Comment # 3 on bug 1181479 from Aaron Puchert

The 3 latest builds have succeeded, and it's almost certainly not a kernel bug.

More likely it's a hang caused by a race condition, but since LLVM 12 is around
the corner I'll probably not have the time to look into it. It's also not
exactly a part of LLVM I'm familiar with. So I suggest to close this bug.

If anyone is curious, the bug is most likely in the gold linker plugin
LLVMgold.so or the LTO library, whichever does the actual parallelization.
ThreadSanitizer is sadly not supported on s390x
(https://clang.llvm.org/docs/ThreadSanitizer.html), but the tool is sensitive
enough to detect the race on other platforms. So this could be worth a try.
However, my machine isn't big enough for that. ;)