Re: [Xen-devel] [PATCH net v2 2/3] xen-netback: don't stop dealloc kthread too early

On Mon, Aug 11, 2014 at 01:10:12PM +0100, David Vrabel wrote:

On 08/08/14 17:37, Wei Liu wrote:

[...]

quoted

 	if (tx_evtchn == rx_evtchn) {
 		/* feature-split-event-channels == 0 */

@@ -687,6 +700,9 @@ void xenvif_disconnect(struct xenvif *vif)
 			queue->task = NULL;
 		}
 
+		wait_event(queue->inflight_wq,
+			   atomic_read(&queue->inflight_packets) == 0);

Just make the dealloc task not stop unless it has deallocated all
outstanding requests.  There's no need for another wait queue here.

Are you suggesting something like

  while (atomic_read(&queue->inflight_packets) !=0)
  	schedule_timeout(SOME_TIMEOUT);

?

quoted

+
 		if (queue->dealloc_task) {
 			kthread_stop(queue->dealloc_task);
 			queue->dealloc_task = NULL;

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 4734472..d2f0c7d7 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c

@@ -107,6 +107,18 @@ static inline unsigned long idx_to_kaddr(struct xenvif_queue *queue,
 #define callback_param(vif, pending_idx) \
 	(vif->pending_tx_info[pending_idx].callback_struct)
 
+/* This function is used to set SKBTX_DEV_ZEROCOPY as well as
+ * increasing the inflight counter. We need to increase the inflight
+ * counter because core driver calls into xenvif_zerocopy_callback
+ * which calls xenvif_dec_inflight_packets.
+ */
+static void set_skb_zerocopy(struct xenvif_queue *queue,
+			     struct sk_buff *skb)
+{
+	skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
+	xenvif_inc_inflight_packets(queue);
+}

This name makes this look like a core function instead of a netback
specific one.

I would suggest a pair of functions:

xenvif_skb_zerocopy_prepare()
xenvif_skb_zerocopy_complete()

This will do.

Wei.

Or similar.

David