- Acquire the dispatcher database lock in PsBlockThread if the caller didn't 
  acquire this lock. This prevents from dead locks on smp machines.

reactos/ntoskrnl/ps

diff -u -r1.138 -r1.139
--- thread.c	1 Nov 2004 19:10:07 -0000	1.138
+++ thread.c	27 Nov 2004 16:52:35 -0000	1.139
@@ -1,4 +1,4 @@

-/* $Id: thread.c,v 1.138 2004/11/01 19:10:07 hbirr Exp $

+/* $Id: thread.c,v 1.139 2004/11/27 16:52:35 hbirr Exp $

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

@@ -490,16 +490,20 @@

   PETHREAD Thread;
   PKWAIT_BLOCK WaitBlock;
 

-  KeAcquireSpinLock(&PiThreadLock, &oldIrql);

+  if (!DispatcherLock)
+    {
+      oldIrql = KeAcquireDispatcherDatabaseLock();
+      KiAcquireSpinLock(&PiThreadLock);
+    }
+  else
+    {
+      KeAcquireSpinLock(&PiThreadLock, &oldIrql);
+    }

 
   KThread = KeGetCurrentThread();
   Thread = CONTAINING_RECORD (KThread, ETHREAD, Tcb);
   if (KThread->ApcState.KernelApcPending)
   {

-    if (!DispatcherLock)
-      {
-	KeAcquireDispatcherDatabaseLockAtDpcLevel();
-      }

     WaitBlock = (PKWAIT_BLOCK)Thread->Tcb.WaitBlockList;
     while (WaitBlock)
       {

@@ -516,10 +520,7 @@

   }
   else
     {

-      if (DispatcherLock)
-	{
-	  KeReleaseDispatcherDatabaseLockFromDpcLevel();
-	}

+      KeReleaseDispatcherDatabaseLockFromDpcLevel();

       Thread->Tcb.Alertable = Alertable;
       Thread->Tcb.WaitMode = (UCHAR)WaitMode;
       Thread->Tcb.WaitIrql = WaitIrql;