Man pages matching name pthread_atfork in section 3:

pthread_atfork.3.en	debian 10 / glibc-doc
pthread_atfork.3.ja	debian 10 / manpages-ja-dev
pthread_atfork.3.en	debian 11 / glibc-doc
pthread_atfork.3.ja	debian 11 / manpages-ja-dev
pthread_atfork.3.en	debian 12 / glibc-doc
pthread_atfork.3.ja	debian 12 / manpages-ja-dev
pthread_atfork.3.en	debian 13 / manpages-dev
pthread_atfork.3.fr	debian 13 / manpages-fr-dev
pthread_atfork.3.ja	debian 13 / manpages-ja-dev
pthread_atfork.3.ro	debian 13 / manpages-ro-dev
pthread_atfork.3.ru	debian 13 / manpages-ru-dev