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发布于 2024-08-20 23:54:23 字数 387 浏览 6 评论 0原文

这段代码是线程安全的吗？或者这样说：

是否有办法调用 GetIt() 并且 GetIt() 会将相同的数字返回给 2 个不同的线程

Private Shared hitCount As Long = 1

Public Shared Function GetIt() As Long
     Threading.Interlocked.Increment(hitCount)
     DoSomethingQuick(hitCount)
     Return hitCount
End Function

看起来这是可能的，那么我应该使用 Interlocked.Read() 还是将整个内容锁定在一个块中？

原文

Is this code thread-safe? or put it this way:

Is there anyway to call GetIt() and that GetIt() will return the same number to 2 different threads

Private Shared hitCount As Long = 1

Public Shared Function GetIt() As Long
     Threading.Interlocked.Increment(hitCount)
     DoSomethingQuick(hitCount)
     Return hitCount
End Function

It seems like it's possible, then am I supposed to use Interlocked.Read() or lock the whole thing in one block?

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海螺姑娘 2024-08-27 23:54:23

是的，有一种可能性：

线程 1 运行 Threading.Interlocked.Increment(hitCount)
线程 2 运行 Threading.Interlocked.Increment(hitCount)
线程 1 运行 返回 hitCount
线程 2 运行 返回 hitCount

在步骤 3 和 4 中，hitCount 将是相同的值。

但解决方法很简单 Interlocked.Increment 返回增量值，因此只需将代码更改为：

Private Shared hitCount As Long = 1L

Public Shared Function GetIt() As Long
     Return Threading.Interlocked.Increment(hitCount)
End Function

编辑
或者现在根据您的编辑，您有一个相当大的时间漏洞。不管怎样，这就是你想要的：

Public Shared Function GetIt() As Long
     Dim localHitCount As Long = Threading.Interlocked.Increment(hitCount)
     Console.Writeline("Something, something....")
     Return localHitCount 
End Function

编辑
然后这样做（这正是迈克尔在下面建议的）

Private Shared hitCount As Long = 1L

Public Shared Function GetIt() As Long
     Dim localHitCount As Long = Threading.Interlocked.Increment(hitCount)
     DoSomethingQuick(localHitCount )
     Return localHitCount 
End Function

Yes there is a possibility:

Thread 1 runs Threading.Interlocked.Increment(hitCount)
Thread 2 runs Threading.Interlocked.Increment(hitCount)
Thread 1 runs Return hitCount
Thread 2 runs Return hitCount

In steps 3 and 4, hitCount will be the same value.

But the fix is easy Interlocked.Increment returns the incremented value, so just change your code to:

Private Shared hitCount As Long = 1L

Public Shared Function GetIt() As Long
     Return Threading.Interlocked.Increment(hitCount)
End Function

Edit
Or now based on your edit, you have a pretty bit timing hole. Anyway then this is what you want:

Public Shared Function GetIt() As Long
     Dim localHitCount As Long = Threading.Interlocked.Increment(hitCount)
     Console.Writeline("Something, something....")
     Return localHitCount 
End Function

Edit
Then do this (which is exactly what Michael suggested below)

Private Shared hitCount As Long = 1L

Public Shared Function GetIt() As Long
     Dim localHitCount As Long = Threading.Interlocked.Increment(hitCount)
     DoSomethingQuick(localHitCount )
     Return localHitCount 
End Function

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