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

[Boqun Feng <boqun@kernel.org>]

On Mon, Aug 03, 2026 at 01:41:28PM +0200, Peter Zijlstra wrote:
> 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.

I will drop this patch entirely per the discussion.

Regards,
Boqun