linux-kernel - Re: [PATCH -next v5 07/22] arm64: entry: preempt_schedule

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Message-ID: <Z6noaWUwn4uCeNN3@J2N7QTR9R3>
Date: Mon, 10 Feb 2025 11:52:09 +0000
From: Mark Rutland <mark.rutland@....com>
To: Jinjie Ruan <ruanjinjie@...wei.com>
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Subject: Re: [PATCH -next v5 07/22] arm64: entry: preempt_schedule_irq() only
 if PREEMPTION enabled

On Fri, Dec 06, 2024 at 06:17:29PM +0800, Jinjie Ruan wrote:
> The generic entry check PREEMPTION for both PREEMPT_DYNAMIC
> enabled and PREEMPT_DYNAMIC disabled.
> 
> Whether PREEMPT_DYNAMIC enabled or not, PREEMPTION should
> be enabled to allow reschedule before EL1 exception return, so
> move PREEMPTION check ahead in preparation for moving arm64 over
> to the generic entry code.

This is just moving the IS_ENABLED() check. It'd be clearer to say
something like "hoist the IS_ENABLED() check earlier", but equally we
could do that earleir in the series by folding this into the prior
patch.

Mark.

> 
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> ---
>  arch/arm64/kernel/entry-common.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
> index 80b47ca02db2..029f8bd72f8a 100644
> --- a/arch/arm64/kernel/entry-common.c
> +++ b/arch/arm64/kernel/entry-common.c
> @@ -109,9 +109,6 @@ void raw_irqentry_exit_cond_resched(void)
>  #ifdef CONFIG_PREEMPT_DYNAMIC
>  	if (!static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
>  		return;
> -#else
> -	if (!IS_ENABLED(CONFIG_PREEMPTION))
> -		return;
>  #endif
>  
>  	if (!preempt_count()) {
> @@ -142,7 +139,8 @@ static __always_inline void __exit_to_kernel_mode(struct pt_regs *regs,
>  			return;
>  		}
>  
> -		raw_irqentry_exit_cond_resched();
> +		if (IS_ENABLED(CONFIG_PREEMPTION))
> +			raw_irqentry_exit_cond_resched();
>  
>  		trace_hardirqs_on();
>  	} else {
> -- 
> 2.34.1
>