Delete `AppDomainIterator` (#78078)

13 files changed, 89 insertions, 404 deletions

diff --git a/src/coreclr/debug/daccess/daccess.cpp b/src/coreclr/debug/daccess/daccess.cpp
index b77e0312e23..f383542abbd 100644
--- a/src/coreclr/debug/daccess/daccess.cpp
+++ b/src/coreclr/debug/daccess/daccess.cpp
@@ -543,32 +543,13 @@ MetaEnum::NextDomainToken(AppDomain** appDomain,
         return NextToken(token, NULL, NULL);
     }
 
-    //
-    // Splay tokens across all app domains.
-    //
-
-    while (true)
+    // Need to fetch a token.
+    if ((status = NextToken(token, NULL, NULL)) != S_OK)
     {
-        if (m_lastToken == mdTokenNil)
-        {
-            // Need to fetch a token.
-            if ((status = NextToken(token, NULL, NULL)) != S_OK)
-            {
-                return status;
-            }
-
-            m_domainIter.Init();
-        }
-
-        if (m_domainIter.Next())
-        {
-            break;
-        }
-
-        m_lastToken = mdTokenNil;
+        return status;
     }
 
-    *appDomain = m_domainIter.GetDomain();
+    *appDomain = AppDomain::GetCurrentDomain();
     *token = m_lastToken;
 
     return S_OK;
@@ -622,33 +603,14 @@ MetaEnum::NextDomainTokenByName(_In_opt_ LPCUTF8 namespaceName,
         return NextTokenByName(namespaceName, name, nameFlags, token);
     }
 
-    //
-    // Splay tokens across all app domains.
-    //
-
-    while (true)
+    // Need to fetch a token.
+    if ((status = NextTokenByName(namespaceName, name, nameFlags,
+                                    token)) != S_OK)
     {
-        if (m_lastToken == mdTokenNil)
-        {
-            // Need to fetch a token.
-            if ((status = NextTokenByName(namespaceName, name, nameFlags,
-                                          token)) != S_OK)
-            {
-                return status;
-            }
-
-            m_domainIter.Init();
-        }
-
-        if (m_domainIter.Next())
-        {
-            break;
-        }
-
-        m_lastToken = mdTokenNil;
+        return status;
     }
 
-    *appDomain = m_domainIter.GetDomain();
+    *appDomain = AppDomain::GetCurrentDomain();
     *token = m_lastToken;
 
     return S_OK;
@@ -1366,35 +1328,16 @@ SplitName::CdNextDomainField(ClrDataAccess* dac,
                            0, NULL, NULL, NULL, NULL);
     }
 
-    //
-    // Splay fields across all app domains.
-    //
-
-    while (true)
+    // Need to fetch a field.
+    if ((status = CdNextField(dac, handle, NULL, NULL, NULL,
+                                0, NULL, NULL, NULL, NULL)) != S_OK)
     {
-        if (!split->m_lastField)
-        {
-            // Need to fetch a field.
-            if ((status = CdNextField(dac, handle, NULL, NULL, NULL,
-                                      0, NULL, NULL, NULL, NULL)) != S_OK)
-            {
-                return status;
-            }
-
-            split->m_metaEnum.m_domainIter.Init();
-        }
-
-        if (split->m_metaEnum.m_domainIter.Next())
-        {
-            break;
-        }
-
-        split->m_lastField = NULL;
+        return status;
     }
 
     return ClrDataValue::
         NewFromFieldDesc(dac,
-                         split->m_metaEnum.m_domainIter.GetDomain(),
+                         AppDomain::GetCurrentDomain(),
                          split->m_fieldEnum.IsFieldFromParentClass() ?
                          CLRDATA_VALUE_IS_INHERITED : 0,
                          split->m_lastField,
@@ -3730,16 +3673,9 @@ ClrDataAccess::StartEnumAppDomains(
 
     EX_TRY
     {
-        AppDomainIterator* iter = new (nothrow) AppDomainIterator(FALSE);
-        if (iter)
-        {
-            *handle = TO_CDENUM(iter);
-            status = S_OK;
-        }
-        else
-        {
-            status = E_OUTOFMEMORY;
-        }
+        // Only one app domain - use 1 to indicate there there is a next value
+        *handle = 1;
+        status = S_OK;
     }
     EX_CATCH
     {
@@ -3765,12 +3701,12 @@ ClrDataAccess::EnumAppDomain(
 
     EX_TRY
     {
-        AppDomainIterator* iter = FROM_CDENUM(AppDomainIterator, *handle);
-        if (iter->Next())
+        if (*handle == 1)
         {
             *appDomain = new (nothrow)
-                ClrDataAppDomain(this, iter->GetDomain());
+                ClrDataAppDomain(this, AppDomain::GetCurrentDomain());
             status = *appDomain ? S_OK : E_OUTOFMEMORY;
+            *handle = 0;
         }
         else
         {
@@ -3800,8 +3736,7 @@ ClrDataAccess::EndEnumAppDomains(
 
     EX_TRY
     {
-        AppDomainIterator* iter = FROM_CDENUM(AppDomainIterator, handle);
-        delete iter;
+        // Nothing to do - we don't actually create an iterator for app domains
         status = S_OK;
     }
     EX_CATCH
@@ -4462,8 +4397,7 @@ ClrDataAccess::TranslateExceptionRecordToNotification(
                 else
                 {
                     // Find a likely domain, because it's the shared domain.
-                    AppDomainIterator adi(FALSE);
-                    appDomain = adi.GetDomain();
+                    appDomain = AppDomain::GetCurrentDomain();
                 }
 
                 pubMethodInst =
@@ -4527,8 +4461,7 @@ ClrDataAccess::TranslateExceptionRecordToNotification(
                 else
                 {
                     // Find a likely domain, because it's the shared domain.
-                    AppDomainIterator adi(FALSE);
-                    appDomain = adi.GetDomain();
+                    appDomain = AppDomain::GetCurrentDomain();
                 }
 
                 pubMethodInst =
diff --git a/src/coreclr/debug/daccess/dacdbiimpl.cpp b/src/coreclr/debug/daccess/dacdbiimpl.cpp
index 3ba32fb341e..e20b0241776 100644
--- a/src/coreclr/debug/daccess/dacdbiimpl.cpp
+++ b/src/coreclr/debug/daccess/dacdbiimpl.cpp
@@ -4457,23 +4457,13 @@ void DacDbiInterfaceImpl::EnumerateAppDomains(
 
     _ASSERTE(fpCallback != NULL);
 
-    // Only include active appdomains in the enumeration.
-    // This includes appdomains sent before the AD load event,
-    // and does not include appdomains that are in shutdown after the AD exit event.
-    const BOOL bOnlyActive = TRUE;
-    AppDomainIterator iterator(bOnlyActive);
+    // It's critical that we don't yield appdomains after the unload event has been sent.
+    // See code:IDacDbiInterface#Enumeration for details.
+    AppDomain * pAppDomain = AppDomain::GetCurrentDomain();
 
-    while(iterator.Next())
-    {
-        // It's critical that we don't yield appdomains after the unload event has been sent.
-        // See code:IDacDbiInterface#Enumeration for details.
-        AppDomain * pAppDomain = iterator.GetDomain();
-
-        VMPTR_AppDomain vmAppDomain = VMPTR_AppDomain::NullPtr();
-        vmAppDomain.SetHostPtr(pAppDomain);
-
-        fpCallback(vmAppDomain, pUserData);
-    }
+    VMPTR_AppDomain vmAppDomain = VMPTR_AppDomain::NullPtr();
+    vmAppDomain.SetHostPtr(pAppDomain);
+    fpCallback(vmAppDomain, pUserData);
 }
 
 // Enumerate all Assemblies in an appdomain.
diff --git a/src/coreclr/debug/daccess/dacimpl.h b/src/coreclr/debug/daccess/dacimpl.h
index 33a2149e9a5..a122d4eb675 100644
--- a/src/coreclr/debug/daccess/dacimpl.h
+++ b/src/coreclr/debug/daccess/dacimpl.h
@@ -279,7 +279,6 @@ class MetaEnum
 {
 public:
     MetaEnum(void)
-        : m_domainIter(FALSE)
     {
         Clear();
         m_appDomain = NULL;
@@ -355,7 +354,6 @@ public:
     ULONG32 m_kind;
     HENUMInternal m_enum;
     AppDomain* m_appDomain;
-    AppDomainIterator m_domainIter;
     mdToken m_lastToken;
 
     static HRESULT New(Module* mod,
@@ -502,13 +500,11 @@ public:
 
 struct ProcessModIter
 {
-    AppDomainIterator m_domainIter;
     bool m_nextDomain;
     AppDomain::AssemblyIterator m_assemIter;
     Assembly* m_curAssem;
 
     ProcessModIter(void)
-        : m_domainIter(FALSE)
     {
         SUPPORTS_DAC;
         m_nextDomain = true;
@@ -518,33 +514,24 @@ struct ProcessModIter
     Assembly * NextAssem()
     {
         SUPPORTS_DAC;
-        for (;;)
-        {
-            if (m_nextDomain)
-            {
-                if (!m_domainIter.Next())
-                {
-                    break;
-                }
-
-                m_nextDomain = false;
 
-                m_assemIter = m_domainIter.GetDomain()->IterateAssembliesEx((AssemblyIterationFlags)(
-                    kIncludeLoaded | kIncludeExecution));
-            }
+        if (m_nextDomain)
+        {
+            m_nextDomain = false;
 
-            CollectibleAssemblyHolder<DomainAssembly *> pDomainAssembly;
-            if (!m_assemIter.Next(pDomainAssembly.This()))
-            {
-                m_nextDomain = true;
-                continue;
-            }
+            m_assemIter = AppDomain::GetCurrentDomain()->IterateAssembliesEx((AssemblyIterationFlags)(
+                kIncludeLoaded | kIncludeExecution));
+        }
 
-            // Note: DAC doesn't need to keep the assembly alive - see code:CollectibleAssemblyHolder#CAH_DAC
-            CollectibleAssemblyHolder<Assembly *> pAssembly = pDomainAssembly->GetAssembly();
-            return pAssembly;
+        CollectibleAssemblyHolder<DomainAssembly *> pDomainAssembly;
+        if (!m_assemIter.Next(pDomainAssembly.This()))
+        {
+            return NULL;
         }
-        return NULL;
+
+        // Note: DAC doesn't need to keep the assembly alive - see code:CollectibleAssemblyHolder#CAH_DAC
+        CollectibleAssemblyHolder<Assembly *> pAssembly = pDomainAssembly->GetAssembly();
+        return pAssembly;
     }
 
     Module* NextModule(void)
@@ -3948,9 +3935,7 @@ public:
     static HRESULT CdEnd(CLRDATA_ENUM handle);
 
     MethodDesc* m_methodDesc;
-    AppDomain* m_givenAppDomain;
-    bool m_givenAppDomainUsed;
-    AppDomainIterator m_domainIter;
+    bool m_appDomainUsed;
     AppDomain* m_appDomain;
     LoadedMethodDescIterator m_methodIter;
 };
diff --git a/src/coreclr/debug/daccess/enummem.cpp b/src/coreclr/debug/daccess/enummem.cpp
index 6763ecb358f..b8b505744ad 100644
--- a/src/coreclr/debug/daccess/enummem.cpp
+++ b/src/coreclr/debug/daccess/enummem.cpp
@@ -702,18 +702,18 @@ HRESULT ClrDataAccess::EnumMemDumpAppDomainInfo(CLRDataEnumMemoryFlags flags)
         SystemDomain::System()->GetLoaderAllocator()->EnumMemoryRegions(flags);
     }
 
-    AppDomainIterator adIter(FALSE);
+    AppDomain* appDomain = AppDomain::GetCurrentDomain();
+    if (appDomain == NULL)
+        return S_OK;
+
     EX_TRY
     {
-        while (adIter.Next())
-        {
-            CATCH_ALL_EXCEPT_RETHROW_COR_E_OPERATIONCANCELLED
-            (
-                // Note that the flags being CLRDATA_ENUM_MEM_MINI prevents
-                // you from pulling entire files loaded into memory into the dump.
-                adIter.GetDomain()->EnumMemoryRegions(flags, true);
-            );
-        }
+        CATCH_ALL_EXCEPT_RETHROW_COR_E_OPERATIONCANCELLED
+        (
+            // Note that the flags being CLRDATA_ENUM_MEM_MINI prevents
+            // you from pulling entire files loaded into memory into the dump.
+            appDomain->EnumMemoryRegions(flags, true);
+        );
     }
     EX_CATCH_RETHROW_ONLY_COR_E_OPERATIONCANCELLED
 
diff --git a/src/coreclr/debug/daccess/request.cpp b/src/coreclr/debug/daccess/request.cpp
index a16aaf8e9b9..74974c3b6f4 100644
--- a/src/coreclr/debug/daccess/request.cpp
+++ b/src/coreclr/debug/daccess/request.cpp
@@ -2214,13 +2214,14 @@ HRESULT ClrDataAccess::GetAppDomainList(unsigned int count, CLRDATA_ADDRESS valu
 {
     SOSDacEnter();
 
-    AppDomainIterator ai(FALSE);
+    AppDomain* appDomain = AppDomain::GetCurrentDomain();
     unsigned int i = 0;
-    while (ai.Next() && (i < count))
+    if (appDomain != NULL && i < count)
     {
         if (values)
-            values[i] = HOST_CDADDR(ai.GetDomain());
-        i++;
+            values[0] = HOST_CDADDR(appDomain);
+
+        i = 1;
     }
 
     if (fetched)
@@ -2240,8 +2241,7 @@ ClrDataAccess::GetAppDomainStoreData(struct DacpAppDomainStoreData *adsData)
 
     // Get an accurate count of appdomains.
     adsData->DomainCount = 0;
-    AppDomainIterator ai(FALSE);
-    while (ai.Next())
+    if (AppDomain::GetCurrentDomain() != NULL)
         adsData->DomainCount++;
 
     SOSDacLeave();
diff --git a/src/coreclr/debug/daccess/task.cpp b/src/coreclr/debug/daccess/task.cpp
index 02751c12c59..5cafc577bef 100644
--- a/src/coreclr/debug/daccess/task.cpp
+++ b/src/coreclr/debug/daccess/task.cpp
@@ -5188,45 +5188,27 @@ EnumMethodDefinitions::CdEnd(CLRDATA_ENUM handle)
 
 EnumMethodInstances::EnumMethodInstances(MethodDesc* methodDesc,
                                          IXCLRDataAppDomain* givenAppDomain)
-    : m_domainIter(FALSE)
 {
     m_methodDesc = methodDesc;
     if (givenAppDomain)
     {
-        m_givenAppDomain =
+        m_appDomain =
             ((ClrDataAppDomain*)givenAppDomain)->GetAppDomain();
     }
     else
     {
-        m_givenAppDomain = NULL;
+        m_appDomain = AppDomain::GetCurrentDomain();
     }
-    m_givenAppDomainUsed = false;
-    m_appDomain = NULL;
+    m_appDomainUsed = false;
 }
 
 HRESULT
 EnumMethodInstances::Next(ClrDataAccess* dac,
                           IXCLRDataMethodInstance **instance)
 {
- NextDomain:
-    if (!m_appDomain)
+    if (!m_appDomainUsed)
     {
-        if (m_givenAppDomainUsed ||
-            !m_domainIter.Next())
-        {
-            return S_FALSE;
-        }
-
-        if (m_givenAppDomain)
-        {
-            m_appDomain = m_givenAppDomain;
-            m_givenAppDomainUsed = true;
-        }
-        else
-        {
-            m_appDomain = m_domainIter.GetDomain();
-        }
-
+        m_appDomainUsed = true;
         m_methodIter.Start(m_appDomain,
                            m_methodDesc->GetModule(),       // module
                            m_methodDesc->GetMemberDef(),    // token
@@ -5239,8 +5221,7 @@ EnumMethodInstances::Next(ClrDataAccess* dac,
         CollectibleAssemblyHolder<DomainAssembly *> pDomainAssembly;
         if (!m_methodIter.Next(pDomainAssembly.This()))
         {
-            m_appDomain = NULL;
-            goto NextDomain;
+            return S_FALSE;
         }
     }
 
diff --git a/src/coreclr/nativeaot/Runtime/eventtrace.cpp b/src/coreclr/nativeaot/Runtime/eventtrace.cpp
index 5893ed4b630..39de4049df0 100644
--- a/src/coreclr/nativeaot/Runtime/eventtrace.cpp
+++ b/src/coreclr/nativeaot/Runtime/eventtrace.cpp
@@ -6487,18 +6487,15 @@ void ETW::EnumerationLog::EnumerationHelper(Module* moduleFilter, BaseDomain* do
         }
         else
         {
-            AppDomainIterator appDomainIterator(FALSE);
-            while (appDomainIterator.Next())
+            AppDomain * pDomain = AppDomain::GetCurrentDomain();
+            if (pDomain != NULL)
             {
-                AppDomain* pDomain = appDomainIterator.GetDomain();
-                if (pDomain != NULL)
-                {
-                    // See code:#TableLockHolder
-                    ReJitManager::TableLockHolder lkRejitMgrAD(pDomain->GetReJitManager());
+                // See code:#TableLockHolder
+                ReJitManager::TableLockHolder lkRejitMgrAD(pDomain->GetReJitManager());
 
-                    ETW::EnumerationLog::IterateAppDomain(pDomain, enumerationOptions);
-                }
+                ETW::EnumerationLog::IterateAppDomain(pDomain, enumerationOptions);
             }
+
             ETW::EnumerationLog::IterateDomain(SharedDomain::GetDomain(), enumerationOptions);
         }
     }
diff --git a/src/coreclr/vm/appdomain.cpp b/src/coreclr/vm/appdomain.cpp
index fe4e901de57..74c74041a49 100644
--- a/src/coreclr/vm/appdomain.cpp
+++ b/src/coreclr/vm/appdomain.cpp
@@ -1032,10 +1032,7 @@ void SystemDomain::DetachEnd()
 void SystemDomain::Stop()
 {
     WRAPPER_NO_CONTRACT;
-    AppDomainIterator i(TRUE);
-
-    while (i.Next())
-        i.GetDomain()->Stop();
+    AppDomain::GetCurrentDomain()->Stop();
 }
 
 void SystemDomain::PreallocateSpecialObjects()
@@ -1220,19 +1217,6 @@ void SystemDomain::LazyInitFrozenObjectsHeap()
     }
     CONTRACT_END;
 
-    // We don't do a normal AppDomainIterator because we can't take the SystemDomain lock from
-    // here.
-    // We're only supposed to call this from a Server GC. We're walking here m_appDomainIdList
-    // m_appDomainIdList will have an AppDomain* or will be NULL. So the only danger is if we
-    // Fetch an AppDomain and then in some other thread the AppDomain is deleted.
-    //
-    // If the thread deleting the AppDomain (AppDomain::~AppDomain)was in Preemptive mode
-    // while doing SystemDomain::EnumAllStaticGCRefs we will issue a GCX_COOP(), which will wait
-    // for the GC to finish, so we are safe
-    //
-    // If the thread is in cooperative mode, it must have been suspended for the GC so a delete
-    // can't happen.
-
     _ASSERTE(GCHeapUtilities::IsGCInProgress() &&
              GCHeapUtilities::IsServerHeap()   &&
              IsGCSpecialThread());
@@ -1910,10 +1894,6 @@ AppDomain::AppDomain()
     m_ForceTrivialWaitOperations = false;
     m_Stage=STAGE_CREATING;
 
-#ifdef _DEBUG
-    m_dwIterHolders=0;
-#endif
-
 #ifdef FEATURE_TYPEEQUIVALENCE
     m_pTypeEquivalenceTable = NULL;
 #endif // FEATURE_TYPEEQUIVALENCE
@@ -5120,7 +5100,7 @@ AppDomain::EnumMemoryRegions(CLRDataEnumMemoryFlags flags, bool enumThis)
     {
         GetLoaderAllocator()->EnumMemoryRegions(flags);
     }
-    
+
     m_Assemblies.EnumMemoryRegions(flags);
     AssemblyIterator assem = IterateAssembliesEx((AssemblyIterationFlags)(kIncludeLoaded | kIncludeExecution));
     CollectibleAssemblyHolder<DomainAssembly *> pDomainAssembly;
diff --git a/src/coreclr/vm/appdomain.hpp b/src/coreclr/vm/appdomain.hpp
index 0dbff5efbf6..18b4d4fd3f5 100644
--- a/src/coreclr/vm/appdomain.hpp
+++ b/src/coreclr/vm/appdomain.hpp
@@ -1468,8 +1468,6 @@ struct FailedAssembly {
     }
 };
 
-class AppDomainIterator;
-
 const DWORD DefaultADID = 1;
 
 // An Appdomain is the managed equivalent of a process.  It is an isolation unit (conceptually you don't
@@ -1974,29 +1972,6 @@ public:
 
     static void ExceptionUnwind(Frame *pFrame);
 
-#ifdef _DEBUG
-
-    BOOL IsHeldByIterator()
-    {
-        LIMITED_METHOD_CONTRACT;
-        return m_dwIterHolders>0;
-    }
-
-    void IteratorRelease()
-    {
-        LIMITED_METHOD_CONTRACT;
-        _ASSERTE(m_dwIterHolders);
-        InterlockedDecrement(&m_dwIterHolders);
-    }
-
-
-    void IteratorAcquire()
-    {
-        LIMITED_METHOD_CONTRACT;
-        InterlockedIncrement(&m_dwIterHolders);
-    }
-
-#endif
     BOOL IsActive()
     {
         LIMITED_METHOD_DAC_CONTRACT;
@@ -2017,7 +1992,6 @@ public:
 #endif
     }
 
-
     static void RaiseExitProcessEvent();
     Assembly* RaiseResourceResolveEvent(DomainAssembly* pAssembly, LPCSTR szName);
     DomainAssembly* RaiseTypeResolveEventThrowing(DomainAssembly* pAssembly, LPCSTR szName, ASSEMBLYREF *pResultingAssemblyRef);
@@ -2208,10 +2182,6 @@ private:
 
     ArrayList        m_failedAssemblies;
 
-#ifdef _DEBUG
-    Volatile<LONG> m_dwIterHolders;
-#endif
-
     //
     // DAC iterator for failed assembly loads
     //
@@ -2348,8 +2318,6 @@ typedef VPTR(class SystemDomain) PTR_SystemDomain;
 class SystemDomain : public BaseDomain
 {
     friend class AppDomainNative;
-    friend class AppDomainIterator;
-    friend class UnsafeAppDomainIterator;
     friend class ClrDataAccess;
 
     VPTR_VTABLE_CLASS(SystemDomain, BaseDomain)
@@ -2675,132 +2643,6 @@ public:
 
 };  // class SystemDomain
 
-
-//
-// an UnsafeAppDomainIterator is used to iterate over all existing domains
-//
-// The iteration is guaranteed to include all domains that exist at the
-// start & end of the iteration. This iterator is considered unsafe because it does not
-// reference count the various appdomains, and can only be used when the runtime is stopped,
-// or external synchronization is used. (and therefore no other thread may cause the appdomain list to change.)
-// In CoreCLR, this iterator doesn't use a list as there is at most 1 AppDomain, and instead will find the only AppDomain, or not.
-//
-class UnsafeAppDomainIterator
-{
-    friend class SystemDomain;
-public:
-    UnsafeAppDomainIterator(BOOL bOnlyActive)
-    {
-        m_bOnlyActive = bOnlyActive;
-    }
-
-    void Init()
-    {
-        LIMITED_METHOD_CONTRACT;
-        m_iterationCount = 0;
-        m_pCurrent = NULL;
-    }
-
-    BOOL Next()
-    {
-        WRAPPER_NO_CONTRACT;
-
-        if (m_iterationCount == 0)
-        {
-            m_iterationCount++;
-            m_pCurrent = AppDomain::GetCurrentDomain();
-            if (m_pCurrent != NULL &&
-                (m_bOnlyActive ?
-                 m_pCurrent->IsActive() : m_pCurrent->IsValid()))
-            {
-                return TRUE;
-            }
-        }
-
-        m_pCurrent = NULL;
-        return FALSE;
-    }
-
-    AppDomain * GetDomain()
-    {
-        LIMITED_METHOD_DAC_CONTRACT;
-
-        return m_pCurrent;
-    }
-
-  private:
-
-    int                 m_iterationCount;
-    AppDomain *         m_pCurrent;
-    BOOL                m_bOnlyActive;
-};  // class UnsafeAppDomainIterator
-
-//
-// an AppDomainIterator is used to iterate over all existing domains.
-//
-// The iteration is guaranteed to include all domains that exist at the
-// start & end of the iteration.  Any domains added or deleted during
-// iteration may or may not be included.  The iterator also guarantees
-// that the current iterated appdomain (GetDomain()) will not be deleted.
-//
-
-class AppDomainIterator : public UnsafeAppDomainIterator
-{
-    friend class SystemDomain;
-
-  public:
-    AppDomainIterator(BOOL bOnlyActive) : UnsafeAppDomainIterator(bOnlyActive)
-    {
-        WRAPPER_NO_CONTRACT;
-        Init();
-    }
-
-    ~AppDomainIterator()
-    {
-        WRAPPER_NO_CONTRACT;
-
-#ifndef DACCESS_COMPILE
-        if (GetDomain() != NULL)
-        {
-#ifdef _DEBUG
-            GetDomain()->IteratorRelease();
-#endif
-            GetDomain()->Release();
-        }
-#endif
-    }
-
-    BOOL Next()
-    {
-        WRAPPER_NO_CONTRACT;
-
-#ifndef DACCESS_COMPILE
-        if (GetDomain() != NULL)
-        {
-#ifdef _DEBUG
-            GetDomain()->IteratorRelease();
-#endif
-            GetDomain()->Release();
-        }
-
-        SystemDomain::LockHolder lh;
-#endif
-
-        if (UnsafeAppDomainIterator::Next())
-        {
-#ifndef DACCESS_COMPILE
-            GetDomain()->AddRef();
-#ifdef _DEBUG
-            GetDomain()->IteratorAcquire();
-#endif
-#endif
-            return TRUE;
-        }
-
-        return FALSE;
-    }
-};  // class AppDomainIterator
-
 #include "comreflectioncache.inl"
 
 #endif
diff --git a/src/coreclr/vm/ceeload.cpp b/src/coreclr/vm/ceeload.cpp
index 73eb37933ab..9399e7bd7b6 100644
--- a/src/coreclr/vm/ceeload.cpp
+++ b/src/coreclr/vm/ceeload.cpp
@@ -2491,17 +2491,11 @@ void Module::SetSymbolBytes(LPCBYTE pbSyms, DWORD cbSyms)
     // the assembly was loaded in.</REVISIT_TODO>
     if (CORDebuggerAttached())
     {
-        AppDomainIterator i(FALSE);
-
-        while (i.Next())
+        AppDomain *pDomain = AppDomain::GetCurrentDomain();
+        if (pDomain->IsDebuggerAttached() && (GetDomain() == SystemDomain::System() ||
+                                                pDomain->ContainsAssembly(m_pAssembly)))
         {
-            AppDomain *pDomain = i.GetDomain();
-
-            if (pDomain->IsDebuggerAttached() && (GetDomain() == SystemDomain::System() ||
-                                                  pDomain->ContainsAssembly(m_pAssembly)))
-            {
-                g_pDebugInterface->SendUpdateModuleSymsEventAndBlock(this, pDomain);
-            }
+            g_pDebugInterface->SendUpdateModuleSymsEventAndBlock(this, pDomain);
         }
     }
 }
diff --git a/src/coreclr/vm/eventtrace.cpp b/src/coreclr/vm/eventtrace.cpp
index 3582cbb6627..3043568b587 100644
--- a/src/coreclr/vm/eventtrace.cpp
+++ b/src/coreclr/vm/eventtrace.cpp
@@ -7668,14 +7668,10 @@ VOID ETW::EnumerationLog::EnumerationHelper(Module *moduleFilter, BaseDomain *do
         }
         else
         {
-            AppDomainIterator appDomainIterator(FALSE);
-            while(appDomainIterator.Next())
+            AppDomain *pDomain = AppDomain::GetCurrentDomain();
+            if (pDomain != NULL)
             {
-                AppDomain *pDomain = appDomainIterator.GetDomain();
-                if (pDomain != NULL)
-                {
-                    ETW::EnumerationLog::IterateAppDomain(pDomain, enumerationOptions);
-                }
+                ETW::EnumerationLog::IterateAppDomain(pDomain, enumerationOptions);
             }
         }
     }
diff --git a/src/coreclr/vm/interoputil.cpp b/src/coreclr/vm/interoputil.cpp
index 087e23b62ae..66130142728 100644
--- a/src/coreclr/vm/interoputil.cpp
+++ b/src/coreclr/vm/interoputil.cpp
@@ -1316,11 +1316,8 @@ static void ReleaseRCWsInCaches(LPVOID pCtxCookie)
     }
     CONTRACTL_END;
 
-    // Go through all the app domains and for each one release all the
-    // RCW's that live in the current context.
-    AppDomainIterator i(TRUE);
-    while (i.Next())
-        i.GetDomain()->ReleaseRCWs(pCtxCookie);
+    // Release all the RCW's that live in the AppDomain.
+    AppDomain::GetCurrentDomain()->ReleaseRCWs(pCtxCookie);
 
     if (!g_fEEShutDown)
     {
diff --git a/src/coreclr/vm/multicorejit.cpp b/src/coreclr/vm/multicorejit.cpp
index 3bcc0e0c2e5..754d4e92976 100644
--- a/src/coreclr/vm/multicorejit.cpp
+++ b/src/coreclr/vm/multicorejit.cpp
@@ -1467,16 +1467,11 @@ void MulticoreJitManager::StopProfileAll()
     }
     CONTRACTL_END;
 
-    AppDomainIterator domain(TRUE);
+    AppDomain * pDomain = AppDomain::GetCurrentDomain();
 
-    while (domain.Next())
+    if (pDomain != NULL)
     {
-        AppDomain * pDomain = domain.GetDomain();
-
-        if (pDomain != NULL)
-        {
-            pDomain->GetMulticoreJitManager().StopProfile(true);
-        }
+        pDomain->GetMulticoreJitManager().StopProfile(true);
     }
 }
 
@@ -1508,16 +1503,11 @@ void MulticoreJitManager::DisableMulticoreJit()
 
 #ifdef PROFILING_SUPPORTED
 
-    AppDomainIterator domain(TRUE);
+    AppDomain * pDomain = AppDomain::GetCurrentDomain();
 
-    while (domain.Next())
+    if (pDomain != NULL)
     {
-        AppDomain * pDomain = domain.GetDomain();
-
-        if (pDomain != NULL)
-        {
-            pDomain->GetMulticoreJitManager().AbortProfile();
-        }
+        pDomain->GetMulticoreJitManager().AbortProfile();
     }
 
 #endif