linux-kernel - Re: [PATCH -next v5 10/22] entry: Add arch_irqentry_exit_need

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Message-ID: <Z6nrhhtTKQpScUd0@J2N7QTR9R3>
Date: Mon, 10 Feb 2025 12:05:26 +0000
From: Mark Rutland <mark.rutland@....com>
To: Jinjie Ruan <ruanjinjie@...wei.com>
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Subject: Re: [PATCH -next v5 10/22] entry: Add
 arch_irqentry_exit_need_resched() for arm64

On Fri, Dec 06, 2024 at 06:17:32PM +0800, Jinjie Ruan wrote:
> ARM64 requires an additional check whether to reschedule on return
> from interrupt.
> 
> Add arch_irqentry_exit_need_resched() as the default NOP
> implementation and hook it up into the need_resched() condition in
> raw_irqentry_exit_cond_resched().
> 
> This allows ARM64 to implement the architecture specific version for
> switching over to the generic entry code.

Please fold this into the earlier changes in this area mad over patches
6 to 8.

> 
> Suggested-by: Mark Rutland <mark.rutland@....com>
> Suggested-by: Kevin Brodsky <kevin.brodsky@....com>
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> ---
>  kernel/entry/common.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/entry/common.c b/kernel/entry/common.c
> index b82032777310..4aa9656fa1b4 100644
> --- a/kernel/entry/common.c
> +++ b/kernel/entry/common.c
> @@ -142,6 +142,20 @@ noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
>  	return ret;
>  }
>  
> +/**
> + * arch_irqentry_exit_need_resched - Architecture specific need resched function
> + *
> + * Invoked from raw_irqentry_exit_cond_resched() to check if need resched.
> + * Defaults return true.
> + *
> + * The main purpose is to permit arch to skip preempt a task from an IRQ.
> + */
> +static inline bool arch_irqentry_exit_need_resched(void);
> +
> +#ifndef arch_irqentry_exit_need_resched
> +static inline bool arch_irqentry_exit_need_resched(void) { return true; }
> +#endif
> +
>  void raw_irqentry_exit_cond_resched(void)
>  {
>  	if (!preempt_count()) {
> @@ -149,7 +163,7 @@ void raw_irqentry_exit_cond_resched(void)
>  		rcu_irq_exit_check_preempt();
>  		if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
>  			WARN_ON_ONCE(!on_thread_stack());
> -		if (need_resched())
> +		if (need_resched() && arch_irqentry_exit_need_resched())
>  			preempt_schedule_irq();
>  	}
>  }
> -- 
> 2.34.1
>