CONFIG PREEMPT RT Patch

The CONFIG_PREEMPT_RT Patch Set

The CONFIG_PREEMPT_RT patch set is maintained by a small group of core developers, led by Ingo Molnar. This patch allows nearly all of the kernel to be preempted, with the exception of a few very small regions of code ("raw_spinlock critical regions"). This is done by replacing most kernel spinlocks with mutexes that support priority inheritance, as well as moving all interrupt and software interrupts to kernel threads.

It further incorporates high resolution timers - a patch set, which is independently maintained.

You can find now a detailed RT_PREEMPT_HOWTO on this page.

Paul McKenney has written a good CONFIG_PREEMPT_RT overview which is a good introduction to the changes introduced to the kernel by the CONFIG_PREEMPT_RT patch.

Download

The patch set is available at Ingo Molnars webspace, as either a single monolithic patch, or in a broken-out tarball. See the announcement regarding the broken-out patch set.

There is also a yum repository with precompiled kernels and source rpms:

  cd /etc/yum.repos.d
  wget http://people.redhat.com/~mingo/realtime-preempt/rt.repo

  yum install kernel-rt.x86_64   # on x86_64
  yum install kernel-rt          # on i686

  yum update kernel-rt           # refresh - or enable yum-updatesd

And also an apt repository for Ubuntu with x86 precompiled kernel. You can find more information in this wiki page:

https://wiki.ubuntu.com/RealTime

Sending patches

Please send patches for the CONFIG_PREEMPT_RT Patch Set to LKML and put Ingo Molnar and Thomas Gleixner on CC.

Please do not send clocksource and clockevents related patches against the -rt patch. Make sure they apply against the latest -hrt-dyntick patch. -hrt-dyntick might be a bit ahead of -rt at times, but the -rt patch pulls -hrt-dyntick on a regular base.

Platforms Tested and in Use with CONFIG_PREEMPT_RT

Processor	Model #'s	Kernel version(s)	Contact(s)
Opteron	IBM LS-20, LS-21, x3455	2.6.16-rt22, 2.6.20-rt8	Theodore Ts'o, Darren Hart
Xeon	IBM 6850-P4U	2.6.20-rt8, 2.6.21-rc6-rt0	Dave Sperry
P4	Compaq Evo N610	2.6.16-rt22	Dave Sperry
P3	Celeron 1300	2.6.21.5-rt14	Oleksandr Natalenko
Prescott	PentiumD 3 GHz	2.6.22.6-rt9	Dmitry Pisklov
Intel	Pentium 4 CPU 2.4 GHz	2.6.23-rc8-rt1	Jaswinder Singh