The signal-chaining facility was introduced in JDK 1.4 nearly 20 years ago and supported three different Linux signal API's: sigset, signal and sigaction:
Only sigaction is a Posix supported API for multi-threaded processes, that we can use cross-platform. Both signal and sigset are obsolete and have undefined behaviour in a multi-threaded process. From the Linux man pages:
sigset: This API is obsolete: new applications should use the POSIX signal API (sigaction(2), sigprocmask(2), etc.)
signal: The behavior of signal() varies across UNIX versions, and has also varied historically across different versions of Linux. Avoid its use: use sigaction(2) instead.
We should deprecate the use of signal and sigset in JDK 16 with a view to their removal in JDK 17.