[dpdk-dev] [PATCH 03/21] vhost: protect virtio_net device struct

[Stephen Hemminger]

> > > This lock has currently two purposes:
> > > 1. Prevent referencing freed virtio_dev struct in case of numa_realloc.
> > > 2. Protect vring pages against invalidation.
> > > 
> > > For 2., it can be fixed by using the per-vq IOTLB lock (it was not the
> > > case in my early prototypes that had per device IOTLB cache).
> > > 
> > > For 1., this is an existing problem, so we might consider it is
> > > acceptable to keep current state. Maybe it could be improved by only
> > > reallocating in case VQ0 is not on the right NUMA node, the other VQs
> > > not being initialized at this point.

Something like RCU does a better job of protecting against freed virtio_dev.
But using RCU requires quiescent callback in the main loop.