pthread_sigsetmask(3T)

pthread_sigsetmask(3T) does for a thread what sigprocmask(2) does for a process--it sets the thread's signal mask. When a new thread is created, its initial mask is inherited from its creator.

The call to sigprocmask() in a multithreaded process is equivalent to a call to pthread_sigsetmask(). See the sigprocmask(2)page for more information.