private void incUsage(int amount) {
    if (amount < 0 && !destroyed) {
      Assert.assertTrue(usageCount - amount >= 0,
          amount + " cannot be subtracted from usageCount " + usageCount);
    }
    usageCount += amount;
  }
Increments or decrements usage count by the specified amount. Caller must synchronize on this
lock token.

@param amount the amount to inc or dec usage count by
geode-core/src/main/java/org/apache/geode/distributed/internal/locks/DLockToken.java