Man pages matching name rt_sigprocmask in section 2:

rt_sigprocmask.2.en	debian 10 / manpages-dev
rt_sigprocmask.2.ja	debian 10 / manpages-ja-dev
rt_sigprocmask.2.en	debian 11 / manpages-dev
rt_sigprocmask.2.ja	debian 11 / manpages-ja-dev
rt_sigprocmask.2.en	debian 12 / manpages-dev
rt_sigprocmask.2.fr	debian 12 / manpages-fr-dev
rt_sigprocmask.2.ja	debian 12 / manpages-ja-dev
rt_sigprocmask.2.ru	debian 12 / manpages-ru-dev