RtlRunOnceComplete - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#ifndef _NTRTL_H
#if (PHNT_VERSION >= PHNT_VISTA)

NTSYSAPI
NTSTATUS
NTAPI
RtlRunOnceComplete(
    _Inout_ PRTL_RUN_ONCE RunOnce,
    _In_ ULONG Flags,
    _In_opt_ PVOID Context
    );

#endif
#endif

View code on GitHub

This function is documented in Windows Driver Kit.