Bug 87570

Summary:	Real time priority broken with systemd 218
Product:	systemd	Reporter:	Adriano Moura <adriano.lols>
Component:	general	Assignee:	systemd-bugs
Status:	RESOLVED WONTFIX	QA Contact:	systemd-bugs
Severity:	normal
Priority:	medium	CC:	martin, patrakov, triode1, zdzichu
Version:	unspecified
Hardware:	x86-64 (AMD64)
OS:	Linux (All)
Whiteboard:
i915 platform:		i915 features:

Description Adriano Moura 2014-12-22 00:03:03 UTC

Can't elevate process scheduling from normal to real time (fifo), neither as a normal user or root. It's a fully updated archlinux system with the just released systemd 218.

Steps to reproduce:
Look for this rtkit-daemon log output, when it starts:
rtkit-daemon[10832]: Successfully called chroot.
rtkit-daemon[10832]: Successfully dropped privileges.
rtkit-daemon[10832]: Successfully limited resources.
rtkit-daemon[10832]: Running.
rtkit-daemon[10832]: Canary thread running.
rtkit-daemon[10832]: Failed to make ourselves RT: Operation not permitted
rtkit-daemon[10832]: Watchdog thread running.

downgrade to systemd 217
notice that rtkit-daemon does not outputs "Failed to make ourselves RT: Operation not permitted" anymore and any process that request real time scheduling (like jack) will now work properly.

Comment 1 triode1 2015-01-25 00:06:40 UTC

I see the same problem on arch linux arm.

Strangely if a unit is created early enough at boot time, I can get real time priority, but if it is restarted then it gets assigned to system.slice and can't get it.

Can a mechanism to always force use the root slice for cpu please be returned?

Comment 2 Harvey 2015-07-10 09:22:20 UTC

Still to be seen on archlinux x86-64 with systemd 222

Comment 3 Lennart Poettering 2015-07-11 17:48:59 UTC

Please turn off RT group scheduling in your kernel. 

For background, please see:

https://bugzilla.redhat.com/show_bug.cgi?id=1229700

and:

https://github.com/systemd/systemd/pull/553

Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.