Re: [PATCH] blk-mq: make synchronous hw_queue runs RT friendly

[Christoph Hellwig]

> +#ifndef CONFIG_PREEMPT_RT

Please don't add these silly inverted ifdefs.

> +static inline void blk_mq_start_sync_run_hw_queue(void)
> +{
> +	preempt_disable();
> +}
> +static inline void blk_mq_end_sync_run_hw_queue(void)
> +{
> +	preempt_enable();
> +}
> +#else
> +static inline void blk_mq_start_sync_run_hw_queue(void)
> +{
> +	migrate_disable();
> +}
> +static inline void blk_mq_end_sync_run_hw_queue(void)
> +{
> +	migrate_enable();
> +}
> +#endif

But more importantly:  why isn't migrate_disable/enable doing the right
thing for !PREEMPT_RT to avoid this mess?