Re: Clang/LLVM 'main' regression testing and -Wthread-safety

[Nathan Chancellor <nathan@kernel.org>]

Hi Marco,

On Wed, Feb 11, 2026 at 11:58:55AM +0100, Marco Elver wrote:
> See below - Clang's -Wthread-safety support was merged.

Congratulations :) I am happy to hear that it has gotten across the
finish line and I look forward to more people trying it out.

> I'm not too familiar with ClangBuiltLinux testing and regression
> testing setups; but I wanted to check if LLVM 'main' is being
> continuously tested somewhere? I know the Intel test robot takes a
> ~1-2 week old snapshot of LLVM 'main' and tests that.

Yes, it is (at the repository that Miguel pointed out):

  https://github.com/ClangBuiltLinux/continuous-integration2/actions/workflows/mainline-clang-23.yml

You can see our full matrix on the ClangBuiltLinux homepage:

  https://ClangBuiltLinux.github.io

We rely on apt.llvm.org for the nightly builds, which are normally
updated every few days but it was down for a little over a month because
of the 22 to 23 transition (if I understand correctly). I actually need
to chase that transition in TuxMake.

I also have a testing framework I use for local validation of LLVM main,
so I should be able to flag issues fairly quickly:

  https://github.com/nathanchance/llvm-kernel-testing

> Basically I want to ensure that we're able to catch -Wthread-safety
> regressions on the Clang side that affect the kernel. While I've been
> adding more and more tests to the LLVM repo for the rather special
> patterns we decided to use in the kernel to make Context Analysis
> work, maybe some slipped through the cracks.
> 
> E.g. I've been reviewing
> https://github.com/llvm/llvm-project/pull/178952 and tested it, too,
> I'm only 99% certain that PR is ok -- being able to quickly catch a
> newly introduced issue before waiting for the Intel test robot to
> start spamming us would be good.

For what it's worth, I have a decent amount of local computing resources
so if you ever want a pull request explicitly tested, ping me on it and
I am happy to put it through my tests, which should flag any major
problems because the context analysis warnings are default on in
Kconfig.

> I recall there was a CI system that did this, but lost track of what's
> the latest.

Aside from our CI and Intel's, I know Linaro's toolchain group has some
testing of LLVM main that seems to be fairly up to date:

  https://lore.kernel.org/llvm/?q=f%3Aci_notify%40linaro.org

Cheers,
Nathan