Creating an interrupt handler - c

Question

const struct sigevent *intHandler(void *arg, int id)
{
start_clock = ClockCycles();
//printf("start clock: %lld\n", start_clock);
return(&event);
}
int ConfigureISR()
{
// Get IO privilege
//
ThreadCtl( _NTO_TCTL_IO, 0 );
//
// Setup COID and event
chid = ChannelCreate( 0 );
SIGEV_INTR_INIT( &event);
interruptID = InterruptAttach(7, intHandler, NULL, 0, 0);
if (interruptID == -1)
{
fprintf(stderr, "can't attach to IRQ\n");
perror (NULL);
exit (EXIT_FAILURE);
}
InterruptWait(0, NULL);
end_clock = ClockCycles();
// printf("end clock: %lld\n", end_clock);
//microseconds
InterruptLatency = (uint32) ((end_clock - start_clock)*1000000/(SYSPAGE_ENTRY(qtime)->cycles_per_sec));
printf("microseconds: %ld\n", InterruptLatency);
measurements[17] = InterruptLatency;
return (EXIT_SUCCESS);
}
int main()
{
ConfigureISR();
// my socket code here to receive data from client.
}
I created an interrupt handler in c for QNX operating system.
my task: kernel should call this interrupt handler, whenever there is a data on the udp layer. I am calculating the interrupt latency in the above code.
CLIENT is sending data and server (above code) is receiving the data from client and sending back the response.
The above code is not interrupted everytime, when ever it receives data on the udp layer. what could be the mistake in the above ?? could someone please help me in that ??