Re: [PATCH] asm-generic: partially revert "Unify uapi bitsperlong.h for arm64, riscv and loongarch"

[Catalin Marinas]

On Fri, Aug 11, 2023 at 10:49:07PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
> 
> Unifying the asm-generic headers across 32-bit and 64-bit architectures
> based on the compiler provided macros was a good idea and appears to work
> with all user space, but it caused a regression when building old kernels
> on systems that have the new headers installed in /usr/include, as this
> combination trips an inconsistency in the kernel's own tools/include
> headers that are a mix of userspace and kernel-internal headers.
> 
> This affects kernel builds on arm64, riscv64 and loongarch64 systems that
> might end up using the "#define __BITS_PER_LONG 32" default from the old
> tools headers. Backporting the commit into stable kernels would address
> this, but it would still break building kernels without that backport,
> and waste time for developers trying to understand the problem.
> 
> arm64 build machines are rather common, and on riscv64 this can also
> happen in practice, but loongarch64 is probably new enough to not
> be used much for building old kernels, so only revert the bits
> for arm64 and riscv.
> 
> Link: https://lore.kernel.org/all/20230731160402.GB1823389@dev-arch.thelio-3990X/
> Reported-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> Fixes: 8386f58f8deda ("asm-generic: Unify uapi bitsperlong.h for arm64, riscv and loongarch")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>

For arm64:

Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>