SNA Server Exception 0xC0000194 (Possible Deadlock) (150795)

SYMPTOMS

After ending a user-written SNA Server application that submitted three concurrent TRANSFER_MS_DATA calls to submit an alert to NetView, the SNA Server will fail with Event 624. You will get the following Drwtsn32.log exception error:

Application exception occurred:
App: snaservr.DBG (pid=223)
Exception number: c0000194 (possible deadlock)

CAUSE

Under certain conditions, the application shutdown was causing an internal SNA Server buffer pool mutex to be left in a signaled state, causing the SNA Server to wait indefinitely for the mutex to be released.

RESOLUTION

To avoid this deadlock, the internal buffer pool mutex time-out interval is now configurable, with the default still set to infinite. Instead of waiting forever for the pool event to be signaled, the code now retries to lock the pool mutex each time the time-out expires.

WARNING: Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at your own risk.

An updated Snadmod.dll now supports a configurable time-out setting using the following new registry parameter:

    HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/SnaBase
          /Parameters/ 

    PoolMutexTimeout:REG_DWORD:<time-out in milliseconds>

Valid values are 100ms through 0xFFFFFFF (infinite). 1000ms is the recommended setting if this problem is being encountered.

STATUS

Microsoft has confirmed this to be a problem in SNA Server version 2.11. This problem was corrected in the latest SNA Server for Windows NT version 2.11 U.S. Service Pack. For information on obtaining this update, query on the following word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K