[sginsberg] 43240: - Fix recursive spinlock acquisition in Mm caused by locking inconsistency between ARM3 and the old ReactOS Mm. The old Mm calls certain routines to modify PFN entries (lock, unlock, reference, dereference, etc) and acquires/releases the PFN lock inside those functions (which is extremely inefficient as you can't, for example, have to acquire/release the PFN lock twice to reference and lock the same page), while ARM3 synchronizes differently and holds the lock while calling th

Author: sginsberg
Date: Wed Sep 30 20:24:00 2009
New Revision: 43240

URL: http://svn.reactos.org/svn/reactos?rev=43240&view=rev
Log:
- Fix recursive spinlock acquisition in Mm caused by locking inconsistency between ARM3
and the old ReactOS Mm. The old Mm calls certain routines to modify PFN entries (lock,
unlock, reference, dereference, etc) and acquires/releases the PFN lock inside those
functions (which is extremely inefficient as you can't, for example, have to
acquire/release the PFN lock twice to reference and lock the same page), while ARM3
synchronizes differently and holds the lock while calling those routines, resulting in a
recursive lock attempt on MP (which works on UP because spinlocks are just IRQL
raise/lower there). Move out locking from MmAllocPage, MmReference/DereferencePage and
MmLock/UnlockPage to the callers to be consistent with ARM3.
- Add missing PFN locking to MmFreePagesFromMdl and MiAllocatePoolPages.
- Get rid of MmLockPageUnsafe and MmReferencePageUnsafe. The "safe" routines
just forwarded to the unsafe versions -- call them directly instead. Remove unused
MmAcquirePageListLock/MmReleasePageListLock.

Modified:
    trunk/reactos/ntoskrnl/include/internal/mm.h
    trunk/reactos/ntoskrnl/mm/ARM3/mdlsup.c
    trunk/reactos/ntoskrnl/mm/ARM3/pool.c
    trunk/reactos/ntoskrnl/mm/anonmem.c
    trunk/reactos/ntoskrnl/mm/balance.c
    trunk/reactos/ntoskrnl/mm/freelist.c
    trunk/reactos/ntoskrnl/mm/mmfault.c
    trunk/reactos/ntoskrnl/mm/section.c

Modified: trunk/reactos/ntoskrnl/include/internal/mm.h
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/include/internal/…
==============================================================================
--- trunk/reactos/ntoskrnl/include/internal/mm.h [iso-8859-1] (original)
+++ trunk/reactos/ntoskrnl/include/internal/mm.h [iso-8859-1] Wed Sep 30 20:24:00 2009
@@ -1095,32 +1095,11 @@
 
 VOID
 NTAPI
-MmLockPageUnsafe(PFN_TYPE Page);
-
-VOID
-NTAPI
 MmUnlockPage(PFN_TYPE Page);
 
 ULONG
 NTAPI
 MmGetLockCountPage(PFN_TYPE Page);
-
-static
-__inline
-KIRQL
-NTAPI
-MmAcquirePageListLock()
-{
-	return KeAcquireQueuedSpinLock(LockQueuePfnLock);
-}
-
-FORCEINLINE
-VOID
-NTAPI
-MmReleasePageListLock(KIRQL oldIrql)
-{
-	KeReleaseQueuedSpinLock(LockQueuePfnLock, oldIrql);
-}
 
 VOID
 NTAPI
@@ -1342,10 +1321,6 @@
 VOID
 NTAPI
 MmReferencePage(PFN_TYPE Page);
-
-VOID
-NTAPI
-MmReferencePageUnsafe(PFN_TYPE Page);
 
 ULONG
 NTAPI

Modified: trunk/reactos/ntoskrnl/mm/ARM3/mdlsup.c
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/mm/ARM3/mdlsup.c?…
==============================================================================
--- trunk/reactos/ntoskrnl/mm/ARM3/mdlsup.c [iso-8859-1] (original)
+++ trunk/reactos/ntoskrnl/mm/ARM3/mdlsup.c [iso-8859-1] Wed Sep 30 20:24:00 2009
@@ -215,6 +215,7 @@
     PPFN_NUMBER Pages;
     LONG NumberOfPages;
     PMMPFN Pfn1;
+    KIRQL OldIrql;
     DPRINT("Freeing MDL: %p\n", Mdl);
     
     //
@@ -229,7 +230,12 @@
     //
     Base = (PVOID)((ULONG_PTR)Mdl->StartVa + Mdl->ByteOffset);
     NumberOfPages = ADDRESS_AND_SIZE_TO_SPAN_PAGES(Base, Mdl->ByteCount);
-    
+
+    //
+    // Acquire PFN lock
+    //
+    OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
+
     //
     // Loop all the MDL pages
     //
@@ -268,7 +274,12 @@
         //
         *Pages++ = -1;
     } while (--NumberOfPages != 0);
-    
+
+    //
+    // Release the lock
+    //
+    KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
+
     //
     // Remove the pages locked flag
     //

Modified: trunk/reactos/ntoskrnl/mm/ARM3/pool.c
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/mm/ARM3/pool.c?re…
==============================================================================
--- trunk/reactos/ntoskrnl/mm/ARM3/pool.c [iso-8859-1] (original)
+++ trunk/reactos/ntoskrnl/mm/ARM3/pool.c [iso-8859-1] Wed Sep 30 20:24:00 2009
@@ -141,6 +141,7 @@
     PMMPFN Pfn1;
     PVOID BaseVa;
     PMMFREE_POOL_ENTRY FreeEntry;
+    PKSPIN_LOCK_QUEUE LockQueue;
     
     //
     // Figure out how big the allocation is in pages
@@ -285,7 +286,8 @@
     //
     // Lock the PFN database too
     //
-    //KeAcquireQueuedSpinLockAtDpcLevel(LockQueuePfnLock);
+    LockQueue = &KeGetCurrentPrcb()->LockQueue[LockQueuePfnLock];
+    KeAcquireQueuedSpinLockAtDpcLevel(LockQueue);
     
     //
     // Loop the pages
@@ -326,7 +328,7 @@
     //
     // Release the PFN and nonpaged pool lock
     //
-    //KeReleaseQueuedSpinLockFromDpcLevel(LockQueuePfnLock);
+    KeReleaseQueuedSpinLockFromDpcLevel(LockQueue);
     KeReleaseQueuedSpinLock(LockQueueMmNonPagedPoolLock, OldIrql);
     
     //

Modified: trunk/reactos/ntoskrnl/mm/anonmem.c
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/mm/anonmem.c?rev=…
==============================================================================
--- trunk/reactos/ntoskrnl/mm/anonmem.c [iso-8859-1] (original)
+++ trunk/reactos/ntoskrnl/mm/anonmem.c [iso-8859-1] Wed Sep 30 20:24:00 2009
@@ -258,6 +258,7 @@
    PMM_REGION Region;
    PMM_PAGEOP PageOp;
    PEPROCESS Process = MmGetAddressSpaceOwner(AddressSpace);
+   KIRQL OldIrql;
     
    /*
     * There is a window between taking the page fault and locking the
@@ -268,7 +269,9 @@
    {
       if (Locked)
       {
+         OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
          MmLockPage(MmGetPfnForProcess(NULL, Address));
+         KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
       }
       return(STATUS_SUCCESS);
    }
@@ -362,7 +365,9 @@
       MmLockAddressSpace(AddressSpace);
       if (Locked)
       {
+         OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
          MmLockPage(MmGetPfnForProcess(NULL, Address));
+         KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
       }
       KeSetEvent(&PageOp->CompletionEvent, IO_NO_INCREMENT, FALSE);
       MmReleasePageOp(PageOp);
@@ -437,7 +442,9 @@
     */
    if (Locked)
    {
+      OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
       MmLockPage(Page);
+      KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
    }
    PageOp->Status = STATUS_SUCCESS;
    KeSetEvent(&PageOp->CompletionEvent, IO_NO_INCREMENT, FALSE);

Modified: trunk/reactos/ntoskrnl/mm/balance.c
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/mm/balance.c?rev=…
==============================================================================
--- trunk/reactos/ntoskrnl/mm/balance.c [iso-8859-1] (original)
+++ trunk/reactos/ntoskrnl/mm/balance.c [iso-8859-1] Wed Sep 30 20:24:00 2009
@@ -105,7 +105,7 @@
 {
    PMM_ALLOCATION_REQUEST Request;
    PLIST_ENTRY Entry;
-   KIRQL oldIrql;
+   KIRQL OldIrql;
 
    if (Page == 0)
    {
@@ -113,20 +113,22 @@
       KeBugCheck(MEMORY_MANAGEMENT);
    }
 
-   KeAcquireSpinLock(&AllocationListLock, &oldIrql);
+   KeAcquireSpinLock(&AllocationListLock, &OldIrql);
    if (MmGetReferenceCountPage(Page) == 1)
    {
       (void)InterlockedDecrementUL(&MiMemoryConsumers[Consumer].PagesUsed);
       if (IsListEmpty(&AllocationListHead) || MmStats.NrFreePages <
MiMinimumAvailablePages)
       {
-         KeReleaseSpinLock(&AllocationListLock, oldIrql);
+         KeReleaseSpinLock(&AllocationListLock, OldIrql);
+         OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
          MmDereferencePage(Page);
+         KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
       }
       else
       {
          Entry = RemoveHeadList(&AllocationListHead);
          Request = CONTAINING_RECORD(Entry, MM_ALLOCATION_REQUEST, ListEntry);
-         KeReleaseSpinLock(&AllocationListLock, oldIrql);
+         KeReleaseSpinLock(&AllocationListLock, OldIrql);
          if(Consumer == MC_USER) MmRemoveLRUUserPage(Page);
          MiZeroPage(Page);
          Request->Page = Page;
@@ -135,9 +137,11 @@
    }
    else
    {
-      KeReleaseSpinLock(&AllocationListLock, oldIrql);
+      KeReleaseSpinLock(&AllocationListLock, OldIrql);
       if(Consumer == MC_USER) MmRemoveLRUUserPage(Page);
+      OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
       MmDereferencePage(Page);
+      KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
    }
 
    return(STATUS_SUCCESS);
@@ -235,7 +239,7 @@
 {
    ULONG OldUsed;
    PFN_TYPE Page;
-   KIRQL oldIrql;
+   KIRQL OldIrql;
 
    /*
     * Make sure we don't exceed our individual target.
@@ -257,7 +261,9 @@
     */
    if ((Consumer == MC_NPPOOL) || (Consumer == MC_SYSTEM) || MiIsBalancerThread())
    {
+      OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
       Page = MmAllocPage(Consumer, 0);
+      KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
       if (Page == 0)
       {
          KeBugCheck(NO_PAGES_AVAILABLE);
@@ -290,14 +296,14 @@
       KeInitializeEvent(&Request.Event, NotificationEvent, FALSE);
       (void)InterlockedIncrementUL(&MiPagesRequired);
 
-      KeAcquireSpinLock(&AllocationListLock, &oldIrql);
+      KeAcquireSpinLock(&AllocationListLock, &OldIrql);
 
       if (MiBalancerThreadHandle != NULL)
       {
          KeSetEvent(&MiBalancerEvent, IO_NO_INCREMENT, FALSE);
       }
       InsertTailList(&AllocationListHead, &Request.ListEntry);
-      KeReleaseSpinLock(&AllocationListLock, oldIrql);
+      KeReleaseSpinLock(&AllocationListLock, OldIrql);
 
       KeWaitForSingleObject(&Request.Event,
                             0,
@@ -321,7 +327,9 @@
    /*
     * Actually allocate the page.
     */
+   OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
    Page = MmAllocPage(Consumer, 0);
+   KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
    if (Page == 0)
    {
       KeBugCheck(NO_PAGES_AVAILABLE);

Modified: trunk/reactos/ntoskrnl/mm/freelist.c
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/mm/freelist.c?rev…
==============================================================================
--- trunk/reactos/ntoskrnl/mm/freelist.c [iso-8859-1] (original)
+++ trunk/reactos/ntoskrnl/mm/freelist.c [iso-8859-1] Wed Sep 30 20:24:00 2009
@@ -830,19 +830,16 @@
 
 VOID
 NTAPI
-MmReferencePageUnsafe(PFN_TYPE Pfn)
-{
-   KIRQL oldIrql;
+MmReferencePage(PFN_TYPE Pfn)
+{
    PPHYSICAL_PAGE Page;
 
-   DPRINT("MmReferencePageUnsafe(PysicalAddress %x)\n", Pfn <<
PAGE_SHIFT);
+   DPRINT("MmReferencePage(PysicalAddress %x)\n", Pfn << PAGE_SHIFT);
 
    if (Pfn == 0 || Pfn > MmHighestPhysicalPage)
    {
       return;
    }
-
-   oldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
 
    Page = MiGetPfnEntry(Pfn);
    ASSERT(Page);
@@ -853,16 +850,6 @@
    }
 
    Page->ReferenceCount++;
-   KeReleaseQueuedSpinLock(LockQueuePfnLock, oldIrql);
-}
-
-VOID
-NTAPI
-MmReferencePage(PFN_TYPE Pfn)
-{
-   DPRINT("MmReferencePage(PysicalAddress %x)\n", Pfn << PAGE_SHIFT);
-
-   MmReferencePageUnsafe(Pfn);
 }
 
 ULONG
@@ -904,13 +891,10 @@
 NTAPI
 MmDereferencePage(PFN_TYPE Pfn)
 {
-   KIRQL oldIrql;
    PPHYSICAL_PAGE Page;
 
    DPRINT("MmDereferencePage(PhysicalAddress %x)\n", Pfn << PAGE_SHIFT);
 
-   oldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
-    
    Page = MiGetPfnEntry(Pfn);
    ASSERT(Page);
 
@@ -962,7 +946,6 @@
          KeSetEvent(&ZeroPageThreadEvent, IO_NO_INCREMENT, FALSE);
       }
    }
-   KeReleaseQueuedSpinLock(LockQueuePfnLock, oldIrql);
 }
 
 ULONG
@@ -993,14 +976,11 @@
 
 VOID
 NTAPI
-MmLockPageUnsafe(PFN_TYPE Pfn)
-{
-   KIRQL oldIrql;
+MmLockPage(PFN_TYPE Pfn)
+{
    PPHYSICAL_PAGE Page;
 
-   DPRINT("MmLockPageUnsafe(PhysicalAddress %x)\n", Pfn << PAGE_SHIFT);
-
-   oldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
+   DPRINT("MmLockPage(PhysicalAddress %x)\n", Pfn << PAGE_SHIFT);
 
    Page = MiGetPfnEntry(Pfn);
    ASSERT(Page);
@@ -1011,28 +991,15 @@
    }
 
    Page->LockCount++;
-   KeReleaseQueuedSpinLock(LockQueuePfnLock, oldIrql);
 }
 
 VOID
 NTAPI
-MmLockPage(PFN_TYPE Pfn)
-{
-   DPRINT("MmLockPage(PhysicalAddress %x)\n", Pfn << PAGE_SHIFT);
-
-   MmLockPageUnsafe(Pfn);
-}
-
-VOID
-NTAPI
 MmUnlockPage(PFN_TYPE Pfn)
 {
-   KIRQL oldIrql;
    PPHYSICAL_PAGE Page;
 
    DPRINT("MmUnlockPage(PhysicalAddress %x)\n", Pfn << PAGE_SHIFT);
-
-   oldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
 
    Page = MiGetPfnEntry(Pfn);
    ASSERT(Page);
@@ -1043,7 +1010,6 @@
    }
 
    Page->LockCount--;
-   KeReleaseQueuedSpinLock(LockQueuePfnLock, oldIrql);
 }
 
 PFN_TYPE
@@ -1053,12 +1019,10 @@
    PFN_TYPE PfnOffset;
    PLIST_ENTRY ListEntry;
    PPHYSICAL_PAGE PageDescriptor;
-   KIRQL oldIrql;
    BOOLEAN NeedClear = FALSE;
 
    DPRINT("MmAllocPage()\n");
 
-   oldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
    if (IsListEmpty(&FreeZeroedPageListHead))
    {
       if (IsListEmpty(&FreeUnzeroedPageListHead))
@@ -1070,7 +1034,6 @@
          }
 
          DPRINT1("MmAllocPage(): Out of memory\n");
-         KeReleaseQueuedSpinLock(LockQueuePfnLock, oldIrql);
          return 0;
       }
       ListEntry = RemoveTailList(&FreeUnzeroedPageListHead);
@@ -1105,8 +1068,6 @@
 
    MmStats.NrSystemPages++;
    MmStats.NrFreePages--;
-
-   KeReleaseQueuedSpinLock(LockQueuePfnLock, oldIrql);
 
    PfnOffset = PageDescriptor - MmPfnDatabase;
    if ((NeedClear) && (Consumer != MC_SYSTEM))

Modified: trunk/reactos/ntoskrnl/mm/mmfault.c
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/mm/mmfault.c?rev=…
==============================================================================
--- trunk/reactos/ntoskrnl/mm/mmfault.c [iso-8859-1] (original)
+++ trunk/reactos/ntoskrnl/mm/mmfault.c [iso-8859-1] Wed Sep 30 20:24:00 2009
@@ -288,6 +288,8 @@
 {
    NTSTATUS Status;
    PFN_TYPE AllocatedPage;
+   KIRQL OldIrql;
+
    Status = MmRequestPageMemoryConsumer(MC_PPOOL, FALSE, &AllocatedPage);
    if (!NT_SUCCESS(Status))
    {
@@ -303,7 +305,9 @@
                              1);
    if (Locked)
    {
+      OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
       MmLockPage(AllocatedPage);
+      KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
    }
    return(Status);
 }

Modified: trunk/reactos/ntoskrnl/mm/section.c
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/mm/section.c?rev=…
==============================================================================
--- trunk/reactos/ntoskrnl/mm/section.c [iso-8859-1] (original)
+++ trunk/reactos/ntoskrnl/mm/section.c [iso-8859-1] Wed Sep 30 20:24:00 2009
@@ -771,6 +771,7 @@
    PMM_REGION Region;
    BOOLEAN HasSwapEntry;
    PEPROCESS Process = MmGetAddressSpaceOwner(AddressSpace);
+   KIRQL OldIrql;
     
    /*
     * There is a window between taking the page fault and locking the
@@ -781,7 +782,9 @@
    {
       if (Locked)
       {
+         OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
          MmLockPage(MmGetPfnForProcess(Process, Address));
+         KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
       }
       return(STATUS_SUCCESS);
    }
@@ -908,7 +911,9 @@
       }
       if (Locked)
       {
+         OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
          MmLockPage(Page);
+         KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
       }
       MmUnlockSectionSegment(Segment);
       PageOp->Status = STATUS_SUCCESS;
@@ -978,7 +983,9 @@
        */
       if (Locked)
       {
+         OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
          MmLockPage(Page);
+         KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
       }
       PageOp->Status = STATUS_SUCCESS;
       MmspCompleteAndReleasePageOp(PageOp);
@@ -1013,7 +1020,9 @@
        */
       if (Locked)
       {
-         MmLockPageUnsafe(Page);
+         OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
+         MmLockPage(Page);
+         KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
       }
 
       /*
@@ -1056,7 +1065,9 @@
       MmInsertRmap(Page, Process, (PVOID)PAddress);
       if (Locked)
       {
+         OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
          MmLockPage(Page);
+         KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
       }
 
       /*
@@ -1156,7 +1167,9 @@
 
       if (Locked)
       {
+         OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
          MmLockPage(Page);
+         KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
       }
       PageOp->Status = STATUS_SUCCESS;
       MmspCompleteAndReleasePageOp(PageOp);
@@ -1230,7 +1243,9 @@
       MmInsertRmap(Page, Process, (PVOID)PAddress);
       if (Locked)
       {
+         OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
          MmLockPage(Page);
+         KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
       }
       PageOp->Status = STATUS_SUCCESS;
       MmspCompleteAndReleasePageOp(PageOp);
@@ -1262,7 +1277,9 @@
       MmInsertRmap(Page, Process, (PVOID)PAddress);
       if (Locked)
       {
+         OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
          MmLockPage(Page);
+         KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
       }
       PageOp->Status = STATUS_SUCCESS;
       MmspCompleteAndReleasePageOp(PageOp);
@@ -1289,6 +1306,7 @@
    PMM_REGION Region;
    ULONG Entry;
    PEPROCESS Process = MmGetAddressSpaceOwner(AddressSpace);
+   KIRQL OldIrql;
     
    DPRINT("MmAccessFaultSectionView(%x, %x, %x, %x)\n", AddressSpace,
MemoryArea, Address, Locked);
 
@@ -1429,8 +1447,10 @@
    }
    if (Locked)
    {
+      OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
       MmLockPage(NewPage);
       MmUnlockPage(OldPage);
+      KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
    }
 
    /*
@@ -1511,6 +1531,7 @@
    BOOLEAN DirectMapped;
    BOOLEAN IsImageSection;
    PEPROCESS Process = MmGetAddressSpaceOwner(AddressSpace);
+   KIRQL OldIrql;
     
    Address = (PVOID)PAGE_ROUND_DOWN(Address);
 
@@ -1599,7 +1620,9 @@
    }
    else
    {
+      OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
       MmReferencePage(Page);
+      KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
    }
 
    MmDeleteAllRmaps(Page, (PVOID)&Context, MmPageOutDeleteMapping);