Bug: paused pool does a hidden busy loop

[guilhermelawless]

Once a pool is paused and a task received, the worker wait is skipped it repeats the loop until unpaused. This makes workers enter a busy loop with max CPU usage.

Did not find a way to test for this in the testing code.

Fix:

• Change the worker wait condition to task_available_cv.wait(tasks_lock, [this] { return (!tasks.empty() && !paused) || !workers_running; });
• Add task_available_cv.notify_all(); in unpause()

[bshoshany]

Thanks for the bug report! This somehow slipped through the cracks. I don't think there's any way to automate this test, since the C++ standard library does not allow you to check CPU utilization of a thread, but I did a quick test and I can confirm that this bug exists and that your fix resolves it.

The fix will be implemented in release v3.6.0, which should hopefully be available within a few weeks (even sooner if I can find the time). Thanks again :)