I looked around but couldn't find a great answer on how to do this correctly in Python on Linux. I have a daemon that attempts to shut down cleanly when it gets a number of signals and it appears to be working correctly. But, it's written like the first example.
Python does the right thing under the hood for you. The signal handler you register in Python isn't run in the dangerous context. There's an internal signal handler which just tells the interpreter a signal happened and when control is returned back to the interpreter outside of the signal handler it knows what to do:
It is possible to write thread safe signal (and portable) signal handlers doing exactly what you've done. Have the handler set a flag. That's is. Then, outside the handler, periodically check that flag and do the real work when it changes.
The main reason I prefer this approach is that sigaction is in the POSIX standard but not the C or C++ standards. sigaction isn't available on Windows, but signal is (then again, very few signals are available on Windows).
