On 09/04/2014 04:39 PM, Michael S. Tsirkin wrote:
> This completes all packets, ensuring that callbacks
> will not run when VM is stopped.
>
> Cc: qemu-sta...@nongnu.org
> Cc: Jason Wang <jasow...@redhat.com>
> Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
> ---
> net/net.c | 33 ++++++++++++++++++++++++++++++++-
> 1 file changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/net/net.c b/net/net.c
> index 6d930ea..25fdb07 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -47,6 +47,7 @@
> # define CONFIG_NET_BRIDGE
> #endif
>
> +static VMChangeStateEntry *net_change_state_entry;
> static QTAILQ_HEAD(, NetClientState) net_clients;
>
> const char *host_net_devices[] = {
> @@ -504,7 +505,8 @@ void qemu_purge_queued_packets(NetClientState *nc)
> qemu_net_queue_purge(nc->peer->incoming_queue, nc);
> }
>
> -void qemu_flush_queued_packets(NetClientState *nc)
> +static
> +void qemu_flush_or_purge_queued_packets(NetClientState *nc, bool purge)
> {
> nc->receive_disabled = 0;
>
> @@ -518,9 +520,17 @@ void qemu_flush_queued_packets(NetClientState *nc)
> * the file descriptor (for tap, for example).
> */
> qemu_notify_event();
> + } else if (purge) {
> + /* Unable to empty the queue, purge remaining packets */
> + qemu_net_queue_purge(nc->incoming_queue, nc);
> }
> }
>
> +void qemu_flush_queued_packets(NetClientState *nc)
> +{
> + qemu_flush_or_purge_queued_packets(nc, false);
> +}
> +
> static ssize_t qemu_send_packet_async_with_flags(NetClientState *sender,
> unsigned flags,
> const uint8_t *buf, int
> size,
> @@ -1168,6 +1178,22 @@ void qmp_set_link(const char *name, bool up, Error
> **errp)
> }
> }
>
> +static void net_vm_change_state_handler(void *opaque, int running,
> + RunState state)
> +{
> + /* Complete all queued packets, to guarantee we don't modify
> + * state later when VM is not running.
> + */
> + if (!running) {
> + NetClientState *nc;
> + NetClientState *tmp;
> +
> + QTAILQ_FOREACH_SAFE(nc, &net_clients, next, tmp) {
> + qemu_flush_or_purge_queued_packets(nc, true);
> + }
> + }
> +}
> +
> void net_cleanup(void)
> {
> NetClientState *nc;
> @@ -1183,6 +1209,8 @@ void net_cleanup(void)
> qemu_del_net_client(nc);
> }
> }
> +
> + qemu_del_vm_change_state_handler(net_change_state_entry);
> }
>
> void net_check_clients(void)
> @@ -1268,6 +1296,9 @@ int net_init_clients(void)
> #endif
> }
>
> + net_change_state_entry =
> + qemu_add_vm_change_state_handler(net_vm_change_state_handler, NULL);
> +
> QTAILQ_INIT(&net_clients);
>
> if (qemu_opts_foreach(qemu_find_opts("netdev"), net_init_netdev, NULL,
> 1) == -1)
A problem is the dependency between state change handlers (e.g. virtio).
Current virtio vmstate change handler will be called before this
handler. Which means vdev->vm_running was false when we purge the queue,
this will trigger the assert of vdev->vm_running in virtio_net_flush_tx().
