I have a many daemon processes that sometimes get hung up during a db transaction, thus blocking other queries ( and causing general havoc )
In order to debug, I've added some code in the daemon process to dump a stacktrace when a SIGCONT signal is sent to it.
Is it generally safe to trap SIGCONT on a processes that isn't stopped?
I'd like to use a signal that doesn't kill the process if it's not setup to trap it
Yes. If a process does not handle SIGCONT it will "discard signal"
See
man signal
for the default actions of all signals.