span.incPinCounter(offset)
			})
		} else {
			// set pin bit
			pinState.setPinned(true)
		}
	} else {
		// unpin
		if pinState.isPinned() {
			if pinState.isMultiPinned() {
				var exists bool
				// TODO(mknyszek): investigate if systemstack is necessary here
				systemstack(func() {
					offset := objIndex * span.elemsize
					exists = span.decPinCounter(offset)
				})