i dont know why my threads in C dont work in parallel - pthreads

Question

I'm trying to write a program to simulate an aircraft carrier running on threads in Cand I don't know why my threads seem to run after each other
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#define N 15 // sapaces for planes on carrier
#define K 9 // a number less than n, and if there are currently fewer than K aircraft on the carrier, landing aircraft have priority
#define S 1
pthread_mutex_t mutex;
pthread_cond_t landing_cond;
pthread_cond_t takeoff_cond;
int planes_on_deck = 0;
void* landing() {
while(1) {
pthread_mutex_lock(&mutex);
while (planes_on_deck>=N) {
pthread_cond_wait(&landing_cond, &mutex);
}
planes_on_deck++;
printf("landing.\n");
Sleep(1000);
printf("number of planes on carrier: %d\n\n", planes_on_deck);
pthread_mutex_unlock(&mutex);
pthread_cond_broadcast(&takeoff_cond);
}
return 0;
}
void* takeoff() {
while(1) {
pthread_mutex_lock(&mutex);
while (planes_on_deck < K) {
pthread_cond_wait(&takeoff_cond, &mutex);
}
planes_on_deck--;
printf("takeoff.\n");
Sleep(1000);
printf("number of planes on carrier: %d\n\n", planes_on_deck);
pthread_mutex_unlock(&mutex);
pthread_cond_broadcast(&landing_cond);
}
return 0;
}
int main() {
printf("number of planes on carrier: %d\n", planes_on_deck);
pthread_t landing_threads[S];
pthread_t takeoff_threads[S];
pthread_mutex_init(&mutex, NULL);
pthread_cond_init(&landing_cond, NULL);
pthread_cond_init(&takeoff_cond, NULL);
for (int i = 0; i < S; i++){
if (pthread_create(&landing_threads[i], NULL, &landing, NULL) != 0){
perror("fail");
}
if (pthread_create(&takeoff_threads[i], NULL, &takeoff, NULL) != 0){
perror("fail");
}
}
for (int i = 0; i < S; i++){
if (pthread_join(takeoff_threads[i], NULL) != 0){
return 2;
}
if (pthread_join(landing_threads[i], NULL) != 0){
return 2;
}
}
pthread_mutex_destroy(&mutex);
pthread_cond_destroy(&landing_cond);
pthread_cond_destroy(&takeoff_cond);
return 0;
}
at the beginning it starts to list landing planes as it should and when it reaches K it should give the opportunity for planes to take off
but he does so only when he reaches the space limit on the ship
Maybe you can tell me, what's wrong with my program, why it behaves the way it does

Answer 1

why it behaves the way it does
You call Sleep() with the mutex held. That prevents the other thread from doing anything. You should unlock the mutex before going to sleep.
In general, sleeping (or doing other long operations, like reading from a remote socket or opening a file) with a mutex held is almost always wrong.