On 07/10/2015 05:24 PM, Fam Zheng wrote:
> On Wed, 07/08 17:40, Jason Wang wrote:
>>
>> On 07/07/2015 05:03 PM, Fam Zheng wrote:
>>> On Tue, 07/07 15:44, Jason Wang wrote:
>>>> On 07/07/2015 09:21 AM, Fam Zheng wrote:
>>>>> Since commit 6e99c63 "net/socket: Drop net_socket_can_send" and friends,
>>>>> net queues need to be explicitly flushed after qemu_can_send_packet()
>>>>> returns false, because the netdev side will disable the polling of fd.
>>>>>
>>>>> This fixes the case of "cont" after "stop" (or migration).
>>>>>
>>>>> Signed-off-by: Fam Zheng <f...@redhat.com>
>>>>>
>>>>> ---
>>>>>
>>>>> v2: Unify with VM stop handler. (Stefan)
>>>>> ---
>>>>> net/net.c | 19 ++++++++++++-------
>>>>> 1 file changed, 12 insertions(+), 7 deletions(-)
>>>>>
>>>>> diff --git a/net/net.c b/net/net.c
>>>>> index 6ff7fec..28a5597 100644
>>>>> --- a/net/net.c
>>>>> +++ b/net/net.c
>>>>> @@ -1257,14 +1257,19 @@ 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;
>>>>> + NetClientState *nc;
>>>>> + NetClientState *tmp;
>>>>>
>>>>> - QTAILQ_FOREACH_SAFE(nc, &net_clients, next, tmp) {
>>>>> + QTAILQ_FOREACH_SAFE(nc, &net_clients, next, tmp) {
>>>>> + if (running) {
>>>>> + /* Flush queued packets and wake up backends. */
>>>>> + if (nc->peer && qemu_can_send_packet(nc)) {
>>>>> + qemu_flush_queued_packets(nc->peer);
>>>>> + }
>>>>> + } else {
>>>>> + /* Complete all queued packets, to guarantee we don't modify
>>>>> + * state later when VM is not running.
>>>>> + */
>>>>> qemu_flush_or_purge_queued_packets(nc, true);
>>>>> }
>>>> Looks like qemu_can_send_packet() checks both nc->peer and runstate. So
>>>> probably, we can simplify this to:
>>>>
>>>> if (qemu_can_send_packet(nc))
>>>> qemu_flush_queued_packets(nc->peer);
>>>> else
>>>> qemu_flush_or_purge_queued_packets(nc, true);
>>>>
>>>>> }
>>> qemu_can_send_packet returns 1 if !nc->peer, so this doesn't work.
>>>
>>> Fam
>> Yes, I was wrong.
>>
>> Btw, instead of depending on vm handler (which seems racy with other
>> state change handler). Can we do this in places like vm_start() and
>> vm_stop(). Like we drain and flush block queue during vm stop.
>>
> Because that's a bit hacky.
>
> It won't be racy if we replace vdev->vm_running with runstate_is_running() in
> virtio-net, and/or don't check it in virtio_net_can_receive(). Is that OK?
Ok but not necessary. I believe this patch will be used with the patch
that drops virtio_net_can_receive(). So at any order two vmstate
handlers were called, the sent_cb will be called and poll will be
enabled again. I'm ok with the patch. So
Reviewed-by: Jason Wang <jasow...@redhat.com>
Thanks
>
> Fam
