Question

我们有一些遗留代码可以测试许多类的线程安全性。最近的硬件升级（从2到4核心）呈现随机故障，异常访问List＆lt;＆gt;中的项目。

        [Test]
        public void CheckThreadSafeInThreadPool()
        {
            Console.WriteLine("Initialised ThreadLocalDataContextStore...");
            var container = new ContextContainerTest();
            Console.WriteLine("Starting...");
            container.StartPool();
            while (container.ThreadNumber < 5)
            {
                Thread.Sleep(1000);
            }

            foreach (var message in container.Messages)
            {
                Console.WriteLine(message);
                if (message.Contains("A supposedly new thread is able to see the old value"))
                {
                    Assert.Fail("Thread leaked values - not thread safe");
                }
            }

            Console.WriteLine("Complete");

        }




public class ContextContainerTest
    {
        private ThreadLocalDataContextStore store;
        public int ThreadNumber;
        public List<string> Messages;

        public void StartPool()
        {
            Messages = new List<string>();

            store = new ThreadLocalDataContextStore();
            store.ClearContext();
            var msoContext = new MsoContext();
            msoContext.Principal = new GenericPrincipal(new GenericIdentity("0"), null);
            store.StoreContext(msoContext);

            for (var counter = 0; counter < 5; counter++)
            {
                Messages.Add(string.Format("Assigning work item {0}", counter));
                ThreadPool.QueueUserWorkItem(ExecuteMe, counter);
            }
        }

        public void ExecuteMe(object input)
        {

            string hashCode = Thread.CurrentThread.GetHashCode().ToString();

            if (store.GetContext() == null || store.GetContext().Principal == null)
            {
                Messages.Add(string.Format("[{0}] A New Thread", hashCode));
                var msoContext = new MsoContext();
                msoContext.Principal = new GenericPrincipal(new GenericIdentity("2"), null);
                store.StoreContext(msoContext);
            }
            else if (store.GetContext().Principal.Identity.Name == "1")
            {
                Messages.Add(string.Format("[{0}] Thread reused", hashCode));
            }
            else
            {
                Messages.Add(string.Format("[{0}] A supposedly new thread is able to see the old value {1}"
                    , hashCode, store.GetContext().GetDiagnosticInformation()));
            }

            Messages.Add(string.Format("[{0}] Context at starting: {1}", hashCode, store.GetContext().GetDiagnosticInformation()));
            store.GetContext().SetAsCurrent(new GenericPrincipal(new GenericIdentity("99"), null));
            Messages.Add(string.Format("[{0}] Context at End: {1}", hashCode, store.GetContext().GetDiagnosticInformation()));
            store.GetContext().SetAsCurrent(new GenericPrincipal(new GenericIdentity("1"), null));

            Thread.Sleep(80);
            ThreadNumber++;
        }


    }

失败是随机的，发生在测试本身的代码的下一部分;

        foreach (var message in container.Messages)
        {
            Console.WriteLine(message);
            if (message.Contains("A supposedly new thread is able to see the old value"))
            {
                Assert.Fail("Thread leaked values - not thread safe");
            }
        }

一个微妙的变化解决了这个问题，但有人在唠叨我们不应该这样做，如果消息不是，为什么消息为空，为什么它在大多数时间工作而不是其他人。

 if (message != null && message.Contains("A supposedly new thread is able to see the old value"))
{
}

另一个解决方案是将List更改为线程安全，但这并不能解决为什么问题首先出现。

Answer 1

List<T>不是线程安全元素，如果您使用.Net 4及更高版本，则可以使用ConcurrentBag<T>中的System.Collection.Concurrent，如果年龄较大，则必须自己实现。{1}}。请参阅this可能会有帮助。

希望我能提供帮助。

测试线程安全的单元测试 - 对象无法随机提供

1 个答案: