PLINQ语句获取内静态构造函数陷入僵局 [英] Plinq statement gets deadlocked inside static constructor

问题描述

我碰到这个情况里面静态构造函数如下PLINQ语句获取陷入僵局：

I came across this situation where the following plinq statement inside static constructor gets deadlocked:

static void Main(string[] args)
{
    new Blah();
}

class Blah
{
     static Blah()
     {
         Enumerable.Range(1, 10000)
            .AsParallel()
            .Select(n => n * 3)
            .ToList();
     }
}

这种事只有当一个构造函数是静态的。 有人可以给我讲解一下吧。

It happens only when a constructor is static. Can someone explain this to me please.

它是TPL错误吗？编译器？我？

Is it TPL bug? Compiler? Me?

推荐答案

它通常是危险的，从静态构造函数调用线程code。为了确保静态构造只执行一次，在CLR执行下一个锁定的静态构造。如果运行静态构造的线程上一个辅助线程等待，有一种危险，即助手线程将需要在CLR-内部锁出于某种原因也和程序将死锁。

It is generally dangerous to call threading code from a static constructor. In order to ensure that the static constructor executes only once, the CLR executes the static constructor under a lock. If the thread running the static constructor waits on a helper thread, there is a risk that the helper thread is going to need the CLR-internal lock for some reason too, and the program will deadlock.

下面是一个简单的code示例，演示此问题：

Here is a simpler code sample that demonstrates the problem:

using System.Threading;
class Blah
{
    static void Main() { /* Won’t run because the static constructor deadlocks. */ }

    static Blah()
    {
        Thread thread = new Thread(ThreadBody);
        thread.Start();
        thread.Join();
    }

    static void ThreadBody() { }
}

第10.5.3.3竞赛和死锁的的 ECMA CLI规范保证如下：

类型单独初始化不得产生死锁，除非一些code   从类型初始化（直接或间接）明确要求   将调用阻塞操作。

Type initialization alone shall not create a deadlock unless some code called from a type initializer (directly or indirectly) explicitly invokes blocking operations.

所以，一个类型初始化（即静态构造函数）不会死锁，但在静态构造函数块没有操作的线程。如果静态构造函数做块，这样做可能会陷入僵局。

So, a type initializer (i.e., a static constructor) will not deadlock, provided that no operation in the static constructor blocks the thread. If the static constructor does block, it risks a deadlock.

这篇关于PLINQ语句获取内静态构造函数陷入僵局的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！