Re: [PATCH 5/9] blk-mq: don't set data->ctx and data->hctx in blk_mq_alloc_request_hctx

Ming Lei
2020-05-20T03:04:44Z

On Wed, May 20, 2020 at 09:18:23AM +0800, Ming Lei wrote:
> On Tue, May 19, 2020 at 05:30:00PM +0200, Christoph Hellwig wrote:
> > On Tue, May 19, 2020 at 09:54:20AM +0800, Ming Lei wrote:
> > > As Thomas clarified, workqueue hasn't such issue any more, and only other
> > > per CPU kthreads can run until the CPU clears the online bit.
> > >
> > > So the question is if IO can be submitted from such kernel context?
> >
> > What other per-CPU kthreads even exist?
>
> I don't know, so expose to wider audiences.

One user is io uring with IORING_SETUP_SQPOLL & IORING_SETUP_SQ_AFF, see
io_sq_offload_start(), and it is a IO submission kthread.

Thanks,
Ming