Hi, Somewhat longer-than-normal-noise follows :) Consider the following pseudo-code which has a race condition: condition g_some_cond; mutex g_condition_mtx; void thread_fn() { { ... // get lock g_some_cond.wait(condition_lock); } // do work } void main_thread() { thread_group grp; // Start all threads and have them wait on the condition for(i in [0,N)) grp.create_thread(&thread_fn); { ... // get lock g_some_cond.notify_all(); // let threads continue } } The race condition is of course that it is possible that not all threads actually start waiting on the condition before notify_all() is called. In this case, it is possible to solve the race condition in two ways: 1) Have the last thread that reaches the condition wait, signal to the main thread 2) Have the main thread checking the condition before notify_all() I don't really like the first case because it requires bi-directional signalling between the threads. Though in my ignorance, I really do consider it the correct solution. The second solution would look something like this: while(true) { scoped_lock cond_lock(g_condition_mtx); // .num_waiting_threads() is made up if(N_EXPECTED_THREADS==g_some_cond.num_waiting_threads()){break;} // release lock } Should the second pattern be encapsulated in the condition object somehow? It is almost like timed_wait(mtx,xt,pred) but there is no timeout. So maybe untimed_wait()? Is there another way to do this? Thanks for your eyes! Sohail