Microsoft KB Archive/106479

= Threaded recv Blocks Indefinitely if no Data Available =

Article ID: 106479

Article Last Modified on 9/30/2003

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APPLIES TO


 * Microsoft LAN Manager 2.2 Standard Edition

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This article was previously published under Q106479



SYMPTOMS
The LAN Manager 2.2 SOCKDRV.OS2 sockets call recv will block indefinitely if data is not available in the receive window when called from a separate thread.



CAUSE
Socket data structures are allocated on a per-process basis. When the first thread calls recv and blocks, flags are set to indicate this. When the second thread calls send the socket's flags are reset, losing the state information on the blocked recv. This is a classic case of one thread stomping on another by means of the shared data segment.



STATUS
This behavior is by design. The problem is avoided if multi-threaded applications send and recv on separate sockets.



STEPS TO DUPLICATE CONDITION
If you want to demonstrate this problem, write an application that calls a thread that issues a recv and then sends data to itself on the same socket.

Additional query words: 2.20

Keywords: KB106479

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