Re: [PATCH bpf] bpf: Make migrate_{disable,enable} always inline if in header file

[Menglong Dong <menglong.dong@linux.dev>]

On 2025/10/30 02:36, Yonghong Song wrote:
> With latest bpf/bpf-next tree and latest pahole master, I got the following
> build failure:
> 
>   $ make LLVM=1 -j
>     ...
>     LD      vmlinux.o
>     GEN     .vmlinux.objs
>     ...
>     BTF     .tmp_vmlinux1.btf.o
>     ...
>     AS      .tmp_vmlinux2.kallsyms.o
>     LD      vmlinux.unstripped
>     BTFIDS  vmlinux.unstripped
>   WARN: resolve_btfids: unresolved symbol migrate_enable
>   WARN: resolve_btfids: unresolved symbol migrate_disable
>   make[2]: *** [/home/yhs/work/bpf-next/scripts/Makefile.vmlinux:72: vmlinux.unstripped] Error 255
>   make[2]: *** Deleting file 'vmlinux.unstripped'
>   make[1]: *** [/home/yhs/work/bpf-next/Makefile:1242: vmlinux] Error 2
>   make: *** [/home/yhs/work/bpf-next/Makefile:248: __sub-make] Error 2
> 
> In pahole patch [1], if two functions having identical names but different
> addresses, then this function name is considered ambiguous and later on
> this function will not be added to vmlinux/module BTF.
> 
> Commit 378b7708194f ("sched: Make migrate_{en,dis}able() inline") changed
> original global funcitons migrate_{enable,disable} to
>   - in kernel/sched/core.c, migrate_{enable,disable} are global funcitons.
>   - in other places, migrate_{enable,disable} may survive as static functions
>     since they are marked as 'inline' in include/linux/sched.h and the
>     'inline' attribute does not garantee inlining.
> 
> If I build with clang compiler (make LLVM=1 -j) (llvm21 and llvm22), I found
> there are four symbols for migrate_{enable,disable} respectively, three
> static functions and one global function. With the above pahole patch [1],
> migrate_{enable,disable} are not in vmlinux BTF and this will cause
> later resolve_btfids failure.
> 
> Making migrate_{enable,disable} always inline in include/linux/sched.h
> can fix the problem.
> 
>   [1] https://lore.kernel.org/dwarves/79a329ef-9bb3-454e-9135-731f2fd51951@oracle.com/
> 
> Fixes: 378b7708194f ("sched: Make migrate_{en,dis}able() inline")
> Cc: Menglong Dong <menglong8.dong@gmail.com>
> Cc: Ihor Solodrai <ihor.solodrai@linux.dev>
> Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
> ---
>  include/linux/sched.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index cbb7340c5866..b469878de25c 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -2407,12 +2407,12 @@ static inline void __migrate_enable(void) { }
>   * be defined in kernel/sched/core.c.
>   */
>  #ifndef INSTANTIATE_EXPORTED_MIGRATE_DISABLE
> -static inline void migrate_disable(void)
> +static __always_inline void migrate_disable(void)
>  {
>  	__migrate_disable();
>  }

Thanks for the fixing :)

Acked-by: Menglong Dong <menglong.dong@linux.dev>

>  
> -static inline void migrate_enable(void)
> +static __always_inline void migrate_enable(void)
>  {
>  	__migrate_enable();
>  }
>