Knowledge Base

3270 Applet Causes Access Violation Error Message in Win3270.exe

Article ID: 261290

Article Last Modified on 11/25/2003

APPLIES TO

Microsoft SNA Server 4.0
Microsoft SNA Server 4.0 Service Pack 1
Microsoft SNA Server 4.0 Service Pack 2
Microsoft SNA Server 4.0 Service Pack 3

This article was previously published under Q261290

SYMPTOMS

When you start the 3270 applet (Win3270.exe), included with the SNA Server client for Windows NT, with the SnaBase service configured to run under a user account, an Access Violation error message may occur. If the Drwtsn32.exe file is configured as the default debugger on the system, a Drwtsn32.log file similar to the following is generated:

Application exception occurred:
        App: exe\win3270.dbg (pid=229)
        When: 2/1/2000 @ 9:56:14.629
        Exception number: c0000005 (access violation)

*----> Task List <----*
  229 WIN3270.exe
  (01000000 - 0101f000) C:\WINNT\Symbols\exe\win3270.dbg

function: RtlpWaitForCriticalSection
        77f6cdc2 e920010000       jmp     RtlpWaitForCriticalSection+0x196 (77f6cee7) 77f6cdc7 803d8859fa7701
        ds:77fa5988=01            cmp     byte ptr [fltused+0xca8 (77fa5988)],0x1
        77f6cdce 1bc0             sbb     eax,eax
        77f6cdd0 25d05afa77       and     eax,0x77fa5ad0
        77f6cdd5 837e1000         cmp     dword ptr [esi+0x10],0x0 ds:682feb26=????????
        77f6cdd9 8945fc           mov     [ebp-0x4],eax          ss:0337e6b6=????????
        77f6cddc 7506             jnz     RtlpWaitForCriticalSection+0x93 (77f6cde4)
        77f6cdde 56               push    esi
        77f6cddf e8b6fdffff       call    RtlSetCriticalSectionSpinCount+0x70 (77f6cb9a)
        77f6cde4 8b06             mov     eax,[esi]              ds:67270120=????????
FAULT ->77f6cde6 ff4010           inc     dword ptr [eax+0x10]   ds:0108ea06=????????
        77f6cde9 8b06             mov     eax,[esi]              ds:67270120=????????
        77f6cdeb ff75fc           push    dword ptr [ebp-0x4]    ss:0337e6b6=????????
        77f6cdee 6a00             push    0x0
        77f6cdf0 ff4014           inc     dword ptr [eax+0x14]   ds:0108ea06=????????
        77f6cdf3 ff7610           push    dword ptr [esi+0x10]   ds:682feb26=????????
        77f6cdf6 e855b4ffff       call    NtWaitForSingleObject (77f68250)
        77f6cdfb 3d02010000       cmp     eax,0x102
        77f6ce00 0f85b2000000     jne     RtlpWaitForCriticalSection+0x167 (77f6ceb8)
        77f6ce06 57               push    edi
        77f6ce07 68bcccf677       push    0x77f6ccbc
        77f6ce0c e873940000       call    DbgPrint (77f76284)

*----> Stack Back Trace <----*

FramePtr ReturnAd Param#1  Param#2  Param#3  Param#4  Function Name
022efcb0 77f67506 67270120 67222d22 67270120 00000000 ntdll!RtlpWaitForCriticalSection 
00000000 00000000 00000000 00000000 00000000 00000000 ntdll!RtlEnterCriticalSection

CAUSE

The SNA Server client dynamic address module (DMOD) is loaded by an emulator to retrieve a list of 3270 LUs that have been assigned to the user. Many 3270 emulators, including the 3270 applet, unload the DMOD after the list of 3270 LUs has been obtained. A small timing window exists that allows the DMOD's event-logging thread to make an attempt at logging an event while the DMOD's main application thread is unloading the DMOD (after the list of 3270 LUs is retrieved). The Access Violation error message occurs when the logging thread tries to access a critical section that is no longer initialized because the DMOD is unloaded by the main thread.

RESOLUTION

To resolve this problem, obtain the latest service pack for SNA Server 4.0. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

215838 How to Obtain the Latest SNA Server Version 4.0 Service Pack

WORKAROUND

To work around this problem, use the local system account, or install the SNA 4.0 Windows 95 or Windows 98 client.

STATUS

Microsoft has confirmed that this is a problem in SNA Server 4.0.

This problem was first corrected in SNA Server 4.0 Service Pack 4.

MORE INFORMATION

This is a timing-related issue. If the local system account is used for the SNABASE service or if tracing has been enabled, the problem does not occur.

NOTE: This problem can also occur with third-party emulators as well.

Keywords: kbbug kbfix kbsna400presp4fix kbqfe kbsna400sp4fix KB261290

Microsoft KB Archive/261290

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