The PREEMPT_RT patchset has been in development since 2005 as an effort to make the Linux kernel capable of real-time computing by reducing unbounded latencies in kernel paths. Early real-time enhancements were proposed by
Ingo Molnár,
Thomas Gleixner, and others. The PREEMPT_RT patch series introduced features such as threaded interrupts, priority-inherited mutexes, and other mechanisms required for deterministic kernel behavior. For many years PREEMPT_RT was maintained as an out-of-tree patch set applied to stable kernel releases. To support the funding of the ongoing development
OSADL, a German software organization with members from PREEMPT_RTs user but also it's creators like Gleixners Linutronix, has a working group. While parts of the PREEMPT_RT work were incrementally merged, the majority of the patch set remained external to mainline Linux for decades. In 2015, the
Linux Foundation established the Real-Time Linux (RTL) Collaborative Project to coordinate efforts toward upstreaming PREEMPT_RT and to provide sustained development resources. The project brought together long term industry members and maintainers to focus on refactoring kernel subsystems and pushing critical real-time code into the mainline. In 2021, the preemption core locking code was merged. 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. == Usage ==