diff --recursive -u usrsrc9.orig/sys/compat/ndis/ntoskrnl_var.h usrsrc9/sys/compat/ndis/ntoskrnl_var.h
--- usrsrc9.orig/sys/compat/ndis/ntoskrnl_var.h	2012-09-08 17:30:39.673644663 -0500
+++ usrsrc9/sys/compat/ndis/ntoskrnl_var.h	2012-09-08 17:31:21.248566542 -0500
@@ -1460,6 +1460,8 @@
 extern uint8_t KeSynchronizeExecution(kinterrupt *, void *, void *);
 extern uintptr_t InterlockedExchange(volatile uint32_t *,
 	uintptr_t);
+extern uintptr_t InterlockedCompareExchange(volatile uint32_t *,
+	uintptr_t, uintptr_t);
 extern void *ExAllocatePoolWithTag(uint32_t, size_t, uint32_t);
 extern void ExFreePool(void *);
 extern uint32_t IoConnectInterrupt(kinterrupt **, void *, void *,
diff --recursive -u usrsrc9.orig/sys/compat/ndis/subr_ntoskrnl.c usrsrc9/sys/compat/ndis/subr_ntoskrnl.c
--- usrsrc9.orig/sys/compat/ndis/subr_ntoskrnl.c	2012-09-08 17:30:27.011560031 -0500
+++ usrsrc9/sys/compat/ndis/subr_ntoskrnl.c	2012-09-08 17:31:21.249568664 -0500
@@ -2361,6 +2361,22 @@
 	return (r);
 }
 
+uintptr_t
+InterlockedCompareExchange(dst, exc, com)
+	volatile uint32_t	*dst;
+	uintptr_t		exc;
+	uintptr_t		com;
+{
+	uintptr_t		r;
+
+	mtx_lock_spin(&ntoskrnl_interlock);
+	r = *dst;
+	if(*dst == com) *dst = exc;
+	mtx_unlock_spin(&ntoskrnl_interlock);
+
+	return (r);
+}
+
 static uint32_t
 InterlockedIncrement(addend)
 	volatile uint32_t	*addend;
@@ -4381,6 +4397,7 @@
 	IMPORT_FFUNC(InterlockedIncrement, 1),
 	IMPORT_FFUNC(InterlockedDecrement, 1),
 	IMPORT_FFUNC(InterlockedExchange, 2),
+	IMPORT_FFUNC(InterlockedCompareExchange, 3),
 	IMPORT_FFUNC(ExInterlockedAddLargeStatistic, 2),
 	IMPORT_SFUNC(IoAllocateMdl, 5),
 	IMPORT_SFUNC(IoFreeMdl, 1),