Re: [PATCH 06/23] sched,psci: Convert to sched_set_fifo*()

[Valentin Schneider]

On 22/04/20 12:27, Peter Zijlstra wrote:
> Because SCHED_FIFO is a broken scheduler model (see previous patches)
> take away the priority field, the kernel can't possibly make an
> informed decision.
>
> Effectively changes prio from 99 to 50.
>
> XXX this thing is horrific, it basically open-codes a stop-machine and
> idle.
>

I went and tried to clean up the thing. I didn't find a clean way to use
stop_machine() + play_idle() (stoppers can't sleep), but I did manage to
get something usable with the existing FIFO threads, play_idle_precise()
and the cpuidle state usage stats, so the whole homebrewed idle thing can
go.

I also just tested it with 50 prio and big surprise it didn't change
anything (it ends up being sibling of idle injection). So FWIW:

Acked-by: Valentin Schneider <valentin.schneider@xxxxxxx>

> Cc: daniel.lezcano@xxxxxxxxxx
> Cc: sudeep.holla@xxxxxxx
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx>