/* Coded By Karthik Ananthapadmanaban 
   9:55 PM 9/27/2007
*/

#include<pthread.h>
#include<semaphore.h>

sem_t sem1;
int global=0;

void * threaded_fn(void *g)
{
	int j;
	//p was 1 when thread was created. Now its decremented to 0, so 1 thread blocks and 
	//1 proceeds
	sem_wait(&sem1);
	printf("\n %d processing...",pthread_self());
	sem_getvalue(&sem1,&j);
	printf("\n Value of sem1 is %d",j);
	for(j=0;j<100;j++)
		global++;
	printf("\n The value of global is %d",global);
	if(global==100){
	sleep(5);
	}
	//Increment p by 1 so that 2nd thread gets a chance!
	sem_post(&sem1);
	sem_getvalue(&sem1,&j);
	printf("\n Value of sem1 now is %d",j);
}

int main()
{
	pthread_t pth[2];
	int i=0,j;

	sem_init(&sem1,0,0);
	//Increments parameter 3 in sem_init to 1, let param 3 be p
	sem_post(&sem1);
	sem_getvalue(&sem1,&j);
	printf("\n Value of sem1 is %d",j);

	for(i=0;i<2;i++)
		pthread_create(&pth[i],NULL,threaded_fn,NULL);

	for(i=0;i<2;i++)
		pthread_join(pth[i],NULL);

	printf("\n Processes done...");

	return 0;
}