As of this writing, 6,778 non-merge changesets have been pulled into the mainline kernel for the 6.12 release — over half of the work that had been staged in linux-next prior to the opening of the merge window. There has been a lot of refactoring and cleanup work this time around, but also some significant changes. Read on for a summary of the first half of the 6.12 merge window.

The kernel normally sits firmly between user space and the system's peripheral devices, and provides a standard interface to those devices. At times, though, a more direct interface to a device is desired — but such interfaces can be controversial. At the 2024 Maintainers Summit, the assembled developers considered a specific case — the proposed fwctl subsystem — as well as the role of such drivers in general.

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.

Tracking of regressions seems like an important task for any project; there is no other way to ensure that known problems are fixed. At the 2024 Maintainers Summit, though, Thorsten Leemhuis, who has been doing that work for the kernel, expressed some doubts about whether it is worth continuing. The result was an energetic session on how regression tracking should be done better, and how this work should be supported.

Version 47 of the GNOME desktop has been released. Changes include configurable accent colors, better small-screen support, some performance improvements, new file open and save dialogs, and more.

The LWN.net Weekly Edition for September 19, 2024 is available.

A Linux system is made up of a large number of interdependent components, all of which must support each other well. It can thus be surprising that, it seems, the developers working on those components do not often speak with each other. In the hope of improving that situation, efforts have been made in recent years to attract toolchain developers to the kernel-heavy Linux Plumbers Conference. This year, though, the opposite happened as well: the 2024 GNU Tools Cauldron hosted a discussion where kernel developers were invited to discuss their needs.

The generation of binary code for the kernel's BPF virtual machine has been limited to the Clang compiler since the beginning; even developers who use GCC to build kernels must use Clang to compile to BPF. Work has been underway for some years on adding a BPF backend to GCC as well; the developers involved ran a session at the 2024 GNU Tools Cauldron to provide an update on that project. It would seem that the BPF backend is close to being ready for production use.

The 6.11 kernel was released on September 15 after a typical nine-week development cycle. This release integrates 13,890 non-merge changesets, so it was a moderately busy cycle, slightly more so that 6.10 was. With a new release comes a new round of development statistics; read on for the details.

Linus has released the 6.11 kernel. "I'm once again on the road and not in my normal timezone, but it's Sunday afternoon here in Vienna, and 6.11 is out." Significant changes in this release include new io_uring operations for bind() and listen(), the nested bottom-half locking patches, the ability to write to busy executable files, support for writing block drivers in Rust, support for atomic write operations in the block layer, the dedicated bucket slab allocator, the vDSO implementation of getrandom(), and more. See the LWN merge-window summaries (part 1, part 2) for more information.

Read-copy-update (RCU) is a synchronization mechanism that was added to the Linux kernel in October 2002. RCU is most frequently used as a replacement for reader-writer locking, but is also used in a number of other ways. This article covers recent changes to the RCU API; it was contributed by Paul McKenney, Boqun Feng, Frederic Weisbecker, Joel Fernandes, Neeraj Upadhyay, and Uladzislau Rezki.

The LWN.net Weekly Edition for September 12, 2024 is available.

CPU scheduling is a challenging job; since it inherently requires making guesses about what the demands on the system will be in the future, it remains reliant on heuristics, despite ongoing efforts to remove them. Some of those heuristics take special note of tasks that are (or appear to be) waiting for fast I/O operations. There is some unhappiness, though, with how this factor is used, leading to a couple of patches taking rather different approaches to improve the situation.

Version 1.0 of the Radicle development platform has been released.

Radicle 1.0 represents the culmination of years of experimentation and hard work from our team and community, where we set out to ensure that free and open source software ecosystems can flourish without having to rely on the whims of Big Tech. We designed Radicle with a first-principles approach, as a natural extension to Git, expanding it to work in a collaborative, local-first, peer-to-peer setting.

LWN looked at Radicle in March.

Security updates have been issued by Debian (cacti), Fedora (aardvark-dns, expat, and firefox), Mageia (ffmpeg, ntfs-3g, and vim), Oracle (emacs, glib2, java-11-openjdk, and qt5-qtbase), Red Hat (emacs, python-setuptools, python3.11, python3.11-setuptools, python3.12-setuptools, python3.9, and python39:3.9), Slackware (netatalk), SUSE (buildah, expat, java-1_8_0-ibm, kanidm, kernel, and postgresql16), and Ubuntu (netty, php7.0, php7.2, tiff, and webkit2gtk).

Jacob Adams wanders into the kernel's hibernation code:

How does Linux move from an awake machine to a hibernating one? How does it then manage to restore all state? These questions led me to read way too much C in trying to figure out how this particular hardware/software boundary is navigated.

Linus has released 6.11-rc7 for testing.

And I wish I could say that things have calmed down, but I can't really say that. In fact, rc7 is slightly bigger than both rc6 and rc5 were, both in number of commits, and in actual diff size. That's not really how it should work out.

That said, there's nothing *scary* in here.

He is apparently "still waffling" about whether to release 6.11 next weekend, which would cause the 6.12 merge window to land on top of the Maintainers Summit, Linux Plumbers Conference, and Open Source Summit.

The 6.10.9, 6.6.50, and 6.1.109 stable kernel updates have been released; each contains another set of important fixes.

Alejandro Colomar, who has been maintaining the Linux man pages for the last four years, has announced that he will have to stop that work.

I've been doing it in my free time, and no company has sponsored that work at all. At the moment, I cannot sustain this work economically any more, and will temporarily and indefinitely stop working on this project. If any company has interests in the future of the project, I'd welcome an offer to sponsor my work here; if so, please let me know.

Work on realtime preemption for the Linux kernel got its start almost exactly 20 years ago (though it had its roots in earlier work, of course). It is fair to say that finishing that job has taken a bit longer than anybody involved would have expected. Now, though, Sebastian Andrzej Siewior has posted a brief patch series making it possible to enable realtime preemption in the mainline kernel on three architectures.

With the printk bits merged, PREEMPT_RT could be enabled on X86, ARM64 and Risc-V. These three architectures merged required changes over the years leaving me in a position where I have no essential changes in the queue that would affect them.

Congratulations are due to the many developers who have worked on this project for the last two decades.