mutex.c

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

long long sum = 0;
pthread_mutex_t mutex;

void *thread_main(void *arg) 
{
    int start = ((int *)arg)[0];
    int end = ((int *)arg)[1];

    for(int i=start; i<=end; i++) {
        pthread_mutex_lock(&mutex);
        sum += i;
        pthread_mutex_unlock(&mutex);
    }

    return NULL;
}

int main(int argc, char **argv) 
{
    pthread_t tid1, tid2;
    int range1[2] = { 1, 10000000};
    int range2[2] = { 10000001, 20000000 };
    
    if(pthread_mutex_init(&mutex, NULL) != 0) {
        perror("pthread mutex init");
        return -1;
    }

    if(pthread_create(&tid1, NULL, thread_main, (void *)range1) != 0) {
        perror("pthread create 1");
        return -1;
    }

    if(pthread_create(&tid2, NULL, thread_main, (void *)range2) != 0) {
        perror("pthread create 2");
        return -1;
    }

    if(pthread_join(tid1, NULL) < 0) {
        perror("pthread join 1");
        return -1;
    }
    
    if(pthread_join(tid2, NULL) < 0) {
        perror("pthread join 2");
        return -1;
    }

    printf("sum = %lld\n", sum);
    return 0;
}