[Boost-users] proper way to wait for threads ends

Hello I m writting a program which create threads following commands received on a socket connection. When exiting, I'd like to wait that all dynamically created threads have ended their jobs. I thought about using a shared variable (with mutual exclusion) that threads would increment at start and decrement at end. And then the program would stop, loop on sleep() while this shared variable is still > 0. Is there a better way to wait for the end of threads ?