US hedge fund Greenlight Capital Thursday filed suit against Apple as it boosted pressure on the tech giant to unleash to shareholders the value of its huge capital stockpile. Greenlight sued the maker of iPhones and iPads to block a shareholder vote that includes a proposal, supported by management, to make it impossible for the Apple board to decide to issue preferred stock. The hedge fund alleged that Apple violated US securities policies by "bundling" the proposal on preferred stock with two other shareholder-friendly measures.