Disable GC Coop mode switching during fatal error handling during GC exception

src/vm/ceemain.cpp

@@ -2919,6 +2919,7 @@ static void TerminateIPCManager(void)
 // Impl for UtilLoadStringRC Callback: In VM, we let the thread decide culture
 // copy culture name into szBuffer and return length
 // ---------------------------------------------------------------------------
+extern BOOL g_fFatalErrorOccuredOnGCThread;
 static HRESULT GetThreadUICultureNames(__inout StringArrayList* pCultureNames)
 {
     CONTRACTL
@@ -2941,7 +2942,23 @@ static HRESULT GetThreadUICultureNames(__inout StringArrayList* pCultureNames)
 
         Thread * pThread = GetThread();
 
-        if (pThread != NULL) {
+        // When fatal errors have occured our invariants around GC modes may be broken and attempting to transition to co-op may hang
+        // indefinately. We want to ensure a clean exit so rather than take the risk of hang we take a risk of the error resource not
+        // getting localized with a non-default thread-specific culture.
+        // A canonical stack trace that gets here is a fatal error in the GC that comes through:
+        // coreclr.dll!GetThreadUICultureNames
+        // coreclr.dll!CCompRC::LoadLibraryHelper
+        // coreclr.dll!CCompRC::LoadLibrary
+        // coreclr.dll!CCompRC::GetLibrary
+        // coreclr.dll!CCompRC::LoadString
+        // coreclr.dll!CCompRC::LoadString
+        // coreclr.dll!SString::LoadResourceAndReturnHR
+        // coreclr.dll!SString::LoadResourceAndReturnHR
+        // coreclr.dll!SString::LoadResource
+        // coreclr.dll!EventReporter::EventReporter
+        // coreclr.dll!EEPolicy::LogFatalError
+        // coreclr.dll!EEPolicy::HandleFatalError
+        if (pThread != NULL && !g_fFatalErrorOccuredOnGCThread) {
 
             // Switch to cooperative mode, since we'll be looking at managed objects
             // and we don't want them moving on us.
@@ -3071,8 +3088,24 @@ static int GetThreadUICultureId(__out LocaleIDValue* pLocale)
 
     Thread * pThread = GetThread();
 
-    if (pThread != NULL) {
-
+    // When fatal errors have occured our invariants around GC modes may be broken and attempting to transition to co-op may hang
+    // indefinately. We want to ensure a clean exit so rather than take the risk of hang we take a risk of the error resource not
+    // getting localized with a non-default thread-specific culture.
+    // A canonical stack trace that gets here is a fatal error in the GC that comes through:
+    // coreclr.dll!GetThreadUICultureNames
+    // coreclr.dll!CCompRC::LoadLibraryHelper
+    // coreclr.dll!CCompRC::LoadLibrary
+    // coreclr.dll!CCompRC::GetLibrary
+    // coreclr.dll!CCompRC::LoadString
+    // coreclr.dll!CCompRC::LoadString
+    // coreclr.dll!SString::LoadResourceAndReturnHR
+    // coreclr.dll!SString::LoadResourceAndReturnHR
+    // coreclr.dll!SString::LoadResource
+    // coreclr.dll!EventReporter::EventReporter
+    // coreclr.dll!EEPolicy::LogFatalError
+    // coreclr.dll!EEPolicy::HandleFatalError
+    if (pThread != NULL && !g_fFatalErrorOccuredOnGCThread)
+    {
         // Switch to cooperative mode, since we'll be looking at managed objects
         // and we don't want them moving on us.
         GCX_COOP();
@@ -3130,7 +3163,24 @@ static int GetThreadUICultureId(__out LocaleIDValue* pLocale)
 
     Thread * pThread = GetThread();
 
-    if (pThread != NULL) {
+    // When fatal errors have occured our invariants around GC modes may be broken and attempting to transition to co-op may hang
+    // indefinately. We want to ensure a clean exit so rather than take the risk of hang we take a risk of the error resource not
+    // getting localized with a non-default thread-specific culture.
+    // A canonical stack trace that gets here is a fatal error in the GC that comes through:
+    // coreclr.dll!GetThreadUICultureNames
+    // coreclr.dll!CCompRC::LoadLibraryHelper
+    // coreclr.dll!CCompRC::LoadLibrary
+    // coreclr.dll!CCompRC::GetLibrary
+    // coreclr.dll!CCompRC::LoadString
+    // coreclr.dll!CCompRC::LoadString
+    // coreclr.dll!SString::LoadResourceAndReturnHR
+    // coreclr.dll!SString::LoadResourceAndReturnHR
+    // coreclr.dll!SString::LoadResource
+    // coreclr.dll!EventReporter::EventReporter
+    // coreclr.dll!EEPolicy::LogFatalError
+    // coreclr.dll!EEPolicy::HandleFatalError
+    if (pThread != NULL && !g_fFatalErrorOccuredOnGCThread)
+    {
 
         // Switch to cooperative mode, since we'll be looking at managed objects
         // and we don't want them moving on us.

src/vm/eepolicy.cpp

@@ -1216,6 +1216,8 @@ inline void DoLogForFailFastException(LPCWSTR pszMessage, PEXCEPTION_POINTERS pE
     EX_END_CATCH(SwallowAllExceptions)
 }
 
+//This starts FALSE and then converts to true if HandleFatalError has ever been called by a GC thread
+BOOL g_fFatalErrorOccuredOnGCThread = FALSE;
 //
 // Log an error to the event log if possible, then throw up a dialog box.
 //
@@ -1349,7 +1351,7 @@ void EEPolicy::LogFatalError(UINT exitCode, UINT_PTR address, LPCWSTR pszMessage
         //Give a managed debugger a chance if this fatal error is on a managed thread.
         Thread *pThread = GetThread();
 
-        if (pThread)
+        if (pThread && !g_fFatalErrorOccuredOnGCThread)
         {
             GCX_COOP();
 
@@ -1491,6 +1493,9 @@ void DECLSPEC_NORETURN EEPolicy::HandleFatalStackOverflow(EXCEPTION_POINTERS *pE
     UNREACHABLE();
 }
 
+
+
+
 void DECLSPEC_NORETURN EEPolicy::HandleFatalError(UINT exitCode, UINT_PTR address, LPCWSTR pszMessage /* = NULL */, PEXCEPTION_POINTERS pExceptionInfo /* = NULL */, LPCWSTR errorSource /* = NULL */, LPCWSTR argExceptionString /* = NULL */)
 {
     WRAPPER_NO_CONTRACT;
@@ -1526,6 +1531,14 @@ void DECLSPEC_NORETURN EEPolicy::HandleFatalError(UINT exitCode, UINT_PTR addres
         // All of the code from here on out is robust to any failures in any API's that are called.
         CONTRACT_VIOLATION(GCViolation | ModeViolation | SOToleranceViolation | FaultNotFatal | TakesLockViolation);
 
+
+        // Setting g_fFatalErrorOccuredOnGCThread allows code to avoid attempting to make GC mode transitions which could
+        // block indefinately if the fatal error occured during the GC.
+        if (IsGCSpecialThread() && GCHeapUtilities::IsGCInProgress())
+        {
+            g_fFatalErrorOccuredOnGCThread = TRUE;
+        }
+
         // ThreadStore lock needs to be released before continuing with the FatalError handling should 
         // because debugger is going to take CrstDebuggerMutex, whose lock level is higher than that of 
         // CrstThreadStore.  It should be safe to release the lock since execution will not be resumed 

src/vm/vars.hpp

@@ -528,6 +528,7 @@ EXTERN BOOL g_fComStarted;
 //
 GVAL_DECL(DWORD, g_fEEShutDown);
 EXTERN DWORD g_fFastExitProcess;
+EXTERN BOOL g_fFatalErrorOccurredOnGCThread;
 #ifndef DACCESS_COMPILE
 EXTERN BOOL g_fSuspendOnShutdown;
 EXTERN BOOL g_fSuspendFinalizerOnShutdown;