[LAD] [OT] Real-time threads on openSuSE 11.4

[Robin Gareus]

On 10/19/2012 03:02 PM, Fons Adriaensen wrote:
> Hello all,
> 
> My ex-collegues at Alcatel are screaming for help. They want to
> run an app (as root, debatable but that's another story) using
> SCHED_FIFO threads on an openSuSE 11.4 system.
> 
> Using the 'default' kernel (which has CONFIG_PREEMPT not set),
> this works. Using the 'desktop' kernel (CONFIG_PREEMPT=y) they get
> an EPERM when trying to start a RT thread, even as root.
> 
> As I haven't used SuSE for ages, has anyone an idea of what is 
> happening here ?

I never used openSuse. and "does not work" is too little info for an
educated guess. So just a few shots in the dark:

/proc/sys/kernel/sched_rt_period_us
/proc/sys/kernel/sched_rt_runtime_us

kernel.sched_rt_runtime_us globally limits realtime
scheduling time.

Maybe cgroups are getting in the way? or possibly grsecurity.

Since it works with the vanilla kernel, PAM and
/etc/security/limits.conf etc do not seem to be the cause, but hey: It
could be related to cgroups, sessions and not su'ing properly.

ciao,
robin