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Linux kernel developer Greg Kroah-Hartman has announced the release of three new kernel updates: Linux 6.14.11, Linux 6.15.2, and Linux 6.12.33 LTS. Notably, the 6.14 series has now reached its official end-of-life, with users strongly encouraged to migrate to more recent and actively maintained branches.
The most significant change in version 6.15.2 is the rollback of a prior commit that had unintentionally led to increased power consumption on certain systems. The issue specifically affected machines with Simultaneous Multithreading (SMT) disabled—i.e., those running with the nosmt parameter. Following the upgrade to kernel 6.15, such systems began consuming substantially more energy during idle states.
As explained by Rafael Wysocki, the Intel engineer responsible for Linux power management, the earlier commit prevented CPUs from entering the deep power-saving PC10 state. Instead, processors became trapped in the C1 state, leading to elevated power draw during both standard idle and suspend-to-idle modes. The root cause was that the “sleeping” SMT cores remained minimally active, hindering the entire system from reaching optimal energy-saving levels.
Wysocki noted that the issue was “difficult to detect and potentially hazardous,” prompting the decision to revert the change to a known stable state, as verified in the Linux 6.16 development branch. This rollback forms the core of the 6.15.2 update, making it a critical release for users running affected configurations.
Concurrently, the final patch for the 6.14 branch—version 6.14.11—has been issued, after which the series is considered discontinued and will no longer receive updates. Migration guidance for switching to maintained branches is provided.
In parallel, the long-term support (LTS) branch has also been updated, with Linux 6.12.33 LTS incorporating a series of accumulated fixes and improvements.
All three versions are now available for download from the official kernel.org website.
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