Question

Is there any way so I can have up to 10 threads in the same mutex?

Something like sem_wait() with value 10.

Edit:

Found this:

it is an implementation of semaphores, using mutexes and condition variables.

typedef struct {
  int value, wakeups;
  Mutex *mutex;
  Cond *cond;
} Semaphore;

// SEMAPHORE

Semaphore *make_semaphore (int value)
{
  Semaphore *semaphore = check_malloc (sizeof(Semaphore));
  semaphore->value = value;
  semaphore->wakeups = 0;
  semaphore->mutex = make_mutex ();
  semaphore->cond = make_cond ();
  return semaphore;
}

void sem_wait (Semaphore *semaphore)
{
  mutex_lock (semaphore->mutex);
  semaphore->value--;

  if (semaphore->value < 0) {
    do {
      cond_wait (semaphore->cond, semaphore->mutex);
    } while (semaphore->wakeups < 1);
    semaphore->wakeups--;
  }
  mutex_unlock (semaphore->mutex);
}

void sem_signal (Semaphore *semaphore)
{
  mutex_lock (semaphore->mutex);
  semaphore->value++;

  if (semaphore->value <= 0) {
    semaphore->wakeups++;
    cond_signal (semaphore->cond);
  }
  mutex_unlock (semaphore->mutex);
}

Answer 1

No, A mutex is a simple lock, having two states: locked and unlocked. When it is created, a mutex is unlocked. A mutex is a mutual exclusion lock. Only one thread can hold the lock.

Although you can implement to allow ten threads to enter in a section using mutex and if and a global variable. (the way count semaphores are implemented)

Read here: Implementing a Counting Semaphore
One Available implementation: C code , Make your own semaphore