Re: [PATCH v2 16/16] virtio: make it possible to detach host notifier from any thread

[Eric Blake]

On Wed, Apr 19, 2023 at 01:28:17PM -0400, Stefan Hajnoczi wrote:
> virtio_queue_aio_detach_host_notifier() does two things:
> 1. It removes the fd handler from the event loop.
> 2. It processes the virtqueue one last time.
> 
> The first step can be peformed by any thread and without taking the
> AioContext lock.
> 
> The second step may need the AioContext lock (depending on the device
> implementation) and runs in the thread where request processing takes
> place. virtio-blk and virtio-scsi therefore call
> virtio_queue_aio_detach_host_notifier() from a BH that is scheduled in
> AioContext
> 
> Scheduling a BH is undesirable for .drained_begin() functions. The next
> patch will introduce a .drained_begin() function that needs to call
> virtio_queue_aio_detach_host_notifier().
> 
> Move the virtqueue processing out to the callers of
> virtio_queue_aio_detach_host_notifier() so that the function can be
> called from any thread. This is in preparation for the next patch.
>

This mentions a next patch, but is 16/16 in the series.  Am I missing
something?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org