Re: io_uring vs CPU hotplug, was Re: [PATCH 5/9] blk-mq: don't set data->ctx and data->hctx in blk_mq_alloc_request_hctx

Thomas Gleixner
2020-05-20T19:41:19Z

Jens Axboe <axboe@kernel.dk> writes:
> On 5/20/20 8:45 AM, Jens Axboe wrote:
>> It just uses kthread_create_on_cpu(), nothing home grown. Pretty sure
>> they just break affinity if that CPU goes offline.
>
> Just checked, and it works fine for me. If I create an SQPOLL ring with
> SQ_AFF set and bound to CPU 3, if CPU 3 goes offline, then the kthread
> just appears unbound but runs just fine. When CPU 3 comes online again,
> the mask appears correct.

When exactly during the unplug operation is it unbound?

Thanks,

tglx