Re: [PATCH v15 04/13] task_isolation: add initial support

[Peter Zijlstra]

On Tue, Aug 16, 2016 at 05:19:27PM -0400, Chris Metcalf wrote:
> +	/*
> +	 * Request rescheduling unless we are in full dynticks mode.
> +	 * We would eventually get pre-empted without this, and if
> +	 * there's another task waiting, it would run; but by
> +	 * explicitly requesting the reschedule, we may reduce the
> +	 * latency.  We could directly call schedule() here as well,
> +	 * but since our caller is the standard place where schedule()
> +	 * is called, we defer to the caller.
> +	 *
> +	 * A more substantive approach here would be to use a struct
> +	 * completion here explicitly, and complete it when we shut
> +	 * down dynticks, but since we presumably have nothing better
> +	 * to do on this core anyway, just spinning seems plausible.
> +	 */
> +	if (!tick_nohz_tick_stopped())
> +		set_tsk_need_resched(current);

This is broken.. and it would be really good if you don't actually need
to do this.