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

On 7/15/26 21:12, Boqun Feng wrote:
> [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/[email protected]/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/[email protected]/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 <[email protected]>
>> | Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
>>
>> 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?

Hi,

Unfortunately if a function is inlined, then noinstr is not honored.
The reason for using noinstr for these functions is interaction of
instrumentation with lockdep, so inlining them into non-noinstr callers
breaks KMSAN in a way that is described in the commit message.

Best regards,
Ilya

> 
> 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