Re: [boqun:rust-rcu 14/27] rust/helpers/interrupt.c:17:9: warning: static function 'arch_local_save_flags' is used in an inline function with external linkage

[Boqun Feng <boqun@kernel.org>]

[Cc s390]

On Mon, Jul 13, 2026 at 12:45:07PM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux.git rust-rcu
> head:   dcecd5f6e71e2437c8abe333ee2426fbe63e6398
> commit: 27e30521043c39ca18ea3e28f825f9c7bd30b580 [14/27] rust: Introduce interrupt module
> config: s390-randconfig-002-20260713 (https://download.01.org/0day-ci/archive/20260713/202607131219.euJHPSJ5-lkp@intel.com/config)
> compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
> rustc: rustc 1.96.0 (ac68faa20 2026-05-25)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260713/202607131219.euJHPSJ5-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@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202607131219.euJHPSJ5-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
>    In file included from rust/helpers/helpers.c:68:
> >> rust/helpers/interrupt.c:17:9: warning: static function 'arch_local_save_flags' is used in an inline function with external linkage [-Wstatic-in-inline]
>       17 |         return irqs_disabled();
>          |                ^
>    include/linux/irqflags.h:256:3: note: expanded from macro 'irqs_disabled'
>      256 |                 raw_local_save_flags(_flags);           \
>          |                 ^
>    include/linux/irqflags.h:184:11: note: expanded from macro 'raw_local_save_flags'
>      184 |                 flags = arch_local_save_flags();        \
>          |                         ^
>    rust/helpers/interrupt.c:15:1: note: use 'static' to give inline function 'rust_helper_irqs_disabled' internal linkage
>       15 | __rust_helper bool rust_helper_irqs_disabled(void)
>          | ^
>          | static 
>    rust/helpers/helpers.c:38:23: note: expanded from macro '__rust_helper'
>       38 | #define __rust_helper __always_inline
>          |                       ^
>    include/linux/compiler_attributes.h:55:41: note: expanded from macro '__always_inline'
>       55 | #define __always_inline                 inline __attribute__((__always_inline__))
>          |                                         ^
>    include/linux/compiler_types.h:235:16: note: expanded from macro 'inline'
>      235 | #define inline inline __gnu_inline __inline_maybe_unused notrace
>          |                ^
>    arch/s390/include/asm/irqflags.h:46:48: note: 'arch_local_save_flags' declared here
>       46 | static arch_local_irq_attributes unsigned long arch_local_save_flags(void)
>          |                                                ^
>    1 warning generated.
> --
>    In file included from rust/helpers/helpers.c:68:
> >> rust/helpers/interrupt.c:17:9: warning: static function 'arch_local_save_flags' is used in an inline function with external linkage [-Wstatic-in-inline]
>    17 |         return irqs_disabled();
>    |                ^
>    include/linux/irqflags.h:256:3: note: expanded from macro 'irqs_disabled'
>    256 |                 raw_local_save_flags(_flags);           \
>    |                 ^
>    include/linux/irqflags.h:184:11: note: expanded from macro 'raw_local_save_flags'
>    184 |                 flags = arch_local_save_flags();        \
>    |                         ^
>    rust/helpers/interrupt.c:15:1: note: use 'static' to give inline function 'rust_helper_irqs_disabled' internal linkage
>    15 | __rust_helper bool rust_helper_irqs_disabled(void)
>    | ^
>    | static
>    rust/helpers/helpers.c:38:23: note: expanded from macro '__rust_helper'
>    38 | #define __rust_helper __always_inline
>    |                       ^
>    include/linux/compiler_attributes.h:55:41: note: expanded from macro '__always_inline'
>    55 | #define __always_inline                 inline __attribute__((__always_inline__))
>    |                                         ^
>    include/linux/compiler_types.h:235:16: note: expanded from macro 'inline'
>    235 | #define inline inline __gnu_inline __inline_maybe_unused notrace
>    |                ^
>    arch/s390/include/asm/irqflags.h:46:48: note: 'arch_local_save_flags' declared here
>    46 | static arch_local_irq_attributes unsigned long arch_local_save_flags(void)
>    |                                                ^
>    1 warning generated.
>    warning: 1 warning emitted
> 

This seems not a Rust-only issue to me, basically you got the warning
whenever you have an inline function calling irqs_disabled(). I'm a bit
curious why 1b301f5f28ba ("s390/irqflags: do not instrument
arch_local_irq_*() with KMSAN") wanted to add noinline when KMSAN=y, all
you need is noinstr, no?

Regards,
Boqun

> 
> vim +/arch_local_save_flags +17 rust/helpers/interrupt.c
> 
>     14	
>     15	__rust_helper bool rust_helper_irqs_disabled(void)
>     16	{
>   > 17		return irqs_disabled();
> 
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki