Microsoft KB Archive/170288

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CMWAIT returns incorrectly after canceling CMALLC with CMCANC

Article ID: 170288

Article Last Modified on 6/28/2004


  • Microsoft SNA Server 3.0
  • Microsoft SNA Server 2.11 Service Pack 1
  • Microsoft SNA Server 2.11 Service Pack 2
  • Microsoft SNA Server 3.0 Service Pack 4
  • Microsoft SNA Server 4.0

This article was previously published under Q170288


When you use the SNA Server Win32 asynchronous CPIC interface, a CPIC application may encounter problems when you cancell an Allocate (CMALLC) call with Cancel_Conversation (CMCANC).

After you cancel a CMALLC using CMCANC, subsequent attempts to issue CMALLC in non-blocking mode appear to show that CMWAIT returns immediately, without waiting for the CMALLC async final completion.


Canceling an asynchronous CPI-C call (not ones that would complete by posting a Windows message) does not work correctly. Later CMWAITs return early because they pick up false completions from the cancelled calls.


Microsoft has confirmed this to be a problem in SNA Server versions 2.11, 2.11 Service Pack 1 (SP1), 2.11 Service Pack 2 (SP2), 3.0, and 3.0 Service Pack 1 (SP1).

This problem was corrected in the latest SNA Server version 3.0 U.S. Service Pack. For information on obtaining this Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):


A supported fix for SNA Server version 2.11 is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.


The following sequence was observed in an SNA Application CPIC API trace:

   CMINIT ->
      <- CMINIT OK
   CMSPM (set non-blocking mode)
      <- CMSPM OK
   CMALLC ->
      <- CMALLC (operation incomplete)
   CMCANC ->
      <- CMALLC (allocation_failure_no_retry)
      <- CMCANC OK
   CMINIT ->
      <- CMINIT OK
   CMSPM (set non-blocking mode) ->
      <- CMSPM OK
   CMALLC ->
      <- CMALLC (operation incomplete)
   CMWAIT ->
      <- CMWAIT OK
   CMDEAL ->
      <- CMDEAL (error = state_check)
      <- CMALLC OK

Keywords: kbbug kbfix kbnetwork kbprogramming KB170288