Microsoft KB Archive/261290

= 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)

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

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

-

[mailto:TECHNET@MICROSOFT.COM Send feedback to Microsoft]

© Microsoft Corporation. All rights reserved.