Linux 6.5-rc3 Released with Multiple Kernel Fixes”

Linus Torvalds has announced the release of Linux kernel 6.15-rc3, the third release candidate in the development cycle for the upcoming 6.15 kernel.

While this release does not introduce major new features, it brings a host of minor fixes and refinements across the kernel, underscoring the project’s dedication to stability and hardware compatibility as it approaches the final release, expected in late May or early June.

Highlights of Linux 6.15-rc3

Torvalds described this release as “just a fair number of small fixes all over the place,” with the most significant changes targeting the ublk driver and its associated selftests.

The ublk (userspace block device) driver, which enables high-performance, flexible block device emulation in userspace, received several bug fixes and test improvements, such as enhanced handling of device resets and improved test coverage for zero-copy features.

Key Technical Updates

• x86 Platform Timer Management (PTM):
  • Increased wait time before retrying PTM operations.
  • Improved handling of the IGC_PTP_ENABLED flag and added locking to prevent simultaneous PTM transactions.
  • Moved ktime snapshots into PTM retry loops for more accurate timing.
• NVMe and Storage Subsystems:
  • Fixed potential NULL dereference in nvmet_auth_sq_free().
  • Ensured full initialization of completion entries and proper clearing of CC and CSTS registers when disabling controllers.
  • Addressed issues in Bcachefs, including missing error handling and improved snapshotting logic.
• Memory Management and Filesystems:
  • Reset old folio orders in memory management to prevent bugs.
  • Added missing error handling in Bcachefs and fixed deadlocks in huge page allocation routines.
  • Filesystem updates for XFS, Btrfs, ext4, and others, with Bcachefs’s on-disk format now considered “soft frozen,” signaling increased stability.
• Driver and Hardware Support:
  • Early-stage NOVA core driver added as a foundation for a modern open-source NVIDIA kernel driver, utilizing the NVIDIA GPU System Processor (GSP) firmware for Turing and newer GPUs.
  • Enhanced AMD and Apple hardware support, including new drivers for AMD graphics and Apple Z2 touchscreen/touchbar devices.
  • Support for the AMD Versal NET SoC and optimizations for AMD Zen 5 CPUs.
• Networking and IO Improvements:
  • io_uring Now supports zero-copy receive operations, reducing overhead for network-intensive applications.
  • Numerous fixes for WiFi, Ethernet, and Bluetooth drivers, addressing memory leaks and error paths.
• Rust Integration:
  • Continued incremental integration of Rust, with new helpers and infrastructure to facilitate safe, modern kernel development.
• Other Notable Fixes:
  • Removal of volatile qualifiers from IO helpers in Rust.
  • Addition of i.MX94 support and updates to device tree bindings.
  • Updates to the Zstandard (Zstd) compression algorithm to version 1.5.7.

Development Cycle and Release Timeline

The Linux kernel follows a time-based development cycle, with new release candidates (RCs) published weekly.

The final release of 6.15 is projected for May 25, 2025, if the cycle follows the typical seven-RC pattern, or June 1, 2025, should an eighth RC be necessary.

Community and Testing

Developers and testers are encouraged to download and evaluate Linux 6.15-rc3, reporting any issues to ensure a robust final release.

As always, pre-release kernels are not recommended for production environments.

Linux 6.15-rc3 exemplifies the kernel community’s commitment to incremental improvement, hardware enablement, and code quality.

While lacking headline-grabbing features, this release candidate lays the groundwork for a stable and feature-rich 6.15 release, supporting a broad spectrum of modern hardware and use cases.

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