> Paul Brook wrote: > >> A major reason for this deadlock could likely be removed by shutting > >> down the tap (if peered) or dropping packets in user space (in case of > >> vlan) when a NIC is stopped or otherwise shut down. Currently most (if > >> not all) NIC models seem to signal both "queue full" and "RX disabled" > >> via !can_receive(). > > > > No. A disabled device should return true from can_recieve, then discard > > the packets in its receive callback. Failure to do so is a bug in the > > device. It looks like the virtio-net device may be buggy. > > That's not a virtio-only issue. In fact, we ran into this over pcnet, > and a quick check of other popular PCI NIC models (except for rtl8139) > revealed the same picture: They only report can_receive if their > receiver unit is up and ready (some also include the queue state, but > that's an "add-on").
If so these are also buggy. > I think it's clear why: "can_receive" strongly suggests that a suspended > receiver should make the model return false. If we want to keep this > handler, it should be refactored to something like "queue_full". I don't see a need to refactor anything. You just need to fix the devices that incorrectly return false when their RX engine is disabled. Paul
