New in LWN (Outside LWN Paywall)

posted by Roy Schestowitz on Sep 18, 2025

• GNU/Linux

  • Kernel Space

    • LWN ☛ How many ways are there to configure the Linux kernel?

      There are a large number of ways to configure the 6.16 Linux kernel. It has 32,468 different configuration options on x86_64, and a comparable number for other platforms. Exploring the ways the kernel can be configured is sufficiently difficult that it requires specialized tools. These show the number of possible configurations that options can be combined in has 6,550 digits. How has that number changed over the history of the kernel, and what does it mean for testing? Analyzing Kconfigs

      With so many configuration options to consider, it can be difficult to even figure out which options are redundant, unused, or otherwise amenable to simplification. For our problem of counting the number of ways to configure the kernel, we need to consider the relationships between different configuration options as well. Happily, there is some software to manage the growing complexity.

      The kernel uses a custom configuration language, Kconfig, to describe how the build can be customized. While Kconfig has spread to a handful of related projects, it remains a mostly home-grown, Linux-specific system. Paul Gazzillo, along with a handful of other contributors, wrote kmax, a GPL-2.0-licensed software suite for analyzing Kconfig declarations. That project includes tools to determine which configuration options need to be enabled in order to test a patch, to find configuration bugs, and to export Kconfig declarations in a language that can be understood by more tools. It has been integrated into the Intel 0-day test suite, finding a number of bugs in the kernel's configuration in the process.

• Free, Libre, and Open Source Software

  • LWN ☛ Rug pulls, forks, and open-source feudalism

    Like almost all human endeavors, open-source software development involves a range of power dynamics. Companies, developers, and users are all concerned with the power to influence the direction of the software — and, often, to profit from it. At the 2025 Open Source Summit Europe, Dawn Foster talked about how those dynamics can play out, with an eye toward a couple of tactics — rug pulls and forks — that are available to try to shift power in one direction or another.

    Power dynamics

    Since the beginning of history, Foster began, those in power have tended to use it against those who were weaker. In the days of feudalism, control of the land led to exploitation at several levels. In the open-source world, the large cloud providers often seem to have the most power, which they use against smaller companies. Contributors and maintainers often have less power than even the smaller companies, and users have less power yet.

  • Programming/Development

    • LWN ☛ The dependency tracker for complex deadlock detection

      Deadlocks are a constant threat in concurrent settings with shared data; it is thus not surprising that the kernel project has long since developed tools to detect potential deadlocks so they can be fixed before they affect production users. Byungchul Park thinks that he has developed a better tool that can detect more deadlock-prone situations. At the 2025 Open Source Summit Europe, he presented an introduction to his dependency tracker (or "DEPT") tool and the kinds of problems it can detect.

      Park began by presenting a simple ABBA deadlock scenario. Imagine two threads running, each of which makes use of two locks, called A and B. The first thread acquires A, then B, ending up holding both locks; meanwhile, the second thread acquires the same two locks but in the opposite order, taking B first. That can work, until the bad day when each thread succeeds in taking the first of its two locks. Then one holds A, the other holds B, and each is waiting for the other to release the second lock it needs. They will wait for a long time.