Conservative GC reporting for suspended green threads

src/coreclr/gc/gc.cpp

@@ -7868,18 +7868,12 @@ bool gc_heap::is_in_condemned_gc (uint8_t* o)
     return true;
 }
 
-// REGIONS TODO -
-// This method can be called by GCHeap::Promote/Relocate which means
-// it could be in the heap range but not actually in a valid region.
-// This would return true but find_object will return 0. But this
-// seems counter-intuitive so we should consider a better implementation.
+// This needs to check the range that's covered by bookkeeping because find_object will
+// need to look at the brick table.
 inline
-bool gc_heap::is_in_condemned (uint8_t* o)
+bool gc_heap::is_in_bookkeeping_range (uint8_t* o)
 {
-    if ((o >= g_gc_lowest_address) && (o < g_gc_highest_address))
-        return is_in_condemned_gc (o);
-    else
-        return false;
+    return ((o >= g_gc_lowest_address) && (o < bookkeeping_covered_committed));
 }
 
 inline
@@ -45433,7 +45427,7 @@ void GCHeap::Promote(Object** ppObject, ScanContext* sc, uint32_t flags)
     gc_heap* hp = gc_heap::heap_of (o);
 
 #ifdef USE_REGIONS
-    if (!gc_heap::is_in_condemned (o))
+    if (!gc_heap::is_in_bookkeeping_range (o) || !gc_heap::is_in_condemned_gc (o))
 #else //USE_REGIONS
     if ((o < hp->gc_low) || (o >= hp->gc_high))
 #endif //USE_REGIONS
@@ -45492,7 +45486,12 @@ void GCHeap::Relocate (Object** ppObject, ScanContext* sc,
     //dprintf (3, ("Relocate location %Ix\n", (size_t)ppObject));
     dprintf (3, ("R: %Ix", (size_t)ppObject));
 
-    if (!object || !((object >= g_gc_lowest_address) && (object < g_gc_highest_address)))
+    if (!object 
+#ifdef USE_REGIONS
+        || !gc_heap::is_in_bookkeeping_range (object))
+#else //USE_REGIONS
+        || !((object >= g_gc_lowest_address) && (object < g_gc_highest_address)))
+#endif //USE_REGIONS
         return;
 
     gc_heap* hp = gc_heap::heap_of (object);
@@ -45947,17 +45946,16 @@ GCHeap::GetContainingObject (void *pInteriorPtr, bool fCollectedGenOnly)
     gc_heap* hp = gc_heap::heap_of (o);
 
 #ifdef USE_REGIONS
-    if (fCollectedGenOnly)
+    if (gc_heap::is_in_bookkeeping_range (o))
     {
-        if (!gc_heap::is_in_condemned (o))
+        if (fCollectedGenOnly && !gc_heap::is_in_condemned_gc (o))
         {
             return NULL;
         }
     }
     else
     {
-        if (!((o >= g_gc_lowest_address) && (o < g_gc_highest_address)))
-            return NULL;
+        return NULL;
     }
 #else //USE_REGIONS
 

src/coreclr/gc/gcpriv.h

@@ -52,7 +52,7 @@ inline void FATAL_GC_ERROR()
 // This means any empty regions can be freely used for any generation. For
 // Server GC we will balance regions between heaps.
 // For now disable regions for StandAlone GC, NativeAOT and MacOS builds
-#if defined (HOST_64BIT) && !defined (BUILD_AS_STANDALONE) && !defined(__APPLE__) && !defined(FEATURE_NATIVEAOT)
+#if defined (HOST_64BIT) && !defined (BUILD_AS_STANDALONE) && !defined(__APPLE__)
 #define USE_REGIONS
 #endif //HOST_64BIT && BUILD_AS_STANDALONE
 
@@ -3127,7 +3127,7 @@ class gc_heap
     bool is_in_condemned_gc (uint8_t* o);
     // requires checking if o is in the heap range first.
     PER_HEAP_ISOLATED
-    bool is_in_condemned (uint8_t* o);
+    bool is_in_bookkeeping_range (uint8_t* o);
     PER_HEAP_ISOLATED
     bool should_check_brick_for_reloc (uint8_t* o);
 #endif //USE_REGIONS

src/coreclr/vm/gcenv.ee.cpp

@@ -274,6 +274,36 @@ void GCToEEInterface::GcScanRoots(promote_func* fn, int condemned, int max_gen,
         STRESS_LOG2(LF_GC | LF_GCROOTS, LL_INFO100, "Ending scan of Thread %p ID = 0x%x }\n", pThread, pThread->GetThreadId());
     }
 
+#ifdef FEATURE_GREENTHREADS
+    {
+        if (sc->promotion && green_head.next)
+        {
+            SuspendedGreenThread* current_green_thread = green_head.next;
+            while (current_green_thread != &green_tail)
+            {
+                GreenThreadStackList* current_thread_stack_segment = current_green_thread->currentThreadStackSegment;
+                while (current_thread_stack_segment->prev != nullptr)
+                {
+                    current_thread_stack_segment = current_thread_stack_segment->prev;
+                }
+                while (current_thread_stack_segment != nullptr)
+                {
+                    PTR_PTR_Object green_object_base = (PTR_PTR_Object)current_thread_stack_segment->stackRange.stackBase;
+                    PTR_PTR_Object green_object_limit = (PTR_PTR_Object)current_thread_stack_segment->stackRange.stackLimit;
+                    PTR_PTR_Object green_current = green_object_base;
+                    while (green_current > green_object_limit)
+                    {
+                        fn(green_current, sc, GC_CALL_INTERIOR|GC_CALL_PINNED);
+                        green_current--;
+                    }
+                    current_thread_stack_segment = current_thread_stack_segment->next;
+                }
+                current_green_thread = current_green_thread->next;
+            }
+        }
+    }
+#endif //FEATURE_GREENTHREADS
+
     // In server GC, we should be competing for marking the statics
     // It's better to do this *after* stack scanning, because this way
     // we can make up for imbalances in stack scanning

src/coreclr/vm/gcenv.ee.standalone.cpp

@@ -17,6 +17,8 @@
 #include "genanalysis.h"
 #include "eventpipeadapter.h"
 
+#include "greenthreads.h"
+
 // the method table for the WeakReference class
 extern MethodTable* pWeakReferenceMT;
 

src/coreclr/vm/gcenv.ee.static.cpp

@@ -17,6 +17,8 @@
 #include "genanalysis.h"
 #include "eventpipeadapter.h"
 
+#include "greenthreads.h"
+
 // the method table for the WeakReference class
 extern MethodTable* pWeakReferenceMT;
 

src/coreclr/vm/greenthreads.cpp

@@ -17,8 +17,11 @@ struct GreenThreadData
     GreenThreadStackList *pStackListCurrent;
     bool inGreenThread;
     bool transitionedToOSThreadOnGreenThread;
+    SuspendedGreenThread* suspendedGreenThread;
 };
 
+extern SuspendedGreenThread green_head = {};
+extern SuspendedGreenThread green_tail = {};
 
 thread_local GreenThreadData t_greenThread;
 
@@ -161,9 +164,8 @@ SuspendedGreenThread* ProduceSuspendedGreenThreadStruct()
     if (t_greenThread.inGreenThread)
     {
         // This is a suspension scenario
-        SuspendedGreenThread *pNewSuspendedThread = (SuspendedGreenThread*)malloc(sizeof(SuspendedGreenThread));
+        SuspendedGreenThread* pNewSuspendedThread = t_greenThread.suspendedGreenThread;
         pNewSuspendedThread->currentStackPointer = t_greenThread.greenThreadStackCurrent;
-        pNewSuspendedThread->currentThreadStackSegment = t_greenThread.pStackListCurrent;
         pNewSuspendedThread->greenThreadFrame = t_greenThread.pFrameInGreenThread;
 
         CleanGreenThreadState();
@@ -241,7 +243,19 @@ bool GreenThread_Yield() // Attempt to yield out of green thread. If the yield f
         }
         GetThread()->m_pFrame = t_greenThread.pFrameInGreenThread->PtrNextFrame();
 
-        // TODO! Enable GC Tracking of green thread at this point.
+        // TODO: AndrewAu: What if we don't have sufficient memory for this?
+        SuspendedGreenThread *pNewSuspendedThread = (SuspendedGreenThread*)malloc(sizeof(SuspendedGreenThread));
+        pNewSuspendedThread->currentThreadStackSegment = t_greenThread.pStackListCurrent;        
+        t_greenThread.suspendedGreenThread = pNewSuspendedThread;
+
+        // TODO: AndrewAu: Synchronization in case multiple threads yield/resume at the same time.
+        if (green_head.next == nullptr) { green_head.next = &green_tail; }
+        if (green_tail.next == nullptr) { green_tail.prev = &green_head; }
+
+        pNewSuspendedThread->prev = green_tail.prev;
+        green_tail.prev->next = pNewSuspendedThread;
+        green_tail.prev = pNewSuspendedThread;
+        pNewSuspendedThread->next = &green_tail;
     }
 
     YieldOutOfGreenThreadHelper(&t_greenThread.osStackRange, t_greenThread.osStackCurrent, &t_greenThread.greenThreadStackCurrent);
@@ -250,7 +264,12 @@ bool GreenThread_Yield() // Attempt to yield out of green thread. If the yield f
         GCX_COOP();
         // At this point we've resumed, and the stack is now in the new state way, but the Frame chain is not hooked up.
 
-        // TODO! Disable separate GC tracking of green thread at this point
+        SuspendedGreenThread* pNewSuspendedThread = t_greenThread.suspendedGreenThread;
+        t_greenThread.suspendedGreenThread = nullptr;
+
+        pNewSuspendedThread->next->prev = pNewSuspendedThread->prev;
+        pNewSuspendedThread->prev->next = pNewSuspendedThread->next;
+        free(pNewSuspendedThread);
 
         t_greenThread.pFrameInGreenThread->UNSAFE_SetNextFrame(t_greenThread.pFrameInOSThread);
         GetThread()->m_pFrame = t_greenThread.pFrameInGreenThread;
@@ -306,8 +325,7 @@ SuspendedGreenThread* GreenThread_ResumeThread(SuspendedGreenThread* pSuspendedT
 
     t_greenThread.pStackListCurrent = pSuspendedThread->currentThreadStackSegment;
     t_greenThread.greenThreadStackCurrent = pSuspendedThread->currentStackPointer;
-
-    free(pSuspendedThread);
+    t_greenThread.suspendedGreenThread = pSuspendedThread;
 
     ResumeSuspendedThreadHelper();
     return ProduceSuspendedGreenThreadStruct();

src/coreclr/vm/greenthreads.h

@@ -22,8 +22,10 @@ struct GreenThreadStackList
 struct SuspendedGreenThread
 {
     uint8_t* currentStackPointer;
-    GreenThreadStackList *currentThreadStackSegment;
+    GreenThreadStackList* currentThreadStackSegment;
     Frame* greenThreadFrame;
+    SuspendedGreenThread* prev;
+    SuspendedGreenThread* next;
 };
 
 typedef uintptr_t (*TakesOneParam)(uintptr_t param);
@@ -41,4 +43,8 @@ void DestroyGreenThread(SuspendedGreenThread* pSuspendedThread); //
 
 bool GreenThread_IsGreenThread();
 
+// TODO: AndrewAu: Better naming
+extern SuspendedGreenThread green_head;
+extern SuspendedGreenThread green_tail;
+
 #endif // GREENTHREADS_H