PREEMPT_RT in Mainline and Microsofters Trying to Use Rust to Destabilise Linux

posted by Roy Schestowitz on Sep 20, 2024,
updated Sep 25, 2024

• ZDNet ☛ 20 years later, real-time Linux makes it to the kernel - really

  After 20 years, Real-Time Linux (PREEMPT_RT) is finally -- finally -- in the mainline kernel. Linus Torvalds blessed the code while he was at Open Source Summit Europe. Why is this a big deal? Let's start by explaining what a real-time operating system (RTOS) is and what it's good for.

• Dev Class ☛ RustConf speakers affirm Rust for Linux project despite challenges of unstable Rust, maintainer resignation [Ed: Microsoft operative Tim Anderson helps Microsoft employees seed discord inside Linux through Rust, which is hosted on Microsoft platforms]

  At RustConf in Montreal last week, Miguel Ojeda, a lead maintainer for the Rust for Linux project, described the resignation of fellow maintainer Wedson Almeida Filho as a “darkest before the dawn” moment for the project, which aims to make Rust a second main programming language for the Linux kernel alongside C.

Update

Torvalds on Rust:

• Torvalds weighs in on 'nasty' Rust vs C for Linux debate

  "C is, in the end, a very simple language. It's one of the reasons I enjoy C and why a lot of C programmers enjoy C, even if the other side of that picture is obviously that because it's simple it's also very easy to make mistakes," he argued.

Also here:

• Linux is becoming a Real-Time Operating System: what does it mean?

  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.

• Real-time Linux is officially part of the kernel after decades of debate

  As is so often the case, a notable change in an upcoming Linux kernel is both historic and no big deal.

  If you wanted to use "Real-Time Linux" for your audio gear, your industrial welding laser, or your Mars rover, you have had that option for a long time (presuming you didn't want to use QNX or other alternatives). Universities started making their own real-time kernels in the late 1990s. A patch set, PREEMPT_RT, has existed since at least 2005. And some aspects of the real-time work, like NO_HZ, were long ago moved into the mainline kernel, enabling its use in data centers, cloud computing, or anything with a lot of CPUs.

  But officialness still matters, and in the 6.12 kernel, PREEMPT_RT will likely be merged into the mainline. As noted by Steven Vaughan-Nichols at ZDNet, the final sign-off by Linus Torvalds occurred while he was attending Open Source Summit Europe. Torvalds wrote the original code for printk, a debugging tool that can pinpoint exact moments where a process crashes, but also introduces latency that runs counter to real-time computing. The Phoronix blog has tracked the progress of PREEMPT_RT into the kernel, along with the printk changes that allowed for threaded/atomic console support crucial to real-time mainlining.

Slashdot:

• 2024-09-19 [Older] 20 Years Later, Real-Time Linux Makes It To the Kernel

Lunduke:

• Linux has Real-Time now. What the fart does that actually mean?

  20 years in the making. But what does a Real-Time Linux Kernel mean for most of us?

LWN:

• The realtime preemption pull request

  On September 19, Thomas Gleixner delivered the pull request for the realtime preemption enablement patches to Linus Torvalds — in printed form, wrapped in gold, with a ribbon, as Torvalds had requested. It was a significant milestone, marking the completion of a project that required 20 years of effort. Congratulations are due to everybody involved. Torvalds acted on the pull request the following morning.
  

Later coverage:

• Real time officially comes to Linux

  The real time capability from the PREEMPT_RT patches for the kernel were officially fully merged with the mainline codebase today for Linux 6.12 for x86, RISC-V and ARM64. This means Linux will soon start appearing in more mission-critical devices and industrial hardware.

• Real-time Linux has been integrated into the main kernel following two decades of development

  What just happened? Linux has long been the versatile open-source workhorse behind everything from web servers to Android phones. A significant milestone now enables the penguin mascot to showcase its capabilities in even more areas, especially where precise real-time performance is critical.

  After two decades of dedicated development, the "PREEMPT_RT" patch set for real-time Linux has finally been integrated into the main kernel code, receiving approval from Linus Torvalds – the lead developer of the Linux kernel.

  For those unfamiliar, a real-time operating system ensures that it will respond to inputs and execute specific tasks, regardless of other processes. This differs from conventional operating systems like Windows, which aim for a consistent user experience and handle tasks sequentially.

Hackaday:

• Linux, Now In Real Time

  Although Linux runs almost every supercomputer, most of the web, the majority of smart phones, and a few writers’ ancient Macbooks, there’s one major weak point in the Linux world that will almost always have developers reaching for a different operating system. Linux is not a real-time operating system (RTOS), meaning that it can’t respond to requests in the real world within a set timeframe. This means that applications needing computer control in industry, medicine, robotics, and other real-world situations generally need a purpose-built RTOS. At least, that was true until recently when an update to the Linux kernel added real-time capabilities.

Very late:

• Linux Can Now Power Real-Time Operating Systems, as the PREEMPT_RT Patch Set Is Merged Into Mainline

  Linux creator and maintainer Linus Torvalds has accepted a submission that makes a major change to the kernel — allowing users on 32-bit and 64-bit x86, 64-bit Arm, and RISC-V systems to enable a real-time scheduler, giving Linux-based operating systems to ability to become hard real-time operating systems (RTOSes).

  "After twenty years of development we finally reached the point to enable PREEMPT_RT support in the mainline kernel," Linux developer Thomas Gleixner explains of the patches. "All prerequisites are merged, so [we will] enable it on the supported architectures ARM64, RISCV and x86 (32/64-bit)."