I've been seeing some hangs in ./test threading

I think one problem can be fixed by this patch:

diff --git a/util/thread_pool.cpp b/util/thread_pool.cpp
index e20aab1..b95bc1d 100644
— a/util/thread_pool.cpp
+++ b/util/thread_pool.cpp
@@ -99,8 +99,8 @@ ThreadPool::~ThreadPool(){
}

void ThreadPool::join(){
+ boostlock lock(_mutex);
while(_tasksRemaining)

{ - boostlock lock(_mutex); _condition.wait(lock); }

}

As is, join() might check _tasksRemaining while task_done() has the mutex but before task_done() has decremented _tasksRemaining. So race condition is:

1) task_done() grabs _mutex
2) join() sees that _tasksRemaining > 0, then waits for _mutex
3) task_done() decrements _tasksRemaining and signals _condition
4) join() grabs _mutex and waits for _condition

Not that familiar w/ the code, let me know what you think.