Re: [PATCH v15 6/8] blk-mq: prevent offlining hk CPUs with associated online isolated CPUs

[Marco Crivellari]

Hi,

On Fri, May 22, 2026 at 1:30 AM Aaron Tomlin <atomlin@xxxxxxxxxxx> wrote:
> [...]
>  static bool blk_mq_hctx_has_online_cpu(struct blk_mq_hw_ctx *hctx,
>                 unsigned int this_cpu)
>  {
> @@ -3771,6 +3821,11 @@ static int blk_mq_hctx_notify_offline(unsigned int cpu, struct hlist_node *node)
>                         struct blk_mq_hw_ctx, cpuhp_online);
>         int ret = 0;
>
> +       if (housekeeping_enabled(HK_TYPE_IO_QUEUE)) {
> +               if (!blk_mq_hctx_can_offline_hk_cpu(hctx, cpu))
> +                       return -EINVAL;
> +       }
> +
>         if (!hctx->nr_ctx || blk_mq_hctx_has_online_cpu(hctx, cpu))
>                 return 0;

I noticed the existing `if` returns 0, while the added code returns
-EINVAL. I'm wondering if this will prevent the system from suspending
because of the -EINVAL error.
Should ` !cpuhp_tasks_frozen` be added to the if statement?

eg.

if (housekeeping_enabled(HK_TYPE_IO_QUEUE) && !cpuhp_tasks_frozen) {
    if (!blk_mq_hctx_can_offline_hk_cpu(hctx, cpu))
        return -EINVAL;
}

Or maybe just handling this inside blk_mq_hctx_can_offline_hk_cpu()
returning true.

Does it make sense?

Thanks!

-- 

Marco Crivellari

SUSE Labs