd there's more of a problem.
I guess I'm none the wiser. I'll try to log times when jackd is and isn't running and match them to the "cannot get freq" lines in the log, but meanwhile I definitely have a problem here when I'm using jackd, and I'm still not sure if it's software-or-hardware-related.
Antony