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.
arch/arc/include/asm/cmpxchg.h | 4 ++++
arch/hexagon/include/asm/cmpxchg.h | 6 ++++++
arch/openrisc/include/asm/cmpxchg.h | 2 ++
3 files changed, 12 insertions(+)
diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
index 66b3743c94008..93f7153eb267a 100644
--- a/arch/arc/include/asm/cmpxchg.h
+++ b/arch/arc/include/asm/cmpxchg.h
@@ -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
/*
diff --git a/arch/hexagon/include/asm/cmpxchg.h
b/arch/hexagon/include/asm/cmpxchg.h
index 9c58fb81f7fd6..e6114e713db9f 100644
--- a/arch/hexagon/include/asm/cmpxchg.h
+++ b/arch/hexagon/include/asm/cmpxchg.h
@@ -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 */
diff --git a/arch/openrisc/include/asm/cmpxchg.h
b/arch/openrisc/include/asm/cmpxchg.h
index 8ee151c072e41..fcf1bc8db8fe9 100644
--- a/arch/openrisc/include/asm/cmpxchg.h
+++ b/arch/openrisc/include/asm/cmpxchg.h
@@ -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().
base-commit: a6303535c2ad9d49598d52556183911f02287791
--
2.53.0
