Vhost-user library locks all VQ's access lock when processing
vring based messages, such as SET_VRING_KICK and SET_VRING_CALL,
and the data processing thread may already be started, e.g: SPDK
vhost-blk and vhost-scsi will start the data processing thread
when one vring is ready, then deadlock may happen when SPDK is
posting interrupts to VM. Here, we add a new API which allows
caller to try again later for this case.
Bugzilla ID: 1015
Fixes: c5736998305d ("vhost: fix missing virtqueue lock protection")
Cc: stable@dpdk.org
Signed-off-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
830f7e7907