Re: [PATCH v11 7/8] cpuidle: Pre-store next timer/tick before selecting an idle state

[Rafael J. Wysocki]

On Tue, Feb 26, 2019 at 3:54 PM Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>
> A common piece of data used by cpuidle governors, is the information about
> when the next timer/tick is going to fire. Rather than having each governor
> calling tick_nohz_get_next_timer|hrtimer() separately, let's consolidate
> the code by calling these functions before invoking the ->select() callback
> of the governor - and store the output data in the struct cpuidle_device.

That misses the point IMO.

You don't need to store two values in struct cpuidle_device, but just
one, and not before running ->select(), but before invoking the
driver's ->enter() callback.

At that point, the decision on whether or not to stop the scheduler
tick has been made already and it should be sufficient to store the
return value of tick_nohz_get_next_hrtimer() introduced by patch
[3/8], because that value represents the next timer regardless of what
has been decided with respect to the tick.

And you won't need the tick_nohz_get_next_timer() any more then.