Index: irp.c
===================================================================
--- ntoskrnl/io/iomgr/irp.c	(revision 71479)
+++ ntoskrnl/io/iomgr/irp.c	(working copy)
@@ -1218,8 +1218,35 @@
     StackPtr->DeviceObject = DeviceObject;
 
     /* Call it */
+#if DBG
+    {
+    KIRQL OldIrql;
+    PKTHREAD Thread;
+    ULONG CombinedApcDisable;
+    NTSTATUS Status;
+    UCHAR MajorFunction;
+
+    Thread = KeGetCurrentThread();
+    OldIrql = KeGetCurrentIrql();
+    CombinedApcDisable = Thread->CombinedApcDisable;
+    MajorFunction = StackPtr->MajorFunction;
+
+    Status = DriverObject->MajorFunction[MajorFunction](DeviceObject,
+                                                        Irp);
+    if (KeGetCurrentIrql() != OldIrql ||
+        Thread->CombinedApcDisable != CombinedApcDisable)
+    {
+        DPRINT1("Dispatch function %p (major %u) changed IRQL (%u -> %u) or APC state (0x%lx -> 0x%lx)\n",
+                DriverObject->MajorFunction[MajorFunction], MajorFunction, OldIrql, KeGetCurrentIrql(), CombinedApcDisable, Thread->CombinedApcDisable);
+        NT_ASSERT(KeGetCurrentIrql() == OldIrql);
+        NT_ASSERT(Thread->CombinedApcDisable == CombinedApcDisable);
+    }
+    return Status;
+    }
+#else
     return DriverObject->MajorFunction[StackPtr->MajorFunction](DeviceObject,
                                                                 Irp);
+#endif
 }
 
 FORCEINLINE