PREEMPT_RT was a set of out-of-tree 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 made kernel v6.12 the first release to include baked-in real-time capability.
The PREEMPT_RT patchset has been in development since 2005. [3] In 2021, the preemption core locking code was merged. [4] [5]
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. [6] [7] The real-time kernel can be added to various existing Ubuntu releases through an enablement process. [7] These kernels include the PREEMPT_RT patchset and offer long-term support. [7]
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 September 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.