docs: public void unlockBuffer() throws IllegalStateException {
          int locks = lockCount.decrementAndGet();
          if (locks < 0) {
              throw new IllegalStateException(
                  "Buffer not locked or released already.");
          }
          if (locks == 0) {
              if (linkedTo != null) {
                  backing = savedBacking;
                  linkedTo.unlockBuffer();
                  linkedTo = null;
              }
              manager.recollect(this);
          }
      }