STOP 0xC000021A in CSRSS After Attempting to Free an Already Freed Screen Buffer

ID: Q234658

The information in this article applies to:

SYMPTOMS

When you run a program as a service that constantly creates and closes consoles, the following blue-screen error message may be displayed when you log off the computer:

STOP: c000021a {Fatal System Error}
The Windows SubSystem system process terminated unexpectedly
with a status of 0xc0000005 (0x77f7d40f 0x187fd70).
The system has been shut down.
The parameters for the status 0xC0000005 can vary.


CAUSE

This problem occurs because a screen buffer owned by CSRSS is freed by a process. During the freeing process, the screen buffer's reference count is incremented. When the screen buffer's reference count decrements to 0, an attempt is made to free the screen buffer. Because the screen buffer has already been released (freed), this causes an access violation, which leads to the Stop 0xC00021A.


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. If you are not severely affected by this specific problem, Microsoft recommends that you wait for the next Windows NT 4.0 service pack that contains this fix.

To resolve this problem immediately, 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:

   Date      Time      Size      File name     Platform
   ----------------------------------------------------
   05/10/99   06:56p   175,376   Winsrv.dll    x86
   05/10/99   06:54p   316,176   Winsrv.dll    Alpha

NOTE: If this product was already installed on your computer when you purchased it from the Original Equipment Manufacturer (OEM) and you need this fix, please call the Pay Per Incident number listed on the above Web site. If you contact Microsoft to obtain this fix, and if it is determined that you only require the fix you requested, no fee will be charged. However, if you request additional technical support, and if your no-charge technical support period has expired, or if you are not eligible for standard no-charge technical support, you may be charged a non-refundable fee.

For more information about eligibility for no-charge technical support, see the following article in the Microsoft Knowledge Base:
Q154871 Determining If You Are Eligible for No-Charge Technical Support


WORKAROUND

To work around this problem, lock the workstation or server instead of logging off. However, this may not be a practical workaround in certain instances.


STATUS

Microsoft has confirmed this to be a problem in Windows NT 4.0.

Additional query words: 


Keywords          : kbbug4.00 kbfix4.00 
Version           : winnt:4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4,4.0 SP5
Platform          : winnt 
Issue type        : kbbug

Last Reviewed: July 1, 1999