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wayofthefuture
wayofthefuture

Reputation: 9445

Thread not seeing global boolean

For some reason, I cannot get the thread to end when calling Thread.Join(). Am I crazy?

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

Upvotes: 0

Views: 60

Answers (2)

dbasnett
dbasnett

Reputation: 11773

Here is the test I ran, slightly modified.

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

Upvotes: 1

usr
usr

Reputation: 171226

You haven't synchronized access to _continue. For that reason it was probably enregistered by the JIT. Synchronize access to it (for example using Thread.MemoryBarrier) before reading it and after writing it.

Sharing data without synchronization is always a red flag. Be it because the program becomes buggy or be it because most people do not understand the rules well enough to make sure it is safe (I certainly don't - so I don't do it).

Upvotes: 0

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