Re: ARC: Use __force to suppress per-CPU cmpxchg complaints

[Vineet Gupta]

On 10/9/24 10:55, Paul E. McKenney wrote:
> Currently, the cast of the first argument to cmpxchg_emu_u8() drops the
> __percpu address-space designator, which results in sparse complaints
> when applying cmpxchg() to per-CPU variables in ARC.  Therefore, use
> __force to suppress these complaints, given that this does not pertain
> to cmpxchg() semantics, which are plently well-defined on variables in
> general, whether per-CPU or otherwise.
>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Closes: https://lore.kernel.org/oe-kbuild-all/202409251336.ToC0TvWB-lkp@xxxxxxxxx/
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Cc: Vineet Gupta <vgupta@xxxxxxxxxx>
> Cc: <linux-snps-arc@xxxxxxxxxxxxxxxxxxx>
>
> diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
> index 58045c8983404..76f43db0890fc 100644
> --- a/arch/arc/include/asm/cmpxchg.h
> +++ b/arch/arc/include/asm/cmpxchg.h
> @@ -48,7 +48,7 @@
>  									\
>  	switch(sizeof((_p_))) {						\
>  	case 1:								\
> -		_prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_);	\
> +		_prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *__force)_p_, (uintptr_t)_o_, (uintptr_t)_n_);	\
>  		break;							\
>  	case 4:								\
>  		_prev_ = __cmpxchg(_p_, _o_, _n_);			\


Added to for-curr.

Thx,
-Vineet