Re: [PATCH RFC] blk-mq: Don't IPI requests on PREEMPT_RT

[Christoph Hellwig]

> -	if (!IS_ENABLED(CONFIG_SMP) ||
> +	if (!IS_ENABLED(CONFIG_SMP) || IS_ENABLED(CONFIG_PREEMPT_RT) ||
>  	    !test_bit(QUEUE_FLAG_SAME_COMP, &rq->q->queue_flags))

This needs a big fat comment explaining your rationale.  And probably
a separate if statement to make it obvious as well.