Functions that can safely be called from signal handlers are Async-Signal-Safe. The IEEE Std 1003.1-2004 (POSIX) standard defines Async-Signal-Safe functions, which are listed in Signal Handlers and Async-Signal Safety. In addition to these standard Async-Signal-Safe functions, the following functions from the Oracle Solaris threads interface are also Async-Signal-Safe:
thr_sigsetmask(3C), similar to pthread_sigmask(3C)
thr_kill(3C), similar to pthread_kill(3C)