THREAD_BLOCKING Error After WinAPPCCleanup Issued

ID: Q236797

The information in this article applies to:

Microsoft SNA Server, versions 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 3.0 SP4, 4.0, 4.0 SP1, 4.0 SP2

SYMPTOMS

An APPC or CPI-C application may receive the following error message when it issues a TP_STARTED call that informs the APPC library that the TP (Transaction Program) is starting:

Primary Return Code = F006 (AP_THREAD_BLOCKING)

The following is an excerpt of a SNA Server APPC API trace that captures the failing TP_STARTED call:


APPC  TP_STARTED request
APPC  
APPC  Type:Sync                                  VerbID:0001C000
APPC  
APPC  ---- Verb Parameter Block at address 0EF40000 ----
APPC  14000000 00000000 00000000 00000000     <................>
APPC  00000000 00000000 00000000 C3D7C9C3     <............CPIC>
APPC  6DC4C5C6 C1D3E36D E3D72020 20202040     <mDEFALTmTP     @>
APPC  40404040 40404040 40404040 40404040     <@@@@@@@@@@@@@@@@>
APPC  40404040 40404040 40404040 40404040     <@@@@@@@@@@@@@@@@>
APPC  40404040 40404040 40404040              <@@@@@@@@@@@@    >
APPC  --------------------------------------------------------------------------------
APPC  TP_STARTED response, result = THREAD_BLOCKING
APPC  
APPC  Type:Sync                                  VerbID:0001C000
APPC  
APPC  ---- Verb Parameter Block at address 0EF40000 ----
APPC  14000000 F0060000 00000000 00000000     <....0...........>
APPC  00000000 00000000 00000000 C3D7C9C3     <............CPIC>
APPC  6DC4C5C6 C1D3E36D E3D72020 20202040     <mDEFALTmTP     @>
APPC  40404040 40404040 40404040 40404040     <@@@@@@@@@@@@@@@@>
APPC  40404040 40404040 40404040 40404040     <@@@@@@@@@@@@@@@@>
APPC  40404040 40404040 40404040              <@@@@@@@@@@@@    >

If a CPI-C application is being used when this occurs, the following error message is returned by the CPI-C library after it receives the THREAD_BLOCKING error from the APPC library:

Primary Return Code = 20 (CM_PRODUCT_SPECIFIC_ERROR)

NOTE: There might be other reasons for getting a PRODUCT_SPECIFIC_ERROR(20) that are not necessarily related to this article. Further reasons for getting a PRODUCT_SPECIFIC_ERROR(20) can be found in Microsoft Knowledge Base articles by searching for "CM_PRODUCT_SPECIFIC_ERROR".

This problem can occur when an APPC or CPI-C application has previously called WinAPPCCleanup or WinCPICCleanup to deregister the application from the APPC or CPI-C library. If the application subsequently calls WinAPPCStartup or WinCPICStartup to reregister the application, the next APPC or CPI-C call may fail with the THREAD_BLOCKING error.

CAUSE

This problem occurs because the APPC library is not properly clearing the internal IS_BLOCKING flag when WinAPPCCleanup is called. The IS_BLOCKING flag is used by the APPC library to determine whether another APPC blocking call is already outstanding on the thread that a next APPC call is being issued on.

This problem has only been reported when the APPC or CPI-C application is designed to issue multiple WinAPPCStartup/WinAPPCCleanup or WinCPICStartup/WinCPICCleanup sequences for each process. WinAPPCStartup or WinCPICStartup should only be issued when the process (that is, application) starts. WinAPPCCleanup or WinCPICCleanup should only be issued when the process is terminating. They should not be issued for each thread that starts or ends within the process.

RESOLUTION

A supported fix that corrects this problem is now available from Microsoft, but it has not been fully regression tested and should be applied only to systems experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://www.microsoft.com/support/supportnet/overview/overview.asp

The English version of this fix should have the following file attributes or later:

File name	Date	Time
Wappc32.dll	xx/xx/xx	xx:xx

NOTE: Date and time information will be provided as soon as it becomes available.

NOTE: Because of file dependencies, the most recent fix that contains the above files may also contain additional files.

WORKAROUND

Modify the APPC or CPI-C application such that it only calls the WinAPPCStartup/WinAPPCCleanup or WinCPICStartup/WinCPICCleanup sequence once for each process startup or termination.

STATUS

Microsoft has confirmed this to be a problem in Microsoft SNA Server versions 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 3.0 SP4, 4.0, 4.0 SP1, 4.0 SP2.

Additional query words:

Keywords : sna3 sna3sp1 sna3sp2 sna3sp3 sna3sp4 sna4 sna4sp1 sna4sp2
Version : WINDOWS:3.0,3.0 SP1,3.0 SP2,3.0 SP3,3.0 SP4,4.0,4.0 SP1,4.0 SP2
Platform : WINDOWS
Issue type : kbbug