I'm trying to write a server application that will wait for incoming connections.

Whenever a client attempts to connect/read/write (basically when the socket
experiences activity) a signal is supposed to be triggered.

I used:
fcntl(socket, F_SETSIG, SIGIO);
fcntl(socket, F_SETFL, O_ASYNC | O_NONBLOCK);
fcntl(socket, F_SETOWN, getpid());

And:
struct sigaction action;
action.sa_sigaction = &MySigHandler;
action.sa_flags = SA_SIGINFO;
sigaction(SIGIO, &action, NULL);

According to the man pages, whenever there is activity in the socket "socket", a
signal will be raised. The signal would be handled by "MySigHandler", and since
the "SA_SIGINFO" flag was set, the signal would provide additional information
to the function. And here is when the unexpected behaviour occurs.

According to the manpages, the second parameter of the handler (siginfo_t *)
should contain additional information. Among the information, si_code is
supposed to have "SI_SIGIO" if the signal was generated by a queued SIGIO.

Instead of having SI_SIGIO (supposed to be -5) I get a value of 1. I also tried
"kill -s SIGIO <pid of server>" and got a value of 0 (SI_USER), which is the
expected value when the signal is raised by kill.

I'm currently using glib version 2.7-2 on Linux version 2.6.23.1-42.fc8.

To reproduce the problem simply setup a socket using fcntl (as above), make it
listen for incoming connections, and use sigaction (as above) to make a function
handle the signal. Inside the function, print out the contents of si_code. If
necessary, I can provide my own code.