The PREEMPT_RT patch is available for every long term stable version of the mainline Linux kernel since kernel version v2.6.11. Most long term stable versions of the Linux kernel have an even subversion number.
There are two git repositories hosting the source code of the Linux mainline kernel versions with the additional PREEMPT_RT Patch.
The first one hosts the current development PREEMPT_RT patches with the corresponding Linux mainline source. The development of a particular version usually stops when the focus switches to the next mainline version. This happens once a new stable candidate is released. After this, the development versions are moved to the second repository and are maintained by Steven Rostedt. The maintainers of the first git repository are Sebastian Siewior and Thomas Gleixner.
The different versions of the PREEMPT_RT patch are additionally available as tar balls. They are hosted on the kernel.org website.
The versions of the PREEMPT_RT patch can be split into two groups. The first one contains those versions which are actively maintained. The second group includes the kernel versions that are no longer actively maintained. The support for a PREEMPT_RT patch version depends on the projected "End of Life" of the mainline kernel version.
5.16-rt Sebastian A. Siewior, development
5.15-rt Clark Williams 2023-10
5.10-rt Luis Claudio R. Goncalves 2026-12
5.4-rt Tom Zanussi 2025-12
4.19-rt Clark Williams 2024-12
4.14-rt Luis Claudio R. Goncalves 2024-01
4.9-rt Mark Gross 2023-01
4.4-rt Daniel Wagner 2022-02
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