Console.WriteLine对线程同步的影响

int a = 0;
List<Task> tasks3 = new List<Task>();
for (int m = 0; m < 20; m++)
{
    Task task = Task.Run(() =>
    {
        for (int i = 0; i < 600; i++)
        {
            a = a + 1;

            Console.WriteLine("task" + Thread.CurrentThread.ManagedThreadId + ":" + i + $",a:{a}");
        }
    });
    tasks3.Add(task);
}

await Task.WhenAll(tasks3);
Console.WriteLine(a);
Console.ReadKey();