Re: [PATCH v8 08/25] timer: Rework idle logic

[Thomas Gleixner]

On Wed, Oct 04 2023 at 14:34, Anna-Maria Behnsen wrote:
>  
> -	if (time_before_eq(nextevt, basej)) {
> -		expires = basem;
> -		base->is_idle = false;
> -	} else {
> -		if (base->timers_pending)
> -			expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
> -		/*
> -		 * If we expect to sleep more than a tick, mark the base idle.
> -		 * Also the tick is stopped so any added timer must forward
> -		 * the base clk itself to keep granularity small. This idle
> -		 * logic is only maintained for the BASE_STD base, deferrable
> -		 * timers may still see large granularity skew (by design).
> -		 */
> -		if ((expires - basem) > TICK_NSEC)
> -			base->is_idle = true;
> +	/*
> +	 * Base is idle if the next event is more than a tick away. Also
> +	 * the tick is stopped so any added timer must forward the base clk
> +	 * itself to keep granularity small. This idle logic is only
> +	 * maintained for the BASE_STD base, deferrable timers may still
> +	 * see large granularity skew (by design).
> +	 */
> +	base->is_idle = time_after(nextevt, basej + 1);

This is wrongly ordered. base->is_idle must be updated _after_
evaluating base->timers_pending because the below can change nextevt,
no?

> +	if (base->timers_pending) {
> +		/* If we missed a tick already, force 0 delta */
> +		if (time_before(nextevt, basej))
> +			nextevt = basej;
> +		expires = basem + (u64)(nextevt - basej) * TICK_NSEC;

Thanks,

        tglx