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

atomic_int lock = 0;     //원자적 변수
int counter = 5;

int TestAndSet(atomic_int *target){
    // atomic으로 비슷하게 흉내.
    // 어셈블리어 수준의 원자적 표현이 없음
    return atomic_exchange(target, 1);
}

void acquire_lock(atomic_int *lock){
    while(TestAndSet(lock) == 1){
        // 바쁜대기중...
    }
}

void release_lock(atomic_int *lock){
    atomic_store(lock, 0);
}

void* producer(void* arg){
    for(int i = 0; i < 1000000; i++){
        acquire_lock(&lock);
        counter++;
        release_lock(&lock);
    }

    return NULL;
}

void *consumer(void* arg){
    for(int i = 0; i < 1000000; i++){
        acquire_lock(&lock);
        counter--;
        release_lock(&lock);
    }

    return NULL;
}

int main(){
    pthread_t t1, t2;

    pthread_create(&t1, NULL, producer, NULL);
    pthread_create(&t2, NULL, consumer, NULL);

    pthread_join(t1, NULL);
    pthread_join(t2, NULL);

    printf("최종 Counter 값 : %d\n", counter);
    return 0;
}