Man pages matching name gearman_worker_unregister_all in section 3:

gearman_worker_unregister_all.3.en	debian 10 / libgearman-dev
gearman_worker_unregister_all.3.en	debian 11 / libgearman-dev
gearman_worker_unregister_all.3.en	debian 12 / libgearman-dev