Non blocking timer in linux user space (in C) - c

Question

Actually I want to implement non-blocking timer, when the timer expires a handler will be called and will do something (for now it prints data). I google and realized that timer_create, timer_settimer are non-blocking timer. BUT still I've issue, I have to wait for my timer to expire (sleep(MAX) or while(1) {;}). But then if I'm calling my start_timer method with different "expiry" time, it should work accordingly, should not block other. e.g. here first time I'm calling timer, and expecting to call handler in 5 sec but before that 2nd call should print its data as, that interval I've given is 1sec only. And of course its not behaving same. Any idea?
#include <time.h>
#include <stdio.h>
#include <signal.h>
#include <pthread.h>
#include <unistd.h>
#include <errno.h>
typedef struct _data{
char *name;
}data;
void handler(union sigval val)
{
data *data_handler = val.sival_ptr;
printf("Handler entered with value :%s\n", data_handler->name);
}
void mod_timer(timer_t timerid, struct sigevent sig, struct itimerspec in, struct itimerspec out)
{
printf("mod_timer\n");
timer_settime(timerid, 0, &in, &out);
while(1)
sleep(1);
//delete the timer.
timer_delete(timerid);
}
void start_timer(void* val, int interval)
{
int Ret;
pthread_attr_t attr;
pthread_attr_init( &attr );
struct sched_param parm;
parm.sched_priority = 255;
pthread_attr_setschedparam(&attr, &parm);
struct sigevent sig;
sig.sigev_notify = SIGEV_THREAD;
sig.sigev_notify_function = handler;
// sig.sigev_value.sival_int = val;
sig.sigev_value.sival_ptr = val;
sig.sigev_notify_attributes = &attr;
//create a new timer.
timer_t timerid;
Ret = timer_create(CLOCK_REALTIME, &sig, &timerid);
if (Ret == 0)
{
struct itimerspec in, out;
in.it_value.tv_sec = 1;
in.it_value.tv_nsec = 0;
in.it_interval.tv_sec = interval;
in.it_interval.tv_nsec = 0;
mod_timer(timerid, sig, in, out);
}
}
void main()
{
// start_timer(1, 5);
// start_timer(2, 1);
data handler_data1 = {"Handler Data 1"};
data handler_data2 = {"Handler Data 2"};
void *data1 = &handler_data1;
void *data2 = &handler_data2;
start_timer(data1, 5);
start_timer(data2, 1);
}

Answer 1

You can use the alarm function to generate a signal, and the signal function to specify the handler to that signal.