c - Creating a thread and passing input through the parent -

i'm trying use mutex make thread wait user input parent thread. current problem i'm facing child doesn't wait, though have mutex lock , unlock, join in parent thread. also, unsure if struct being used correctly? main() , *chthread() using same instance of "lock"? understand when user input before thread creation works, requirements of exercise states meant pass information after thread created.

#define _gnu_source #include <stdio.h> #include <pthread.h> #include <errno.h> #include <string.h> #include <stdlib.h> #include <readline/readline.h> #include <readline/history.h>  # define buffer_size 256  void *chthread(void *arg);  struct  { pthread_t pth; pthread_mutex_t lock; int ret; void* ex; } muinfo;  int main(int argc, char *argv[]) { //struct mutex args;  char line[buffer_size]; char *temp = null;    pthread_mutex_init(&muinfo.lock, null); if((pthread_create(&muinfo.pth, null, chthread, line)) != 0) {         perror("problem creating thread"); }  using_history(); temp = readline("enter string:  "); strcpy(line, temp);  if((pthread_join(muinfo.pth, &muinfo.ex)) !=0) {         perror("thread join error"); } free(temp);  pthread_mutex_destroy(&muinfo.lock);     pthread_exit(null);  }  void *chthread(void *arg) { //struct mutex args; pthread_mutex_lock(&muinfo.lock); char *line = (char*)arg;   printf("testing %s\n", line);  pthread_mutex_unlock(&muinfo.lock);  pthread_exit(&muinfo.ret);     //return null; } 

as main problem, need lock mutex @ main first(likely after init it),
, unlock after getting input user,
child thread wait until main unlock.

pthread_mutex_init(&muinfo.lock, null); pthread_mutex_lock(&muinfo.lock); if((pthread_create(&muinfo.pth, null, chthread, line)) != 0) {         perror("problem creating thread"); }  using_history(); temp = readline("enter string:  "); strcpy(line, temp); pthread_mutex_unlock(&muinfo.lock); 

i remove using_history() , use delayed strcpy fixed string instead readline test,
, work fine me.