Java与多个对象/锁的同步

问题描述

我想知道是否有一个包或模型可以帮助我解决这种情况。

假设我有3个线程和一堆对象A，B ，C，D，E，F

• T1需要锁A，B


• B，C，D


• T3需要锁E，F

如果T1& T3同时运行。此外，T2& T3可以同时运行。但T1&

• 线程可以获得任意数量的锁，而不只是2.（我看到一个优雅的解决方案这个问题与固定数量的锁，但不确定我可以应用它在这里。）


• 显然， d喜欢每个线程同时获取所有需要的锁，以防止死锁。

如果有人可以指定一个包支持这个用例，或解析这个的一些代码段，请让我知道。

非常感谢。

解决方案

步骤1

为您的资源提供自然顺序。例如，如果您的资源是字母， A 会出现在 B ， code>会出现在 C 之前，等等。

现在你的线程不可能在任何时候达到死锁



• 线程1需要锁定资源 A ， B ， D code> E


• 线程2需要锁定资源 B 和 E

我们的线程必须争夺资源上的锁 B 和 D 。因为我们强制执行一个自然顺序，首先获得 B 锁的线程保证获得 D 并顺利进行。失败的线程将等待 B 被释放。

I'm wondering if there's a package or model that will help me solve this scenario.

Let's say I have 3 threads and a bunch of objects A,B,C,D,E,F

• T1 needs locks A,B
• T2 needs locks B,C,D
• T3 needs locks E,F

In this scenario, it'd be ok if T1 & T3 ran simultaneously. Also, T2 & T3 can run simultaneously. But T1 & T2 should never run simultaneously.

Also, note that

• Threads can obtain an arbitrary number of locks, not just 2. (I saw an elegant solution to this problem with a fixed number of locks but not sure I can apply it here.)
• Obviously, I'd like each thread to acquire all the needed locks at the same time to prevent deadlock.

If someone can point me to a package that supports this use case, or some snippet of code that resolves this, please let me know.

Thanks so much.

解决方案

Step 1

Provide a natural ordering for your resources. For example, if your resources were letters, A would come before B, B would come before C, and so on.

Step 2

Only allow your threads to grab resources in order.

Now your threads cannot possibly reach deadlock in any situation.

Example

• Thread 1 needs locks on resources A, B, D, and E
• Thread 2 needs locks on resources B and E

Our threads must fight for locks on resources B and D. Because we have enforced a natural order, the thread that obtains the lock on B first is guaranteed to get the lock on D and proceed smoothly. The losing thread will be waiting for B to be released.

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