Signal notification

To send a signal, set the sigev_notify field to one of:

SIGEV_SIGNAL: Send a regular signal to the process.
SIGEV_SIGNAL_CODE: Send a signal containing an 8-bit code to the process.
SIGEV_SIGNAL_THREAD: Send a signal containing an 8-bit code to a specific thread.

For SIGEV_SIGNAL*, the additional fields you'll have to fill are:

Field	Value and meaning
`sigev_signo`	Signal number to send (from <signal.h>, e.g., SIGALRM).
`sigev_code`	An 8-bit code (if using SIGEV_SIGNAL_CODE or SIGEV_SIGNAL_THREAD).