Delete HAS_FLS_SUPPORT and related code (#21035)

10 files changed, 25 insertions, 974 deletions

diff --git a/src/debug/daccess/dacdbiimpl.cpp b/src/debug/daccess/dacdbiimpl.cpp
index 988f6734fa..cc68cdc930 100644
--- a/src/debug/daccess/dacdbiimpl.cpp
+++ b/src/debug/daccess/dacdbiimpl.cpp
@@ -4667,8 +4667,7 @@ CONNID DacDbiInterfaceImpl::GetConnectionID(VMPTR_Thread vmThread)
 {
     DD_ENTER_MAY_THROW;
 
-    Thread * pThread = vmThread.GetDacPtr();
-    return pThread->GetConnectionId();
+    return INVALID_CONNECTION_ID;
 }
 
 // Return the task ID of the specified thread.
@@ -4676,8 +4675,7 @@ TASKID DacDbiInterfaceImpl::GetTaskID(VMPTR_Thread vmThread)
 {
     DD_ENTER_MAY_THROW;
 
-    Thread * pThread = vmThread.GetDacPtr();
-    return pThread->GetTaskId();
+    return INVALID_TASK_ID;
 }
 
 // Return the OS thread ID of the specified thread
diff --git a/src/debug/daccess/request.cpp b/src/debug/daccess/request.cpp
index 3607916317..c196d7f2a4 100644
--- a/src/debug/daccess/request.cpp
+++ b/src/debug/daccess/request.cpp
@@ -765,26 +765,7 @@ ClrDataAccess::GetThreadData(CLRDATA_ADDRESS threadAddr, struct DacpThreadData *
     threadData->allocContextPtr = TO_CDADDR(thread->m_alloc_context.alloc_ptr);
     threadData->allocContextLimit = TO_CDADDR(thread->m_alloc_context.alloc_limit);
 
-    // @todo Microsoft: the following assignment is pointless--we're just getting the
-    // target address of the m_pFiberData field of the Thread instance. Then we're going to
-    // compute it again as the argument to ReadVirtual. Ultimately, we want the value of 
-    // that field, not its address. We already have that value as part of thread (the 
-    // marshaled Thread instance).This should just go away and we should simply have:
-    // threadData->fiberData = TO_CDADDR(thread->m_pFiberData );
-    // instead of the next 11 lines. 
-    threadData->fiberData = (CLRDATA_ADDRESS)PTR_HOST_MEMBER_TADDR(Thread, thread, m_pFiberData);
-
-    ULONG32 returned = 0;
-    TADDR Value = NULL;
-    HRESULT hr = m_pTarget->ReadVirtual(PTR_HOST_MEMBER_TADDR(Thread, thread, m_pFiberData),
-                                        (PBYTE)&Value,
-                                        sizeof(TADDR),
-                                        &returned);
-    
-    if ((hr  == S_OK) && (returned == sizeof(TADDR)))
-    {
-        threadData->fiberData = (CLRDATA_ADDRESS) Value;
-    }
+    threadData->fiberData = NULL;
 
     threadData->pFrame = PTR_CDADDR(thread->m_pFrame);
     threadData->context = PTR_CDADDR(thread->m_Context);
diff --git a/src/debug/ee/debugger.cpp b/src/debug/ee/debugger.cpp
index c6fb4192e5..b23a1ca905 100644
--- a/src/debug/ee/debugger.cpp
+++ b/src/debug/ee/debugger.cpp
@@ -11429,20 +11429,8 @@ bool Debugger::HandleIPCEvent(DebuggerIPCEvent * pEvent)
 
     case DB_IPCE_GET_THREAD_FOR_TASKID:
         {
-             TASKID taskid = pEvent->GetThreadForTaskId.taskid;
-             Thread *pThread = ThreadStore::GetThreadList(NULL);
              Thread *pThreadRet = NULL;
 
-             while (pThread != NULL)
-             {
-                 if (pThread->GetTaskId() == taskid)
-                 {
-                     pThreadRet = pThread;
-                     break;
-                 }
-                 pThread = ThreadStore::GetThreadList(pThread);
-             }
-
              // This is a synchronous event (reply required)
              pEvent = m_pRCThread->GetIPCEventReceiveBuffer();
 
diff --git a/src/vm/ceemain.h b/src/vm/ceemain.h
index 9a14af54ca..451bbc58b1 100644
--- a/src/vm/ceemain.h
+++ b/src/vm/ceemain.h
@@ -69,10 +69,6 @@ public:
     // Delete on TLS block
     static void DeleteTLS(void **pTlsData);
 
-    // Fiber switch notifications
-    static void SwitchIn();
-    static void SwitchOut();
-
     static void **CheckThreadState(DWORD slot, BOOL force = TRUE);
     static void **CheckThreadStateNoCreate(DWORD slot
 #ifdef _DEBUG
diff --git a/src/vm/codeman.cpp b/src/vm/codeman.cpp
index 1ea4303e34..815507fa60 100644
--- a/src/vm/codeman.cpp
+++ b/src/vm/codeman.cpp
@@ -2311,11 +2311,6 @@ extern "C" PT_RUNTIME_FUNCTION GetRuntimeFunctionCallback(IN ULONG     ControlPc
     BEGIN_PRESERVE_LAST_ERROR;
 
 #ifdef ENABLE_CONTRACTS
-    // See comment in code:Thread::SwitchIn and SwitchOut.
-    Thread *pThread = GetThread();
-    if (!(pThread && pThread->HasThreadStateNC(Thread::TSNC_InTaskSwitch)))
-    {
-
     // Some 64-bit OOM tests use the hosting interface to re-enter the CLR via
     // RtlVirtualUnwind to track unique stacks at each failure point. RtlVirtualUnwind can
     // result in the EEJitManager taking a reader lock. This, in turn, results in a
@@ -2336,10 +2331,6 @@ extern "C" PT_RUNTIME_FUNCTION GetRuntimeFunctionCallback(IN ULONG     ControlPc
 
     LOG((LF_EH, LL_INFO1000000, "GetRuntimeFunctionCallback(%p) returned %p\n", ControlPc, prf));
 
-#ifdef ENABLE_CONTRACTS
-    }
-#endif // ENABLE_CONTRACTS
-
     END_PRESERVE_LAST_ERROR;
 
     return  prf;
diff --git a/src/vm/corhost.cpp b/src/vm/corhost.cpp
index b58d75d676..17079082b7 100644
--- a/src/vm/corhost.cpp
+++ b/src/vm/corhost.cpp
@@ -2719,64 +2719,9 @@ ULONG STDMETHODCALLTYPE CExecutionEngine::Release()
 struct ClrTlsInfo
 {
     void* data[MAX_PREDEFINED_TLS_SLOT];
-    // When hosted, we may not be able to delete memory in DLL_THREAD_DETACH.
-    // We will chain this into a side list, and free these on Finalizer thread.
-    ClrTlsInfo *next;
 };
 
-#define DataToClrTlsInfo(a) (a)?(ClrTlsInfo*)((BYTE*)a - offsetof(ClrTlsInfo, data)):NULL
-
-
-#ifdef HAS_FLS_SUPPORT
-
-static BOOL fHasFlsSupport = FALSE;
-
-typedef DWORD (*Func_FlsAlloc)(PFLS_CALLBACK_FUNCTION lpCallback);
-typedef BOOL (*Func_FlsFree)(DWORD dwFlsIndex);
-typedef BOOL (*Func_FlsSetValue)(DWORD dwFlsIndex,PVOID lpFlsData);
-typedef PVOID (*Func_FlsGetValue)(DWORD dwFlsIndex);
-
-static DWORD FlsIndex = FLS_OUT_OF_INDEXES;
-static Func_FlsAlloc pFlsAlloc;
-static Func_FlsSetValue pFlsSetValue;
-static Func_FlsFree pFlsFree;
-static Func_FlsGetValue pFlsGetValue;
-static Volatile<BOOL> fFlsSetupDone = FALSE;
-
-VOID WINAPI FlsCallback(
-  PVOID lpFlsData
-)
-{
-    LIMITED_METHOD_CONTRACT;
-
-    _ASSERTE (pFlsGetValue);
-    if (pFlsGetValue(FlsIndex) != lpFlsData)
-    {
-        // The current running fiber is being destroyed.  We can not destroy the memory yet,
-        // because our DllMain function may still need the memory.
-        CExecutionEngine::ThreadDetaching((void **)lpFlsData);        
-    }
-    else
-    {
-        // The thread is being wound down.
-        // In hosting scenarios the host will have already called ICLRTask::ExitTask, which 
-        // ends up calling CExecutionEngine::SwitchOut, which will have reset the TLS at TlsIndex.
-        // 
-        // Unfortunately different OSes have different ordering of destroying FLS data and sending
-        // the DLL_THREAD_DETACH notification (pre-Vista FlsCallback is called after DllMain, while 
-        // in Vista and up, FlsCallback is called before DllMain).  Additionally, starting with 
-        // Vista SP1 and Win2k8, the OS will set the FLS slot to 0 after the call to FlsCallback, 
-        // effectively removing our last reference to this data. Since in EEDllMain we need to be 
-        // able to access the FLS data, we save lpFlsData in the TLS slot at TlsIndex, if needed.
-        if (CExecutionEngine::GetTlsData() == NULL)
-        {
-            CExecutionEngine::SetTlsData((void **)lpFlsData);
-        }
-    }
-}
-
-#endif // HAS_FLS_SUPPORT
-
+#define DataToClrTlsInfo(a) ((ClrTlsInfo*)a)
 
 void** CExecutionEngine::GetTlsData()
 {
@@ -2821,10 +2766,6 @@ void **CExecutionEngine::CheckThreadState(DWORD slot, BOOL force)
     STATIC_CONTRACT_CANNOT_TAKE_LOCK;
     STATIC_CONTRACT_SO_TOLERANT;
 
-    // !!! This function is called during Thread::SwitchIn and SwitchOut
-    // !!! It is extremely important that while executing this function, we will not
-    // !!! cause fiber switch.  This means we can not allocate memory, lock, etc...
-
     //<TODO> @TODO: Decide on an exception strategy for all the DLLs of the CLR, and then
     // enable all the exceptions out of this method.</TODO>
 
@@ -2833,68 +2774,9 @@ void **CExecutionEngine::CheckThreadState(DWORD slot, BOOL force)
 //    if (slot >= MAX_PREDEFINED_TLS_SLOT)
 //        COMPlusThrow(kArgumentOutOfRangeException);
 
-#ifdef HAS_FLS_SUPPORT
-    if (!fFlsSetupDone)
-    {
-        // Contract depends on Fls support.  Don't use contract here.
-        HMODULE hmod = GetModuleHandleA(WINDOWS_KERNEL32_DLLNAME_A);
-        if (hmod)
-        {
-            pFlsSetValue = (Func_FlsSetValue) GetProcAddress(hmod, "FlsSetValue");
-            pFlsGetValue = (Func_FlsGetValue) GetProcAddress(hmod, "FlsGetValue");
-            pFlsAlloc = (Func_FlsAlloc) GetProcAddress(hmod, "FlsAlloc");
-            pFlsFree = (Func_FlsFree) GetProcAddress(hmod, "FlsFree");
-
-            if (pFlsSetValue && pFlsGetValue && pFlsAlloc && pFlsFree )
-            {
-                fHasFlsSupport = TRUE;
-            }
-            else
-            {
-                // Since we didn't find them all, we shouldn't have found any
-                _ASSERTE( pFlsSetValue == NULL && pFlsGetValue == NULL && pFlsAlloc == NULL && pFlsFree == NULL);
-            }
-            fFlsSetupDone = TRUE;
-        }
-    }
-
-    if (fHasFlsSupport && FlsIndex == FLS_OUT_OF_INDEXES)
-    {
-        // PREFIX_ASSUME needs TLS.  If we use it here, we will loop forever
-#if defined(_PREFAST_) || defined(_PREFIX_) 
-        if (pFlsAlloc == NULL) __UNREACHABLE();
-#else
-        _ASSERTE(pFlsAlloc != NULL);
-#endif // _PREFAST_ || _PREFIX_
-
-        DWORD tryFlsIndex = pFlsAlloc(FlsCallback);
-        if (tryFlsIndex != FLS_OUT_OF_INDEXES)
-        {
-            if (FastInterlockCompareExchange((LONG*)&FlsIndex, tryFlsIndex, FLS_OUT_OF_INDEXES) != FLS_OUT_OF_INDEXES)
-            {
-                pFlsFree(tryFlsIndex);
-            }
-        }
-        if (FlsIndex == FLS_OUT_OF_INDEXES)
-        {
-            COMPlusThrowOM();
-        }
-    }
-#endif // HAS_FLS_SUPPORT
-
     void** pTlsData = CExecutionEngine::GetTlsData();
     BOOL fInTls = (pTlsData != NULL);
 
-#ifdef HAS_FLS_SUPPORT
-    if (fHasFlsSupport)
-    {
-        if (pTlsData == NULL)
-        {
-            pTlsData = (void **)pFlsGetValue(FlsIndex);
-        }
-    }
-#endif
-
     ClrTlsInfo *pTlsInfo = DataToClrTlsInfo(pTlsData);
     if (pTlsInfo == 0 && force)
     {
@@ -2910,12 +2792,6 @@ void **CExecutionEngine::CheckThreadState(DWORD slot, BOOL force)
             goto LError;
         }
         memset (pTlsInfo, 0, sizeof(ClrTlsInfo));
-#ifdef HAS_FLS_SUPPORT
-        if (fHasFlsSupport && !pFlsSetValue(FlsIndex, pTlsInfo))
-        {
-            goto LError;
-        }
-#endif
         // We save the last intolerant marker on stack in this slot.  
         // -1 is the larget unsigned number, and therefore our marker is always smaller than it.
         pTlsInfo->data[TlsIdx_SOIntolerantTransitionHandler] = (void*)(-1);
@@ -2923,31 +2799,10 @@ void **CExecutionEngine::CheckThreadState(DWORD slot, BOOL force)
 
     if (!fInTls && pTlsInfo)
     {
-#ifdef HAS_FLS_SUPPORT
-        // If we have a thread object or are on a non-fiber thread, we are safe for fiber switching.
-        if (!fHasFlsSupport ||
-            GetThread() ||
-            (g_fEEStarted || g_fEEInit) ||
-            (((size_t)pTlsInfo->data[TlsIdx_ThreadType]) & (ThreadType_GC | ThreadType_Gate | ThreadType_Timer | ThreadType_DbgHelper)))
-        {
-#ifdef _DEBUG
-            Thread *pThread = GetThread();
-            if (pThread)
-            {
-                pThread->AddFiberInfo(Thread::ThreadTrackInfo_Lifetime);
-            }
-#endif
-            if (!CExecutionEngine::SetTlsData(pTlsInfo->data) && !fHasFlsSupport)
-            {
-                goto LError;
-            }
-        }
-#else
         if (!CExecutionEngine::SetTlsData(pTlsInfo->data))
         {
             goto LError;
         }
-#endif
     }
 
     return pTlsInfo?pTlsInfo->data:NULL;
@@ -2991,16 +2846,6 @@ void **CExecutionEngine::CheckThreadStateNoCreate(DWORD slot
 
     void **pTlsData = CExecutionEngine::GetTlsData();
 
-#ifdef HAS_FLS_SUPPORT
-    if (fHasFlsSupport)
-    {
-        if (pTlsData == NULL)
-        {
-            pTlsData = (void **)pFlsGetValue(FlsIndex);
-        }
-    }
-#endif
-
     ClrTlsInfo *pTlsInfo = DataToClrTlsInfo(pTlsData);
 
     return pTlsInfo?pTlsInfo->data:NULL;
@@ -3016,10 +2861,6 @@ void CExecutionEngine::SetupTLSForThread(Thread *pThread)
     STATIC_CONTRACT_SO_TOLERANT;
     STATIC_CONTRACT_MODE_ANY;
 
-#ifdef _DEBUG
-    if (pThread)
-        pThread->AddFiberInfo(Thread::ThreadTrackInfo_Lifetime);
-#endif
 #ifdef STRESS_LOG
     if (StressLog::StressLogOn(~0u, 0))
     {
@@ -3041,57 +2882,6 @@ void CExecutionEngine::SetupTLSForThread(Thread *pThread)
 #endif
 }
 
-void CExecutionEngine::SwitchIn()
-{
-    // No real contracts here.  This function is called by Thread::SwitchIn.
-    STATIC_CONTRACT_NOTHROW;
-    STATIC_CONTRACT_GC_NOTRIGGER;
-    STATIC_CONTRACT_MODE_ANY;
-    STATIC_CONTRACT_ENTRY_POINT;
-
-    // @TODO - doesn't look like we can probe here....
-
-#ifdef HAS_FLS_SUPPORT
-    if (fHasFlsSupport)
-    {
-        void **pTlsData = (void **)pFlsGetValue(FlsIndex);
-
-        BOOL fResult = CExecutionEngine::SetTlsData(pTlsData);
-        if (fResult)
-        {
-#ifdef STRESS_LOG
-            // We are in task transition period.  We can not call into host to create stress log.
-            if (ClrTlsGetValue(TlsIdx_StressLog) != NULL)
-            {
-                STRESS_LOG1(LF_SYNC, LL_INFO100, ThreadStressLog::TaskSwitchMsg(), ::GetCurrentThreadId());
-            }
-#endif
-        }
-        // It is OK for UnsafeTlsSetValue to fail here, since we can always go back to Fls to get value.
-    }
-#endif
-}
-
-void CExecutionEngine::SwitchOut()
-{
-    // No real contracts here.  This function is called by Thread::SwitchOut
-    STATIC_CONTRACT_NOTHROW;
-    STATIC_CONTRACT_GC_NOTRIGGER;
-    STATIC_CONTRACT_MODE_ANY;
-    STATIC_CONTRACT_ENTRY_POINT;
-
-#ifdef HAS_FLS_SUPPORT
-    // @TODO - doesn't look like we can probe here.
-    if (fHasFlsSupport && pFlsGetValue != NULL  && (void **)pFlsGetValue(FlsIndex) != NULL)
-    {
-        // Clear out TLS unless we're in the process of ThreadDetach 
-        // We establish that we're in ThreadDetach because fHasFlsSupport will
-        // be TRUE, but the FLS will not exist.
-        CExecutionEngine::SetTlsData(NULL);
-    }
-#endif // HAS_FLS_SUPPORT
-}
-
 static void ThreadDetachingHelper(PTLS_CALLBACK_FUNCTION callback, void* pData)
 {
     // Do not use contract.  We are freeing TLS blocks.
@@ -3099,8 +2889,8 @@ static void ThreadDetachingHelper(PTLS_CALLBACK_FUNCTION callback, void* pData)
     STATIC_CONTRACT_GC_NOTRIGGER;
     STATIC_CONTRACT_MODE_ANY;
 
-        callback(pData);
-    }
+    callback(pData);
+}
 
 // Called here from a thread detach or from destruction of a Thread object.  In
 // the detach case, we get our info from TLS.  In the destruct case, it comes from
@@ -3178,14 +2968,6 @@ void CExecutionEngine::DeleteTLS(void ** pTlsData)
         ThreadDetachingHelper(Callbacks[TlsIdx_ClrDebugState], pData);
     }
 
-#ifdef _DEBUG
-    Thread *pThread = GetThread();
-    if (pThread)
-    {
-        pThread->AddFiberInfo(Thread::ThreadTrackInfo_Lifetime);
-    }
-#endif
-
     // NULL TLS and FLS entry so that we don't double free.
     // We may get two callback here on thread death
     // 1. From EEDllMain
@@ -3195,13 +2977,6 @@ void CExecutionEngine::DeleteTLS(void ** pTlsData)
         CExecutionEngine::SetTlsData(0);
     }
 
-#ifdef HAS_FLS_SUPPORT
-    if (fHasFlsSupport && pFlsGetValue(FlsIndex) == pTlsData)
-    {
-        pFlsSetValue(FlsIndex, NULL);
-    }
-#endif
-
 #undef HeapFree
 #undef GetProcessHeap
     ::HeapFree (GetProcessHeap(),0,pTlsInfo);
diff --git a/src/vm/stackprobe.cpp b/src/vm/stackprobe.cpp
index 6663300e90..7e40ca8738 100644
--- a/src/vm/stackprobe.cpp
+++ b/src/vm/stackprobe.cpp
@@ -1381,16 +1381,6 @@ void BaseStackGuard::ProtectMarkerPageInDebugger()
         return;
     }
 
-#ifdef _DEBUG
-    BEGIN_GETTHREAD_ALLOWED;
-    Thread* pThread = GetThread();
-    if (pThread)
-    {
-        pThread->AddFiberInfo(Thread::ThreadTrackInfo_Escalation);
-    }
-    END_GETTHREAD_ALLOWED;
-#endif
-
     DWORD flOldProtect;
 
     LOG((LF_EH, LL_INFO100000, "BSG::PMP: m_pMarker 0x%p, value 0x%p\n", m_pMarker, *m_pMarker));
@@ -1436,16 +1426,6 @@ void BaseStackGuard::UndoPageProtectionInDebugger()
 
     _ASSERTE(IsProbeGuard());
 
-#ifdef _DEBUG
-    BEGIN_GETTHREAD_ALLOWED;
-    Thread* pThread = GetThread();
-    if (pThread)
-    {
-        pThread->AddFiberInfo(Thread::ThreadTrackInfo_Escalation);
-    }
-    END_GETTHREAD_ALLOWED;
-#endif
-
     DWORD flOldProtect;
     // EEVirtualProtect installs a BoundaryStackGuard.  To avoid recursion, we call
     // into OS for VirtualProtect instead.
diff --git a/src/vm/threads.cpp b/src/vm/threads.cpp
index 7a638a9c66..707330a30f 100644
--- a/src/vm/threads.cpp
+++ b/src/vm/threads.cpp
@@ -745,10 +745,6 @@ Thread* SetupThread(BOOL fInternal)
 
     FastInterlockOr((ULONG *) &pThread->m_State, Thread::TS_FullyInitialized);
 
-#ifdef _DEBUG
-    pThread->AddFiberInfo(Thread::ThreadTrackInfo_Lifetime);
-#endif
-
 #ifdef DEBUGGING_SUPPORTED
     //
     // If we're debugging, let the debugger know that this
@@ -997,7 +993,24 @@ HRESULT Thread::DetachThread(BOOL fDLLThreadDetach)
 
     END_CONTRACT_VIOLATION;
 
-    InternalSwitchOut();
+    HANDLE hThread = GetThreadHandle();
+    SetThreadHandle (SWITCHOUT_HANDLE_VALUE);
+    while (m_dwThreadHandleBeingUsed > 0)
+    {
+        // Another thread is using the handle now.
+#undef Sleep
+        // We can not call __SwitchToThread since we can not go back to host.
+        ::Sleep(10);
+#define Sleep(a) Dont_Use_Sleep(a)
+    }
+    if (m_WeOwnThreadHandle && m_ThreadHandleForClose == INVALID_HANDLE_VALUE)
+    {
+        m_ThreadHandleForClose = hThread;
+    }
+
+    // We need to make sure that TLS are touched last here.
+    SetThread(NULL);
+    SetAppDomain(NULL);
 
 #ifdef ENABLE_CONTRACTS_DATA
     m_pClrDebugState = NULL;
@@ -1535,27 +1548,6 @@ Thread::Thread()
     m_dwAbortPoint = 0;
 #endif
 
-    m_pFiberData = NULL;
-
-    m_TaskId = INVALID_TASK_ID;
-    m_dwConnectionId = INVALID_CONNECTION_ID;
-
-#ifdef _DEBUG
-    DWORD_PTR *ttInfo = NULL;
-    size_t nBytes = MaxThreadRecord *
-                  (sizeof(FiberSwitchInfo)-sizeof(size_t)+MaxStackDepth*sizeof(size_t));
-    if (g_pConfig->SaveThreadInfo()) {
-        ttInfo = new DWORD_PTR[(nBytes/sizeof(DWORD_PTR))*ThreadTrackInfo_Max];
-        memset(ttInfo,0,nBytes*ThreadTrackInfo_Max);
-    }
-    for (DWORD i = 0; i < ThreadTrackInfo_Max; i ++)
-    {
-        m_FiberInfoIndex[i] = 0;
-        m_pFiberInfo[i] = (FiberSwitchInfo*)((DWORD_PTR)ttInfo + i*nBytes);
-    }
-    NewArrayHolder<DWORD_PTR> fiberInfoHolder(ttInfo);
-#endif
-
     m_OSContext = new CONTEXT();
     NewHolder<CONTEXT> contextHolder(m_OSContext);
 
@@ -1566,7 +1558,6 @@ Thread::Thread()
     m_pRCWStack = new RCWStackHeader();
 #endif
 
-    m_pCerPreparationState = NULL;
 #ifdef _DEBUG
     m_bGCStressing = FALSE;
     m_bUniqueStacking = FALSE;
@@ -1646,9 +1637,6 @@ Thread::Thread()
 #if defined(_DEBUG) && defined(TRACK_SYNC)
     trackSyncHolder.SuppressRelease();
 #endif
-#ifdef _DEBUG
-    fiberInfoHolder.SuppressRelease();
-#endif
     contextHolder.SuppressRelease();
     savedRedirectContextHolder.SuppressRelease();
 
@@ -1932,10 +1920,6 @@ BOOL Thread::HasStarted(BOOL bRequiresTSL)
             ThrowOutOfMemory();
         }
 
-#ifdef _DEBUG
-        AddFiberInfo(Thread::ThreadTrackInfo_Lifetime);
-#endif
-
         SetupThreadForHost();
 
 
@@ -2531,9 +2515,6 @@ int Thread::DecExternalCount(BOOL holdingLock)
             m_ExceptionState.FreeAllStackTraces();
             if (SelfDelete) {
                 SetThread(NULL);
-#ifdef _DEBUG
-                AddFiberInfo(ThreadTrackInfo_Lifetime);
-#endif
             }
             delete this;
         }
@@ -2742,12 +2723,6 @@ Thread::~Thread()
     }
 #endif
 
-#ifdef _DEBUG
-    if (m_pFiberInfo != NULL) {
-        delete [] (DWORD_PTR*)m_pFiberInfo[0];
-    }
-#endif
-
 #ifdef FEATURE_EVENT_TRACE
     // Destruct the thread local type cache for allocation sampling
     if(m_pAllLoggedTypes) {
@@ -4287,9 +4262,6 @@ void Thread::UserInterrupt(ThreadInterruptMode mode)
     if (HasValidThreadHandle() &&
         HasThreadState (TS_Interruptible))
     {
-#ifdef _DEBUG
-        AddFiberInfo(ThreadTrackInfo_Abort);
-#endif
         Alert();
     }
 }
@@ -4413,9 +4385,6 @@ OBJECTREF Thread::GetExposedObject()
             // already hold the thread lock and IncExternalCount won't be able to take it.
             ULONG retVal = FastInterlockIncrement ((LONG*)&m_ExternalRefCount);
 
-#ifdef _DEBUG
-            AddFiberInfo(ThreadTrackInfo_Lifetime);
-#endif
             // Check to see if we need to store a strong pointer to the object.
             if (retVal > 1)
                 StoreObjectInHandle(m_StrongHndToExposedObject, (OBJECTREF) attempt);
@@ -5387,14 +5356,6 @@ void ThreadStore::InitThreadStore()
     ThreadSuspend::g_pGCSuspendEvent = new CLREvent();
     ThreadSuspend::g_pGCSuspendEvent->CreateManualEvent(FALSE);
 
-#ifdef _DEBUG
-    Thread::MaxThreadRecord = EEConfig::GetConfigDWORD_DontUse_(CLRConfig::INTERNAL_MaxThreadRecord,Thread::MaxThreadRecord);
-    Thread::MaxStackDepth = EEConfig::GetConfigDWORD_DontUse_(CLRConfig::INTERNAL_MaxStackDepth,Thread::MaxStackDepth);
-    if (Thread::MaxStackDepth > 100) {
-        Thread::MaxStackDepth = 100;
-    }
-#endif
-
     s_pWaitForStackCrawlEvent = new CLREvent();
     s_pWaitForStackCrawlEvent->CreateManualEvent(FALSE);
 
@@ -6141,10 +6102,6 @@ void Thread::HandleThreadInterrupt (BOOL fWaitForADUnload)
         ResetThreadState ((ThreadState)(TS_Interrupted | TS_Interruptible));
         FastInterlockAnd ((DWORD*)&m_UserInterrupt, ~TI_Interrupt);
 
-#ifdef _DEBUG
-        AddFiberInfo(ThreadTrackInfo_Abort);
-#endif
-
         COMPlusThrow(kThreadInterruptedException);
     }
     END_SO_INTOLERANT_CODE;
@@ -9520,324 +9477,6 @@ BOOL ThreadStore::HoldingThreadStore(Thread *pThread)
     }
 }
 
-
-#ifdef _DEBUG
-
-int Thread::MaxThreadRecord = 20;
-int Thread::MaxStackDepth = 20;
-
-const int Thread::MaxThreadTrackInfo = Thread::ThreadTrackInfo_Max;
-
-void Thread::AddFiberInfo(DWORD type)
-{
-    STATIC_CONTRACT_NOTHROW;
-    STATIC_CONTRACT_GC_NOTRIGGER;
-    STATIC_CONTRACT_MODE_ANY;
-    STATIC_CONTRACT_SO_TOLERANT;
-
-#ifndef FEATURE_PAL
-    
-    if (m_pFiberInfo[0] == NULL) {
-        return;
-    }
-
-    DWORD mask = g_pConfig->SaveThreadInfoMask();
-    if ((mask & type) == 0)
-    {
-        return;
-    }
-
-    int slot = -1;
-    while (type != 0)
-    {
-        type >>= 1;
-        slot ++;
-    }
-
-    _ASSERTE (slot < ThreadTrackInfo_Max);
-
-    // use try to force ebp frame.
-    PAL_TRY_NAKED {
-        ULONG index = FastInterlockIncrement((LONG*)&m_FiberInfoIndex[slot])-1;
-        index %= MaxThreadRecord;
-        size_t unitBytes = sizeof(FiberSwitchInfo)-sizeof(size_t)+MaxStackDepth*sizeof(size_t);
-        FiberSwitchInfo *pInfo = (FiberSwitchInfo*)((char*)m_pFiberInfo[slot] + index*unitBytes);
-        pInfo->timeStamp = getTimeStamp();
-        pInfo->threadID = GetCurrentThreadId();
-
-#ifdef FEATURE_HIJACK
-        // We can't crawl the stack of a thread that currently has a hijack pending
-        // (since the hijack routine won't be recognized by any code manager). So we
-        // undo any hijack, the EE will re-attempt it later.
-        // Stack crawl happens on the current thread, which may not be 'this' thread.
-        Thread* pCurrentThread = GetThread();
-        if (pCurrentThread != NULL && (pCurrentThread->m_State & TS_Hijacked)) 
-        {
-            pCurrentThread->UnhijackThread();
-        }
-#endif
-        
-        int count = UtilCaptureStackBackTrace (2,MaxStackDepth,(PVOID*)pInfo->callStack,NULL);
-        while (count < MaxStackDepth) {
-            pInfo->callStack[count++] = 0;
-        }
-    }
-    PAL_EXCEPT_NAKED (EXCEPTION_EXECUTE_HANDLER)
-    {
-    }
-    PAL_ENDTRY_NAKED;
-#endif // !FEATURE_PAL
-}
-
-#endif // _DEBUG
-
-HRESULT Thread::SwitchIn(HANDLE threadHandle)
-{
-    // can't have dynamic contracts because this method is going to mess with TLS
-    STATIC_CONTRACT_NOTHROW;
-    STATIC_CONTRACT_GC_NOTRIGGER;
-    STATIC_CONTRACT_MODE_ANY;
- 
-    //can't do heap allocation in this method
-    CantAllocHolder caHolder;
-
-    // !!! Can not use the following line, since it uses an object which .dctor calls
-    // !!! FLS_SETVALUE, and a new FLS is created after SwitchOut.
-    // CANNOTTHROWCOMPLUSEXCEPTION();
-
-    // Case Cookie to thread object and add to tls
-#ifdef _DEBUG
-    Thread *pThread = GetThread();
-    // If this is hit, we need to understand.
-    // Sometimes we see the assert but the memory does not match the assert.
-    if (pThread) {
-        DebugBreak();
-    }
-    //_ASSERT(GetThread() == NULL);
-#endif
-
-    if (GetThread() != NULL) {
-        return HOST_E_INVALIDOPERATION;
-    }
-
-    CExecutionEngine::SwitchIn();
-
-    // !!! no contract for this class.
-    // !!! We have not switched in tls block.
-    class EnsureTlsData
-    {
-    private:
-        Thread *m_pThread;
-        BOOL m_fNeedReset;
-    public:
-        EnsureTlsData(Thread* pThread){m_pThread = pThread; m_fNeedReset = TRUE;}
-        ~EnsureTlsData()
-        {
-            if (m_fNeedReset)
-            {
-                SetThread(NULL);
-                SetAppDomain(NULL);
-                CExecutionEngine::SwitchOut();
-            }
-        }
-        void SuppressRelease()
-        {
-            m_fNeedReset = FALSE;
-        }
-    };
-
-    EnsureTlsData ensure(this);
-
-    if (SetThread(this))
-    {
-        Thread *pThread = GetThread();
-        if (!pThread)
-            return E_OUTOFMEMORY;
-
-        // !!! make sure that we switchin TLS so that FLS is available for Contract etc.
-
-        // We redundantly keep the domain in its own TLS slot, for faster access from
-        // stubs
-        if (!SetAppDomain(m_pDomainAtTaskSwitch))
-        {
-            return E_OUTOFMEMORY;
-        }
-
-        CANNOTTHROWCOMPLUSEXCEPTION();
-#if 0
-        // We switch out a fiber only if the fiber is in preemptive gc mode.
-        _ASSERTE (!PreemptiveGCDisabled());
-#endif
-
-
-        // We have to be switched in on the same fiber
-        _ASSERTE (GetCachedStackBase() == GetStackUpperBound());
-
-        if (m_pFiberData)
-        {
-            // only set the m_OSThreadId to bad food in Fiber mode
-            m_OSThreadId = ::GetCurrentThreadId();
-#ifdef PROFILING_SUPPORTED
-            // If a profiler is present, then notify the profiler that a
-            // thread has been created.
-            {
-                BEGIN_PIN_PROFILER(CORProfilerTrackThreads());
-                g_profControlBlock.pProfInterface->ThreadAssignedToOSThread(
-                    (ThreadID)this, m_OSThreadId);
-                END_PIN_PROFILER();
-            }
-#endif // PROFILING_SUPPORTED
-        }
-        SetThreadHandle(threadHandle);
-
-#ifndef FEATURE_PAL
-        m_pTEB = (struct _NT_TIB*)NtCurrentTeb();
-#endif // !FEATURE_PAL
-
-#if 0
-        if (g_TrapReturningThreads && m_fPreemptiveGCDisabled && this != ThreadSuspend::GetSuspensionThread()) {
-            WorkingOnThreadContextHolder workingOnThreadContext(this);
-            if (workingOnThreadContext.Acquired())
-            {
-                HandledJITCase(TRUE);
-            }
-        }
-#endif
-
-#ifdef _DEBUG
-        // For debugging purpose, we save callstack during task switch.  On Win64, the callstack
-        // is done within OS loader lock, and obtaining managed callstack may cause fiber switch.
-        SetThreadStateNC(TSNC_InTaskSwitch);
-        AddFiberInfo(ThreadTrackInfo_Schedule);
-        ResetThreadStateNC(TSNC_InTaskSwitch);
-#endif
-
-        ensure.SuppressRelease();
-        return S_OK;
-    }
-    else
-    {
-        return E_FAIL;
-    }
-}
-
-HRESULT Thread::SwitchOut()
-{
-    LIMITED_METHOD_CONTRACT;
-
-    return E_NOTIMPL;
-}
-
-void Thread::InternalSwitchOut()
-{
-    INDEBUG( BOOL fNoTLS = (CExecutionEngine::CheckThreadStateNoCreate(0) == NULL));
-
-    CONTRACTL
-    {
-        NOTHROW;
-        GC_NOTRIGGER;
-        SO_TOLERANT;
-        MODE_ANY;
-    }
-    CONTRACTL_END;
-
-    {
-        // Can't do heap allocation in this method.
-        // We need to scope this holder because its destructor accesses FLS.
-    CantAllocHolder caHolder;
-    
-    // !!! Can not use the following line, since it uses an object which .dctor calls
-    // !!! FLS_SETVALUE, and a new FLS is created after SwitchOut.
-    // CANNOTTHROWCOMPLUSEXCEPTION();
-
-    _ASSERTE(GetThread() == this);
-
-    _ASSERTE (!fNoTLS ||
-              (CExecutionEngine::CheckThreadStateNoCreate(0) == NULL));
-
-#if 0
-    // workaround wwl: for SQL reschedule
-#ifndef _DEBUG
-        if (PreemptiveGCDisabled)
-        {
-        DebugBreak();
-    }
-#endif
-    _ASSERTE(!PreemptiveGCDisabled());
-#endif
-
-    // Can not assert here.  If a mutex is orphaned, the thread will have ThreadAffinity.
-    //_ASSERTE(!HasThreadAffinity());
-
-    _ASSERTE (!fNoTLS ||
-              (CExecutionEngine::CheckThreadStateNoCreate(0) == NULL));
-
-#ifdef _DEBUG
-    // For debugging purpose, we save callstack during task switch.  On Win64, the callstack
-    // is done within OS loader lock, and obtaining managed callstack may cause fiber switch.
-    SetThreadStateNC(TSNC_InTaskSwitch);
-    AddFiberInfo(ThreadTrackInfo_Schedule);
-    ResetThreadStateNC(TSNC_InTaskSwitch);
-#endif
-
-    _ASSERTE (!fNoTLS ||
-              (CExecutionEngine::CheckThreadStateNoCreate(0) == NULL));
-
-    m_pDomainAtTaskSwitch = GetAppDomain();
-
-    if (m_pFiberData)
-    {
-        // only set the m_OSThreadId to bad food in Fiber mode
-        m_OSThreadId = SWITCHED_OUT_FIBER_OSID;
-#ifdef PROFILING_SUPPORTED
-        // If a profiler is present, then notify the profiler that a
-        // thread has been created.
-        {
-            BEGIN_PIN_PROFILER(CORProfilerTrackThreads());
-            g_profControlBlock.pProfInterface->ThreadAssignedToOSThread(
-                (ThreadID)this, m_OSThreadId);
-            END_PIN_PROFILER();
-        }
-#endif // PROFILING_SUPPORTED
-    }
-
-    _ASSERTE (!fNoTLS ||
-              (CExecutionEngine::CheckThreadStateNoCreate(0) == NULL));
-
-    HANDLE hThread = GetThreadHandle();
-
-    SetThreadHandle (SWITCHOUT_HANDLE_VALUE);
-    while (m_dwThreadHandleBeingUsed > 0)
-    {
-        // Another thread is using the handle now.
-#undef Sleep
-        // We can not call __SwitchToThread since we can not go back to host.
-        ::Sleep(10);
-#define Sleep(a) Dont_Use_Sleep(a)
-    }
-
-        if (m_WeOwnThreadHandle && m_ThreadHandleForClose == INVALID_HANDLE_VALUE)
-        {
-        m_ThreadHandleForClose = hThread;
-    }
-
-    _ASSERTE (!fNoTLS ||
-              (CExecutionEngine::CheckThreadStateNoCreate(0) == NULL));
-    }
-
-    CExecutionEngine::SwitchOut();
-
-    // We need to make sure that TLS are touched last here.
-    // Contract uses TLS.
-    SetThread(NULL);
-    SetAppDomain(NULL);
-
-    _ASSERTE (!fNoTLS ||
-              (CExecutionEngine::CheckThreadStateNoCreate(0) == NULL));
-}
-
-
-
 LONG Thread::GetTotalThreadPoolCompletionCount()
 {
     CONTRACTL
@@ -10014,149 +9653,6 @@ void Thread::InternalReset(BOOL fFull, BOOL fNotFinalizerThread, BOOL fThreadObj
     }
 }
 
-HRESULT Thread::Reset(BOOL fFull)
-{
-    // !!! Can not use non-static contract here.
-    // !!! Contract depends on Thread object for GC_TRIGGERS.
-    // !!! At the end of this function, we call InternalSwitchOut,
-    // !!! and then GetThread()=NULL, and dtor of contract does not work any more.
-    STATIC_CONTRACT_NOTHROW;
-    STATIC_CONTRACT_GC_TRIGGERS;
-    STATIC_CONTRACT_ENTRY_POINT;
-
-    if ( !g_fEEStarted)
-        return(E_FAIL);
-
-    HRESULT hr = S_OK;
-
-    BEGIN_SO_INTOLERANT_CODE_NOPROBE;
-
-#ifdef _DEBUG
-    _ASSERTE (GetThread() == this);
-#ifdef _TARGET_X86_
-    _ASSERTE (GetExceptionState()->GetContextRecord() == NULL);
-#endif
-#endif
-
-    if (GetThread() != this)
-    {
-        IfFailGo(E_UNEXPECTED);
-    }
-
-    _ASSERTE (!PreemptiveGCDisabled());
-    _ASSERTE (m_pFrame == FRAME_TOP);
-    // A host should not recycle a CLRTask if the task is created by us through CreateNewThread.
-    // We need to make Thread.Join work for this case.
-    if ((m_StateNC & (TSNC_CLRCreatedThread | TSNC_CannotRecycle)) != 0)
-    {
-        // Todo: wwl better returning code.
-        IfFailGo(E_UNEXPECTED);
-    }
-
-#ifdef FEATURE_COMINTEROP_APARTMENT_SUPPORT
-    if (IsCoInitialized())
-    {
-        // The current thread has done CoInitialize
-        IfFailGo(E_UNEXPECTED);
-    }
-#endif
-
-#ifdef _DEBUG
-    AddFiberInfo(ThreadTrackInfo_Lifetime);
-#endif
-
-    SetThreadState(TS_TaskReset);
-
-    if (IsAbortRequested())
-    {
-        EEResetAbort(Thread::TAR_ALL);
-    }
-  
-    InternalReset(fFull);
-
-    if (PreemptiveGCDisabled())
-    {
-        EnablePreemptiveGC();
-    }
-
-    {
-
-#ifdef WIN64EXCEPTIONS
-    ExceptionTracker::PopTrackers((void*)-1);
-#endif // WIN64EXCEPTIONS
-
-        ResetThreadStateNC(TSNC_UnbalancedLocks);
-        m_dwLockCount = 0;
-
-    InternalSwitchOut();
-    m_OSThreadId = SWITCHED_OUT_FIBER_OSID;
-    }
-
-ErrExit:
-
-    END_SO_INTOLERANT_CODE_NOPROBE;
-
-#ifdef ENABLE_CONTRACTS_DATA
-    // Decouple our cache from the Task.
-    // Next time, the thread may be run on a different thread.
-    if (SUCCEEDED(hr))
-    {
-    m_pClrDebugState = NULL;
-    }
-#endif
-
-    return hr;
-}
-
-HRESULT Thread::ExitTask ()
-{
-    // !!! Can not use contract here.
-    // !!! Contract depends on Thread object for GC_TRIGGERS.
-    // !!! At the end of this function, we call InternalSwitchOut,
-    // !!! and then GetThread()=NULL, and dtor of contract does not work any more.
-    STATIC_CONTRACT_NOTHROW;
-    STATIC_CONTRACT_GC_TRIGGERS;
-    STATIC_CONTRACT_ENTRY_POINT;
-
-    if ( !g_fEEStarted)
-        return(E_FAIL);
-
-    HRESULT hr = S_OK;
-
-    // <TODO> We need to probe here, but can't introduce destructors etc.</TODO>
-    BEGIN_CONTRACT_VIOLATION(SOToleranceViolation);
-
-    //OnThreadTerminate(FALSE);
-    _ASSERTE (this == GetThread());
-    _ASSERTE (!PreemptiveGCDisabled());
-
-    // Can not assert the following.  SQL may call ExitTask after addref and abort a task.
-    //_ASSERTE (m_UnmanagedRefCount == 0);
-    if (this != GetThread())
-        IfFailGo(HOST_E_INVALIDOPERATION);
-
-#ifdef FEATURE_COMINTEROP_APARTMENT_SUPPORT
-    if (IsCoInitialized())
-    {
-        // This thread has used ole32.  We need to balance CoInitialize call on this thread.
-        // We also need to free any COM objects created on this thread.
-
-        // If we don't do this work, ole32 is going to do the same during its DLL_THREAD_DETACH,
-        // and may re-enter CLR.
-        CleanupCOMState();
-    }
-#endif
-    m_OSThreadId = SWITCHED_OUT_FIBER_OSID;
-    hr = DetachThread(FALSE);
-    // !!! Do not touch any field of Thread object.  The Thread object is subject to delete
-    // !!! after DetachThread call.
-ErrExit:;
-
-    END_CONTRACT_VIOLATION;
-
-    return hr;
-}
-
 HRESULT Thread::Abort ()
 {
     CONTRACTL
@@ -10230,15 +9726,6 @@ HRESULT Thread::LocksHeld(SIZE_T *pLockCount)
     return S_OK;
 }
 
-HRESULT Thread::SetTaskIdentifier(TASKID asked)
-{
-    LIMITED_METHOD_CONTRACT;
-
-    // @todo: Should be check for uniqueness?
-    m_TaskId = asked;
-    return S_OK;
-}
-
 HRESULT Thread::BeginPreventAsyncAbort()
 {
     WRAPPER_NO_CONTRACT;
@@ -10250,7 +9737,6 @@ HRESULT Thread::BeginPreventAsyncAbort()
 
 #ifdef _DEBUG
     ASSERT(count > 0);
-    AddFiberInfo(ThreadTrackInfo_Abort);
 
     FastInterlockIncrement((LONG*)&m_dwDisableAbortCheckCount);
 #endif
@@ -10269,7 +9755,6 @@ HRESULT Thread::EndPreventAsyncAbort()
 
 #ifdef _DEBUG
     ASSERT(count >= 0);
-    AddFiberInfo(ThreadTrackInfo_Abort);
 
     FastInterlockDecrement((LONG*)&m_dwDisableAbortCheckCount);
 #endif
@@ -10287,9 +9772,6 @@ ULONG Thread::AddRef()
     _ASSERTE (m_UnmanagedRefCount != (DWORD) -1);
     ULONG ref = FastInterlockIncrement((LONG*)&m_UnmanagedRefCount);
 
-#ifdef _DEBUG
-    AddFiberInfo(ThreadTrackInfo_Lifetime);
-#endif
     return ref;
 }
 
@@ -10301,9 +9783,6 @@ ULONG Thread::Release()
     _ASSERTE (m_ExternalRefCount > 0);
     _ASSERTE (m_UnmanagedRefCount > 0);
     ULONG ref = FastInterlockDecrement((LONG*)&m_UnmanagedRefCount);
-#ifdef _DEBUG
-    AddFiberInfo(ThreadTrackInfo_Lifetime);
-#endif
     return ref;
 }
 
diff --git a/src/vm/threads.h b/src/vm/threads.h
index 444d4d48d7..44a30b0b5b 100644
--- a/src/vm/threads.h
+++ b/src/vm/threads.h
@@ -162,7 +162,6 @@ struct    HelperMethodFrameCallerList;
 class     ThreadLocalIBCInfo;
 class     EECodeInfo;
 class     DebuggerPatchSkip;
-class     MethodCallGraphPreparer;
 class     FaultingExceptionFrame;
 class     ContextTransitionFrame;
 enum      BinderMethodID : int;
@@ -206,22 +205,6 @@ public:
 
     StackingAllocator    m_MarshalAlloc;
 
-private:
-    MethodCallGraphPreparer * m_pCerPreparationState;
-
-public:
-    MethodCallGraphPreparer * GetCerPreparationState()
-    {
-        LIMITED_METHOD_CONTRACT;
-        return m_pCerPreparationState;
-    }
-
-    void SetCerPreparationState(MethodCallGraphPreparer * pCerPreparationState)
-    {
-        LIMITED_METHOD_CONTRACT;
-        m_pCerPreparationState = pCerPreparationState;
-    }
-
  private:
     LoadLevelLimiter *m_pLoadLimiter;
 
@@ -1189,7 +1172,7 @@ public:
         TSNC_OSAlertableWait            = 0x00001000, // Preparing abort.  This avoids recursive HandleThreadAbort call.
         TSNC_ADUnloadHelper             = 0x00002000, // This thread is AD Unload helper.
         TSNC_CreatingTypeInitException  = 0x00004000, // Thread is trying to create a TypeInitException
-        TSNC_InTaskSwitch               = 0x00008000, // A task is switching
+        // unused                       = 0x00008000,
         TSNC_AppDomainContainUnhandled  = 0x00010000, // Used to control how unhandled exception reporting occurs.
                                                       // See detailed explanation for this bit in threads.cpp
         TSNC_InRestoringSyncBlock       = 0x00020000, // The thread is restoring its SyncBlock for Object.Wait.
@@ -1246,14 +1229,6 @@ public:
         DAC_EMPTY_RET(0);
     STDMETHODIMP_(ULONG) Release(void)
         DAC_EMPTY_RET(0);
-    STDMETHODIMP SwitchIn(HANDLE threadHandle)
-        DAC_EMPTY_RET(E_FAIL);
-    STDMETHODIMP SwitchOut()
-        DAC_EMPTY_RET(E_FAIL);
-    STDMETHODIMP Reset (BOOL fFull)
-        DAC_EMPTY_RET(E_FAIL);
-    STDMETHODIMP ExitTask()
-        DAC_EMPTY_RET(E_FAIL);
     STDMETHODIMP Abort()
         DAC_EMPTY_RET(E_FAIL);
     STDMETHODIMP RudeAbort()
@@ -1265,17 +1240,12 @@ public:
         DAC_EMPTY_RET(E_FAIL);
     STDMETHODIMP LocksHeld(SIZE_T *pLockCount)
         DAC_EMPTY_RET(E_FAIL);
-    STDMETHODIMP SetTaskIdentifier(TASKID asked)
-        DAC_EMPTY_RET(E_FAIL);
 
     STDMETHODIMP BeginPreventAsyncAbort()
         DAC_EMPTY_RET(E_FAIL);
     STDMETHODIMP EndPreventAsyncAbort()
         DAC_EMPTY_RET(E_FAIL);
 
-    STDMETHODIMP SetLocale(LCID lcid);
-    STDMETHODIMP SetUILocale(LCID lcid);
-
     void InternalReset (BOOL fFull, BOOL fNotFinalizerThread=FALSE, BOOL fThreadObjectResetNeeded=TRUE, BOOL fResetAbort=TRUE);
     INT32 ResetManagedThreadObject(INT32 nPriority); 
     INT32 ResetManagedThreadObjectInCoopMode(INT32 nPriority);
@@ -1284,8 +1254,6 @@ private:
     //Helpers for reset...
     void FullResetThread();
 public:
-    void InternalSwitchOut();
-
     HRESULT DetachThread(BOOL fDLLThreadDetach);
 
     void SetThreadState(ThreadState ts)
@@ -2722,24 +2690,6 @@ public:
         return m_OSThreadId;
     }
 
-    TASKID      GetTaskId()
-    {
-        LIMITED_METHOD_CONTRACT;
-        return m_TaskId;
-    }
-    CONNID      GetConnectionId()
-    {
-        LIMITED_METHOD_CONTRACT;
-        return m_dwConnectionId;
-    }
-
-
-    void SetConnectionId(CONNID dwConnectionId)
-    {
-        LIMITED_METHOD_CONTRACT;
-        m_dwConnectionId = dwConnectionId;
-    }
-
     BOOL        IsThreadPoolThread()
     {
         LIMITED_METHOD_CONTRACT;
@@ -4012,11 +3962,6 @@ private:
     UINT_PTR             m_LastAllowableStackAddress;
 
 private:
-
-    // Save the domain when a task is switched out, and restore it when
-    // the task is switched in.
-    PTR_AppDomain m_pDomainAtTaskSwitch;
-
     //---------------------------------------------------------------
     // m_debuggerFilterContext holds the thread's "filter context" for the
     // debugger.  This filter context is used by the debugger to seed
@@ -4508,69 +4453,13 @@ public:
     size_t *m_pCleanedStackBase;
 #endif
 
-private:
-    PVOID      m_pFiberData;
-
-    TASKID     m_TaskId;
-    CONNID     m_dwConnectionId;
-
-public:
-    void SetupFiberData();
-
-#ifdef _DEBUG
-public:
-    void AddFiberInfo(DWORD type);
-    enum {
-        ThreadTrackInfo_Lifetime=0x1,   // creation, destruction, ref-count
-        ThreadTrackInfo_Schedule=0x2,   // switch in/out
-        ThreadTrackInfo_UM_M=0x4,       // Unmanaged <-> managed transtion
-        ThreadTrackInfo_Abort=0x8,      // Thread abort
-        ThreadTrackInfo_Affinity=0x10,  // Thread's affinity
-        ThreadTrackInfo_GCMode=0x20,
-        ThreadTrackInfo_Escalation=0x40,// escalation point
-        ThreadTrackInfo_SO=0x80,
-        ThreadTrackInfo_Max=8
-    };
-private:
-    static int MaxThreadRecord;
-    static int MaxStackDepth;
-    static const int MaxThreadTrackInfo;
-    struct FiberSwitchInfo
-    {
-        unsigned __int64 timeStamp;
-        DWORD threadID;
-        size_t callStack[1];
-    };
-    FiberSwitchInfo *m_pFiberInfo[ThreadTrackInfo_Max];
-    DWORD m_FiberInfoIndex[ThreadTrackInfo_Max];
-#endif
-
 #ifdef DACCESS_COMPILE
 public:
     void EnumMemoryRegions(CLRDataEnumMemoryFlags flags);
     void EnumMemoryRegionsWorker(CLRDataEnumMemoryFlags flags);
 #endif
 
-private:
-    // Head of a linked list of opaque records that record if and how the thread is currently preparing a
-    // graph of methods for CER usage. This is used to determine if a re-entrant preparation request should
-    // complete immediately as a no-op (because it would lead to an infinite recursion) or should proceed
-    // recursively.
-    MethodCallGraphPreparer * m_pCerPreparationState;
-
 public:
-    MethodCallGraphPreparer * GetCerPreparationState()
-    {
-        LIMITED_METHOD_CONTRACT;
-        return m_pCerPreparationState;
-    }
-
-    void SetCerPreparationState(MethodCallGraphPreparer * pCerPreparationState)
-    {
-        LIMITED_METHOD_CONTRACT;
-        m_pCerPreparationState = pCerPreparationState;
-    }
-
     // Is the current thread currently executing within a constrained execution region?
     static BOOL IsExecutingWithinCer();
 
diff --git a/src/vm/threadsuspend.cpp b/src/vm/threadsuspend.cpp
index fd070a666d..67acec280a 100644
--- a/src/vm/threadsuspend.cpp
+++ b/src/vm/threadsuspend.cpp
@@ -1370,9 +1370,6 @@ Thread::UserAbort(ThreadAbortRequester requester,
     CONTRACTL_END;
 
     STRESS_LOG2(LF_SYNC | LF_APPDOMAIN, LL_INFO100, "UserAbort Thread %p Thread Id = %x\n", this, GetThreadId());
-#ifdef _DEBUG
-    AddFiberInfo(ThreadTrackInfo_Abort);
-#endif
 
     BOOL fHoldingThreadStoreLock = ThreadStore::HoldingThreadStore();
 
@@ -2441,10 +2438,6 @@ void Thread::MarkThreadForAbort(ThreadAbortRequester requester, EEPolicy::Thread
 
         // The thread is asked for abort the first time
         SetAbortRequestBit();
-
-#ifdef _DEBUG
-        AddFiberInfo(ThreadTrackInfo_Abort);
-#endif
     }
     STRESS_LOG4(LF_APPDOMAIN, LL_ALWAYS, "Mark Thread %p Thread Id = %x for abort from requester %d (type %d)\n", this, GetThreadId(), requester, abortType);
 }
@@ -2575,10 +2568,6 @@ void Thread::UnmarkThreadForAbort(ThreadAbortRequester requester, BOOL fForce)
         FastInterlockAnd((DWORD*)&m_State,~(TS_AbortInitiated));
         m_fRudeAbortInitiated = FALSE;
         ResetUserInterrupted();
-
-#ifdef _DEBUG
-        AddFiberInfo(ThreadTrackInfo_Abort);
-#endif
     }
 
     STRESS_LOG3(LF_APPDOMAIN, LL_ALWAYS, "Unmark Thread %p Thread Id = %x for abort from requester %d\n", this, GetThreadId(), requester);
@@ -2597,9 +2586,6 @@ void Thread::InternalResetAbort(ThreadAbortRequester requester, BOOL fResetRudeA
 
     // managed code can not reset Rude thread abort
     UnmarkThreadForAbort(requester, fResetRudeAbort);
-#ifdef _DEBUG
-    AddFiberInfo(ThreadTrackInfo_Abort);
-#endif
 }
 
 
@@ -2847,11 +2833,6 @@ void Thread::RareDisablePreemptiveGC()
         goto Exit;
     }
 
-
-#ifdef _DEBUG
-    AddFiberInfo(ThreadTrackInfo_GCMode);
-#endif
-
     // This should NEVER be called if the TSNC_UnsafeSkipEnterCooperative bit is set!
     _ASSERTE(!(m_StateNC & TSNC_UnsafeSkipEnterCooperative) && "DisablePreemptiveGC called while the TSNC_UnsafeSkipEnterCooperative bit is set");
 
@@ -3145,9 +3126,6 @@ void Thread::HandleThreadAbort (BOOL fForce)
             exceptObj = CLRException::GetThrowableFromException(&eeExcept);
         }
 
-#ifdef _DEBUG
-        AddFiberInfo(ThreadTrackInfo_Abort);
-#endif
         RaiseTheExceptionInternalOnly(exceptObj, FALSE);
     }
     END_SO_INTOLERANT_CODE;
@@ -3282,10 +3260,6 @@ void Thread::RareEnablePreemptiveGC()
     if (IsAtProcessExit())
         return;
 
-#ifdef _DEBUG
-    AddFiberInfo(ThreadTrackInfo_GCMode);
-#endif
-
     // EnablePreemptiveGC already set us to preemptive mode before triggering the Rare path.
     // Force other threads to see this update, since the Rare path implies that someone else
     // is observing us (e.g. SuspendRuntime).