virtio-blk: Avoid processing requests on the main context on restart

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

Sergio Lopez posted 2 patches 3 years, 11 months ago

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git fetch https://github.com/patchew-project/qemu tags/patchew/20200603093240.40489-1-slp@redhat.com

Maintainers: Kevin Wolf <kwolf@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, Max Reitz <mreitz@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>

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(-)

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

Posted by Sergio Lopez 3 years, 11 months ago

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(-)

-- 
2.26.2

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

Posted by Kevin Wolf 3 years, 11 months ago

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