A data race requires multiple threads to access the same memory at the same time and at least one of them to be writing the data. There is no data race in your

A data race requires multiple threads to access the same memory at the same time and at least one of them to be writing the data. There is no data race in your example, since the fragments are all written to different parts of memory, unless you had something else reading the message while the individual fragments were still being written.