线程编程练习 - 阅读和写作。互联网不需要？

Question

我正在尝试线程编程练习（来自HERE）并进行一些调整。我想尝试2个（或更多）线程，一次从一个字符串读取一个字，然后写入缓冲区。最后主线程将打印线程写入的缓冲区。

即使我不使用互斥锁来保护写缓冲区，我的代码也能正常工作，我感到很惊讶？在目前的状态 - 这是正确的做事方式吗？它产生正确的输出。

特别是'Hello'函数中的while循环：如果使用互斥锁会更有效吗？在这种情况下如何编写代码？

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

int threadCount = 3;
int finish = 0;
int turn = 0;
void *Hello(void *rank);

char *str = "This is a really long string.. such a long string this really is... !";
char buff[512];
int index = 0;
int main() {
    long thread;
    pthread_t *hThread;

    hThread = (pthread_t *)malloc(threadCount*sizeof(pthread_t));
    if(hThread == NULL) {
        printf("\nERROR: malloc failed");
    }

    for(thread = 0; thread < threadCount; thread++) {
        pthread_create(&hThread[thread], NULL, Hello, (void *)thread);
    } 

    printf("Hello from main thread !\n");

    for(thread = 0; thread < threadCount; thread++) {
        pthread_join(hThread[thread], NULL);
    }

    printf("All threads finished !\n");
    printf("%s\n", buff);
    free(hThread);

    return 0;
}

void printMsg(void) {
    if(finish)
        return;     

    while(*str != '\0' && *str != ' ') {        
        buff[index++] = *str;       
        printf("%c",*str++);                
    }
    printf("\n");
    if(*str == ' ') {
        buff[index++] = ' ';
        str++;
    }
    if(*str == '\0') {
        buff[index++] = '\0';
        finish = 1;
    }
    turn = (turn +1)%threadCount;
}

void *Hello(void *rank) {
    long id = (long)rank;   
    while(!finish) {
        if(turn == (int)id) {
            printf("%ld : ", id);
            printMsg();     
        }
    }   
    return NULL;
}

我可以看到输出产生为：

0 : This
Hello from main thread !
1 : is
2 : a
0 : really
1 : long
2 : string..
0 : such
1 : a
2 : long
0 : string
1 : this
2 : really
0 : is...
1 : !
All threads finished !
This is a really long string.. such a long string this really is... !