A barrier breakpoint is similar to a simple breakpoint, differing only in that it holds processes and threads that reach the barrier point. Other processes and threads continue to run. TotalView holds these processes or threads until all processes or threads defined in the barrier point reach this same place. When the last one reaches a barrier point, TotalView releases all the held processes or threads, but they do not continue executing until you explicitly restart execution. In this way, barrier points let you synchronize your program’s execution.
“About Barrier Breakpoint States”