Creating Task cause Site/CP to hang
I recently dealt with a similar issue. Keep your tasks small and quick by using subtasks or by creating multiple instances of your main task. In your example, make each entry creation its own tasks or subtask, so that each step only has one process to take care of. You can have a private array on the task object to store an array of entry data to iterate through. 

private $entry_data = array();
//Fill array with the data you want to use

public function runStep($step)
{

    $new_entry = $entry_data[$step];
    //code to create new entry

    return true;

}