It looks thread synchronization is missing a signal

Question

I was testing thread synchronization with very simple example.

Here is the example code and results. I don't understand why I cannot see "data : 1" or [[data : 1]] from the result. Does it mean printData thread and printDataFormat thread does not receive the signal sent from increase thread at the line 23?

  1 #include <stdio.h>
  2 #include <stdlib.h>
  3 #include <string.h>
  4 #include <stdint.h>
  5 #include <unistd.h>
  6 #include <pthread.h>
  7
  8 pthread_mutex_t mutex;
  9 pthread_cond_t cond;
 10
 11 static int32_t data = 0;
 12
 13 void *increase(void *arg)
 14 {
 15    int32_t ldata = 0;
 16    while(1)
 17    {
 18       pthread_mutex_lock(&mutex);
 19       data++;
 20       if (data == (ldata + 1))
 21       {
 22          printf(">>data = %d\n", data);
 23          pthread_cond_signal(&cond);
 24       }
 25       ldata++;
 26       pthread_mutex_unlock(&mutex);
 27       sleep(2);
 28    }
 29 }
 30
 31 void *printData(void *arg)
 32 {
 33    while(1)
 34    {
 35       pthread_mutex_lock(&mutex);
 36       pthread_cond_wait(&cond, &mutex);
 37       printf("data : %d\n", data);
 38       pthread_mutex_unlock(&mutex);
 39    }
 40 }
 41
 42 void *printDataFormat(void *arg)
 43 {
 44    while(1)
 45    {
 46       pthread_mutex_lock(&mutex);
 47       pthread_cond_wait(&cond, &mutex);
 48       printf("[[data : %d]]\n", data);
 49       pthread_mutex_unlock(&mutex);
 50    }
 51 }
 52
 53 int32_t main(void)
 54 {
 55    pthread_t thread1, thread2, thread3;
 56
 57    pthread_mutex_init(&mutex, NULL);
 58    pthread_cond_init(&cond, NULL);
 59
 60    pthread_create(&thread1, NULL, increase, NULL);
 61    pthread_create(&thread2, NULL, printData, NULL);
 62    pthread_create(&thread3, NULL, printDataFormat, NULL);
 63
 64    pthread_join(thread1, NULL);
 65    pthread_join(thread2, NULL);
 66
 67    return 0;
 68 }

And the output of this example is

$ ./a.out
>>data = 1
>>data = 2
data : 2
>>data = 3
[[data : 3]]
>>data = 4
data : 4
>>data = 5
[[data : 5]]
>>data = 6
data : 6

I also tried a little different test using the code below.

  1 #include <stdio.h>
  2 #include <stdlib.h>
  3 #include <string.h>
  4 #include <stdint.h>
  5 #include <unistd.h>
  6 #include <pthread.h>
  7
  8 pthread_mutex_t mutex;
  9 pthread_cond_t cond;
 10
 11 static int32_t data = 0;
 12
 13 void *increase(void *arg)
 14 {
 15    int32_t ldata = 0;
 16    while(1)
 17    {
 18       pthread_mutex_lock(&mutex);
 19       data++;
 20       if (data == 1)
 21       {
 22          printf(">>data = %d\n", data);
 23          pthread_cond_signal(&cond);
 24       }
 25       ldata++;
 26       pthread_mutex_unlock(&mutex);
 27       sleep(2);
 28    }
 29 }
 30
 31 void *printData(void *arg)
 32 {
 33    while(1)
 34    {
 35       pthread_mutex_lock(&mutex);
 36       pthread_cond_wait(&cond, &mutex);
 37       printf("data : %d\n", data);
 38       pthread_mutex_unlock(&mutex);
 39    }
 40 }
 41
 42 int32_t main(void)
 43 {
 44    pthread_t thread1, thread2, thread3;
 45
 46    pthread_mutex_init(&mutex, NULL);
 47    pthread_cond_init(&cond, NULL);
 48
 49    pthread_create(&thread1, NULL, increase, NULL);
 50    pthread_create(&thread2, NULL, printData, NULL);
 51
 52    pthread_join(thread1, NULL);
 53    pthread_join(thread2, NULL);
 54
 55    return 0;
 56 }

And the result is

$ ./a.out
>>data = 1

It also looks thread printData does not receive the signal from increase. Am I misunderstanding something? Or do I have something wrong in my example code?