Example concurrency test programs for WT-10905, WT-12349, and WT-13450 showed the need for a new control point action: barrier.

In all of them a thread waits for another thread to trigger a control point. If the control point is triggered before the waiting thread waits, the waiting thread never wakes up.

This is not always a problem. The example control point program does not have this problem.

The solution is new control point action “Barrier” where the thread(s) calling the control point wait and the thread defining the control point waits if the control point triggers. When all are waiting, all wakeup.