Mainline real-time Linux based on 2.6.33 is "Latest Stable" now

By: Carsten Emde

The later - the better

Finally, there is a "Latest Stable" release of the PREEMPT_RT version of Linux 2.6.33! It is

• linux-2.6.33.7.2-rt30

and available at the usual download locations. More details of this version are available in the git log and in Thomas Gleixner's announcement. In addition to the mainline upgrade changes from 2.6.31 to 2.6.33, this release contains a number of backports and security fixes from later kernels. The combined timer and wakeup latency histogram published earlier and already heavily in use is also included.

Why are we so late?

Some months ago, OSADL has started to populate its test racks with a wide variety of commonly used systems to create a testing environment for quality assurance of the real-time Linux kernel. Care was taken to consider as many different architectures, bit lengths, endiannesses, CPU topologies, peripheral controllers, storage media etc. as possible into this "QA Farm". The advantage of this newly available tool set, obviously, is that a kernel that continuously runs on all these systems in a stable, reliable way and does not show any regression with respect to its real-time capabilities may, in fact, be called "Stable". The disadvantage - another truism - is that we actually found a number of bugs - the more you test, the more you crash. Fixing these bugs took us much longer than in earlier kernels, but we had to keep our promise to never release a "Latest Stable" real-time kernel that still has more than zero known bugs. Since these fixes are now part of the real-time code, not only this but also future versions will profit. Before you ask: Kernel versions 2.6.34 to 2.6.36 will be left out, the next "Latest Stable" real-time kernel will be based on 2.6.37.