It's not official, but the lineup for Chicago's annual summer festival Lollapalooza is beginning to leak -- and Lady Gaga, Green Day, and reunited Seattle grunge rockers Soundgarden are expected to headline the three-day event this August, sources tell the Daily Swarm. Meanwhile, the Chicago Tribune is reporting that negotiations with Arcade Fire and the Strokes are nearly finalized, and adds that Yeasayer, the xx, Dirty Projectors, Cut Copy, and Hot Chip are confirmed to perform. The complete lineup for the festival -- slated to hit Grant Park Aug. 6-8 -- will be announced in late Spring. Lady Gaga, Green Day, and Soundgarden have all played Lollapalooza before. Green Day rocked the 1994 installation of the fest, then a touring event before it planted roots in the Windy City. Soundgarden was a mainstage act on the 1992 tour, alongside Ice Cube, Pearl Jam, and Red Hot Chili Peppers, and performed in 1996, too. The 2010 fest is the first scheduled performance from Chris Cornell and Co. since ending a 12-year split and officially reuniting in January. Gaga performed at the 2007 edition of Lollapalooza -- but you'd hardly recognize her. Then a brunette, she wore knee-high lace stockings, a black bikini bottom, and a glittery, mirror-ball bra. Check out sexy photos of her '07 performance here. Can't wait for Lolla 2010? Relive last year's festival right here.