From: Paul Durrant <paul.durrant@citrix.com>
Date: Fri, 2 Nov 2018 11:42:47 +0000 (+0000)
Subject: Get rid of the 'Retry' exit from the ring poll routines
X-Git-Tag: 9.0.0-rc1~16
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=df7f5b1911484ad212247f91ef61b4016d12cf05;p=pvdrivers%2Fwin%2Fxenvif.git

Get rid of the 'Retry' exit from the ring poll routines

This was supposed to allow better interleaving of receive and transmit
polling, but this does not really seem to help so it really only makes
the code more complex than it needs to be.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
---

diff --git a/src/xenvif/receiver.c b/src/xenvif/receiver.c
index ed362ff..5353294 100644
--- a/src/xenvif/receiver.c
+++ b/src/xenvif/receiver.c
@@ -1975,23 +1975,19 @@ __ReceiverRingQueuePacket(
     } while (InterlockedCompareExchangePointer(&Ring->PacketQueue, (PVOID)New, (PVOID)Old) != Old);
 }
 
-static DECLSPEC_NOINLINE BOOLEAN
+static DECLSPEC_NOINLINE VOID
 ReceiverRingPoll(
     IN  PXENVIF_RECEIVER_RING   Ring
     )
 {
-#define XENVIF_RECEIVER_BATCH(_Ring) (RING_SIZE(&(_Ring)->Front) / 4)
-
     PXENVIF_RECEIVER            Receiver;
     PXENVIF_FRONTEND            Frontend;
-    BOOLEAN                     Retry;
 
     Receiver = Ring->Receiver;
     Frontend = Receiver->Frontend;
-    Retry = FALSE;
 
     if (!Ring->Enabled)
-        goto done;
+        return;
 
     for (;;) {
         BOOLEAN                 Error;
@@ -2016,9 +2012,6 @@ ReceiverRingPoll(
         TailMdl = NULL;
         EOP = TRUE;
 
-        if (Retry)
-            break;
-
         KeMemoryBarrier();
 
         rsp_prod = Ring->Shared->rsp_prod;
@@ -2036,7 +2029,7 @@ ReceiverRingPoll(
             break;
         }
 
-        while (rsp_cons != rsp_prod && !Retry) {
+        while (rsp_cons != rsp_prod) {
             netif_rx_response_t         *rsp;
             uint16_t                    id;
             PXENVIF_RECEIVER_FRAGMENT   Fragment;
@@ -2193,9 +2186,6 @@ ReceiverRingPoll(
                     __ReceiverRingQueuePacket(Ring, Packet);
                 }
 
-                if (rsp_cons - Ring->Front.rsp_cons > XENVIF_RECEIVER_BATCH(Ring))
-                    Retry = TRUE;
-
                 Error = FALSE;
                 Info = 0;
                 MaximumSegmentSize = 0;
@@ -2226,11 +2216,6 @@ ReceiverRingPoll(
     if (Ring->PacketQueue != NULL &&
         KeInsertQueueDpc(&Ring->QueueDpc, NULL, NULL))
         Ring->QueueDpcs++;
-
-done:
-    return Retry;
-
-#undef  XENVIF_RECEIVER_BATCH
 }
 
 static FORCEINLINE VOID
@@ -2274,16 +2259,12 @@ ReceiverRingPollDpc(
     ASSERT(Ring != NULL);
 
     for (;;) {
-        BOOLEAN Retry;
-
         __ReceiverRingAcquireLock(Ring);
-        Retry = ReceiverRingPoll(Ring);
+        ReceiverRingPoll(Ring);
         __ReceiverRingReleaseLock(Ring);
 
-        if (!Retry) {
-            __ReceiverRingUnmask(Ring);
-            break;
-        }
+        __ReceiverRingUnmask(Ring);
+        break;
     }
 }
 
diff --git a/src/xenvif/transmitter.c b/src/xenvif/transmitter.c
index 6895f2c..5e53f9a 100644
--- a/src/xenvif/transmitter.c
+++ b/src/xenvif/transmitter.c
@@ -2614,32 +2614,25 @@ done:
     Ring->PacketsCompleted++;
 }
 
-static DECLSPEC_NOINLINE BOOLEAN
+static DECLSPEC_NOINLINE VOID
 TransmitterRingPoll(
     IN  PXENVIF_TRANSMITTER_RING    Ring
     )
 {
-#define XENVIF_TRANSMITTER_BATCH(_Ring) (RING_SIZE(&(_Ring)->Front) / 4)
-
     PXENVIF_TRANSMITTER             Transmitter;
     PXENVIF_FRONTEND                Frontend;
-    BOOLEAN                         Retry;
 
     Transmitter = Ring->Transmitter;
     Frontend = Transmitter->Frontend;
-    Retry = FALSE;
 
     if (!Ring->Enabled)
-        goto done;
+        return;
 
     for (;;) {
         RING_IDX    rsp_prod;
         RING_IDX    rsp_cons;
         ULONG       Extra;
 
-        if (Retry)
-            break;
-
         KeMemoryBarrier();
 
         rsp_prod = Ring->Shared->rsp_prod;
@@ -2658,7 +2651,7 @@ TransmitterRingPoll(
         }
 
         Extra = 0;
-        while (rsp_cons != rsp_prod && !Retry) {
+        while (rsp_cons != rsp_prod) {
             netif_tx_response_t             *rsp;
             uint16_t                        id;
             PXENVIF_TRANSMITTER_FRAGMENT    Fragment;
@@ -2785,9 +2778,6 @@ TransmitterRingPoll(
                 Packet->Completion.Status = XENVIF_TRANSMITTER_PACKET_OK;
 
             __TransmitterRingCompletePacket(Ring, Packet);
-
-            if (rsp_cons - Ring->Front.rsp_cons > XENVIF_TRANSMITTER_BATCH(Ring))
-                Retry = TRUE;
         }
         ASSERT3U(Extra, ==, 0);
 
@@ -2795,11 +2785,6 @@ TransmitterRingPoll(
 
         Ring->Front.rsp_cons = rsp_cons;
     }
-
-done:
-    return Retry;
-
-#undef XENVIF_TRANSMITTER_BATCH
 }
 
 static FORCEINLINE VOID
@@ -3270,16 +3255,12 @@ TransmitterRingPollDpc(
     ASSERT(Ring != NULL);
 
     for (;;) {
-        BOOLEAN Retry;
-
         __TransmitterRingAcquireLock(Ring);
-        Retry = TransmitterRingPoll(Ring);
+        TransmitterRingPoll(Ring);
         __TransmitterRingReleaseLock(Ring);
 
-        if (!Retry) {
-            __TransmitterRingUnmask(Ring);
-            break;
-        }
+        __TransmitterRingUnmask(Ring);
+        break;
     }
 }