Microsoft KB Archive/138812

= Calls to an OLE Object Should Not Be Done from DllMain =

Article ID: 138812

Article Last Modified on 12/3/2003

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APPLIES TO

 Microsoft OLE 4.0, when used with:  Microsoft Windows NT 3.51 Service Pack 5

 Microsoft Windows NT 4.0

 Microsoft Windows 95

 Microsoft Windows 2000 Standard Edition</li></ul> </li></ul>

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This article was previously published under Q138812

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SUMMARY
OLE operations involving calls to an OLE object should not be done in the DllMain function of a DLL because a deadlock can occur.

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MORE INFORMATION
This is because these OLE operations can cause the creation of a background OLE thread (for RPC), and that background OLE thread needs to call into each DllMain in the process. However this thread cannot call the DllMain of the DLL that is doing the OLE operation because DllMain is not re-entrant. Consequently a deadlock occurs. This deadlock always occurs with Windows NT and under certain conditions with Windows 95.

The DLL should do these OLE operations in another function and should export this function so that the DLL client can call the function after the DLL is loaded.

Additional query words: COM hang respond

Keywords: kbprogramming KB138812

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