DOCUMENT:Q242896  08-MAY-2002  [winnt]
TITLE   :SFM Causes a Problem When FastIoUnlockSingle() Returns FALSE
PRODUCT :Microsoft Windows NT
PROD/VER:winnt:4.0,4.0 SP4,4.0 SP5,4.0 SP6,4.0 SP6a
OPER/SYS:
KEYWORDS:kbWinNT400PreSP7Fix

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The information in this article applies to:

 - Microsoft Windows NT Server versions 4.0, 4.0 SP4, 4.0 SP5, 4.0 SP6, 4.0 SP6a 
 - Microsoft Windows NT Server, Enterprise Edition versions 4.0, 4.0 SP4, 4.0 SP5, 4.0 SP6, 4.0 SP6a 
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SYMPTOMS
========

Services for Macintosh (SFM) may cause the computer to stop responding (hang)
when FastIoUnlockSingle (a FastIO dispatch routine) returns FALSE. This corrupts
the kernel memory and is sufficient to cause the computer to hang within a small
number of input/output (I/O) operations. File systems and file system filter
drivers sometimes need to prevent the FastIO path, usually because outstanding
synchronization (for example, OpLocks and ByteRange locks) does not allow a
simple pass-through of the operation to FsRtl or Cache Manager. Because the
majority of FastIO routines are Boolean functions, the FastIO path can be
disabled a FALSE response, thereby forcing an operation to take the Input/Output
Request Packets (IRP) path instead.

Depending on how often a driver must disable FastIoUnlockSingle and the pattern
of unlocks on a given computer, the problem may occur very frequently or very
rarely.

CAUSE
=====

Because SFM attempts to free the IRP twice in the completion routine and once in
the routine that allocated the IRP, it causes Kernel-mode memory corruption.
This in turn causes the computer to hang with a STOP error message.

RESOLUTION
==========

A supported fix is now available from Microsoft, but it is only intended to
correct the problem described in this article 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://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

NOTE: In special cases, charges that are normally incurred for support calls may
be canceled, if a Microsoft Support Professional determines that a specific
update will resolve your problem. Normal support costs will apply to additional
support questions and issues that do not qualify for the specific update in
question.

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

   Date      Time                 Size     File name     Platform
   --------------------------------------------------------------
   09/29/99  07:49 PM             134,416  Sfmsrv.sys    Intel
   09/29/99  07:48 PM             241,744  Sfmsrv.sys    Alpha



STATUS
======

Microsoft has confirmed this to be a problem in the Microsoft products that are
listed at the beginning of this article.

Additional query words: halt

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Keywords          : kbWinNT400PreSP7Fix 
Technology        : kbWinNTsearch kbWinNT400search kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400sp6 kbWinNTSEnt400sp5 kbWinNTSEnt400sp4 kbWinNTSEnt400 kbWinNTS400sp6 kbWinNTS400sp5 kbWinNTS400sp4 kbWinNTS400search kbWinNTS400 kbWinNTSEnt400SP6a
Version           : winnt:4.0,4.0 SP4,4.0 SP5,4.0 SP6,4.0 SP6a
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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