- Implement KiRecalculateDueTime to handle cases where a timeout wait has been interu...
[reactos.git] / reactos / ntoskrnl / ke / queue.c
index 35095ee..3149645 100644 (file)
 /*
- *  ReactOS kernel
- *  Copyright (C) 1998, 1999, 2000, 2001, 2002 ReactOS Team
- *
- *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation; either version 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License
- *  along with this program; if not, write to the Free Software
- *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
- */
-/* $Id$
- *
- * PROJECT:         ReactOS kernel
+ * PROJECT:         ReactOS Kernel
+ * LICENSE:         GPL - See COPYING in the top level directory
  * FILE:            ntoskrnl/ke/queue.c
  * PURPOSE:         Implements kernel queues
- * PROGRAMMER:      Eric Kohl (ekohl@rz-online.de)
- * UPDATE HISTORY:
- *                  Created 04/01/2002
+ * PROGRAMMERS:     Alex Ionescu (alex.ionescu@reactos.org)
+ *                  Gunnar Dalsnes
+ *                  Eric Kohl (ekohl@rz-online.de)
  */
 
-/* INCLUDES *****************************************************************/
+/* INCLUDES ******************************************************************/
 
 #include <ntoskrnl.h>
 #define NDEBUG
 #include <internal/debug.h>
 
-/* FUNCTIONS *****************************************************************/
+/* PRIVATE FUNCTIONS *********************************************************/
 
+/*
+ * Called when a thread which has a queue entry is entering a wait state
+ */
+VOID
+FASTCALL
+KiWakeQueue(IN PKQUEUE Queue)
+{
+    PLIST_ENTRY QueueEntry;
+    PLIST_ENTRY WaitEntry;
+    PKWAIT_BLOCK WaitBlock;
+    PKTHREAD Thread;
+    ASSERT_QUEUE(Queue);
+
+    /* Decrement the number of active threads */
+    Queue->CurrentCount--;
+
+    /* Make sure the counts are OK */
+    if (Queue->CurrentCount < Queue->MaximumCount)
+    {
+        /* Get the Queue Entry */
+        QueueEntry = Queue->EntryListHead.Flink;
+
+        /* Get the Wait Entry */
+        WaitEntry = Queue->Header.WaitListHead.Blink;
+
+        /* Make sure that the Queue entries are not part of empty lists */
+        if ((WaitEntry != &Queue->Header.WaitListHead) &&
+            (QueueEntry != &Queue->EntryListHead))
+        {
+            /* Remove this entry */
+            RemoveEntryList(QueueEntry);
+            QueueEntry->Flink = NULL;
+
+            /* Decrease the Signal State */
+            Queue->Header.SignalState--;
+
+            /* Unwait the Thread */
+            WaitBlock = CONTAINING_RECORD(WaitEntry,
+                                          KWAIT_BLOCK,
+                                          WaitListEntry);
+            Thread = WaitBlock->Thread;
+            KiAbortWaitThread(Thread, (NTSTATUS)QueueEntry, IO_NO_INCREMENT);
+        }
+    }
+}
 
 /*
- * @implemented
+ * Returns the previous number of entries in the queue
  */
-VOID STDCALL
-KeInitializeQueue(IN PKQUEUE Queue,
-                 IN ULONG Count OPTIONAL)
+LONG
+NTAPI
+KiInsertQueue(IN PKQUEUE Queue,
+              IN PLIST_ENTRY Entry,
+              BOOLEAN Head)
 {
-  KeInitializeDispatcherHeader(&Queue->Header,
-                              InternalQueueType,
-                              sizeof(KQUEUE)/sizeof(ULONG),
-                              0);
-  InitializeListHead(&Queue->EntryListHead);
-  InitializeListHead(&Queue->ThreadListHead);
-  Queue->CurrentCount = 0;
-  Queue->MaximumCount = (Count == 0) ? (ULONG) KeNumberProcessors : Count;
+    ULONG InitialState;
+    PKTHREAD Thread = KeGetCurrentThread();
+    PKWAIT_BLOCK WaitBlock;
+    PLIST_ENTRY WaitEntry;
+    ASSERT_QUEUE(Queue);
+
+    /* Save the old state */
+    InitialState = Queue->Header.SignalState;
+
+    /* Get the Entry */
+    WaitEntry = Queue->Header.WaitListHead.Blink;
+
+    /*
+     * Why the KeGetCurrentThread()->Queue != Queue?
+     * KiInsertQueue might be called from an APC for the current thread.
+     * -Gunnar
+     */
+    if ((Queue->CurrentCount < Queue->MaximumCount) &&
+        (WaitEntry != &Queue->Header.WaitListHead) &&
+        ((Thread->Queue != Queue) ||
+         (Thread->WaitReason != WrQueue)))
+    {
+        /* Remove the wait entry */
+        RemoveEntryList(WaitEntry);
+
+        /* Get the Wait Block and Thread */
+        WaitBlock = CONTAINING_RECORD(WaitEntry, KWAIT_BLOCK, WaitListEntry);
+        Thread = WaitBlock->Thread;
+
+        /* Remove the queue from the thread's wait list */
+        Thread->WaitStatus = (NTSTATUS)Entry;
+        if (Thread->WaitListEntry.Flink) RemoveEntryList(&Thread->WaitListEntry);
+        Thread->WaitReason = 0;
+
+        /* Increase the active threads and set the status*/
+        Queue->CurrentCount++;
+
+        /* Check if there's a Thread Timer */
+        if (Thread->Timer.Header.Inserted)
+        {
+            /* Cancel the Thread Timer with the no-lock fastpath */
+            Thread->Timer.Header.Inserted = FALSE;
+            RemoveEntryList(&Thread->Timer.TimerListEntry);
+        }
+
+        /* Reschedule the Thread */
+        KiReadyThread(Thread);
+    }
+    else
+    {
+        /* Increase the Entries */
+        Queue->Header.SignalState++;
+
+        /* Check which mode we're using */
+        if (Head)
+        {
+            /* Insert in the head */
+            InsertHeadList(&Queue->EntryListHead, Entry);
+        }
+        else
+        {
+            /* Insert at the end */
+            InsertTailList(&Queue->EntryListHead, Entry);
+        }
+    }
+
+    /* Return the previous state */
+    return InitialState;
 }
 
+/* PUBLIC FUNCTIONS **********************************************************/
 
 /*
  * @implemented
- *
- * Returns number of entries in the queue
  */
-LONG STDCALL
-KeReadStateQueue(IN PKQUEUE Queue)
+VOID
+NTAPI
+KeInitializeQueue(IN PKQUEUE Queue,
+                  IN ULONG Count OPTIONAL)
 {
-  return(Queue->Header.SignalState);
+    /* Initialize the Header */
+    KeInitializeDispatcherHeader(&Queue->Header,
+                                 QueueObject,
+                                 sizeof(KQUEUE) / sizeof(ULONG),
+                                 0);
+
+    /* Initialize the Lists */
+    InitializeListHead(&Queue->EntryListHead);
+    InitializeListHead(&Queue->ThreadListHead);
+
+    /* Set the Current and Maximum Count */
+    Queue->CurrentCount = 0;
+    Queue->MaximumCount = (Count == 0) ? (ULONG) KeNumberProcessors : Count;
 }
 
 /*
- * Returns the previous number of entries in the queue
+ * @implemented
  */
-LONG STDCALL
-KiInsertQueue(
-   IN PKQUEUE Queue,
-   IN PLIST_ENTRY Entry,
-   BOOLEAN Head
-   )
+LONG
+NTAPI
+KeInsertHeadQueue(IN PKQUEUE Queue,
+                  IN PLIST_ENTRY Entry)
 {
-   ULONG InitialState;
-  
-   DPRINT("KiInsertQueue(Queue %x, Entry %x)\n", Queue, Entry);
-   
-   InitialState = Queue->Header.SignalState;
-
-   if (Head)
-   {
-      InsertHeadList(&Queue->EntryListHead, Entry);
-   }
-   else
-   {
-      InsertTailList(&Queue->EntryListHead, Entry);
-   }
-   
-   //inc. num entries in queue
-   Queue->Header.SignalState++;
-   
-   /* Why the KeGetCurrentThread()->Queue != Queue?
-    * KiInsertQueue might be called from an APC for the current thread. 
-    * -Gunnar
-    */
-   if (Queue->CurrentCount < Queue->MaximumCount &&
-       !IsListEmpty(&Queue->Header.WaitListHead) &&
-       KeGetCurrentThread()->Queue != Queue)
-   {
-      KiDispatcherObjectWake(&Queue->Header, IO_NO_INCREMENT);
-   }
-
-   return InitialState;
-}
+    LONG PreviousState;
+    KIRQL OldIrql;
+    ASSERT_QUEUE(Queue);
+    ASSERT_IRQL_LESS_OR_EQUAL(DISPATCH_LEVEL);
+
+    /* Lock the Dispatcher Database */
+    OldIrql = KeAcquireDispatcherDatabaseLock();
 
+    /* Insert the Queue */
+    PreviousState = KiInsertQueue(Queue, Entry, TRUE);
 
+    /* Release the Dispatcher Lock */
+    KeReleaseDispatcherDatabaseLock(OldIrql);
+
+    /* Return previous State */
+    return PreviousState;
+}
 
 /*
  * @implemented
  */
-LONG STDCALL
-KeInsertHeadQueue(IN PKQUEUE Queue,
-                 IN PLIST_ENTRY Entry)
+LONG
+NTAPI
+KeInsertQueue(IN PKQUEUE Queue,
+              IN PLIST_ENTRY Entry)
 {
-   LONG Result;
-   KIRQL OldIrql;
-   
-   OldIrql = KeAcquireDispatcherDatabaseLock();
-   Result = KiInsertQueue(Queue,Entry,TRUE);
-   KeReleaseDispatcherDatabaseLock(OldIrql);
-   
-   return Result;
-}
+    LONG PreviousState;
+    KIRQL OldIrql;
+    ASSERT_QUEUE(Queue);
+    ASSERT_IRQL_LESS_OR_EQUAL(DISPATCH_LEVEL);
+
+    /* Lock the Dispatcher Database */
+    OldIrql = KeAcquireDispatcherDatabaseLock();
 
+    /* Insert the Queue */
+    PreviousState = KiInsertQueue(Queue, Entry, FALSE);
+
+    /* Release the Dispatcher Lock */
+    KeReleaseDispatcherDatabaseLock(OldIrql);
+
+    /* Return previous State */
+    return PreviousState;
+}
 
 /*
  * @implemented
+ *
+ * Returns number of entries in the queue
  */
-LONG STDCALL
-KeInsertQueue(IN PKQUEUE Queue,
-             IN PLIST_ENTRY Entry)
+LONG
+NTAPI
+KeReadStateQueue(IN PKQUEUE Queue)
 {
-   LONG Result;
-   KIRQL OldIrql;
-   
-   OldIrql = KeAcquireDispatcherDatabaseLock();
-   Result = KiInsertQueue(Queue,Entry,FALSE);
-   KeReleaseDispatcherDatabaseLock(OldIrql);
-   
-   return Result;
+    /* Returns the Signal State */
+    ASSERT_QUEUE(Queue);
+    return Queue->Header.SignalState;
 }
 
-
 /*
  * @implemented
  */
-PLIST_ENTRY STDCALL
+PLIST_ENTRY
+NTAPI
 KeRemoveQueue(IN PKQUEUE Queue,
-             IN KPROCESSOR_MODE WaitMode,
-             IN PLARGE_INTEGER Timeout OPTIONAL)
+              IN KPROCESSOR_MODE WaitMode,
+              IN PLARGE_INTEGER Timeout OPTIONAL)
 {
-   
-   PLIST_ENTRY ListEntry;
-   NTSTATUS Status;
-   PKTHREAD Thread = KeGetCurrentThread();
-   KIRQL OldIrql;
-
-   OldIrql = KeAcquireDispatcherDatabaseLock ();
-
-   if (Thread->Queue != Queue)
-   {
-      /*
-       * INVESTIGATE: What is the Thread->QueueListEntry used for? It's linked it into the
-       * Queue->ThreadListHead when the thread registers with the queue and unlinked when
-       * the thread registers with a new queue. The Thread->Queue already tells us what
-       * queue the thread is registered with.
-       * -Gunnar
-       */
-
-      //unregister thread from previous queue (if any)
-      if (Thread->Queue)
-      {
-         RemoveEntryList(&Thread->QueueListEntry);
-         Thread->Queue->CurrentCount--;
-         
-         if (Thread->Queue->CurrentCount < Thread->Queue->MaximumCount && 
-             !IsListEmpty(&Thread->Queue->EntryListHead))
-         {
-            KiDispatcherObjectWake(&Thread->Queue->Header, 0);
-         }
-      }
-
-      // register thread with this queue
-      InsertTailList(&Queue->ThreadListHead, &Thread->QueueListEntry);
-      Thread->Queue = Queue;
-   }
-   else /* if (Thread->Queue == Queue) */
-   {
-      //dec. num running threads
-      Queue->CurrentCount--;
-   }
-   
-   
-   
-   
-   while (TRUE)
-   {
-      if (Queue->CurrentCount < Queue->MaximumCount && !IsListEmpty(&Queue->EntryListHead))
-      {
-         ListEntry = RemoveHeadList(&Queue->EntryListHead);
-         //dec. num entries in queue
-         Queue->Header.SignalState--;
-         //inc. num running threads
-         Queue->CurrentCount++;
-         
-         KeReleaseDispatcherDatabaseLock(OldIrql);
-         return ListEntry;
-      }
-      else
-      {
-         //inform KeWaitXxx that we are holding disp. lock
-         Thread->WaitNext = TRUE;
-         Thread->WaitIrql = OldIrql;
-
-         Status = KeWaitForSingleObject(Queue,
-                                        WrQueue,
-                                        WaitMode,
-                                        TRUE, //bAlertable
-                                        Timeout);
-
-         if (Status == STATUS_TIMEOUT || Status == STATUS_USER_APC)
-         {
-            return (PVOID)Status;
-         }
-         
-         OldIrql = KeAcquireDispatcherDatabaseLock ();
-      }
-   }
+    PLIST_ENTRY QueueEntry;
+    NTSTATUS Status;
+    PKTHREAD Thread = KeGetCurrentThread();
+    KIRQL OldIrql;
+    PKQUEUE PreviousQueue;
+    PKWAIT_BLOCK WaitBlock;
+    PKTIMER Timer;
+    BOOLEAN Swappable;
+    PLARGE_INTEGER OriginalDueTime = Timeout;
+    LARGE_INTEGER DueTime, NewDueTime;
+    ASSERT_QUEUE(Queue);
+    ASSERT_IRQL_LESS_OR_EQUAL(DISPATCH_LEVEL);
+
+    /* Check if the Lock is already held */
+    if (Thread->WaitNext)
+    {
+        /* It is, so next time don't do expect this */
+        Thread->WaitNext = FALSE;
+    }
+    else
+    {
+        /* Lock the Dispatcher Database */
+        OldIrql = KeAcquireDispatcherDatabaseLock();
+        Thread->WaitIrql = OldIrql;
+    }
+
+    /*
+     * This is needed so that we can set the new queue right here,
+     * before additional processing
+     */
+    PreviousQueue = Thread->Queue;
+    Thread->Queue = Queue;
+
+    /* Check if this is a different queue */
+    if (Queue != PreviousQueue)
+    {
+        /* Get the current entry */
+        QueueEntry = &Thread->QueueListEntry;
+        if (PreviousQueue)
+        {
+            /* Remove from this list */
+            RemoveEntryList(QueueEntry);
+
+            /* Wake the queue */
+            KiWakeQueue(PreviousQueue);
+        }
+
+        /* Insert in this new Queue */
+        InsertTailList(&Queue->ThreadListHead, QueueEntry);
+    }
+    else
+    {
+        /* Same queue, decrement waiting threads */
+        Queue->CurrentCount--;
+    }
+
+    /* Loop until the queue is processed */
+    while (TRUE)
+    {
+        /* Check if the counts are valid and if there is still a queued entry */
+        QueueEntry = Queue->EntryListHead.Flink;
+        if ((Queue->CurrentCount < Queue->MaximumCount) &&
+            (QueueEntry != &Queue->EntryListHead))
+        {
+            /* Decrease the number of entries */
+            Queue->Header.SignalState--;
+
+            /* Increase numbef of running threads */
+            Queue->CurrentCount++;
+
+            /* Check if the entry is valid. If not, bugcheck */
+            if (!(QueueEntry->Flink) || !(QueueEntry->Blink))
+            {
+                KEBUGCHECK(INVALID_WORK_QUEUE_ITEM);
+            }
+
+            /* Remove the Entry */
+            RemoveEntryList(QueueEntry);
+            QueueEntry->Flink = NULL;
+
+            /* Nothing to wait on */
+            break;
+        }
+        else
+        {
+            /* Use the Thread's Wait Block, it's big enough */
+            Thread->WaitBlockList = &Thread->WaitBlock[0];
+
+            /* Check if a kernel APC is pending and we're below APC_LEVEL */
+            if ((Thread->ApcState.KernelApcPending) &&
+                !(Thread->SpecialApcDisable) && (Thread->WaitIrql < APC_LEVEL))
+            {
+                /* Increment the count and unlock the dispatcher */
+                Queue->CurrentCount++;
+                KeReleaseDispatcherDatabaseLock(Thread->WaitIrql);
+            }
+            else
+            {
+                /* Fail if there's a User APC Pending */
+                if ((WaitMode != KernelMode) &&
+                    (Thread->ApcState.UserApcPending))
+                {
+                    /* Return the status and increase the pending threads */
+                    QueueEntry = (PLIST_ENTRY)STATUS_USER_APC;
+                    Queue->CurrentCount++;
+                    break;
+                }
+
+                /* Build the Wait Block */
+                WaitBlock = &Thread->WaitBlock[0];
+                WaitBlock->Object = (PVOID)Queue;
+                WaitBlock->WaitKey = STATUS_SUCCESS;
+                WaitBlock->WaitType = WaitAny;
+                WaitBlock->Thread = Thread;
+                Thread->WaitStatus = STATUS_WAIT_0;
+
+                /* Check if we can swap the thread's stack */
+                Thread->WaitListEntry.Flink = NULL;
+                KiCheckThreadStackSwap(WaitMode, Thread, Swappable);
+
+                /* We need to wait for the object... check for a timeout */
+                if (Timeout)
+                {
+                    /* Check if it's zero */
+                    if (!Timeout->QuadPart)
+                    {
+                        /* Don't wait. Return and increase pending threads */
+                        QueueEntry = (PLIST_ENTRY)STATUS_TIMEOUT;
+                        Queue->CurrentCount++;
+                        break;
+                    }
+
+                    /*
+                     * Set up the Timer. We'll use the internal function so
+                     * that we can hold on to the dispatcher lock.
+                     */
+                    Timer = &Thread->Timer;
+                    WaitBlock->NextWaitBlock = &Thread->WaitBlock[1];
+                    WaitBlock = &Thread->WaitBlock[1];
+
+                    /* Set up the Timer Wait Block */
+                    WaitBlock->Object = (PVOID)Timer;
+                    WaitBlock->Thread = Thread;
+                    WaitBlock->WaitKey = STATUS_TIMEOUT;
+                    WaitBlock->WaitType = WaitAny;
+
+                    /* Link the timer to this Wait Block */
+                    Timer->Header.WaitListHead.Flink =
+                        &WaitBlock->WaitListEntry;
+                    Timer->Header.WaitListHead.Blink =
+                        &WaitBlock->WaitListEntry;
+                    WaitBlock->WaitListEntry.Flink =
+                        &Timer->Header.WaitListHead;
+                    WaitBlock->WaitListEntry.Blink =
+                        &Timer->Header.WaitListHead;
+
+                    /* Create Timer */
+                    if (!KiInsertTimer(Timer, *Timeout))
+                    {
+                        /* FIXME */
+                        DPRINT1("If you see thie message contact Alex ASAP\n");
+                        KEBUGCHECK(0);
+                    }
+
+                    /* Set timer due time */
+                    DueTime.QuadPart = Timer->DueTime.QuadPart;
+                }
+
+                /* Close the loop */
+                WaitBlock->NextWaitBlock = &Thread->WaitBlock[0];
+
+                /* Insert the wait block into the Queues's wait list */
+                WaitBlock = &Thread->WaitBlock[0];
+                InsertTailList(&Queue->Header.WaitListHead,
+                               &WaitBlock->WaitListEntry);
+
+                /* Setup the wait information */
+                Thread->WaitMode = WaitMode;
+                Thread->WaitReason = WrQueue;
+                Thread->Alertable = FALSE;
+                Thread->WaitTime = ((PLARGE_INTEGER)&KeTickCount)->LowPart;
+                Thread->State = Waiting;
+
+                /* Find a new thread to run */
+                KiAddThreadToWaitList(Thread, Swappable);
+                Status = KiSwapThread();
+
+                /* Reset the wait reason */
+                Thread->WaitReason = 0;
+
+                /* Check if we were executing an APC */
+                if (Status != STATUS_KERNEL_APC)
+                {
+                    /* Done Waiting  */
+                    return (PLIST_ENTRY)Status;
+                }
+
+                /* Check if we had a timeout */
+                if (Timeout)
+                {
+                    /* Recalculate due times */
+                    Timeout = KiRecalculateDueTime(OriginalDueTime,
+                                                   &DueTime,
+                                                   &NewDueTime);
+                }
+            }
+
+            /* Reacquire the lock */
+            OldIrql = KeAcquireDispatcherDatabaseLock();
+
+            /* Save the new IRQL and decrease number of waiting threads */
+            Thread->WaitIrql = OldIrql;
+            Queue->CurrentCount--;
+        }
+    }
+
+    /* Unlock Database and return */
+    KeReleaseDispatcherDatabaseLock(Thread->WaitIrql);
+    return QueueEntry;
 }
 
-
 /*
  * @implemented
  */
-PLIST_ENTRY STDCALL
+PLIST_ENTRY
+NTAPI
 KeRundownQueue(IN PKQUEUE Queue)
 {
-   PLIST_ENTRY EnumEntry;
-   PKTHREAD Thread;
-   KIRQL OldIrql;
-
-   DPRINT("KeRundownQueue(Queue %x)\n", Queue);
-
-   /* I'm just guessing how this should work:-/
-    * -Gunnar 
-    */
-     
-   OldIrql = KeAcquireDispatcherDatabaseLock ();
-
-   //no thread must wait on queue at rundown
-   ASSERT(IsListEmpty(&Queue->Header.WaitListHead));
-   
-   // unlink threads and clear their Thread->Queue
-   while (!IsListEmpty(&Queue->ThreadListHead))
-   {
-      EnumEntry = RemoveHeadList(&Queue->ThreadListHead);
-      Thread = CONTAINING_RECORD(EnumEntry, KTHREAD, QueueListEntry);
-      Thread->Queue = NULL;
-   }
-
-   if (IsListEmpty(&Queue->EntryListHead))
-   {
-      EnumEntry = NULL;
-   }
-   else
-   {
-      EnumEntry = Queue->EntryListHead.Flink;
-   }
-
-   KeReleaseDispatcherDatabaseLock (OldIrql);
-
-   return EnumEntry;
+    PLIST_ENTRY EnumEntry;
+    PLIST_ENTRY FirstEntry = NULL;
+    PKTHREAD Thread;
+    KIRQL OldIrql;
+    ASSERT_QUEUE(Queue);
+    ASSERT_IRQL_LESS_OR_EQUAL(DISPATCH_LEVEL);
+    ASSERT(IsListEmpty(&Queue->Header.WaitListHead));
+
+    /* Get the Dispatcher Lock */
+    OldIrql = KeAcquireDispatcherDatabaseLock();
+
+    /* Make sure the list is not empty */
+    if (!IsListEmpty(&Queue->EntryListHead))
+    {
+        /* Remove it */
+        FirstEntry = RemoveHeadList(&Queue->EntryListHead);
+    }
+
+    /* Unlink threads and clear their Thread->Queue */
+    while (!IsListEmpty(&Queue->ThreadListHead))
+    {
+        /* Get the Entry and Remove it */
+        EnumEntry = RemoveHeadList(&Queue->ThreadListHead);
+
+        /* Get the Entry's Thread */
+        Thread = CONTAINING_RECORD(EnumEntry, KTHREAD, QueueListEntry);
+
+        /* Kill its Queue */
+        Thread->Queue = NULL;
+    }
+
+    /* Release the lock and return */
+    KeReleaseDispatcherDatabaseLock(OldIrql);
+    return FirstEntry;
 }
 
 /* EOF */