Don't use KTIMERs in receive path

They appear to always defer by at least one timer tick, which is about 16ms
by default... just too long.

Instead, to avoid DPC watchdog issues in the MPE_Ethernet test, use a
threaded DPC. This is a real-time thread that can be pre-empted by normal
DPCs but not by standard system threads.

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

diff --git a/src/xenvif/poller.c b/src/xenvif/poller.c
index ba3fbcf9d57c542d549651812bf3eec32d9272d0..a7ce37a40956c9640890e78514cfa4cfc9efde1a 100644 (file)
--- a/src/xenvif/poller.c
+++ b/src/xenvif/poller.c
@@ -80,8 +80,6 @@ struct _XENVIF_POLLER_INSTANCE {
     KSPIN_LOCK              Lock;
     KDPC                    Dpc;
     ULONG                   Dpcs;
-    KTIMER                  Timer;
-    KDPC                    TimerDpc;
     PXENVIF_POLLER_CHANNEL  Channel[XENVIF_POLLER_CHANNEL_TYPE_COUNT];
     BOOLEAN                 Enabled;
     LONG                    Pending;
@@ -533,63 +531,9 @@ done:
     KeReleaseSpinLockFromDpcLevel(&Instance->Lock);
 }
 
-#define TIME_US(_us)        ((_us) * 10)
-#define TIME_MS(_ms)        (TIME_US((_ms) * 1000))
-#define TIME_S(_s)          (TIME_MS((_s) * 1000))
-#define TIME_RELATIVE(_t)   (-(_t))
-
-__drv_requiresIRQL(DISPATCH_LEVEL)
-static VOID
-PollerInstanceDefer(
-    IN  PXENVIF_POLLER_INSTANCE Instance
-    )
-{
-    LARGE_INTEGER               Delay;
-
-    ASSERT3U(KeGetCurrentIrql(), ==, DISPATCH_LEVEL);
-
-    KeAcquireSpinLockAtDpcLevel(&Instance->Lock);
-
-    if (!Instance->Enabled)
-        goto done;
-
-    Delay.QuadPart = TIME_RELATIVE(TIME_US(100));
-    KeSetTimer(&Instance->Timer, Delay, &Instance->TimerDpc);
-
-done:
-    KeReleaseSpinLockFromDpcLevel(&Instance->Lock);
-}
-
-static FORCEINLINE BOOLEAN
-PollerInstanceDpcTimeout(
-    IN  PXENVIF_POLLER_INSTANCE Instance
-    )
-{
-    KDPC_WATCHDOG_INFORMATION   Watchdog;
-    NTSTATUS                    status;
-
-    UNREFERENCED_PARAMETER(Instance);
-
-    RtlZeroMemory(&Watchdog, sizeof (Watchdog));
-
-    status = KeQueryDpcWatchdogInformation(&Watchdog);
-    ASSERT(NT_SUCCESS(status));
-
-    if (Watchdog.DpcTimeLimit == 0 ||
-        Watchdog.DpcWatchdogLimit == 0)
-        return FALSE;
-
-    if (Watchdog.DpcTimeCount > (Watchdog.DpcTimeLimit / 2) &&
-        Watchdog.DpcWatchdogCount > (Watchdog.DpcWatchdogLimit / 2))
-        return FALSE;
-
-    return TRUE;
-}
-
 __drv_functionClass(KDEFERRED_ROUTINE)
 __drv_maxIRQL(DISPATCH_LEVEL)
-__drv_minIRQL(DISPATCH_LEVEL)
-__drv_requiresIRQL(DISPATCH_LEVEL)
+__drv_minIRQL(PASSIVE_LEVEL)
 __drv_sameIRQL
 static VOID
 PollerInstanceDpc(
@@ -613,8 +557,17 @@ PollerInstanceDpc(
     Frontend = Poller->Frontend;
 
     for (;;) {
+        BOOLEAN Enabled;
         BOOLEAN NeedReceiverPoll;
         BOOLEAN NeedTransmitterPoll;
+        KIRQL   Irql;
+
+        KeAcquireSpinLock(&Instance->Lock, &Irql);
+        Enabled = Instance->Enabled;
+        KeReleaseSpinLock(&Instance->Lock, Irql);
+
+        if (!Enabled)
+            break;
 
         NeedReceiverPoll =
             (InterlockedBitTestAndReset(&Instance->Pending,
@@ -633,8 +586,12 @@ PollerInstanceDpc(
 
         if (NeedReceiverPoll)
         {
-            BOOLEAN Retry = ReceiverPoll(FrontendGetReceiver(Frontend),
-                                         Instance->Index);
+            BOOLEAN Retry;
+
+            KeRaiseIrql(DISPATCH_LEVEL, &Irql);
+
+            Retry = ReceiverPoll(FrontendGetReceiver(Frontend),
+                                 Instance->Index);
 
             if (!Retry) {
                 PollerInstanceUnmask(Instance, XENVIF_POLLER_EVENT_RECEIVE);
@@ -642,12 +599,18 @@ PollerInstanceDpc(
                 (VOID) InterlockedBitTestAndSet(&Instance->Pending,
                                                 XENVIF_POLLER_EVENT_RECEIVE);
             }
+
+            KeLowerIrql(Irql);
         }
 
         if (NeedTransmitterPoll)
         {
-            BOOLEAN Retry = TransmitterPoll(FrontendGetTransmitter(Frontend),
-                                            Instance->Index);
+            BOOLEAN Retry;
+
+            KeRaiseIrql(DISPATCH_LEVEL, &Irql);
+
+            Retry = TransmitterPoll(FrontendGetTransmitter(Frontend),
+                                    Instance->Index);
 
             if (!Retry) {
                 PollerInstanceUnmask(Instance, XENVIF_POLLER_EVENT_TRANSMIT);
@@ -655,48 +618,12 @@ PollerInstanceDpc(
                 (VOID) InterlockedBitTestAndSet(&Instance->Pending,
                                                 XENVIF_POLLER_EVENT_TRANSMIT);
             }
-        }
 
-        if (PollerInstanceDpcTimeout(Instance)) {
-            PollerInstanceDefer(Instance);
-            break;
+            KeLowerIrql(Irql);
         }
     }
 }
 
-__drv_functionClass(KDEFERRED_ROUTINE)
-__drv_maxIRQL(DISPATCH_LEVEL)
-__drv_minIRQL(DISPATCH_LEVEL)
-__drv_requiresIRQL(DISPATCH_LEVEL)
-__drv_sameIRQL
-static VOID
-PollerInstanceTimerDpc(
-    IN  PKDPC               Dpc,
-    IN  PVOID               Context,
-    IN  PVOID               Argument1,
-    IN  PVOID               Argument2
-    )
-{
-    PXENVIF_POLLER_INSTANCE Instance = Context;
-
-    UNREFERENCED_PARAMETER(Dpc);
-    UNREFERENCED_PARAMETER(Argument1);
-    UNREFERENCED_PARAMETER(Argument2);
-
-    ASSERT(Instance != NULL);
-
-    KeAcquireSpinLockAtDpcLevel(&Instance->Lock);
-
-    if (!Instance->Enabled)
-        goto done;
-
-    if (KeInsertQueueDpc(&Instance->Dpc, NULL, NULL))
-        Instance->Dpcs++;
-
-done:
-    KeReleaseSpinLockFromDpcLevel(&Instance->Lock);
-}
-
 static NTSTATUS
 PollerInstanceInitialize(
     IN  PXENVIF_POLLER          Poller,
@@ -736,9 +663,7 @@ PollerInstanceInitialize(
 
     KeInitializeSpinLock(&(*Instance)->Lock);
 
-    KeInitializeDpc(&(*Instance)->Dpc, PollerInstanceDpc, *Instance);
-    KeInitializeTimer(&(*Instance)->Timer);
-    KeInitializeDpc(&(*Instance)->TimerDpc, PollerInstanceTimerDpc, *Instance);
+    KeInitializeThreadedDpc(&(*Instance)->Dpc, PollerInstanceDpc, *Instance);
 
     return STATUS_SUCCESS;
 
@@ -786,6 +711,7 @@ PollerInstanceConnect(
     ASSERT(NT_SUCCESS(status));
 
     KeSetTargetProcessorDpcEx(&Instance->Dpc, &ProcNumber);
+    KeSetImportanceDpc(&Instance->Dpc, MediumHighImportance);
 
     for (Type = 0; Type < XENVIF_POLLER_CHANNEL_TYPE_COUNT; Type++)
     {
@@ -978,12 +904,6 @@ PollerInstanceDisable(
     KeAcquireSpinLockAtDpcLevel(&Instance->Lock);
     Instance->Enabled = FALSE;
     KeReleaseSpinLockFromDpcLevel(&Instance->Lock);
-
-    //
-    // No new timers can be scheduled once Enabled goes to FALSE.
-    // Cancel any existing ones.
-    //
-    (VOID) KeCancelTimer(&Instance->Timer);
 }
 
 __drv_requiresIRQL(DISPATCH_LEVEL)
@@ -1024,8 +944,6 @@ PollerInstanceTeardown(
     Poller = Instance->Poller;
     Frontend = Poller->Frontend;
 
-    RtlZeroMemory(&Instance->TimerDpc, sizeof (KDPC));
-    RtlZeroMemory(&Instance->Timer, sizeof (KTIMER));
     RtlZeroMemory(&Instance->Dpc, sizeof (KDPC));
 
     RtlZeroMemory(&Instance->Lock, sizeof (KSPIN_LOCK));