Re: [patch V2 05/10] timer: Retrieve next expiry of pinned/non-pinned timers seperately

[Peter Zijlstra]

On Tue, Apr 18, 2017 at 01:11:07PM +0200, Thomas Gleixner wrote:
> --- a/kernel/time/timer.c
> +++ b/kernel/time/timer.c
> @@ -1472,23 +1472,27 @@ static u64 cmp_next_hrtimer_event(u64 ba
>   * get_next_timer_interrupt - return the time (clock mono) of the next timer
>   * @basej:	base time jiffies
>   * @basem:	base time clock monotonic
> + * @global_evt:	Pointer to store the expiry time of the next global timer
>   *
>   * Returns the tick aligned clock monotonic time of the next pending
>   * timer or KTIME_MAX if no timer is pending.
>   */
> -u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
> +u64 get_next_timer_interrupt(unsigned long basej, u64 basem, u64 *global_evt)

Another tortured function signature. It seems entirely possible
@global_evt will be the next.


> +
> +	/*
> +	 * If the local queue expires first, there is no requirement for
> +	 * queuing the CPU in the global expiry mechanism.

The comment doesn't make sense... (maybe at this stage)

> +	 */
> +	if (!local_first && !global_empty)
> +		*global_evt = basem + (nextevt_global - basej) * TICK_NSEC;

I was initially thinking !local_first would have to imply !global_empty,
but after going back and reading the previous patches again, I found
this was not so. Still slightly surprising.

> +
> +	return cmp_next_hrtimer_event(basem, local_evt);
>  }
>  
>  /**
> 
>