virtio-scsi: replace AioContext lock with tmf_bh_lock

Protect the Task Management Function BH state with a lock. The TMF BH
runs in the main loop thread. An IOThread might process a TMF at the
same time as the TMF BH is running. Therefore tmf_bh_list and tmf_bh
must be protected by a lock.

Run TMF request completion in the IOThread using aio_wait_bh_oneshot().
This avoids more locking to protect the virtqueue and SCSI layer state.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20231205182011.1976568-2-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2 files changed