Data race

gistfile1.txt

~ $ cc -fPIC -pie -fsanitize=thread -pthread test3.c -Wall -Wextra -g
~ $ ./a.out 5                                                        
i am thread 1 .created a new thread(132118272) in the itaration 0
i am thread 1 .created a new thread(123725568) in the itaration 1
==================
WARNING: ThreadSanitizer: data race (pid=20232)
  Read of size 4 at 0x7ffcdeefaadc by thread T1:
    #0 thread /home/depp/test3.c:10 (a.out+0x000000000c14)
    #1 <null> <null> (libtsan.so.0+0x000000023519)

  Previous write of size 4 at 0x7ffcdeefaadc by main thread:
    #0 main /home/depp/test3.c:23 (a.out+0x000000000d67)

  Location is stack of main thread.

  Thread T1 (tid=20234, running) created by main thread at:
    #0 pthread_create <null> (libtsan.so.0+0x0000000273d4)
    #1 main /home/depp/test3.c:29 (a.out+0x000000000d11)

test3.c

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <time.h>
#include <unistd.h>
void *thread(void *a) {
  pthread_t myid;
  myid = pthread_self();
  int *i = (int *)a;
  printf("Hello from thread %u-I was created in iteration %d\n", (unsigned)myid, *i);
  pthread_exit(NULL);
}

int main(int argc, char *argv[]) {
  if (argc < 2) {
    printf("Usege <%s number of thread>", argv[0]);
    exit(1);
  }
  pthread_t tid;
  int i;
  int itr = atoi(argv[1]);
  int flag = 1;
  for (i = 0; i < itr; i++) {
    if (flag == 5) {
      printf("Sleeping for 2 sec\n");
      sleep(10);
      flag = 0;
    }
    pthread_create(&tid, NULL, thread, (void *)&i);
    printf("i am thread 1 .created a new thread(%u) in the itaration %d\n", (unsigned)tid,
           i);
    flag++;
  }

  pthread_join(tid, NULL);
  pthread_exit(NULL);

  return 0;
}