[PATCH v2 3/4] Conditionally restart the RX ring from packet return

[Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>]

Currently, the RX ring is restarted on packet return regardless of
whether there are sufficient resources to afford it. In cases where the
packet cache has been exhausted, restarting the RX ring will be
counterproductive.

Make ReceiverRingFill return STATUS_SUCCESS only if the RX ring has
been filled without errors. Base the decision of restarting the RX ring
from __ReceiverRingReturnPacket on this return status.

Signed-off-by: Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>
---
 src/xenvif/receiver.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/xenvif/receiver.c b/src/xenvif/receiver.c
index bc6dcef..ca83ee3 100644
--- a/src/xenvif/receiver.c
+++ b/src/xenvif/receiver.c
@@ -1787,7 +1787,7 @@ __ReceiverRingPushRequests(
     Ring->RequestsPushed = Ring->RequestsPosted;
 }
 
-static VOID
+static NTSTATUS
 ReceiverRingFill(
     IN  PXENVIF_RECEIVER_RING   Ring
     )
@@ -1796,6 +1796,7 @@ ReceiverRingFill(
     PXENVIF_FRONTEND            Frontend;
     RING_IDX                    req_prod;
     RING_IDX                    rsp_cons;
+    NTSTATUS                    status;
 
     Receiver = Ring->Receiver;
     Frontend = Receiver->Frontend;
@@ -1807,6 +1808,7 @@ ReceiverRingFill(
 
     KeMemoryBarrier();
 
+    status = STATUS_SUCCESS;
     while (req_prod - rsp_cons < RING_SIZE(&Ring->Front)) {
         PXENVIF_RECEIVER_PACKET     Packet;
         PXENVIF_RECEIVER_FRAGMENT   Fragment;
@@ -1816,6 +1818,7 @@ ReceiverRingFill(
         Packet = __ReceiverRingGetPacket(Ring, TRUE);
 
         if (Packet == NULL) {
+            status = STATUS_INSUFFICIENT_RESOURCES;
             __ReceiverRingStop(Ring);
             break;
         }
@@ -1823,6 +1826,7 @@ ReceiverRingFill(
         Fragment = __ReceiverRingPreparePacket(Ring, Packet);
         
         if (Fragment == NULL) {
+            status = STATUS_INSUFFICIENT_RESOURCES;
             __ReceiverRingPutPacket(Ring, Packet, TRUE);
             break;
         }
@@ -1848,6 +1852,8 @@ ReceiverRingFill(
     Ring->Front.req_prod_pvt = req_prod;
 
     __ReceiverRingPushRequests(Ring);
+
+    return status;
 }
 
 _IRQL_requires_(DISPATCH_LEVEL)
@@ -1881,7 +1887,8 @@ __ReceiverRingReturnPacket(
         if (!Locked)
             __ReceiverRingAcquireLock(Ring);
 
-        if (__ReceiverRingIsStopped(Ring)) {
+        if (__ReceiverRingIsStopped(Ring) &&
+            NT_SUCCESS(ReceiverRingFill(Ring))) {
             __ReceiverRingStart(Ring);
             __ReceiverRingTrigger(Ring, TRUE);
         }
-- 
2.54.0.windows.1



--
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