Re: arch/x86/include/asm/timex.h:10:7: error: call to undeclared function 'DISABLED_MASK_BIT_SET'; ISO C99 and later do not support implicit function declarations

[Thomas Weißschuh]

On Fri, Aug 21, 2026 at 04:49:41AM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   cb8a75eec0877810b50aa1c5a833f929525cd2ee
> commit: 3ed403bbc967a3138b8e37566510e9b062751372 treewide: Remove CLOCK_TICK_RATE
> date:   5 weeks ago
> config: um-randconfig-r053-20260820 (https://download.01.org/0day-ci/archive/20260821/202608210426.fkFfnASG-lkp@xxxxxxxxx/config)
> compiler: clang version 24.0.0git (https://github.com/llvm/llvm-project 935bfc708590c60147a79c7df145bb6e68b1d388)
> rustc: rustc 1.96.0 (ac68faa20 2026-05-25)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260821/202608210426.fkFfnASG-lkp@xxxxxxxxx/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
> | Fixes: 3ed403bbc967 ("treewide: Remove CLOCK_TICK_RATE")
> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202608210426.fkFfnASG-lkp@xxxxxxxxx/
> 
> All errors (new ones prefixed by >>):
> 
>    In file included from arch/um/kernel/asm-offsets.c:6:
>    In file included from include/linux/crypto.h:18:
>    In file included from include/linux/slab.h:17:
>    In file included from include/linux/gfp.h:7:
>    In file included from include/linux/mmzone.h:22:
>    In file included from include/linux/mm_types.h:16:
>    In file included from include/linux/uprobes.h:18:
>    In file included from include/linux/timer.h:6:
>    In file included from include/linux/ktime.h:25:
>    In file included from include/linux/jiffies.h:10:
>    In file included from include/linux/time.h:60:
>    In file included from include/linux/time32.h:13:
>    In file included from include/linux/timex.h:67:
>    In file included from arch/x86/include/asm/timex.h:6:
>    arch/x86/include/asm/tsc.h:79:7: error: call to undeclared function 'DISABLED_MASK_BIT_SET'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>       79 |         if (!cpu_feature_enabled(X86_FEATURE_TSC))
>          |              ^
>    arch/um/include/asm/cpufeature.h:52:32: note: expanded from macro 'cpu_feature_enabled'

(...)

For the record, this is handled by [0]. See also the discussion in [1].

[0] https://lore.kernel.org/all/20260819-uml-timex-fix-v1-1-f690b514fc9f@xxxxxxxxxxxxx/
[1] https://lore.kernel.org/lkml/20260823201521.2576344-1-fabian@xxxxxxxxxxxxxxxxx/