According to alex_ionescu, callers of IoAllocateIrp should set the
Tail.Overlay.Thread member themselves in the new Irp.  These calls
to IoAllocateIrp were not followed by setting the thread.

reactos/drivers/storage/class2

diff -u -r1.54 -r1.55
--- class2.c	10 Jun 2004 07:56:42 -0000	1.54
+++ class2.c	12 Aug 2004 05:59:25 -0000	1.55
@@ -16,7 +16,7 @@

  *  along with this program; if not, write to the Free Software
  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */

-/* $Id: class2.c,v 1.54 2004/06/10 07:56:42 hbirr Exp $

+/* $Id: class2.c,v 1.55 2004/08/12 05:59:25 arty Exp $

  *
  * COPYRIGHT:       See COPYING in the top level directory
  * PROJECT:         ReactOS kernel

@@ -1887,6 +1887,7 @@

 			  NULL);
 
   /* Attach SRB to the IRP */

+  Irp->Tail.Overlay.Thread = PsGetCurrentThread();

   Stack = IoGetNextIrpStackLocation(Irp);
   Stack->MajorFunction = IRP_MJ_SCSI;
   Stack->Parameters.Scsi.Srb = Srb;

@@ -2201,6 +2202,7 @@

 
       /* Initialize the new IRP */
       NewIrp->MdlAddress = Irp->MdlAddress;

+      NewIrp->Tail.Overlay.Thread = PsGetCurrentThread();

 
       IoSetNextIrpStackLocation(NewIrp);
       NewStack = IoGetCurrentIrpStackLocation(NewIrp);