.net - 线程没有看到全局布尔值

Question

出于某种原因，我无法在调用 Thread.Join() 时结束线程。我疯了吗？

Public Sub StartThread()
    _opsthread = New Thread(AddressOf OpsThread)
    _opsthread.IsBackground = True
    _opsthread.Start()
End Sub

Public Sub StopThread()
    _continue = False
    _opsthread.Join()
    'Application Hangs Here
End Sub

Public Sub OpsThread()
    While _continue
        Thread.Sleep(1000)
    End While
End Sub

Answer 1

这是我运行的测试，稍作修改。

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Button1.Enabled = False
    StartThread()
End Sub

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
    StopThread()
End Sub

Dim _opsthread As Threading.Thread
Dim _continue As New Threading.AutoResetEvent(False)

Public Sub StartThread()
    _continue.Reset()
    _opsthread = New Threading.Thread(AddressOf OpsThread)
    _opsthread.IsBackground = True
    _opsthread.Start()
End Sub

Public Sub StopThread()
    If IsNothing(_opsthread) Then Exit Sub
    _continue.Set()
    _opsthread.Join()
    'Application Hangs Here
    ' Debug.WriteLine("end")
End Sub

Public Sub OpsThread()
    Dim cont As Boolean = False
    While Not cont
        cont = _continue.WaitOne(1000)
    End While
End Sub

Answer 2

您尚未同步访问_continue. 出于这个原因，它可能是由 JIT 注册的。Thread.MemoryBarrier在读取它之前和写入它之后同步对它的访问（例如使用）。

在没有同步的情况下共享数据始终是一个危险信号。是因为程序变得有问题，还是因为大多数人对规则的理解不够好，无法确保它是安全的（我当然不知道——所以我不这样做）。