Linus Torvalds, the principal developer of the Linux kernel, announced the release of Linux Kernel 6.11 RC2 on August 4th, 2024. This release focuses on addressing build and test issues identified in RC1, while continuing to refine and improve various aspects of the kernel.
Table of Contents
Key Areas of Improvement
The second release candidate (RC2) of Linux Kernel 6.11 introduces a variety of enhancements, updates and bug fixes. The following are some notable improvements and fixes in Kernel 6.11 RC2.
Kernel Virtualization (KVM)
Several improvements and fixes were made to the Kernel-based Virtual Machine (KVM) subsystem:
- Fixed determination of max NPT mapping level for private pages in x86 KVM
- Eliminated log spam from limited APIC timer periods
- Disallowed pre-fault for SNP VMs before initialization
Networking
The networking stack saw numerous updates and bug fixes:
- Improved handling of RSS (Receive Side Scaling) contexts
- Fixed issues in the Mellanox MLX5 driver
- Enhanced MPTCP (Multipath TCP) scheduling and connection management
- Addressed various Bluetooth-related bugs
Graphics and Display
The Direct Rendering Manager (DRM) subsystem received attention:
- Fixed issues with overlay handling when using Screen Targets in VMware graphics
- Improved AMD GPU power management support
- Addressed various small bugs in Intel and other graphics drivers
File Systems
Both the XFS and Btrfs file systems saw improvements:
- Fixed memory leaks and improved error handling in XFS
- Addressed potential corruption issues in Btrfs
Architecture-Specific Changes
Several architecture-specific improvements were made:
- Enhanced support for various ARM and ARM64 CPU models
- Improved handling of CPU features on RISC-V
- Fixed issues related to x86 performance events and CPU identification
There are also several inaccuracies and outdated information in the existing documentation are fixed.
Specific Driver Updates
While the 6.11-rc2 primarily focus on bug fixes and stability improvements, a few driver updates to specific drivers, including those for GPUs and network adapters, are also addressed. These updates include:
- drm/amdgpu: Fixes for APU handling, contiguous handling for IB parsing, and support for the gpu_metrics sysfs interface.
- drm/i915: Fix for a potential integer overflow issue.
- drm/vmwgfx: Fixes for overlay issues, deadlock during dma buf fence polling, and handling of dumb buffers.
- ice: Improvements to Rx queue handling, XSK pool management, and interrupt mapping.
- net/mlx5: Fixes for error handling, health draining, and lock management.
- net/mlx5e: Addition of a check for return values, requirement for mlx5 tc classifier action support, and a fix for CT entry update leaks.
- net/phy: realtek: Fix for the KSZ9131 MDI-X status issue.
Addressing Build and Test Issues
A significant focus of 6.11-rc2 is resolving the build and test issues encountered in the previous release candidate.
Linus Torvalds noted that RC1 encountered several small but annoying build and test failures in Guenter's test matrix. While these issues were mostly "stupid and trivial", they highlighted areas needing attention. RC2 aims to eliminate much of this "silly noise" without introducing significant new problems.
Geert Uytterhoeven's analysis, presented to the Linux Kernel Mailing List, provides a detailed breakdown of these resolutions.
- Error Resolutions: A total of 20 error improvements are listed, demonstrating a commitment to code stability. Notably, several errors related to the Sparc architecture and the bcachefs file system were addressed.
- Warning Resolutions: The report highlights 19 warning improvements in 6.11-rc2, indicating a focus on code quality and maintainability. Many of these warning resolutions involved missing prototypes and uninitialized variables.
Build Error Regressions in Linux kernel 6.11-rc2
The build error regressions in Linux kernel version 6.11-rc2 when compared to v6.10 include:
- An incompatible pointer type error in
arch/mips/sgi-ip22/ip22-gio.cfor the m68k architecture. - A logical not error in
drivers/md/dm-integrity.c. - A frame size error in
fs/bcachefs/data_update.cfor the m68k architecture. - A constant error in
include/linux/compiler_types.hfor the powerpc architecture. - Several overflow errors and unknown pseudo-op errors for the sh4 architecture.
The build error improvements in Linux kernel version 6.11-rc2 when compared to v6.10 include:
- Fixes for various errors in
arch/sparc, including missing prototypes, undefined symbols, and relocation errors. - Removal of unused variables and corrections for pragma and option usage in
drivers/gpu/drm/msm/adreno.
The build warning regressions in Linux kernel version 6.11-rc2 when compared to v6.10 include:
- A possible use of an uninitialized variable in
fs/btrfs/fiemap.c. - A warning about a missing clone3() entry point in
kernel/fork.c.
The build warning improvements in Linux kernel version 6.11-rc2 when compared to v6.10 include:
- Resolution of override warnings in various
.configfiles. - Fixes for missing prototypes in
arch/mips/sgi-ip22andarch/sparc/prom. - Resolution of uninitialized variable warnings in
drivers/base/regmap/regcache-maple.c. - A fix for a possible use of an uninitialized variable in
fs/btrfs/extent_io.c.
In summary, Linux kernel version 6.11-rc2 brought about a reduction in both build errors and warnings across various architectures, including MIPS, PowerPC, SH4, and SPARC.
The improvements largely revolve around fixing missing prototypes, resolving variable initialization issues, and addressing compiler errors.
Test Linux Kernel 6.11 RC2
The Linux Kernel 6.11 RC2 has brought numerous improvements and fixes across various subsystems.
Users and developers are encouraged to test the second release candidate of 6.11 by downloading it from the Kernel.org website or the Linus Torvalds's git tree.
Please note that these development versions should not be used on production systems due to their experimental nature.
If the typical development cycle is followed, we can expect the final release of Linux 6.11 on or around September 22, 2024.
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