Re: [PATCH v4 21/21] arm64: percpu: Remove _pcp_protect*() wrappers

[Vladimir Murzin <vladimir.murzin@arm.com>]

On 9/8/26 16:17, Mark Rutland wrote:
> Now that all this_cpu_*() operations are preemptible, there are no users
> of _pcp_protect() or _pcp_protect_return().
> 
> Remove them both, along with the associated comment regarding
> preemption.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Tested-by: Muhammad Usama Anjum <usama.anjum@arm.com>
> Cc: Ada Couprie Diaz <ada.coupriediaz@arm.com>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: James Morse <james.morse@arm.com>
> Cc: Jinjie Ruan <ruanjinjie@huawei.com>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Vladimir Murzin <vladimir.murzin@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Yang Shi <yang@os.amperecomputing.com>
> ---
>  arch/arm64/include/asm/percpu.h | 27 ---------------------------
>  1 file changed, 27 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
> index 5cd98e20e825d..6ec6e212932d3 100644
> --- a/arch/arm64/include/asm/percpu.h
> +++ b/arch/arm64/include/asm/percpu.h
> @@ -368,33 +368,6 @@ PERCPU_CMPXCHG_OP(x,  , 64)
>  #undef PERCPU_XCHG_OP
>  #undef PERCPU_CMPXCHG_OP
>  
> -/*
> - * It would be nice to avoid the conditional call into the scheduler when
> - * re-enabling preemption for preemptible kernels, but doing that in a way
> - * which builds inside a module would mean messing directly with the preempt
> - * count. If you do this, peterz and tglx will hunt you down.
> - *
> - * Not to mention it'll break the actual preemption model for missing a
> - * preemption point when TIF_NEED_RESCHED gets set while preemption is
> - * disabled.
> - */
> -
> -#define _pcp_protect(op, pcp, ...)					\
> -({									\
> -	preempt_disable_notrace();					\
> -	op(raw_cpu_ptr(&(pcp)), __VA_ARGS__);				\
> -	preempt_enable_notrace();					\
> -})
> -
> -#define _pcp_protect_return(op, pcp, args...)				\
> -({									\
> -	typeof(pcp) __retval;						\
> -	preempt_disable_notrace();					\
> -	__retval = (typeof(pcp))op(raw_cpu_ptr(&(pcp)), ##args);	\
> -	preempt_enable_notrace();					\
> -	__retval;							\
> -})
> -
>  #define _pcp_wrap(op, pcp, ...)						\
>  ({									\
>  	op(&(pcp), __VA_ARGS__);					\
> -- 2.30.2
> 

FWIW,

Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>