Recently, I started exploring setting up a self-hosted GitHub Actions runner for the work-in-progress LLVM builds that ClangBuiltLinux is looking to distribute on kernel.org, as GitHub Actions hosted runners are pretty underwhelming in terms of performance and we want to soup these builds up with Profile Guided Optimization. Additionallly, GitHub Actions does not have a hosted arm64 Linux option, which is becoming increasingly important with chips such as Apple’s M1 getting strong mainline Linux support....

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org. Linux kernel patches Build failures: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)...

Occasionally, compiling the Linux kernel with a new compiler flag will result in a boot failure. If you are lucky, there will be some output to the serial console but that may not happen if the issue happens in early boot code before the serial driver has loaded. When this happens, it usually requires building part of the kernel without the compiler flag (or the “negative” version of it) to try and figure out the exact translation unit and function that causes the problem....

As a Linux kernel developer, I will often need to build and boot new kernels to hunt down issues or test new functionality for regressions. While it is possible to manually install these kernels on machines, it is easiest to use the distribution’s package manager, as the kernel does not need to be built on the machine it is being installed on. With .deb and .rpm-based systems, it is easy to build a kernel package within the kernel source itself, using the bindeb-pkg and binrpm-pkg targets respectively....

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org. Linux kernel patches Boot fixes: These patches fix boot failures that we have seen in testing. In this case, it is a User Mode Linux fix, which we are looking to enable in our continuous integration setup, as it is useful for quick testing....

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org. Linux kernel patches Miscellaneous improvements: These are series or patches that do not really fit into any of the other categories I typically use with my reports. Allow CONFIG_DEBUG_INFO_DWARF5=y + CONFIG_DEBUG_INFO_BTF=y (v1) tools/resolve_btfids: Do not print any commands when building silently (v1) -Wenum-conversion: This warning occurs when one enumerated type is implicitly converted to another enumerated type, which is typically a bug, although it might not actually be a problem in practice if the used enum has the same value as the intended enum (which is the case here)....

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org. Linux kernel patches Stable patches: The stable trees are the trees that most users consume so keeping them building and as warning and issue free as reasonable is important. [PATCH 5.4] Input: touchscreen - Fix backport of a02dcde595f7cbd240ccd64de96034ad91cffc40 (v1) [PATCH RFC 4....

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org. Linux kernel patches Android patches: Android is one of the biggest downstream consumers of our work. Making sure that it stays working is incredibly important so that it can reach real users. Revert "ANDROID: disable INFINIBAND_QIB from allmodconfig build"...

Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org. Linux kernel patches Build errors: These are hard errors that appear for one reason or another. The first two are from a recent change in LLVM to avoid crashing the compiler (see the commit message for more details, I learned floating point literals exist in C)....

My co-maintainer Nick Desaulniers wrote a great post about taking a several thousand line C file that exposed a compiler bug down to 12 lines with creduce. I thought I would do the same thing with a bug that only happens with link time optimization (LTO) in the Linux kernel, which is a bit of a different beast. Hopefully this post can help others reduce their own bugs and think about the best way to triage a bug....