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.

    • um: Fix filtering '-mno-global-merge' (v1)
  • 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 :)

    • crypto: virtio - Select new dependencies (v1)

    • arm64: Do not include __READ_ONCE() block in assembly files (v1)

    • ARM: Do not use NOCROSSREFS directive with ld.lld (v1)

    • x86/ibt: Fix CC_HAS_IBT check for clang (v1)

    • x86: Avoid CONFIG_X86_X32_ABI=y with llvm-objcopy (v1)

    • Fix CONFIG_X86_KERNEL_IBT for clang and ld.lld < 14.0.0 (v1)

  • Kbuild improvements: These are patches to improve or fix issues with how we build the kernel with LLVM. The first one is particularly notable, as it was requested by a high profile kernel developer.

    • kbuild: Make $(LLVM) more flexible (v1, v2)

    • Remove '-mno-global-merge' from KBUILD_CFLAGS (v1)

  • Warning fixes: These are patches to fix various warnings that appear with LLVM. I used to go into detail about the different warnings and what they mean, but the important takeaway for this section is that the kernel should build warning free, as everyone should be using CONFIG_WERROR, which will turn these all into failures. Maybe these should be in the build failures section…

    • drm/selftest: plane_helper: Put test structures in static storage (v1)

    • KVM: x86: Fix clang -Wimplicit-fallthrough in do_host_cpuid() (v1)

    • netfs: Ensure ret is always initialized in netfs_begin_read() (v1)

    • btrfs: Remove unused variable in btrfs_{start,write}_dirty_block_groups() (v1)

    • clocksource/drivers/imx-tpm: Move tpm_read_sched_clock() under CONFIG_ARM (v1)

    • i2c: designware: Mark dw_i2c_plat_{suspend,resume}() as __maybe_unused (v1)

    • drm/msm/gpu: Avoid -Wunused-function with !CONFIG_PM_SLEEP (v1)

Patch review and input

For the next sections, I link directly to my first response in the thread when possible but there are times where the link is to the main post. My responses can be seen inline by going to the bottom of the thread and clicking on my name.

Reviewing patches that are submitted is incredibly important, as it helps ensure good code quality due to catching mistakes before the patches get accepted and it can help get patches accepted faster, as some maintainers will blindly pick up patches that have been reviewed by someone that they trust.

Issue triage and reporting

The unfortunate thing about working at the intersection of two projects is we will often find bugs that are not strictly related to the project, which require some triage and reporting back to the original author of the breakage so that they can be fixed and not impact our own testing. Some of these bugs fall into that category while others are issues strictly related to this project.

Tooling improvements

Behind the scenes

  • Every day that there is a new linux-next release, I rebase and build a few different kernel trees then boot and runtime test them on several different machines, including a Windows Subsystem for Linux instance, a Raspberry Pi 3 and 4, an Intel-based desktop, an AMD-based desktop, and an Intel-based laptop. This is not always visible because I do not report anything unless there is something broken but it can take up to a few hours each day, depending on the amount of churn and issues uncovered.

Special thanks to: