typedef struct _RTL_CRITICAL_SECTION
{
     PRTL_CRITICAL_SECTION_DEBUG DebugInfo;
     LONG LockCount;
     LONG RecursionCount;
     PVOID OwningThread;
     PVOID LockSemaphore;
     ULONG SpinCount;
} RTL_CRITICAL_SECTION, *PRTL_CRITICAL_SECTION;

Windows Vista Kernel Structures