뮤텍스 질문입니다..

      1 #include<stdio.h>
      2 #include<unistd.h>
      3 #include<stdlib.h>
      4 #include<string.h>
      5 #include<pthread.h>
      6 #include<semaphore.h>
      7
      8 void *thread_function(void *arg);
      9 pthread_mutex_t work_mutex;
     10
     11 #define WORK_SIZE 1024
     12 char work_area[WORK_SIZE];
     13 int  time_to_exit = 0;
     14
     15 int main(){
     16     int res;
     17     pthread_t a_thread;
     18     void *thread_result;
     19     res = pthread_mutex_init(&work_mutex,NULL);
     20     if(res != 0){
     21         perror("Mutex initialization failed");
     22         exit(EXIT_FAILURE);
     23     }
     24     res = pthread_create(&a_thread, NULL, thread_function,NULL);
     25     if(res != 0){
     26         perror("Thread creation failed");
     27         exit(EXIT_FAILURE);
     28     }
     29     pthread_mutex_lock(&work_mutex);
     30     printf("Input some text. Enter 'end' to finish\n");
     31     while(!time_to_exit){
     32         fgets(work_area, WORK_SIZE, stdin);
     33         printf("1")
     34         pthread_mutex_unlock(&work_mutex);
     35         while(1){
     36             pthread_mutex_lock(&work_mutex);
     37             if(work_area[0] != '\0'){
     38                 pthread_mutex_unlock(&work_mutex);
     39                 sleep(1);
     40             }
     41             else{
     42                 break;
     43             }
     44         }
     45     }
     46     pthread_mutex_unlock(&work_mutex);
     47     printf("\nWainting for thread to finish...\n");
     48     res = pthread_join(a_thread, &thread_result);
     49     if(res != 0){
     50         perror("Thread join failed");
     51         exit(EXIT_FAILURE);
     52     }
     53     printf("Thread join \n");
     54     pthread_mutex_destroy(&work_mutex);
     55     exit(EXIT_SUCCESS);
     56 }
     57
     58 void *thread_function(void *arg)
     59 {
     60     printf("2");
     61     sleep(1);
     62     pthread_mutex_lock(&work_mutex);
     63     while(strncmp("end",work_area, 3) != 0){
     64         printf("You input %d characters\n", strlen(work_area) -1);
     65         work_area[0] = '\0';
     66         pthread_mutex_unlock(&work_mutex);
     67         sleep(1);
     68         pthread_mutex_lock(&work_mutex);
     69         while(work_area[0] == '\0'){
     70             pthread_mutex_unlock(&work_mutex);
     71             sleep(1);
     72             pthread_mutex_lock(&work_mutex);
     73         }
     74     }
     75
     76     time_to_exit = 1;
     77     work_area[0] = '\0';
     78     pthread_mutex_unlock(&work_mutex);
     79     pthread_exit(0);
     80 }
 

[root@localhost chapter12]# ./thread4
Input some text. Enter 'end' to finish
asdf
21You input 4 characters
end
1
Wainting for thread to finish...
Thread join
[root@localhost chapter12]#

뮤텍스에 대해 잠시 보고 있습니다.
의문나는 점이 있어서 이렇게 질문을 하내요.

실행화면을 보면 숫자 1이 2뒤에 출력되는것을 볼수 있습니다.
소스를아무리 봐도 이해가 가지 않습니다
숫자 1이 먼저 출력 되야 하지 않을까요?
fgets()로 문자열을 입력 받은 후에 바로 출력 해줬는데
어찌 숫자2가 먼저 출력 될까요???