I had the same problem. It is due to a hardware bug.
I posted the solution here : https://help.ubuntu.com/community/MacBookPro#head-5064fd602c07a77f22bba3b2a5e31335acb16ccd
I had the same problem. It is due to a hardware bug.
I posted the solution here : https:/ /help.ubuntu. com/community/ MacBookPro# head-5064fd602c 07a77f22bba3b2a 5e31335acb16ccd