[0/2] virtio-blk: Avoid processing requests on the main context on restart

Message

Sergio Lopez Pascual June 3, 2020, 9:32 a.m. UTC

On restart, we were scheduling a BH to process queued requests, which
would run before starting up the data plane, leading to those requests
being assigned and started on coroutines on the main context.

This could cause requests to be wrongly processed in parallel from
different threads (the main thread and the iothread managing the data
plane), potentially leading to multiple issues.

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1812765

See "virtio-blk: Disable request queuing while switching contexts" for
previous discussion:

 - https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00304.html

Sergio Lopez (2):
  virtio-blk: Refactor the code that processes queued requests
  virtio-blk: On restart, process queued requests in the proper context

 include/hw/virtio/virtio-blk.h  |  1 +
 hw/block/dataplane/virtio-blk.c |  8 ++++++++
 hw/block/virtio-blk.c           | 30 +++++++++++++++++++++---------
 3 files changed, 30 insertions(+), 9 deletions(-)

Comments

Kevin Wolf June 3, 2020, 2:14 p.m. UTC | #1

Am 03.06.2020 um 11:32 hat Sergio Lopez geschrieben:
> On restart, we were scheduling a BH to process queued requests, which
> would run before starting up the data plane, leading to those requests
> being assigned and started on coroutines on the main context.
> 
> This could cause requests to be wrongly processed in parallel from
> different threads (the main thread and the iothread managing the data
> plane), potentially leading to multiple issues.
> 
> Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1812765
> 
> See "virtio-blk: Disable request queuing while switching contexts" for
> previous discussion:
> 
>  - https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00304.html

Thanks, applied to the block branch.

Kevin