While building Linux stable-rc 6.1.153-rc1 the s390 allmodconfig with
clang-20 toolchain build failed.

Regression Analysis:
- New regression? yes
- Reproducibility? yes

Build regression: s390 clang-20-allmodconfig

Build error:
arch/s390/kernel/perf_cpum_cf.c:556:10: error: variable 'err' is uninitialized when used here [-Werror,-Wuninitialized]
  556 |                 return err;
      |                        ^~~
arch/s390/kernel/perf_cpum_cf.c:553:9: note: initialize the variable 'err' to silence this warning
  553 |         int err;
      |                ^
      |                 = 0
1 error generated.

The bad commit pointing to,
  s390/cpum_cf: Deny all sampling events by counter PMU
  [ Upstream commit ce971233242b5391d99442271f3ca096fb49818d ]

Build log: https://qa-reports.linaro.org/api/testruns/29914085/log_file/
Build details: https://regressions.linaro.org/lkft/linux-stable-rc-linux-6.1.y/v6.1.151-87-gb31770c84f52/log-parser-build-clang/clang-compiler-arch_s_kernel_perf_cpum_cf_c-error-variable-err-is-uninitialized-when-used-here/


Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>

## Build
* kernel: 6.1.153-rc1
* git: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
* git commit: b31770c84f5240661141c61344d502129a9bda56
* git describe: v6.1.151-87-gb31770c84f52
* test details: https://qa-reports.linaro.org/lkft/linux-stable-rc-linux-6.1.y/build/v6.1.151-87-gb31770c84f52


--
Linaro LKFT
https://lkft.linaro.org