Re: [LAU] Jack hanging when a usb soundcard is disconnected

On Sat, 17 Oct 2015 18:44:40 +0000
Fons Adriaensen <fons@email-addr-hidden> wrote:

> On Sat, Oct 17, 2015 at 07:24:02PM +0100, Will Godfrey wrote:
> > On Sat, 17 Oct 2015 13:58:37 -0400
> > Ivica Ico Bukvic <ico@email-addr-hidden> wrote:
> >
> > > Hi all,
> > >
> > > This is a long-standing problem. While it is not intentional, sometimes
> > > newcomers to jack on Linux tend to pull out the soundcard (USB) before
> > > shutting down jack. This results in jack permanently hanging to the
> > > point where one has to force-shutdown the machine. That is at least the
> > > case on Ubuntu 14.04 (and was on 12.04) with lowlatency kernel. Trying
> > > to do sudo killall -9 jackd makes no difference. Essentially, it is
> > > impossible to destroy the process and reboot hangs because of it.
> > >
> > > Any idea what can be done to minimize this problem or alleviate it
> > > altogether?
> > >
> > > Best,
> > >
> > > Ico
> >
> >
> > a workaround is from a terminal type:
> >
> > pidof jackd
> >
> > you'll get a number such as 3772
> >
> > then type
> >
> > kill -9 3772
>
> That's what killall or pkill will do anyway, so
> I don't think this is a solution.
>
> I also don't think that Jack is involved. You'd
> probably get the same effect when unplugging the
> USB device while some ALSA app is using it.
>
> There is a similar problem with the hdsp-madi module,
> and it has hit me a number of times when installing
> the card in a new system. Apparently the default
> configuration expects an external clock, and when
> that isn't connected any process that uses the device
> hangs and can't be killed. The first process to do so
> will be alsactl, called as part of the boot sequence.
> And since that will be called again as part of reboot
> or poweroff, those will hang as well. The only thing
> you can do to pull the power plug, remove the card,
> boot, edit the file used by alsactl, switch off, put
> the card back and boot.
>
> Ciao,
>

Interesting. I just tried this on my 'office' machine with a KA6 and it worked,
albeit the response was like treacle! I wonder if the fact that the default
motherboard sound was *not* disabled might have had some bearing on it.

-- 
Will J Godfrey
http://www.musically.me.uk
Say you have a poem and I have a tune.
Exchange them and we can both have a poem, a tune, and a song.
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