message: avoiding a subtract with overflow
diff: @@ -75,7 +75,10 @@ impl RecursiveMutex {
  // But let's just trust our code using this function for the sake of simplicity and performance.
  // Decrement the counter (recursive mutex behavior).
  + if locked_state.count > 0 {
  locked_state.count -= 1;
  + }
  +
  if locked_state.count == 0 {
  // Release the entire recursive mutex.
  locked_state.current_tid = None;
  