Improve signal and thread handling

[joakimr-axis]

Describe your changes

Fixes signal handling and also improves the thread handling.

Checklist before requesting a review

• [x] I have performed a self-review of my own code
• [x] I have verified that the code builds perfectly fine on my local system
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have verified that my code follows the style already available in the repository
• [x] I have made corresponding changes to the documentation