Re: [PATCH] sched/cpufreq: don't trigger cpufreq update w/o real rt/deadline tasks running

[Peter Zijlstra <peterz@infradead.org>]

On Thu, Apr 21, 2016 at 09:09:43AM +0800, Wanpeng Li wrote:
> >> Sometimes .update_curr hook is called w/o tasks actually running, it is
> >> captured by:
> >>
> >>          u64 delta_exec = rq_clock_task(rq) - curr->se.exec_start;
> >>
> >> We should not trigger cpufreq update in this case for rt/deadline
> >> classes, and this patch fix it.

> I add a print to print when delta_exec is zero for rt class, something

So its zero, so what?

> like below:

>       watchdog/5-48    [005] d...   568.449105: update_curr_rt: rt
> delta_exec is zero
>       watchdog/5-48    [005] d...   568.449111: <stack trace>
>  => put_prev_task_rt
>  => pick_next_task_idle

So we'll go idle, but as of this point we're still running the rt task.

So your Changelog is actively wrong, the tasks _are_ still running,
albeit not for very much longer.