pthread cnt lines mtx

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <string.h>
#include <sched.h>

#define LINE_SIZE (1 << 12)

int n;

pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
int totalCnt = 0;

static char target;
void *routine(void *arg) {
    char *line = (char*)arg;
    int cnt = 0, r = 0;
    for (int i = 0; line[i]; i++) {
        if (line[i] == target) {
            cnt++;
        }
    }
    if ((r = pthread_mutex_lock(&mtx)) != 0) {
        fprintf(stderr, "pthread_mutex_lock: %s\n", strerror(r));
        pthread_exit(NULL);
    }
    totalCnt += cnt;
    if ((r = pthread_mutex_unlock(&mtx)) != 0) {
        fprintf(stderr, "pthread_mutex_unlock: %s\n", strerror(r));
        pthread_exit(NULL);
    }

    return NULL;
}

int main(int argc, char *argv[]) {
    if (argc != 2) {
        fprintf(stderr, "WRONG USAGE!\n");
        exit(1);
    }
    target = argv[1][0];

    cpu_set_t cpuset;
    CPU_ZERO(&cpuset);
    CPU_SET(0, &cpuset);

    pthread_attr_t attr;
    pthread_attr_init(&attr);
    pthread_attr_setaffinity_np(&attr, sizeof(cpu_set_t), &cpuset);

    scanf("%d", &n);
    getchar();

    char line[n][LINE_SIZE];
    for (int i = 0; i < n; i++) {
        fgets(line[i], LINE_SIZE, stdin);
    }

    pthread_t thread[n];
    int r = 0;
    pthread_mutex_init(&mtx, NULL);
    for (int i = 0; i < n; i++) {
        if ((r = pthread_create(&thread[i], &attr, routine, line[i])) != 0) {
            fprintf(stderr, "pthread_create: %s\n", strerror(r));
            exit(1);
        }
    }
    for (int i = 0; i < n; i++) {
        if ((r = pthread_join(thread[i], NULL)) != 0) {
            fprintf(stderr, "pthread_join: %s\n", strerror(r));
            exit(1);
        }
    }
    pthread_attr_destroy(&attr);
    pthread_mutex_destroy(&mtx);
    printf("%d\n", totalCnt);
    return 0;
}