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


pthread_mutex_t sv_mutex; // Mutex to protect shared_variable

int shared_variable = 0;

void *thread_work(void *param){
	char* id = (char*)param;
	for(int i = 0; i < 10; i++){
		sleep(1);
		pthread_mutex_lock(&sv_mutex);
		int old_value = shared_variable;
		sleep(1);
		shared_variable = old_value + 10;;
		printf("thread_%s:  Changing shared_variable to %d\n", id, shared_variable);
		pthread_mutex_unlock(&sv_mutex);
	}
	return 0;
}

int main(){

	pthread_t a, b;
	pthread_mutex_init(&sv_mutex, 0);
	pthread_create(&a, 0, thread_work, (void*)"a");
	pthread_create(&b, 0, thread_work, (void*)"b");
 	pthread_join(a, 0);
	printf("thread a finished\n");
	pthread_join(b, 0);
	printf("thread b finished\n");
	return 0;
}