When one process sends a signal to another process, under what circumstances does receiving process wait until it is rescheduled to run? Under what circumstances does the installed signal handler get invoked immediately? How much overhead does the process incur when raising a signal compared to just call the corresponding signal handler directly?

How long does it take for a non-blocked signal get delivered?

When one process sends a signal to another process, under what circumstances does receiving process wait until it is rescheduled to run?
Under what circumstances does the installed signal handler get invoked immediately?
How much overhead does the process incur when raising a signal compared to just call the corresponding signal handler directly?