struct VI_TRACK_IRQL

typedef struct _VI_TRACK_IRQL
{
     PVOID Thread;
     UCHAR OldIrql;
     UCHAR NewIrql;
     UCHAR Processor;
     ULONG TickCount;
     VOID * StackTrace[5];
} VI_TRACK_IRQL, *PVI_TRACK_IRQL;

Windows Vista Kernel Structures