FS#10063 - jack-audio-connection-kit and problem with SHM filesystem

Attached to Project: Arch Linux
Opened by Maciej Ciemborowicz (ciembor) - Wednesday, 02 April 2008, 16:07 GMT
Last edited by Roman Kyrylych (Romashka) - Sunday, 06 April 2008, 08:36 GMT
Task Type Support Request
Category Packages: Extra
Status Closed
Assigned To No-one
Architecture i686
Severity Medium
Priority Normal
Reported Version 2007.08-2
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 0
Private No

Details

Description:
I installed jack-audio-connection-kit and it doesn't start. I think I done everything what I should.

1. I have kdm login manager
2. I log into the system as usual user
3. I changed line "none /dev/shm tmpfs defaults 0 0" in the /etc/fstab to "shmfs /dev/shm shm defaults 0 0"

Additional info:
package version: 0.109.2-1

Here is jack output:
"[ciembor@peace ~]# jackd -R -d alsa
jackd 0.109.2
Copyright 2001-2005 Paul Davis and others.
jackd comes with ABSOLUTELY NO WARRANTY
This is free software, and you are welcome to redistribute it
under certain conditions; see the file COPYING for details

JACK compiled with POSIX SHM support.
cannot open existing shm registry segment (Function not implemented)
no access to shm registry"

And I can see this line when system is starting:
"unknown filestystems type shm"

Steps to reproduce:
This task depends upon

Closed by  Roman Kyrylych (Romashka)
Sunday, 06 April 2008, 08:36 GMT
Reason for closing:  Fixed
Comment by Jan de Groot (JGC) - Wednesday, 02 April 2008, 17:46 GMT
I don't know what weird kernel you're using, but both "shm" and "shmfs" are unknown filesystems on my default kernel26 installation.
Comment by Maciej Ciemborowicz (ciembor) - Wednesday, 02 April 2008, 18:32 GMT
I'm using kernel with low latency support - kernel26rt from AUR. However maintainer assure me, that shm support is enabled. Here is part of our conversation"

ciembor: "Is it possible to enable shmfs in official config? I have problem, becouse JACK Server wont start without POSIX SHM support."
maintainer: "That's already done - CONFIG_TMPFS and SHMEM. Try shmfs /dev/shm shm defaults 0 0 in fstab. Remember that you need a login manager for pam security to work."

But I will check it of course, if it works under official kernel26.
Comment by Maciej Ciemborowicz (ciembor) - Wednesday, 02 April 2008, 18:43 GMT
I read wrong your comment. You wrote, that it isn't working under official kernel26:P. So... someone make a mistake, becouse jack-audio-connection-kit from repository is compiled with shm support. Shm support should be enable in official kernel26 package or shm should be DISABLE in jack (but it isn't good idea;/).
Comment by Maciej Ciemborowicz (ciembor) - Wednesday, 02 April 2008, 18:55 GMT
Sorry for my english;P.
Comment by Maciej Ciemborowicz (ciembor) - Wednesday, 02 April 2008, 19:36 GMT
Sorry for my english;P.
Comment by Maciej Ciemborowicz (ciembor) - Wednesday, 02 April 2008, 19:39 GMT
I checked configuration of kernel26rt and "Virtual memory file system support (former shm fs)" is enabled... everything should be fine. But I can't find shm in "cat /proc/filesystems".
Comment by Ray Rashif (schivmeister) - Thursday, 03 April 2008, 01:47 GMT
Sorry, I did not know it would not work. "shmfs /dev/shm shm" is actually a deprecated (not used anymore) method to use memory filesystems, but JACK's FAQ still mentions it. TMPFS was previously SHMFS, however a "tmpfs" mounted on "/dev/shm" is also an "shmfs". I thought maybe it would work, but expected you to fall back to the default fstab in case it did not.

Well, all you need to know is that there is no problem with SHMFS in any of the Arch Linux kernels, and that it is now known primarily as just TMPFS. You will not see "shm" or "shmfs" in /proc/filesystems either, but there is "tmpfs" which is today's SHMFS.

1) Revert to "none /dev/shm tmpfs"
2) Make sure you are in audio group
3) Use qjackctl to disable realtime
4) Restart JACK/qjackctl and then try
5) Failing above, edit /etc/security/limits.conf to use realtime (you should not need to but looks like you have no other choice):

@audio - rtprio 99
@audio - nice -10
@audio - memlock unlimited
Comment by Maciej Ciemborowicz (ciembor) - Thursday, 03 April 2008, 10:09 GMT
Yeah, it works now:). I tried "none /dev/shm tmpfs" before, but it wasn't the only problem. So... here is solution

1. Install some login manager (kdm, gdm)
2. Make sure you are in audio group
3. Use qjackctl to disable realtime
4. Restart JACK/qjackctl and then try
5. Failing above, edit /etc/security/limits.conf to use realtime (you should not need to but looks like you have no other choice):

@audio - rtprio 99
@audio - nice -10
@audio - memlock unlimited

6. Don't start jackd as deamon from rc.config. Remove /dev/shm/jack* as root before you will start qjackctl as usual user.

Thanks for your kernel package and for great support:).
Comment by Ray Rashif (schivmeister) - Saturday, 05 April 2008, 09:48 GMT
Sure, I think I see your problem now. It's (6) only. Well, great that you have solved it ;)

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