On 15/01/14 10:37, Wei Liu wrote:
On Tue, Jan 14, 2014 at 07:28:39PM +0000, Zoltan Kiss wrote:
The recent patch to fix receive side flow control (11b57f) solved the spinning
thread problem, however caused an another one. The receive side can stall, if:
- xenvif_rx_action sets rx_queue_stopped to false
- interrupt happens, and sets rx_event to true
- then xenvif_kthread sets rx_event to false
If you mean "rx_work_todo" returns false.
In this case
(!skb_queue_empty(&vif->rx_queue) && !vif->rx_queue_stopped) || vif->rx_event;
can still be true, can't it?
Sorry, I should wrote rx_queue_stopped to true
Also, through rx_event a malicious guest can force the RX thread to spin. This
patch ditch that two variable, and rework rx_work_todo. If the thread finds it
This seems to be a bigger problem. Can you elaborate?
My mistake too. I forgot that rx_action set it to false, so it's not
really a spinning. However the thread should still run xenvif_rx_action
to figure out there is no space in the ring before it sets rx_event to
false. In my patch we can quit earlier.
Zoli
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