在这种情况下会发生死锁吗？ [英] Does a Deadlock Occur in This Case?

问题描述

我是否正确地说在以下情况下应该发生死锁：

Am I right in saying that a deadlock is supposed to happen in the following case:

对象 P 调用对象的synch方法 A ，

调用对象 B 的同步方法，

调用对象 A的同步方法。

Object P calls a synch method of object A,
that calls a synch method of object B,
that calls a synch method of object A.

很抱歉，如果它看起来很愚蠢，很可能就是这样。但那是为什么我在问。谢谢！

Sorry if it looks stupid of me, most probably it is. But that's why I'm asking. Thanks!

推荐答案

根据您提供的信息 - 不，不会发生死锁：

By the information you give - no, a deadlock can't occur:

首先，你没有提到多个线程。单个线程不会导致死锁。但是我们假设您有多个线程。

First, you don't mention multiple threads. A single thread can't cause a deadlock. But let's assume you have multiple threads.

因此，如果任何其他对象，来自不同的线程以相反的顺序调用其中一些方法，那么可能发生死锁。

So, if any other object, from different thread invokes some of these methods in reverse order, then a deadlock can occur.

情况说明如下： Thread-1 获取所需的锁定输入 methodA ，然后尝试输入 methodB 。如果在同一时刻另一个线程 - Thread-2 调用 methodB 并获取它的锁定，然后尝试进入 methodA ，但 Thread-1 已经有锁，所以 Thread-2 等待。但是， Thread-1 无法输入 methodB ，因为 Thread-2 有锁。他们永远等待（死锁）。

The explanation of the situation is as follows: Thread-1 obtains the lock required to enter methodA, and then tries to enter methodB. If at the same moment another thread - Thread-2 invokes methodB and obtains the lock for it, then tries to enter methodA, but Thread-1 already has the lock, so Thread-2 waits. However, Thread-1 can't enter methodB because Thread-2 has the lock. And they wait forever (deadlock).

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