Searched hist:cbdadbbf (Results 1 – 1 of 1) sorted by relevance
/openbmc/linux/drivers/net/ |
H A D | virtio_net.c | cbdadbbf Tue Jul 09 00:13:04 CDT 2013 Michael S. Tsirkin <mst@redhat.com> virtio_net: fix race in RX VQ processing
virtio net called virtqueue_enable_cq on RX path after napi_complete, so with NAPI_STATE_SCHED clear - outside the implicit napi lock. This violates the requirement to synchronize virtqueue_enable_cq wrt virtqueue_add_buf. In particular, used event can move backwards, causing us to lose interrupts. In a debug build, this can trigger panic within START_USE.
Jason Wang reports that he can trigger the races artificially, by adding udelay() in virtqueue_enable_cb() after virtio_mb().
However, we must call napi_complete to clear NAPI_STATE_SCHED before polling the virtqueue for used buffers, otherwise napi_schedule_prep in a callback will fail, causing us to lose RX events.
To fix, call virtqueue_enable_cb_prepare with NAPI_STATE_SCHED set (under napi lock), later call virtqueue_poll with NAPI_STATE_SCHED clear (outside the lock).
Reported-by: Jason Wang <jasowang@redhat.com> Tested-by: Jason Wang <jasowang@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
|