Jack Audio refuses to start in realtime mode

neuromancer85

Hi, I've just installed Solus 4 and I'm trying to use it as my DAW.
Unfortunately I'm finding some problems in starting Jack with realtime support. It gives me this error:

JACK is running in realtime mode, but you are not allowed to use realtime scheduling.
Please check your /etc/security/limits.conf for the following line
and correct/add it if necessary:

@audio - rtprio 99

After applying these changes, please re-login in order for them to take effect.

You don't appear to have a sane system configuration. It is very likely that you
encounter xruns. Please apply all the above mentioned changes and start jack again!

However I've checked in /etc/security/limits.d/90-jack.conf and the correct configs are there:

@audio  - rtprio   99
@audio  - memlock  unlimited

I thought the problem was pam, so I added in /usr/share/defaults/etc/pam.d/login this config:
session required pam_limits.so

I'm already in the "audio" group... what am I missing? 😅

Thank you!

[deleted]

I have the exact same stuff put into the same file. I think I never did anything with pam. On my system it works.

TeenCorn

Have you logged out and back in? It should work OOTB. Changes with limits require a logout to take effect.

eryvile

Here's what I did, following the instructions on http://jackaudio.org/faq/linux_rt_config.html:
Put

@realtime - rtprio 99
@realtime - memlock unlimited

in etc/security/limits.d/99-realtime.conf

and

Create a “realtime” group (as root)

groupadd realtime
usermod -a -G realtime yourUserID

Logout and back in...

Edit: After re-reading your post, I realized that you basically did the same thing already. Should read more carefully 🤦‍♂️

[deleted]

After clean install, can confirm that the instructions at http://jackaudio.org/faq/linux_rt_config.html do work.

kyrios

[deleted] Could you elaborate ?
Because jack package already install a limits.conf file with the same values and users are in the audio group by default.
So I don't get what's the difference between the out of the box settings and the instructions on the link you provide... they look the same to me, unless I missed something ???

[deleted]

kyrios Oh, you're right

Jacalz

I am sorry to be posting here quite some time since this is active, but I think that I have found the root cause. The wiki page for jack was updated not that long ago about information regarding kernels that have CONFIG_RT_GROUP_SCHED enabled. This will probably need to be fixed with one of the solutions mentioned in https://github.com/jackaudio/jackaudio.github.com/wiki/Cgroups because it looks like linux-current has the option enabled.

mefistofeles

Jacalz So, it does seem to be related to the CONFIG_RT_GROUP_SCHED flag. I recompiled a linux-current kernel package without it and I now can start jack with realtime support without problem. This seems odd and as far as I can tell it may be an issue with upstream (jack). I'll report with upstream and see if anything comes up.

Jacalz

mefistofeles
Thank you so much for looking in to it. I never managed to solve it myself. Would be amazing to finally get JACK real-time working properly 🙂

Jacalz

mefistofeles I might be wrong, but I think there might be a rule to not share .eopkg files in the forums, but I might be wrong.

Anyway, have you reached out to upstream to see if the issues could be resolved there? I think that the config option is useful for Docker and other things, if I remember correctly. But other distros might not be using it if they have real-time JACK working, so I am a bit confused as to how they have it working and not us. It worked for a while sometime back though and I wonder if later kernel releases broke it, or if we just turned on the config around the same time.

mefistofeles

Jacalz I know archlinux is not using that option and JACK + realtime works fine there. Fwiw. I tried reaching the JACK people via IRC and haven't got a response. I may try reporting an issue in their github repository, though.
Sorry about the eopkg files, hope it isn't much of a problem.

Jacalz

mefistofeles We all make mistakes. I think you should be fine 🙂

Looking forward you seeing if we can finally get this fixed. Is I’ll be great 👍

TeenCorn

Has this issue been solved?
I ended up fixing the RT issue on my end by fixing the spacing in the limits.conf.

I've reported it here