From 766e02e43ef8fcb055f3a4370f69d926778bbfad Mon Sep 17 00:00:00 2001
From: vsadov <vsadov@microsoft.com>
Date: Mon, 7 Sep 2020 01:53:50 -0700
Subject: [PATCH] Dependent Handles

---
 src/coreclr/src/gc/satori/SatoriRecycler.cpp | 69 +++++++++++++++++---
 src/coreclr/src/gc/satori/SatoriRecycler.h   |  3 +
 2 files changed, 63 insertions(+), 9 deletions(-)

diff --git a/src/coreclr/src/gc/satori/SatoriRecycler.cpp b/src/coreclr/src/gc/satori/SatoriRecycler.cpp
index d83083f0601..9586c483337 100644
--- a/src/coreclr/src/gc/satori/SatoriRecycler.cpp
+++ b/src/coreclr/src/gc/satori/SatoriRecycler.cpp
@@ -96,26 +96,38 @@ void SatoriRecycler::Collect()
         // drain queues
         DrainMarkQueues();
 
-        // mark handles to queues
+        // mark handles
         MarkHandles();
 
         while (m_workList->Count() > 0)
         {
             DrainMarkQueues();
-            //mark through cards   (could be due to overflow)
+            //TODO: VS clean cards   (could be due to overflow)
         }
 
-        // all marked here 
+        // all strongly reachable objects are marked here 
+
+        DependentHandlesInitialScan();
+        while (m_workList->Count() > 0)
+        {
+            DrainMarkQueues();
+            //TODO: VS clean cards   (could be due to overflow)
+            DependentHandlesRescan();
+        }
 
-        // TODO: VS
-        //       DH initial scan (could be a part of loop above?)
         //       sync
         WeakPtrScan(/*isShort*/ true);
         //       sync
         ScanFinalizables();
-        DrainMarkQueues();
 
-        //       scan DH again     (why no sync before?)
+        // TODO: VS why no sync before?
+        while (m_workList->Count() > 0)
+        {
+            DrainMarkQueues();
+            //TODO: VS clean cards   (could be due to overflow)
+            DependentHandlesRescan();
+        }
+
         //       sync 
         WeakPtrScan(/*isShort*/ false);
         WeakPtrScanBySingleThread();
@@ -424,7 +436,6 @@ void SatoriRecycler::DrainMarkQueues()
 
 void SatoriRecycler::MarkHandles()
 {
-    // mark roots for the current stack
     ScanContext sc;
     sc.promotion = TRUE;
     sc.thread_number = 0;
@@ -444,7 +455,6 @@ void SatoriRecycler::MarkHandles()
 
 void SatoriRecycler::WeakPtrScan(bool isShort)
 {
-    // mark roots for the current stack
     ScanContext sc;
     sc.promotion = TRUE;
     sc.thread_number = 0;
@@ -602,3 +612,44 @@ void SatoriRecycler::ScanFinalizables()
         m_workList->Push(c.m_markChunk);
     }
 }
+
+void SatoriRecycler::DependentHandlesInitialScan()
+{
+    ScanContext sc;
+    sc.promotion = TRUE;
+    sc.thread_number = 0;
+
+    MarkContext c = MarkContext(this);
+    sc._unused1 = &c;
+
+    // concurrent, per thread/heap
+    // relies on thread_number to select handle buckets and specialcases #0
+    GCScan::GcDhInitialScan(MarkFn, 2, 2, &sc);
+
+    if (c.m_markChunk != nullptr)
+    {
+        m_workList->Push(c.m_markChunk);
+    }
+}
+
+void SatoriRecycler::DependentHandlesRescan()
+{
+    ScanContext sc;
+    sc.promotion = TRUE;
+    sc.thread_number = 0;
+
+    MarkContext c = MarkContext(this);
+    sc._unused1 = &c;
+
+    // concurrent, per thread/heap
+    // relies on thread_number to select handle buckets and specialcases #0
+    if (GCScan::GcDhUnpromotedHandlesExist(&sc))
+    {
+        GCScan::GcDhReScan(&sc);
+    }
+
+    if (c.m_markChunk != nullptr)
+    {
+        m_workList->Push(c.m_markChunk);
+    }
+}
diff --git a/src/coreclr/src/gc/satori/SatoriRecycler.h b/src/coreclr/src/gc/satori/SatoriRecycler.h
index edc84ceeae1..11765509953 100644
--- a/src/coreclr/src/gc/satori/SatoriRecycler.h
+++ b/src/coreclr/src/gc/satori/SatoriRecycler.h
@@ -67,6 +67,9 @@ private:
     void WeakPtrScan(bool isShort);
     void WeakPtrScanBySingleThread();
     void ScanFinalizables();
+
+    void DependentHandlesInitialScan();
+    void DependentHandlesRescan();
 };
 
 #endif