linux-kernel - Re: [peterz-queue:locking/core 21/21] WARNING: modpost: vmlinux.o(.text.unlikely+0x253ac): Section mismatch in reference from the function __set_bit() to the variable .init.data:initcall_level

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Date:   Wed, 14 Jul 2021 20:55:38 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     kernel test robot <lkp@...el.com>
Cc:     kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [peterz-queue:locking/core 21/21] WARNING: modpost:
 vmlinux.o(.text.unlikely+0x253ac): Section mismatch in reference from the
 function __set_bit() to the variable .init.data:initcall_level_names

Hi,

On Wed, Jul 14, 2021 at 09:08:08AM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git locking/core
> head:   ceb71d863ae0bfca14303c189bbf5903a02ff95a
> commit: ceb71d863ae0bfca14303c189bbf5903a02ff95a [21/21] locking/atomic: add generic arch_*() bitops
> config: xtensa-allyesconfig (attached as .config)
> compiler: xtensa-linux-gcc (GCC) 9.3.0
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?id=ceb71d863ae0bfca14303c189bbf5903a02ff95a
>         git remote add peterz-queue https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git
>         git fetch --no-tags peterz-queue locking/core
>         git checkout ceb71d863ae0bfca14303c189bbf5903a02ff95a
>         # save the attached .config to linux build tree
>         mkdir build_dir
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross O=build_dir ARCH=xtensa SHELL=/bin/bash
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
> 
> All warnings (new ones prefixed by >>, old ones prefixed by <<):
> 
> >> WARNING: modpost: vmlinux.o(.text.unlikely+0x253ac): Section mismatch in reference from the function __set_bit() to the variable .init.data:initcall_level_names
> The function __set_bit() references
> the variable __initdata initcall_level_names.

I can reproduce this with the kernel.org cross toolchain:

https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/9.3.0/x86_64-gcc-9.3.0-nolibc-xtensa-linux.tar.gz

... but the warning looks to be bogus; __set_bit() doesn't use that
symbol, and where that symbol is defined it looks to be used safely.

On the prior commit there was a similarly bogus warning in place of this
one:

| WARNING: modpost: vmlinux.o(.text.unlikely+0x24a10): Section mismatch in reference from the function bfq_pos_tree_add_move() to the variable .init.data:initcall_level_names
| The function bfq_pos_tree_add_move() references
| the variable __initdata initcall_level_names.
| This is often because bfq_pos_tree_add_move lacks a __initdata
| annotation or the annotation of initcall_level_names is wrong.

... so I think there is a latent bug here with the section mismatch
warning, and this commit has simply changed the bogus symbol it reports.

Given that, I think we should ignore this.

Thanks,
Mark.