RtlDllShutdownInProgress - NtDoc

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

/**
 * Gets a value indicating whether the process is currently in the shutdown phase.
 *
 * @return TRUE if a shutdown of the current dll process is in progress; otherwise, FALSE.
 */
NTSYSAPI
BOOLEAN
NTAPI
RtlDllShutdownInProgress(
    VOID
    );

#endif

View code on GitHub

This function is documented in Windows SDK.