On Sun Oct 18, 2026 at 1:29 PM UTC, Sasha Levin wrote:
> Commit ccb88db8dac8 ("bpf: Don't hand out a linked element as extra
> element") made alloc_htab_elem() take the per-cpu spare element with
> try_cmpxchg_local(), the first caller of cmpxchg_local() outside of
> architecture code. It doesn't build on arc, hexagon and openrisc:
>
> include/linux/atomic/atomic-arch-fallback.h:384:27: error: implicit
> declaration of function 'arch_cmpxchg_local'; did you mean
> 'raw_cmpxchg_local'? [-Werror=implicit-function-declaration]
>
> raw_cmpxchg_local() maps to arch_cmpxchg_local() unconditionally, but
> these three architectures don't define it, and unlike nios2 and
> microblaze they don't get it from asm-generic/cmpxchg.h either.
>
> cmpxchg_local() only has to be atomic with respect to the local CPU, so
> an architecture's own arch_cmpxchg() can serve for the sizes it
> supports. arc uses its relaxed LLOCK/SCOND variant when ARC_HAS_LLSC is
> set and its atomic_ops_lock() variant otherwise, and openrisc uses its
> LL/SC arch_cmpxchg(), the way arm64, riscv and s390 alias theirs. The
> hexagon arch_cmpxchg() only handles 32-bit words, so hexagon uses the
> generic version that disables interrupts, like sh, sparc32 and xtensa
> do. Linux has no NMIs on hexagon, so that is sufficient there.
>
> Fixes: ccb88db8dac8 ("bpf: Don't hand out a linked element as extra element")
> Reported-by: kernelci.org bot <[email protected]>
> Closes:
> https://d.kernelci.org/i/maestro:78b65519ee4561df1fbf1e72f1dec9da7e5b153e
> Reported-by: kernel test robot <[email protected]>
> Closes:
> https://lore.kernel.org/oe-kbuild-all/[email protected]/
> Closes:
> https://lore.kernel.org/oe-kbuild-all/[email protected]/
> Signed-off-by: Sasha Levin <[email protected]>
> ---
> The only user is in bpf-next, so it is probably easiest to take this
> through bpf-next with acks from the arc, hexagon and openrisc
> maintainers. A similar change was posted in 2023 for objpool and
> stalled once objpool stopped using try_cmpxchg_local():
> https://lore.kernel.org/all/[email protected]/
>
> Build tested on arc with and without LLSC (including both KernelCI
> configs), hexagon (clang) and openrisc.
Thanks for the quick fix. Applied.
