Add heuristic to trigger GC to finalize dead threads and clean up han…

src/debug/daccess/dacdbiimpl.cpp

@@ -5452,15 +5452,8 @@ CorDebugUserState DacDbiInterfaceImpl::GetPartialUserState(VMPTR_Thread vmThread
         result |= USER_WAIT_SLEEP_JOIN;          
     }
 
-    // Don't report a SuspendRequested if the thread has actually Suspended.
-    if ((ts & Thread::TS_UserSuspendPending) && (ts & Thread::TS_SyncSuspended))
-    {
-        result |= USER_SUSPENDED;
-    }
-    else if (ts & Thread::TS_UserSuspendPending)
-    {
-        result |= USER_SUSPEND_REQUESTED;
-    }
+    // CoreCLR does not support user-requested thread suspension
+    _ASSERTE(!(ts & Thread::TS_UserSuspendPending));
 
     if (pThread->IsThreadPoolThread())
     {

src/inc/clrconfigvalues.h

@@ -936,6 +936,12 @@ CONFIG_DWORD_INFO(INTERNAL_SuspendDeadlockTimeout, W("SuspendDeadlockTimeout"),
 CONFIG_DWORD_INFO(INTERNAL_SuspendThreadDeadlockTimeoutMs, W("SuspendThreadDeadlockTimeoutMs"), 2000, "")
 RETAIL_CONFIG_DWORD_INFO(INTERNAL_ThreadSuspendInjection, W("INTERNAL_ThreadSuspendInjection"), 1, "Specifies whether to inject activations for thread suspension on Unix")
 
+//
+// Thread (miscellaneous)
+//
+RETAIL_CONFIG_DWORD_INFO(INTERNAL_Thread_DeadThreadCountThresholdForGCTrigger, W("Thread_DeadThreadCountThresholdForGCTrigger"), 75, "In the heuristics to clean up dead threads, this threshold must be reached before triggering a GC will be considered. Set to 0 to disable triggering a GC based on dead threads.")
+RETAIL_CONFIG_DWORD_INFO(INTERNAL_Thread_DeadThreadGCTriggerPeriodMilliseconds, W("Thread_DeadThreadGCTriggerPeriodMilliseconds"), 1000 * 60 * 30, "In the heuristics to clean up dead threads, this much time must have elapsed since the previous max-generation GC before triggering another GC will be considered")
+
 // 
 // Threadpool
 // 

src/vm/comsynchronizable.cpp

@@ -926,18 +926,8 @@ FCIMPL1(INT32, ThreadNative::GetThreadState, ThreadBaseObject* pThisUNSAFE)
     if (state & Thread::TS_Interruptible)
         res |= ThreadWaitSleepJoin;
 
-    // Don't report a SuspendRequested if the thread has actually Suspended.
-    if ((state & Thread::TS_UserSuspendPending) &&
-        (state & Thread::TS_SyncSuspended)
-       )
-    {
-        res |= ThreadSuspended;
-    }
-    else
-    if (state & Thread::TS_UserSuspendPending)
-    {
-        res |= ThreadSuspendRequested;
-    }
+    // CoreCLR does not support user-requested thread suspension
+    _ASSERTE(!(state & Thread::TS_UserSuspendPending));
 
     HELPER_METHOD_POLL();
     HELPER_METHOD_FRAME_END();

src/vm/debugdebugger.cpp

@@ -937,62 +937,8 @@ void DebugStackTrace::GetStackFramesHelper(Frame *pStartFrame,
             goto LSafeToTrace;
         }
 
-        if (state & Thread::TS_UserSuspendPending)
-        {
-            if (state & Thread::TS_SyncSuspended)
-            {
-                goto LSafeToTrace;
-            }
-
-#ifndef DISABLE_THREADSUSPEND
-            // On Mac don't perform the optimization below, but rather wait for 
-            // the suspendee to set the TS_SyncSuspended flag
-
-            // The target thread is not actually suspended yet, but if it is
-            // in preemptive mode, then it is still safe to trace.  Before we
-            // can look at another thread's GC mode, we have to suspend it:
-            // The target thread updates its GC mode flag with non-interlocked
-            // operations, and Thread::SuspendThread drains the CPU's store
-            // buffer (by virtue of calling GetThreadContext).
-            switch (pThread->SuspendThread())
-            {
-            case Thread::STR_Success:
-                if (!pThread->PreemptiveGCDisabledOther())
-                {
-                    pThread->ResumeThread();
-                    goto LSafeToTrace;
-                }
-
-                // Refuse to trace the stack.
-                //
-                // Note that there is a pretty large window in-between when the
-                // target thread sets the GC mode to cooperative, and when it
-                // actually sets the TS_SyncSuspended bit.  In this window, we
-                // will refuse to take a stack trace even though it would be
-                // safe to do so.
-                pThread->ResumeThread();
-                break;
-            case Thread::STR_Failure:
-            case Thread::STR_NoStressLog:
-                break;
-            case Thread::STR_UnstartedOrDead:
-                // We know the thread is not unstarted, because we checked for
-                // TS_Unstarted above.
-                _ASSERTE(!(state & Thread::TS_Unstarted));
-
-                // Since the thread is dead, it is safe to trace.
-                goto LSafeToTrace;
-            case Thread::STR_SwitchedOut:
-                if (!pThread->PreemptiveGCDisabledOther())
-                {
-                    goto LSafeToTrace;
-                }
-                break;
-            default:
-                UNREACHABLE();
-            }
-#endif  // DISABLE_THREADSUSPEND
-        }
+        // CoreCLR does not support user-requested thread suspension
+        _ASSERTE(!(state & Thread::TS_UserSuspendPending));
 
         COMPlusThrow(kThreadStateException, IDS_EE_THREAD_BAD_STATE);
 

src/vm/eedbginterfaceimpl.cpp

@@ -1588,15 +1588,8 @@ CorDebugUserState EEDbgInterfaceImpl::GetPartialUserState(Thread *pThread)
         ret |= (unsigned)USER_WAIT_SLEEP_JOIN;          
     }
 
-    // Don't report a SuspendRequested if the thread has actually Suspended.
-    if ( ((ts & Thread::TS_UserSuspendPending) && (ts & Thread::TS_SyncSuspended)))
-    {
-        ret |= (unsigned)USER_SUSPENDED;
-    }
-    else if (ts & Thread::TS_UserSuspendPending)
-    {
-        ret |= (unsigned)USER_SUSPEND_REQUESTED;
-    }
+    // CoreCLR does not support user-requested thread suspension
+    _ASSERTE(!(ts & Thread::TS_UserSuspendPending));
 
     LOG((LF_CORDB,LL_INFO1000, "EEDbgII::GUS: thread 0x%x (id:0x%x)"
         " userThreadState is 0x%x\n", pThread, pThread->GetThreadId(), ret));

src/vm/finalizerthread.cpp

@@ -1345,6 +1345,8 @@ BOOL FinalizerThread::FinalizerThreadWatchDogHelper()
         }
         ULONGLONG dwCurTickCount = CLRGetTickCount64();
         if (pThread && pThread->m_State & (Thread::TS_UserSuspendPending | Thread::TS_DebugSuspendPending)) {
+            // CoreCLR does not support user-requested thread suspension
+            _ASSERTE(!(pThread->m_State & Thread::TS_UserSuspendPending));
             dwBeginTickCount = dwCurTickCount;
         }
         if (dwCurTickCount - dwBeginTickCount >= maxTotalWait)

src/vm/gcenv.ee.cpp

@@ -626,6 +626,11 @@ void GCToEEInterface::GcStartWork (int condemned, int max_gen)
     // 
     RCWWalker::OnGCStarted(condemned);
 #endif // FEATURE_COMINTEROP
+
+    if (condemned == max_gen)
+    {
+        ThreadStore::s_pThreadStore->OnMaxGenerationGCStarted();
+    }
 }
 
 void GCToEEInterface::GcDone(int condemned)