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Date:   Mon, 17 Jul 2023 06:24:26 -0700
From:   Nathan Chancellor <nathan@kernel.org>
To:     Naresh Kamboju <naresh.kamboju@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Sasha Levin <sashal@kernel.org>
Cc:     linux-stable <stable@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        clang-built-linux <llvm@lists.linux.dev>,
        lkft-triage@lists.linaro.org,
        Nick Desaulniers <ndesaulniers@google.com>,
        Anders Roxell <anders.roxell@linaro.org>
Subject: Re: stable-rc 6.1: x86: clang build failed -
 block/blk-cgroup.c:1237:6: error: variable 'ret' is used uninitialized
 whenever 'if' condition is true
Message-ID: <20230717132426.GA2561862@dev-arch.thelio-3990X>
References: <CA+G9fYs5n6aobE04YZy3Qy1ZMhAvH6-uQRqidgFmSoei91iW8g@mail.gmail.com>
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On Mon, Jul 17, 2023 at 12:55:42AM +0530, Naresh Kamboju wrote:
> Linux stable-rc 6.1 build failed x86 and i386 with clang.
> 
> Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
> 
> Build log:
> -----------
> block/blk-cgroup.c:1237:6: error: variable 'ret' is used uninitialized
> whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
>         if (init_blkcg_llists(blkcg))
>             ^~~~~~~~~~~~~~~~~~~~~~~~
> block/blk-cgroup.c:1287:9: note: uninitialized use occurs here
>         return ret;
>                ^~~
> block/blk-cgroup.c:1237:2: note: remove the 'if' if its condition is
> always false
>         if (init_blkcg_llists(blkcg))
>         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> block/blk-cgroup.c:1222:33: note: initialize the variable 'ret' to
> silence this warning
>         struct cgroup_subsys_state *ret;
>                                        ^
>                                         = NULL
> 1 error generated.
> 
> Links,
>  - https://qa-reports.linaro.org/lkft/linux-stable-rc-linux-6.1.y-sanity/build/v6.1.38-599-g5071846d06ef/testrun/18327562/suite/build/test/clang-lkftconfig/history/
>  - https://storage.tuxsuite.com/public/linaro/lkft/builds/2SfFoWj9NmKWHRijR0hcoXGjLhr/
> 
>  tuxmake \
>  --runtime podman --target-arch x86_64 \
>  --toolchain clang-16 \
>  --kconfig https://storage.tuxsuite.com/public/linaro/lkft/builds/2SfFoWj9NmKWHRijR0hcoXGjLhr/config
> \
>  LLVM=1 LLVM_IAS=1
> 

It looks like 6.1 needs commit b5a9adcbd5dc ("blk-cgroup: Return -ENOMEM
directly in blkcg_css_alloc() error path") if it wants to take commit
3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()").

Cheers,
Nathan