如何理解 SIGSTOP 交付？

Question

My problem is handling SIGSTOP. I know SIGSTOP cannot be catched, handled and blocked but in some place of code, if SIGSTOP signal is delivered, execution must continue. I understand that I need to signal my process with SIGCONT but how can i understand SIGSTOP is delivered? Is there has to be another process that constantly sending SIGCONT? Is it must be external process?

Answer 1

Your process cannot detect SIGSTOP any more than it can detect SIGKILL. The way that a process detects that it has received a signal is by receiving a notification via a signal handler (or equivalent, such as signalfd on Linux). Since SIGSTOP cannot be caught, your process cannot receive any notification of it.

You can use an external process to send it SIGCONT if you like, but perhaps it's a good time to question why your process is receiving SIGSTOP when that is unwanted. If this is purely precautionary, it's probably not worth worrying about unless your software is highly safety or security critical, in which case you may want to run it as a separate user to restrict who can signal it.