Thread question

Hi I'm new to thread programming so please be gentle

I have a main function which has a while(1) loop which always runs. I also want to create another thread which also has a while(1) loop which will run constantly like so:

int main (int argc, char **argv)
{
        pthread_t thread1;     
	
	char *message1 = "This is Thread 1";
	pthread_create( &thread,
                NULL,print_message_function,(void*) message1);
	
	pthread_join( thread1, NULL);
	
	while(1)
	{
		printf("This is the MAIN Thread\n");
                //so some stuff	
	}
}
void *print_message_function( void *ptr )
{     
	while(1)
	{
		char *message;     
		message = (char *) ptr;     
		printf("%s \n", message);
	}
}

The problem I'm having is that the thread which I start is always runing and control is never passed back to the main loop The "This is the MAIN Thread" never gets printed. I thought the two loops would share time equally. What do I have to do in order to get this to happen.

Hi

The problem is the line:

pthread_join( thread1, NULL);

It means it will wait at this line until the other thread (thread1) returns. And since the function print_message_function never returns, it will wait forever (or till you terminate the application). Try removing the pthread_join.

Yes this now works, thank you
Another question, in my main loop I detect if certain keys are pressed on the keyboard but it does not detect them straight away if it is busy processing the thread1. How can I design my program so that the main loop executes once only then the thread1 executes once only then back to main and so on?

Thanks

Hmm. I don't really understand the last part. The point of threads is to execute many things at the same time. To me it seems you don't want threads after all? If so, why not skip all the thread stuff, and call print_message_function in the main loop?

Ok the code outlined above is a simplified version of what I want to do, the thread which I start will use directfb to draw various stuff to screen and the main() while loop is actually a dbus loop which is constantly waiting for dbus events.

So in one thread I am constantly drawing to screen and the other (main) thread is listening for dbus events. The dbus events will determine what is drawn to screen.

I hope you get what I am trying to achieve and I appreciate any help u can offer.

Thanks

Originally Posted by HarryBoy How can I design my program so that the main loop executes once only then the thread1 executes once only then back to main and so on?

Use a pthread_mutex_t. Read the man pages for pthread_mutex_lock.