For the first time, Real Time Linux (RTLinux) is completely hidden in the kernel. At this week’s Open Source Summit Europe, the implementation was endorsed by Linux founder Linus Torvalds. Why is this relevant? And what can users do with it?
A Real-Time Operating System (RTOS) is very important for mission-critical workloads. However, the nomenclature is somewhat confusing. The timeliness of an RTOS is crucial because it guarantees that some tasks will be executed at all times, regardless of what the OS does. In other words: Normally, an OS completes tasks sequentially, with interrupts affecting the precise order. For example, a hardware driver may interrupt the normal flow of an application, which can cause mistimed responses. An RTOS prevents this from happening.
Déjà vu
RTOS implementations have been around for a long time. Most components of PREEMPT_RT, the series of patches from the Real Time Linux project, were already in the Linux kernel. There are also already RTOSs outside Linux, such as BlackBerry’s QNX, Nucleus RTOS (Mentor Graphics of Siemens), ThreadX (Express Logic of Microsoft) and VxWorks. They can run alongside a Linux distribution in embedded environments, such as within hospitals or on the factory floor. In that case, they fulfill mission-critical tasks for which a conventional OS is not suited.
As of now, that could change. Future Linux releases will include all the work of Real Time Linux in the kernel. For Canonical, maker of the popular Linux distribution Ubuntu, that may not be good news. In May, it became apparent that the real-time kernel for Ubuntu 24.04 LTS was only available to users with a PRO subscription. It was only free if individuals used it or smaller organizations installing it on five or fewer devices. This was not received at all positively by the Linux community, but followed the behavioral trend set by Red Hat by shutting down RHEL for downstream development.
Now all Linux maintainers, whether individuals or Canonical, have real-time Linux capabilities within the kernel.
Why did this take so long?
RTLinux itself is anything but a new project. It has been under construction for 20 years, but out of caution, it has been introduced extremely gradually within the kernel. In conversation with ZDNET, developer Steven Rostedt says that every piece of code was rewritten at least three times. Funding for the project was also turbulent for a long time, until the Linux Foundation picked it up in 2015 and gave it some stability.
So as of now, Linux at large is competing with players like BlackBerry, Siemens and Microsoft to provide an RTOS for NASA missions, medical devices and self-driving cars. Thus, the spread of the open-source operating system may extend even further than it already does, far beyond the servers, desktops and laptops it already occupies.
Also read: 33-year-old Linux is a staple of IT infrastructures