是可变的分配和读取原子操作？ [英] Is variable assignment and reading atomic operation?

问题描述

我无法找到在任何单证参考这个...

I was unable to find any reference to this in the documentations...

时分配给一个双（或任何其它的简单类型，包括布尔值）的原子操作从线程的角度来看

Is assigning to a double (or any other simple type, including boolean) an atomic operation viewed from the perspective of threads?

double value = 0;

public void First() {
 while(true) {
  value = (new Random()).NextDouble();
 }
}

public void Second() {
 while(true) {
  Console.WriteLine(value);
 }
}

在此code样品，第一种方法称为在一个线程中，并且第二中另一个。第二种方法可以得到一个搞砸值，如果它分配期间得到其执行的变量在另一个线程？

In this code sample, first method is called in one thread, and the second in another. Can the second method get a messed up value if it gets its execution during assignment to the variable in another thread?

我不在乎，如果我收到的旧值，这是唯一重要的，以获得一个有效的值（并非出2出的8字节设置）。我知道这是一个愚蠢的问题，但我想可以肯定的，因为我不知道CLR实际上是怎样设置的变量。

I don't care if I receive the old value, it's only important to receive a valid value (not one where 2 out of 8 bytes are set). I know it's a stupid question, but I want to be sure, cause I don't know how CLR actually sets the variables.

推荐答案

要回答你的问题，没有。分配到双打不保证为是原子的。该文档可这里。基本上，＆LT; = 32位内置类型是原子，> = 64位的类型都没有。有关64位类型的原子操作，您可以使用<一的方法href="http://msdn.microsoft.com/en-us/library/system.threading.interlocked.aspx">System.Threading.Interlocked

To answer your question, no. Assignments to doubles are not guarenteed to be atomic. The docs are available here. Basically, <= 32-bit built-in types are atomic, >= 64-bit types aren't. For atomic operations on 64bit types, you can use the methods on System.Threading.Interlocked

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