linux-kernel - Re: [PATCH -next v5 06/22] arm64: entry: Expand the need_irq

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Message-ID: <Z6nno7db_6iOYkT2@J2N7QTR9R3>
Date: Mon, 10 Feb 2025 11:48:51 +0000
From: Mark Rutland <mark.rutland@....com>
To: Jinjie Ruan <ruanjinjie@...wei.com>
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Subject: Re: [PATCH -next v5 06/22] arm64: entry: Expand the
 need_irq_preemption() macro ahead

On Fri, Dec 06, 2024 at 06:17:28PM +0800, Jinjie Ruan wrote:
> The generic entry has the same logic as need_irq_preemption()
> macro and use a helper function to check other resched condition.
> 
> In preparation for moving arm64 over to the generic entry code,
> check and expand need_irq_preemption() ahead and extract arm64 resched
> check code to a helper function.

I think this is just saying that the goal is to align the structure of
the code with raw_irqentry_exit_cond_resched() from the generic entry
code.

It'd be a bit clearer to say that, and to do this *before* moving the
call into __exit_to_kernel_mode().

Mark.

> 
> No functional changes.
> 
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> ---
>  arch/arm64/include/asm/preempt.h |  1 +
>  arch/arm64/kernel/entry-common.c | 28 +++++++++++++++++-----------
>  2 files changed, 18 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h
> index 0159b625cc7f..d0f93385bd85 100644
> --- a/arch/arm64/include/asm/preempt.h
> +++ b/arch/arm64/include/asm/preempt.h
> @@ -85,6 +85,7 @@ static inline bool should_resched(int preempt_offset)
>  void preempt_schedule(void);
>  void preempt_schedule_notrace(void);
>  
> +void raw_irqentry_exit_cond_resched(void);
>  #ifdef CONFIG_PREEMPT_DYNAMIC
>  
>  DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
> diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
> index efd1a990d138..80b47ca02db2 100644
> --- a/arch/arm64/kernel/entry-common.c
> +++ b/arch/arm64/kernel/entry-common.c
> @@ -77,17 +77,10 @@ static noinstr irqentry_state_t enter_from_kernel_mode(struct pt_regs *regs)
>  
>  #ifdef CONFIG_PREEMPT_DYNAMIC
>  DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
> -#define need_irq_preemption() \
> -	(static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
> -#else
> -#define need_irq_preemption()	(IS_ENABLED(CONFIG_PREEMPTION))
>  #endif
>  
>  static inline bool arm64_need_resched(void)
>  {
> -	if (!need_irq_preemption())
> -		return false;
> -
>  	/*
>  	 * DAIF.DA are cleared at the start of IRQ/FIQ handling, and when GIC
>  	 * priority masking is used the GIC irqchip driver will clear DAIF.IF
> @@ -111,6 +104,22 @@ static inline bool arm64_need_resched(void)
>  	return true;
>  }
>  
> +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()) {
> +		if (need_resched() && arm64_need_resched())
> +			preempt_schedule_irq();
> +	}
> +}
> +
>  /*
>   * Handle IRQ/context state management when exiting to kernel mode.
>   * After this function returns it is not safe to call regular kernel code,
> @@ -133,10 +142,7 @@ static __always_inline void __exit_to_kernel_mode(struct pt_regs *regs,
>  			return;
>  		}
>  
> -		if (!preempt_count() && need_resched()) {
> -			if (arm64_need_resched())
> -				preempt_schedule_irq();
> -		}
> +		raw_irqentry_exit_cond_resched();
>  
>  		trace_hardirqs_on();
>  	} else {
> -- 
> 2.34.1
>