Re: [paulmckrcu:cmpxchg2.2026.09.22a 25/28] arch/arc/include/asm/cmpxchg.h:46:58: error: pointer type mismatch in conditional expression
Bradley Morgan
brads at mainlining.org
Thu Sep 24 13:58:04 PDT 2026
On 24 September 2026 21:52:55 BST, Vineet Gupta <vgupta at kernel.org> wrote:
>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/
Well thanks but I didn't have a proper server till yesterday.
I'll post all arch patches when Paul tells me how he wants it
Like if he wants u16 in first then arch changes sent.
>
>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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>
--- Thanks!
"I'm not a very positive person" - Linus torvalds
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