On June 10, a new fix released that fixes a bug in SQL 2012 SP1. It's not included in CU#9 that's included in SP2 so if you choose to install it, you need to delay SP2 until the first CU#1 for SP2 relaeased. 

​The fix is very important becuase the bug is causing data loss when rebuilding indexes with some options enabled and deadlock happened during the rebuilding. The full documentation in the link below. 

FIX: Data loss in clustered index occurs when you run online build index in SQL Server 2012: