This article was previously published under Q198839
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Debugging a multithreaded application on a multiprocessor machine mayshow that at some point the asynchronous break fails after abreakpoint is encountered more than once. The CPU usage shows 100 percent busy for all processors in the application that is being debugged. However, this application is not running any useful code and you can not break into it.
In some cases, you may find that the debugger does not break at abreakpoint.
This occurs because of the way that a breakpoint is marked and resumed in a multithreaded application, which affects thread resume operations in amultiprocessor machine.
Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article. This bug was corrected in Visual Studio 6.0 Service Pack 3. For more information about Visual Studio service packs, please see the following articles in the Microsoft Knowledge Base: