> > This causes a practical problem. When a runaway real-time task is
> > eating 100% CPU and we attempt to put the CPU offline, sometimes we
> > block while waiting for the creation of the highest-priority
> > "kstopmachine" thread.
sched-devel.git has new mechanisms against runaway RT tasks. There's a
new RLIMIT_RTTIME rlimit - if an RT task exceeds that rlimit then it is
sent SIGXCPU.
there's also a new group scheduling extension that is driven via a
sysctl:
/proc/sys/kernel/sched_rt_ratio
this way if a user has a runaway RT task, other users (and root) will
still have some CPU time left. (in Peter's latest patchset that is
replaced via rt_runtime_ns - but this is a detail)
so instead of the never-ending arms race of kernel thread priorities
against RT task priorities, we are going towards making RT tasks safer
on a policy level.
Ingo
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