如何在不使用dispatch_get_current_queue()的情况下验证我正在一个给定的GCD队列上运行?

Recently, I had the need for a function that I could use to guarantee synchronous execution of a given block on a particular serial dispatch queue. There was the possibility that this shared function could be called from something already running on that queue, so I needed to check for this case in order to prevent a deadlock from a synchronous dispatch to the same queue.Recently, I had the need for a function that I