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locking/atomic: arc, hexagon, openrisc: Define arch_cmpxchg_local()

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Commit ccb88db8da ("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: ccb88db8da ("bpf: Don't hand out a linked element as extra element")
Reported-by: kernelci.org bot <bot@kernelci.org>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20261018132907.3823160-1-sashal@kernel.org
Closes: https://d.kernelci.org/i/maestro:78b65519ee4561df1fbf1e72f1dec9da7e5b153e
Closes: https://lore.kernel.org/oe-kbuild-all/202610181750.BoqAddaF-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202610182048.aEaiBP8W-lkp@intel.com/
This commit is contained in:
Sasha Levin 2026-10-18 09:29:07 -04:00 committed by Alexei Starovoitov
parent 73a5accbfd
commit 8cebaa3be8
No known key found for this signature in database
3 changed files with 12 additions and 0 deletions
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4
arch/arc/include/asm/cmpxchg.h
View File

@ -59,6 +59,8 @@
_prev_; \
})
#define arch_cmpxchg_local arch_cmpxchg_relaxed
#else
#define arch_cmpxchg(ptr, old, new) \
@ -80,6 +82,8 @@
_prev_; \
})
#define arch_cmpxchg_local arch_cmpxchg
#endif
/*

6
arch/hexagon/include/asm/cmpxchg.h
View File

@ -8,6 +8,8 @@
#ifndef _ASM_CMPXCHG_H
#define _ASM_CMPXCHG_H
#include <asm-generic/cmpxchg-local.h>
/*
* __arch_xchg - atomically exchange a register and a memory location
* @x: value to swap
@ -72,4 +74,8 @@ __arch_xchg(unsigned long x, volatile void *ptr, int size)
__oldval; \
})
#define arch_cmpxchg_local(ptr, o, n) \
((__typeof__(*(ptr)))__generic_cmpxchg_local((ptr), \
(unsigned long)(o), (unsigned long)(n), sizeof(*(ptr))))
#endif /* _ASM_CMPXCHG_H */

2
arch/openrisc/include/asm/cmpxchg.h
View File

@ -140,6 +140,8 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
sizeof(*(ptr))); \
})
#define arch_cmpxchg_local arch_cmpxchg
/*
* This function doesn't exist, so you'll get a linker error if
* something tries to do an invalidly-sized xchg().