Linus Torvalds announced the fourth release candidate (RC4) of Linux Kernel 6.12 on 20 October 2024. While not the biggest rc4 release ever, it is the biggest in the 6.x series in terms of the number of commits.
Torvalds expressed some concern about the size, hoping the next week would be calmer. However, he reassured users that the commits primarily consist of small fixes, with nothing "particularly scary going on".
Table of Contents
Release Highlights
While the number of commits in Linux 6.12 RC4 is higher than expected, the overall nature of changes remains mostly small, with an emphasis on fixing bugs and improving stability.
Below are some notable changes across different components:
1. Drivers
Approximately one-third of the changes pertain to drivers, with a significant focus on GPU and networking. There are also updates for other devices like Bluetooth and RDMA (Remote Direct Memory Access).
- GPU: Changes to the AMDGPU driver include optimizations for power-saving features and handling of virtual functions (VFs).
- Networking: The RDMA subsystem has seen multiple fixes aimed at resolving errors related to queue work entries (CQ WQEs) for older adapters and addressing specific event handling.
- Bluetooth: Issues with module unload and debug files have been addressed, ensuring that the system behaves correctly when modules are removed or fail to initialize.
2. Filesystems
This release sees considerable activity around filesystems, particularly with fixes for bcachefs, a new copy-on-write filesystem that has been gaining attention. There are also improvements for SMB, XFS, and Btrfs.
- bcachefs: The dominant focus in filesystems, this copy-on-write (COW) filesystem has received numerous fixes aimed at improving transaction handling and resolving deadlocks.
- XFS: The XFS filesystem has received updates to improve its handling of certain fork allocations and address issues in the write path.
- Btrfs: There have been several small fixes related to inode references and extent handling in Btrfs, helping improve stability and performance.
3. Core Kernel
Several core kernel subsystems such as the scheduler, networking, BPF (Berkeley Packet Filter), and tracing have received updates. These changes range from small optimizations to fixes that address specific issues.
- Scheduler: A fix in the scheduler subsystem addresses a wakeup-preempt issue, ensuring that task switching behaves as expected when certain conditions arise.
- BPF (Berkeley Packet Filter): The BPF subsystem has been updated to correct issues related to delta propagation between registers and to handle edge cases in task filters.
Bug Fixes and Minor Improvements
Many of the changes in RC4 are small, one-liner fixes that address specific bugs. These fixes span a wide range of areas, including:
- Documentation: Corrections to technical documentation, ensuring accuracy for developers and users alike.
- Architecture: Updates for architectures like RISC-V, with a focus on BPF and interrupt handling.
- I/O Subsystems: Several fixes for USB, IOMMU, and block devices, including addressing race conditions and correcting buffer management issues.
Try Linux Kernel 6.12 RC4
Despite the size of this release candidate, the focus on small fixes suggests a stable and incremental improvement over previous versions.
The users and developers are encouraged to test Linux 6.12-rc4 thoroughly to ensure that all subsystems function as expected. You can download it from the Kernel.org website or the Linus Torvalds's git tree.
