FcAtomicCreate man page
FcAtomicCreate — create an FcAtomic object
#include <fontconfig/fontconfig.h> FcAtomic * FcAtomicCreate (const FcChar8 *file);
Creates a data structure containing data needed to control access to file. Writing is done to a separate file. Once that file is complete, the original configuration file is atomically replaced so that reading process always see a consistent and complete file without the need to lock for reading.