1 #include <stdio.h>
  2 #include <pthread.h>
  3 #include <stdio.h>
  4 #include <errno.h>
  5 #include <stdlib.h>
  6 static pthread_rwlock_t rwlock;
  7 #define WORK_SIZE 1024
  8 char work_area[WORK_SIZE];
  9 int time_to_exit=0;
 10 
 11 void *thread_function_read_o(void *arg);
 12 void *thread_function_read_t(void *arg);
 13 void *thread_function_write_o(void *arg);
 14 void *thread_function_write_t(void *arg);
 15 
 16 int main(int argc, char *argv[])
 17 {
 18     int res;
 19     pthread_t a_thread,b_thread,c_thread,d_thread;
 20     void *thread_result;
 21     res=pthread_rwlock_init(&rwlock,NULL);
 22     if(res!=0)
 23         exit(EXIT_FAILURE);
 24     res=pthread_create(&a_thread,NULL,thread_function_read_o,NULL);
 25     if(res!=0)
 26         exit(EXIT_FAILURE);
 27     res=pthread_create(&b_thread,NULL,thread_function_read_t,NULL);
 28     if(res!=0)
 29         exit(EXIT_FAILURE);
 30     res=pthread_create(&c_thread,NULL,thread_function_write_o,NULL);
 31     if(res!=0)
 32         exit(EXIT_FAILURE);
 33     res=pthread_create(&d_thread,NULL,thread_function_write_t,NULL);
 34     if(res!=0)
 35         exit(EXIT_FAILURE);
 36     res=pthread_join(a_thread,&thread_result);
 37     if(res!=0)
 38         exit(EXIT_FAILURE);
 39     res=pthread_join(b_thread,&thread_result);
 40     if(res!=0)
 41         exit(EXIT_FAILURE);
 42     res=pthread_join(c_thread,&thread_result);
 43     if(res!=0)
 44         exit(EXIT_FAILURE);
 45     res=pthread_join(d_thread,&thread_result);
 46     pthread_rwlock_destroy(&rwlock);
 47     return 0;
 48 }
 49 void *thread_function_read_o(void *arg)
 50 {
 51     printf("thread read one try to get lock\n");
 52     pthread_rwlock_rdlock(&rwlock);
 53     while(strncmp("end",work_area,3)!=0)
 54     {
 55         printf("this is thread read one.");
 56         printf("the characters is %s\n",work_area);
 57         pthread_rwlock_unlock(&rwlock);
 58         sleep(2);
 59         pthread_rwlock_rdlock(&rwlock);
 60         while(work_area[0]==‘\0‘)
 61         {
 62             pthread_rwlock_unlock(&rwlock);
 63             sleep(2);
 64             pthread_rwlock_rdlock(&rwlock);
 65         }
 66     }
 67     pthread_rwlock_unlock(&rwlock);
 68     time_to_exit=1;
 69     pthread_exit(0);
 70 }
 71 void *thread_function_read_t(void *arg)
 72 {
 73     printf("thread read two try to get lock\n");
 74     pthread_rwlock_rdlock(&rwlock);
 75     while(strncmp("end",work_area,3)!=0)
 76     {
 77         printf("this is thread read two.");
 78         printf("the characters is %s\n",work_area);
 79         pthread_rwlock_unlock(&rwlock);
 80         sleep(5);
 81         pthread_rwlock_rdlock(&rwlock);
 82         while(work_area[0]==‘\0‘)
 83         {
 84             pthread_rwlock_unlock(&rwlock);
 85             sleep(5);
 86             pthread_rwlock_rdlock(&rwlock);
 87         }
 88 
 89     }
 90     pthread_rwlock_unlock(&rwlock);
 91     time_to_exit=1;
 92     pthread_exit(0);
 93 }
 94 
 95 void *thread_function_write_o(void *arg)
 96 {
 97     printf("this is write thread one try to get lock\n");
 98     while(!time_to_exit)
 99     {
100         pthread_rwlock_wrlock(&rwlock);
101         printf("this is write thread one.\nInput some text. Enter ‘end‘ to finish\n");
102         fgets(work_area,WORK_SIZE,stdin);
103         pthread_rwlock_unlock(&rwlock);
104         sleep(15);
105     }
106     pthread_rwlock_unlock(&rwlock);
107     pthread_exit(0);
108 }
109 
110 void *thread_function_write_t(void *arg)
111 {
112     printf("this is write thread two try to get lock\n");
113     while(!time_to_exit)
114     {
115         pthread_rwlock_wrlock(&rwlock);
116         printf("this is write thread two.\nInput some text. Enter ‘end‘ to finish\n");
117         fgets(work_area,WORK_SIZE,stdin);
118         pthread_rwlock_unlock(&rwlock);
119         sleep(20);
120     }
121     pthread_rwlock_unlock(&rwlock);
122     pthread_exit(0);
123 }