Re: [PATCH 13/24] irq: Optimize reschedule check in local_interrupt_enable()

[Peter Zijlstra <peterz@infradead.org>]

On Fri, Jul 31, 2026 at 01:30:14PM -0700, Boqun Feng wrote:
> In local_interrupt_enable(), we could avoid re-reading preempt count
> because of should_resched() by using the result from
> hardirq_disable_exit(), however this means __preempt_count_add_return()
> and __preempt_count_sub_return() need to return all the preempt count
> bits (including the PREEMPT_NEED_RESCHED bit), since the only user of
> __preempt_count_{add,sub}_return() is hardirq_disable_{enter,exit}(),
> hence make them return "unsigned long" to optimize this.

>  static inline void local_interrupt_enable(void)
>  {
> -	int new_count;
> +	unsigned long new_count;
>  
>  	new_count = hardirq_disable_exit();
>  
> @@ -52,15 +68,8 @@ static inline void local_interrupt_enable(void)
>  
>  		flags = raw_cpu_read(local_interrupt_disable_state.flags);
>  		local_irq_restore(flags);
> -		/*
> -		 * TODO: re-read preempt count can be avoided, but it needs
> -		 * should_resched() taking another parameter as the current
> -		 * preempt count
> -		 */
> -#ifdef CONFIG_PREEMPTION
> -		if (should_resched(0))
> -			__preempt_schedule();
> -#endif
> +
> +		local_interrupt_enable_reched(new_count);
>  	}
>  }

As stated before; this whole thing is a mystery to me, this should not
be needed.