If you are running java instead of a c program the proc stacktrace shows you just the virtual machine state. You can still get a stacktrace of your java threads[1].
How about other languages? Python, ruby?
[1] https://stackoverflow.com/questions/4876274/kill-3-to-get-ja...
I wrote something that will get you the python interpreter stack from any running cpython process : https://github.com/benfred/py-spy/ , and rbspy can do the same for ruby https://github.com/rbspy/rbspy