Try to fix GCPoll regression.

Author: AaronRobinsonMSFT

src/coreclr/System.Private.CoreLib/src/System/Threading/Thread.CoreCLR.cs

@@ -491,6 +491,9 @@ private void ResetFinalizerThreadSlow()
             }
         }
 
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern bool CatchAtSafePoint();
+
         [LibraryImport(RuntimeHelpers.QCall, EntryPoint = "ThreadNative_PollGC")]
         private static partial void PollGCInternal();
 
@@ -499,8 +502,7 @@ private void ResetFinalizerThreadSlow()
         // as a small assembly stub which checks the global g_TrapReturningThreads flag and tail-call to this helper
         private static unsafe void PollGC()
         {
-            NativeThreadState catchAtSafePoint = ((NativeThreadClass*)Thread.DirectOnThreadLocalData.pNativeThread)->m_State & NativeThreadState.TS_CatchAtSafePoint;
-            if (catchAtSafePoint != NativeThreadState.None)
+            if (CatchAtSafePoint())
             {
                 PollGCWorker();
             }

src/coreclr/vm/comsynchronizable.cpp

@@ -714,6 +714,14 @@ FCIMPL1(void, ThreadNative::Finalize, ThreadBaseObject* pThisUNSAFE)
 }
 FCIMPLEND
 
+FCIMPL0(FC_BOOL_RET, ThreadNative::CatchAtSafePoint)
+{
+    FCALL_CONTRACT;
+
+    FC_RETURN_BOOL(GetThread()->CatchAtSafePoint());
+}
+FCIMPLEND
+
 // Get whether or not this is a background thread.
 extern "C" BOOL QCALLTYPE ThreadNative_GetIsBackground(QCall::ThreadHandle thread)
 {

src/coreclr/vm/comsynchronizable.h

@@ -39,8 +39,9 @@ class ThreadNative
         ThreadAbortRequested = 128,
     };
 
-    static FCDECL0(INT32,   GetOptimalMaxSpinWaitsPerSpinIteration);
-    static FCDECL1(void,    Finalize,                       ThreadBaseObject* pThis);
+    static FCDECL0(INT32,       GetOptimalMaxSpinWaitsPerSpinIteration);
+    static FCDECL1(void,        Finalize, ThreadBaseObject* pThis);
+    static FCDECL0(FC_BOOL_RET, CatchAtSafePoint);
 };
 
 extern "C" void QCALLTYPE ThreadNative_Start(QCall::ThreadHandle thread, int threadStackSize, int priority, BOOL isThreadPool, PCWSTR pThreadName);

src/coreclr/vm/ecalllist.h

@@ -238,6 +238,7 @@ FCFuncEnd()
 
 FCFuncStart(gThreadFuncs)
     FCFuncElement("InternalFinalize", ThreadNative::Finalize)
+    FCFuncElement("CatchAtSafePoint", ThreadNative::CatchAtSafePoint)
     FCFuncElement("get_OptimalMaxSpinWaitsPerSpinIteration", ThreadNative::GetOptimalMaxSpinWaitsPerSpinIteration)
 FCFuncEnd()