typedef struct _KDPC
{
     UCHAR Type;
     UCHAR Importance;
     WORD Number;
     LIST_ENTRY DpcListEntry;
     PVOID DeferredRoutine;
     PVOID DeferredContext;
     PVOID SystemArgument1;
     PVOID SystemArgument2;
     PVOID DpcData;
} KDPC, *PKDPC;

Windows Vista Kernel Structures