Ensuring task execution order in threadpool

Question

I have been reading about the thread-pool pattern and I can\'t seem to find the usual solution for the following problem.

I sometimes want tasks to be executed serial

Answer 1

Since you only need to wait for a single task to complete before starting the dependent task, it can be easily done if you can schedule the dependent task in the first task. So in your second example: at the end of task 2, schedule task 7 and at the end of task 3, schedule task 4 and so on for 4->6 and 6->8.

In the beginning, just schedule tasks 1,2,5,9... and the rest should follow.

An even more general problem is when you have to wait for multiple tasks before a dependent task can start. Handling that efficiently is a non-trivial exercise.