A benign data-race is an intentional data-race whose existence does not affect the correctness of the program.
Some multi-threaded applications intentionally use code that may cause data-races. Since the data-races are there by design, no fix is required. In some cases, however, it is quite tricky to get such codes to run correctly. These data-races should be reviewed carefully.
See 2.5 False Positives for more detailed information about benign races.