PREEMPT_RT was a set of patches for the Linux kernel which implement both hard and soft real-time computing capabilities.[1] On September 20, 2024, PREEMPT_RT was fully merged and enabled in mainline Linux on the supported architectures x86, x86_64, RISC-V and ARM64.[2] This will make kernel v6.12 the first release to include baked-in real-time capability. Support for LoongArch is added in v6.13.[3]
The PREEMPT_RT patchset has been in development since 2005.[4] In 2021, the preemption core locking code was merged.[5] [6]
Since February 2023, Canonical has been releasing real-time versions of Ubuntu Pro, free for personal and small-scale commercial use in up to 5 machines.[7] [8] The real-time kernel can be added to various existing Ubuntu releases through an enablement process. These kernels include the PREEMPT_RT patchset and offer long-term support.
MontaVista Software has been releasing a real-time Linux distribution containing the PREEMPT_RT patchset since the early 2000. Montavista's current main embedded Linux product, CGX, contains real-time preemption as a standard feature.
At the Sep. 2024 European Open Source Summit, Linus Torvalds announced that PREEMPT_RT had been accepted into the mainline linux kernel after a protracted development hurdle involving the [[printk]] kernel logging facility.