[paulmckrcu:cmpxchg2.2026.09.22a 25/28] arch/arc/include/asm/cmpxchg.h:46:58: error: pointer type mismatch in conditional expression
Vineet Gupta
vgupta at kernel.org
Thu Sep 24 13:52:55 PDT 2026
On 9/24/26 00:51, kernel test robot wrote:
> tree: https://github.com/paulmckrcu/linux cmpxchg2.2026.09.22a
> head: 54c282c15475ebfae4712fe3ab637c9d19c723d6
> commit: b6d4f6af38f85e7948fd64f9bf09cbb858b4dade [25/28] ARC: Emulate two-byte cmpxchg
> config: arc-allyesconfig (https://download.01.org/0day-ci/archive/20260924/202609241517.SSV1Goz3-lkp@intel.com/config)
> compiler: arc-linux-gcc (GCC) 16.1.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260924/202609241517.SSV1Goz3-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp at intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202609241517.SSV1Goz3-lkp@intel.com/
>
> All errors (new ones prefixed by >>):
>
> In file included from arch/arc/include/asm/atomic.h:13,
> from include/linux/atomic.h:7,
> from include/asm-generic/bitops/lock.h:5,
> from arch/arc/include/asm/bitops.h:190,
> from include/linux/bitops.h:67,
> from include/linux/log2.h:12,
> from include/asm-generic/div64.h:55,
> from ./arch/arc/include/generated/asm/div64.h:1,
> from include/linux/math.h:6,
> from include/linux/math64.h:6,
> from include/linux/time.h:6,
> from include/linux/stat.h:19,
> from include/linux/fs_dirent.h:5,
> from include/linux/fs/super_types.h:5,
> from include/linux/fs/super.h:5,
> from include/linux/fs.h:5,
> from include/linux/fscrypt.h:16,
> from fs/crypto/fscrypt_private.h:15,
> from fs/crypto/hooks.c:10:
> fs/crypto/hooks.c: In function 'fscrypt_get_symlink':
>>> arch/arc/include/asm/cmpxchg.h:46:58: error: pointer type mismatch in conditional expression [-Wincompatible-pointer-types]
> 46 | unsigned long _new_ = (unsigned long)(0 ? *(_p_) : (new)); \
Issue is in fs/crypto/hooks.c doing cmpxchg_release(&inode->i_link,
NULL, pstr.name)
where i_link is char * and pstr.name is unsigned char *),
The problem is when pointer types are incompatible and that's exactly
the W toggle above.
So Bradley's patch needs this fixup
diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
index 4596edfefa95..9053098bb152 100644
--- a/arch/arc/include/asm/cmpxchg.h
+++ b/arch/arc/include/asm/cmpxchg.h
@@ -42,8 +42,10 @@
#define arch_cmpxchg_relaxed(ptr, old, new) \
({ \
__typeof__(ptr) _p_ = (ptr); \
- unsigned long _old_ = (unsigned long)(0 ? *(_p_) : (old));
\
- unsigned long _new_ = (unsigned long)(0 ? *(_p_) : (new));
\
+ __typeof__(*(ptr)) _o_ = (old); \
+ __typeof__(*(ptr)) _n_ = (new); \
+ unsigned long _old_ = (unsigned long)_o_; \
+ unsigned long _new_ = (unsigned long)_n_; \
P.S: For arch changes shouldn't the submitter be required to at least
test the building, specially when this involves the macro maze. Its
really easy with crosstool hosting all the cross-compilers [1] - just
download and untar.
[1]
https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/16.2.0/
Thx,
-Vineet
> | ^
> include/linux/atomic.h:68:9: note: in expansion of macro 'arch_cmpxchg_relaxed'
> 68 | op##_relaxed(args); \
> | ^~
> include/linux/atomic/atomic-arch-fallback.h:80:9: note: in expansion of macro '__atomic_op_release'
> 80 | __atomic_op_release(arch_cmpxchg, __VA_ARGS__)
> | ^~~~~~~~~~~~~~~~~~~
> include/linux/atomic/atomic-instrumented.h:4803:9: note: in expansion of macro 'raw_cmpxchg_release'
> 4803 | raw_cmpxchg_release(__ai_ptr, __VA_ARGS__); \
> | ^~~~~~~~~~~~~~~~~~~
> fs/crypto/hooks.c:420:13: note: in expansion of macro 'cmpxchg_release'
> 420 | cmpxchg_release(&inode->i_link, NULL, pstr.name) != NULL)
> | ^~~~~~~~~~~~~~~
> arch/arc/include/asm/cmpxchg.h:46:51: note: first expression has type 'char *'
> 46 | unsigned long _new_ = (unsigned long)(0 ? *(_p_) : (new)); \
> | ^~~~~~
> include/linux/atomic.h:68:9: note: in expansion of macro 'arch_cmpxchg_relaxed'
> 68 | op##_relaxed(args); \
> | ^~
> include/linux/atomic/atomic-arch-fallback.h:80:9: note: in expansion of macro '__atomic_op_release'
> 80 | __atomic_op_release(arch_cmpxchg, __VA_ARGS__)
> | ^~~~~~~~~~~~~~~~~~~
> include/linux/atomic/atomic-instrumented.h:4803:9: note: in expansion of macro 'raw_cmpxchg_release'
> 4803 | raw_cmpxchg_release(__ai_ptr, __VA_ARGS__); \
> | ^~~~~~~~~~~~~~~~~~~
> fs/crypto/hooks.c:420:13: note: in expansion of macro 'cmpxchg_release'
> 420 | cmpxchg_release(&inode->i_link, NULL, pstr.name) != NULL)
> | ^~~~~~~~~~~~~~~
> arch/arc/include/asm/cmpxchg.h:46:60: note: second expression has type 'unsigned char *'
> 46 | unsigned long _new_ = (unsigned long)(0 ? *(_p_) : (new)); \
> | ^~~~~
> include/linux/atomic.h:68:9: note: in expansion of macro 'arch_cmpxchg_relaxed'
> 68 | op##_relaxed(args); \
> | ^~
> include/linux/atomic/atomic-arch-fallback.h:80:9: note: in expansion of macro '__atomic_op_release'
> 80 | __atomic_op_release(arch_cmpxchg, __VA_ARGS__)
> | ^~~~~~~~~~~~~~~~~~~
> include/linux/atomic/atomic-instrumented.h:4803:9: note: in expansion of macro 'raw_cmpxchg_release'
> 4803 | raw_cmpxchg_release(__ai_ptr, __VA_ARGS__); \
> | ^~~~~~~~~~~~~~~~~~~
> fs/crypto/hooks.c:420:13: note: in expansion of macro 'cmpxchg_release'
> 420 | cmpxchg_release(&inode->i_link, NULL, pstr.name) != NULL)
> | ^~~~~~~~~~~~~~~
>
>
> vim +46 arch/arc/include/asm/cmpxchg.h
>
> 41
> 42 #define arch_cmpxchg_relaxed(ptr, old, new) \
> 43 ({ \
> 44 __typeof__(ptr) _p_ = (ptr); \
> 45 unsigned long _old_ = (unsigned long)(0 ? *(_p_) : (old)); \
> > 46 unsigned long _new_ = (unsigned long)(0 ? *(_p_) : (new)); \
> 47 __typeof__(*(ptr)) _prev_; \
> 48 \
> 49 switch (sizeof(*(_p_))) { \
> 50 case 1: \
> 51 _prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *__force)_p_, _old_, _new_); \
> 52 break; \
> 53 case 2: \
> 54 _prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *__force)_p_, _old_, _new_); \
> 55 break; \
> 56 case 4: \
> 57 _prev_ = (__typeof__(*(ptr)))__cmpxchg(_p_, _old_, _new_); \
> 58 break; \
> 59 default: \
> 60 BUILD_BUG(); \
> 61 } \
> 62 _prev_; \
> 63 })
> 64
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
>
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