Non blocking thread TIMER

[evariste]

Hi all,

I'm trying to do some timer thread but i have some trouble to do this, because i use sleep and it is a blocking call, so i need some more flexible function that do the job and don't block other threads. my code is :

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

/* call back function - inform the user the time has expired */
void timeout_call_back()
{
    printf("=== your time is up ===\n");
	// doing some other stuff
}

/* Go to sleep for a period of seconds */
static void* start_timer(void *args)
{
    /* function pointer */
    void (*finish_function)();

    
    int seconds = *((int*) args);
    pthread_mutex_lock(&mutex); // I want to do this action atomically
    printf("thread ID : %ld, go to sleep for %d\n", pthread_self(), seconds);
    
    finish_function = timeout_call_back;
    
    sleep(seconds); // THIS IS MY PROBLEM I WANT TO WAIT for (seconds) seconds but i don't want to block other threads

    /* call the cb to inform the user time is out */
    (*finish_function)();
    pthread_mutex_unlock(&mutex);
	
    pthread_exit(NULL);
}

int main()
{
    pthread_t thread1, thread2, thread3;
    int seconds1 = 300;
    int seconds2 = 600;
    int seconds3 = 900;

    int rc1, rc2, rc3;

    rc1 =  pthread_create(&thread1, NULL, start_timer, (void *) &seconds1);
    if(rc1)
	printf("=== Failed to create thread1\n");
    rc2 =  pthread_create(&thread2, NULL, start_timer, (void *) &seconds2);
    if(rc2)
	printf("=== Failed to create thread2\n");

    rc3 =  pthread_create(&thread3, NULL, start_timer, (void *) &seconds3);
    if(rc3)
	printf("=== Failed to create thread3\n");

    pthread_join(thread1, NULL);
    pthread_join(thread2, NULL);
    pthread_join(thread3, NULL);

    printf("=== End of all threads in ===\n");

    return 0;
}

Thanks for your help.

[GReaper]

Well, i don't know if there's a way to get past this, but you should think of the alternative: Reduce the thread's priority instead calling sleep;

[evariste]

Thanks "Sipher" what you mean by reducing priority? May be i'm wrong instead of use sleep to launch the timer ther's other tips to do that?

[GReaper]

Every running process takes a time slice from the OS. If you lower its priority, it will take less than the average time slice, and in effect it won't make CPU so busy. I don't know how to implement it though, i'm a bit rusty on threads.

[Codeplug]

I don't recommend changing thread priorities. 99% of the time it's best to let the OS handle all the scheduling.

You could use timer_create() with a SIGEV_THREAD notification.

gg

[evariste]

Thanks for timer_create(), how can i deal with this function tin my case?

[Codeplug]

I'm not sure what your case is...what do you want to accomplish with these timers?

gg

[evariste]

Thanks for the reply "Codeplug",

When you run my code, you can see that the

sleep(seconds)

inside the

start_timer(void *args)

function blocks other threads until she terminates (This code is atomic), and i want threads to run simultaneously.

Thanks

[kona49er]

Hi all,

I'm trying to do some timer thread but i have some trouble to do this, because i use sleep and it is a blocking call, so i need some more flexible function that do the job and don't block other threads. my code is :

Are you sure it not your mutex lock that's causing you problem. If a thread locks a
mutex and then sleeps holding the lock that will block the other threads waiting
for the lock to free.

[evariste]

Thanks "kona49er",

I said before that i want this part to be atomic and at the same time launch the timer inside this step, so i know that my problem is (sleep + mutex), but i don't know how to do this :

1. create a timer thread, start it as non blocking and be able to test from other functions if my timer has expired and finally at expiration run "timeout_call_back" function.

If you have an idea on how to do this feel free to answer me.

Thanks.

[Codeplug]

>> ... be able to test from other functions if my timer has expired and finally at expiration run "timeout_call_back" function.
Use timer_create() and timer_settime(). Use the SIGEV_THREAD notification type.

/* this is called "as-if" it were a new thread */
void timeout_call_back(union sigval)
{
...
}

...
sev.sigev_notify = SIGEV_THREAD;
sev.sigev_value.sival_ptr = &timerid; /* sigev_value is passed to our callback */
sev.sigev_notify_function = &timeout_call_back;
sev.sigev_notify_attributes = NULL;

https://www.kernel.org/doc/man-pages...igevent.7.html

gg