如何使C（P /调用）code，从C＃＆QUOT调用;线程安全＆QUOT; [英] How to make C (P/invoke) code called from C# "Thread-safe"

问题描述

我有一些简单的C code，它使用一个全局变量。显然，这不是线程安全的，所以当我使用P / Invoke在C＃中调用它从多个线程，事情搞砸了。

I have some simple C-code which uses a single global-variable. Obviously this is not thread-safe, so when I call it from multiple threads in C# using P/invoke, things screw up.

如何可以我要么导入该功能分别为每个线程，或使其线程安全的？

我试过声明变量 __ declspec（线程），但导致程序崩溃。我也试着做一个C ++ / CLI类，但它不允许成员函数是 __ declspec（裸），这是我需要的（我使用内联汇编）的。我不是很有经验编写多线程C ++ code，所以有可能是我丢失的东西。

I tried declaring the variable __declspec(thread), but that caused the program to crash. I also tried making a C++/CLI class, but it doesn't allow member-functions to be __declspec(naked), which I need (I'm using inline-assembly). I'm not very experienced writing multi-threaded C++ code, so there might be something I'm missing.

下面是一些例子code：

Here is some example code:

C＃

[DllImport("MyDll.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern int SomeFunction(int parameter1, int parameter2);

C ++

extern "C"
{
    int someGlobalVariable;
    int __declspec(naked) _someFunction(int parameter1, int parameter2)
    {
        __asm
        {
            //someGlobalVariable read/written here
        }
    }
    int __declspec(dllexport) SomeFunction(int parameter1, int parameter2)
    {
        return _someFunction(parameter1, parameter2);
    }
}

---

：结果 SomeFunction（）必须基于一些prescribed秩序someGlobalVariable 的（想想如的。一个PRNG，与 someGlobalVariable 作为内部状态）的。因此，使用互斥体或其他类型的锁是不是一种选择 - 每个线程的必须的有它自己的拷贝 someGlobalVariable

---

: The result of SomeFunction() must go in some prescribed order based on someGlobalVariable (think of eg. a PRNG, with someGlobalVariable as the internal state). So, using a mutex or other sort of lock is not an option - each thread must have its own copy of someGlobalVariable.

推荐答案

一个常见的​​模式是有

A common pattern is to have

• 对于国家分配内存功能，


• 有没有副作用，但功能突变传入的状态，


• ，释放为国家memoy的功能。

C＃的一面是这样的：

The C# side would look like this:

的用法：的

var state = new ThreadLocal<SomeSafeHandle>(NativeMethods.CreateSomeState);

Parallel.For(0, 100, i =>
{
    var result = NativeMethods.SomeFunction(state.Value, i, 42);

    Console.WriteLine(result);
});

的声明：的

internal static class NativeMethods
{
    [DllImport("MyDll.dll", CallingConvention = CallingConvention.Cdecl)]
    public static extern SomeSafeHandle CreateSomeState();

    [DllImport("MyDll.dll", CallingConvention = CallingConvention.Cdecl)]
    public static extern int SomeFunction(SomeSafeHandle handle,
                                          int parameter1,
                                          int parameter2);

    [DllImport("MyDll.dll", CallingConvention = CallingConvention.Cdecl)]
    internal static extern int FreeSomeState(IntPtr handle);
}

的的SafeHandle法宝：的

[SecurityPermission(SecurityAction.InheritanceDemand, UnmanagedCode = true)]
[SecurityPermission(SecurityAction.Demand, UnmanagedCode = true)]
internal class SomeSafeHandle : SafeHandle
{
    [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
    public SomeSafeHandle()
        : base(IntPtr.Zero, true)
    {
    }

    public override bool IsInvalid
    {
        get { return this.handle == IntPtr.Zero; }
    }

    [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
    protected override bool ReleaseHandle()
    {
        return NativeMethods.FreeSomeState(this.handle) == 0;
    }
}

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