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"). 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". But before starting any refactoring endeavor: Do we have a consensus on the direction? Refactor can_receive to queue_full? Or even drop it? Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
