我正在阅读
tips and tricks帖子,我想我会尝试一些我之前从未做过的C#.因此,以下代码没有实际用途,但只是一个’测试函数’来查看发生了什么.
无论如何,我有两个静态私有字段：
private static volatile string staticVolatileTestString = ""; [ThreadStatic] private static int threadInt = 0;
如您所见,我正在测试ThreadStaticAttribute和volatile关键字.
无论如何,我有一个看起来像这样的测试方法：
private static string TestThreadStatic() {
// Firstly I'm creating 10 threads (DEFAULT_TEST_SIZE is 10) and starting them all with an anonymous method
List<Thread> startedThreads = new List<Thread>();
for (int i = 0; i < DEFAULT_TEST_SIZE; ++i) {
Thread t = new Thread(delegate(object o) {
// The anon method sets a newValue for threadInt and prints the new value to the volatile test string,then waits between 1 and 10 seconds,then prints the value for threadInt to the volatile test string again to confirm that no other thread has changed it
int newVal = randomNumberGenerator.Next(10,100);
staticVolatileTestString += Environment.NewLine + "\tthread " + ((int) o) + " setting threadInt to " + newVal;
threadInt = newVal;
Thread.Sleep(randomNumberGenerator.Next(1000,10000));
staticVolatileTestString += Environment.NewLine + "\tthread " + ((int) o) + " finished: " + threadInt;
});
t.Start(i);
startedThreads.Add(t);
}
foreach (Thread th in startedThreads) th.Join();
return staticVolatileTestString;
}
thread 0 setting threadInt to 88 thread 1 setting threadInt to 97 thread 2 setting threadInt to 11 thread 3 setting threadInt to 84 thread 4 setting threadInt to 67 thread 5 setting threadInt to 46 thread 6 setting threadInt to 94 thread 7 setting threadInt to 60 thread 8 setting threadInt to 11 thread 9 setting threadInt to 81 thread 5 finished: 46 thread 2 finished: 11 thread 4 finished: 67 thread 3 finished: 84 thread 9 finished: 81 thread 6 finished: 94 thread 7 finished: 60 thread 1 finished: 97 thread 8 finished: 11 thread 0 finished: 88
但是,我得到的是：
thread 0 setting threadInt to 88 thread 4 setting threadInt to 67 thread 6 setting threadInt to 94 thread 7 setting threadInt to 60 thread 8 setting threadInt to 11 thread 9 setting threadInt to 81 thread 5 finished: 46 thread 2 finished: 11 thread 4 finished: 67 thread 3 finished: 84 thread 9 finished: 81 thread 6 finished: 94 thread 7 finished: 60 thread 1 finished: 97 thread 8 finished: 11 thread 0 finished: 88
输出的第二个“一半”是预期的(我想这意味着ThreadStatic字段的工作方式与我想的一样),但似乎有一些初始输出已从第一个“半”中“跳过”.
另外,第一个“half”中的线程是乱序的,但我知道一旦调用Start(),线程就不会立即运行;但相反,内部操作系统控件将按其认为合适的方式启动线程.
编辑：不,他们不是,实际上,我只是认为他们是因为我的大脑错过了连续数字
所以,我的问题是：导致我在输出的前半部分丢失几行会出现什么问题？例如,’thread 3将threadInt设置为84’的位置在哪里？
解决方法
线程正在同时执行.从概念上讲,这是：
staticVolatileTestString += Environment.NewLine + "\tthread " + ((int) o) + " setting threadInt to " + newVal;
>线程1读取staticVolatileTestString
>线程2读取staticVolatileTestString
>线程3读取staticVolatileTestString
>线程1附加内容并写回staticVolatileTestString
>线程2附加内容并写回staticVolatileTestString
>线程3附加内容并写回staticVolatileTestString
这会导致你的线路丢失.挥发无助于此;连接字符串的整个过程不是原子的.您需要围绕这些操作使用锁定：
private static object sync = new object();
lock (sync) {
staticVolatileTestString += Environment.NewLine + "\tthread " + ((int) o) + " setting threadInt to " + newVal;
}
