2.6.28 has unconfigurable group sched?

[Mark Glines <mark@glines.org>]

Hi,

I've got an issue on x86-64 where I can't configure the system to allow
RT tasks for a non-root user.

In 2.6.26.5, I was able to do the following to set things up nicely:
echo 450000 >/sys/kernel/uids/0/cpu_rt_runtime
echo 450000 >/sys/kernel/uids/1000/cpu_rt_runtime

I've searched lkml archives and am unable to figure out what changed.
As far as I can tell, the documentation (sched-rt-group.txt) says this
should work, and indeed, it did work with 2.6.26.

Seems like every value I try to echo into the /sys files returns EINVAL.
 Even when I'm just writing the same value it already had:

chirp uids # pwd
/sys/kernel/uids
chirp uids # cat 0/cpu_rt_period
1000000
chirp uids # cat 0/cpu_rt_runtime
950000
chirp uids # cat 1000/cpu_rt_period
1000000
chirp uids # cat 1000/cpu_rt_runtime
0
chirp uids # echo 450000 >0/cpu_rt_runtime
echo: write error: invalid argument
chirp uids # echo 450000 >1000/cpu_rt_runtime
echo: write error: invalid argument
chirp uids # echo 950000 >0/cpu_rt_runtime
echo: write error: invalid argument
chirp uids # echo 0 >0/cpu_rt_runtime
echo: write error: invalid argument

So it seems rt_schedulable() is never succeeding.  Any ideas?


sched-related snippets from .config:

CONFIG_X86_SMP=y
CONFIG_USE_GENERIC_SMP_HELPERS=y
CONFIG_X86_64_SMP=y
CONFIG_X86_HT=y

# CONFIG_CGROUPS is not set
CONFIG_HAVE_UNSTABLE_SCHED_CLOCK=y
CONFIG_GROUP_SCHED=y
CONFIG_FAIR_GROUP_SCHED=y
CONFIG_RT_GROUP_SCHED=y
CONFIG_USER_SCHED=y
# CONFIG_CGROUP_SCHED is not set