LogSeq/pages/OSTEP Code Snippets.md

• Spin Lock Implement id:: 6436aafd-c85f-414c-8aee-acdc71e9138e

  • void lock(lock_t *lock) {
      while (TestAndSet(&lock->status, 1) == 1);
    }
    void unlock(lock_t *lock) { lock->status = 0; }
    

• Test-And-Set Code Description id:: 6436af87-3f1b-4ee8-a2c8-4de0f1961f1a

  • int TestAndSet(int *old_ptr, int new) {
      int old = *old_ptr;
      *old_ptr = new;
      return old;
    }
    

• Ticket Lock Implement id:: 6436af5c-0000-4bfb-9a27-1d7cf0a830db

  • struct lock_t{
      int ticket;
      int turn;
    };
    void lock(lock_t *lock) {
      int myturn = FetchAndAdd(&lock->ticket);
      // atomically allocate a ticket as the thread's turn
      while (lock->turn != myturn) ;
      // wait for its turn
    }
    void unlock(lock_t *lock) {
      lock->turn += 1;
    }
    

• Lock with Queue Implement id:: 6436b05f-2873-4af4-952c-86d82685b583

  • struct lock_t{
      int lk;
      int guard; // spin lock for the whole lock
      queue_t *q; // control who gets the lock next
    };
    void lock(lock_t *lock) {
      while (TestAndSet(&m->guard, 1) == 1) ;
      if (m->lk == 0) {
        m->lk =  1;
        m->guard = 0;
      }
      else {
        m->q->add(get_tid());
        setpark(); // newly added
        m->guard = 0;
        // ---- wakeup/waiting race ----
        park();
      }
    }
    void unlock(lock_t *lock) {
      while (TestAndSet(&m->guard, 1) == 1) ;
      if (m->q->empty())
        m->flag = 0;
      else
        unpark(m->q->pop()); // should not clear flag here
      // Wake up Only one waiting thread
      m->guard = 0;
    }
    

• Producer/Consumer Solution with Condition Variable id:: 6436b07d-9279-46bb-9c6b-985eb2324df8

  • cond_t empty, fill;
    mutex_t mutex;
    void *producer(void *arg) {
      int i;
      for (i = 0; i < loops; i++) {
        Pthread_mutex_lock(&mutex);
        while (count == MAX)
          Pthread_cond_wait(&empty, &mutex);
        put(i);
        Pthread_cond_signal(&fill);
        Pthread_mutex_unlock(&mutex);
      }
    }
    void *consumer(void *arg) {
      int i;
      for (i = 0; i < loops; i++) {
        Pthread_mutex_lock(&mutex);
        while (count == 0)
          Pthread_cond_wait(&fill, &mutex);
        int tmp = get();
        Pthread_cond_signal(&empty);
        Pthread_mutex_unlock(&mutex);
        printf("%d\n", tmp);
      }
    }
    

• Producer/Consumer Solution with Semaphore id:: 6436b15a-98b4-49be-8cdf-abefcf7e60b1

  • int empty = MAX, full = 0, mutex = 1;
    void *producer() {
      for (int i = 0; i < loops; ++ i) {
        sem_wait(&empty);
        sem_wait(&mutex);
        put(i);
        sem_post(&mutex);
        sem_post(&full);
      }
    }
    void *consumer() {
      for (int i = 0; i < loops; ++ i) {
        sem_wait(&full);
        sem_wait(&mutex);
        int tmp = get();
        sem_post(&mutex);
        sem_post(&empty);
        printf("%d\n", tmp);
      }
    }