Man pages matching name pthread_setconcurrency in section 3:

pthread_setconcurrency.3.en	debian 10 / manpages-dev
pthread_setconcurrency.3.ja	debian 10 / manpages-ja-dev
pthread_setconcurrency.3.en	debian 11 / manpages-dev
pthread_setconcurrency.3.fr	debian 11 / manpages-fr-dev
pthread_setconcurrency.3.ja	debian 11 / manpages-ja-dev
pthread_setconcurrency.3.en	debian 12 / manpages-dev
pthread_setconcurrency.3.fr	debian 12 / manpages-fr-dev
pthread_setconcurrency.3.ja	debian 12 / manpages-ja-dev
pthread_setconcurrency.3.ru	debian 12 / manpages-ru-dev