[sgen] Mark togglerefs before processing ephemerons. Fixes #40108.

Strong Togglerefs must be considered as roots for the purpose of Ephemeron processing.

Otherwise you make it not possible to use a toggleref object as key.

diff --git a/mono/sgen/sgen-gc.c b/mono/sgen/sgen-gc.c
index 57e6f6931fc85ae980bee580694ee17c045b6d6f..e6b8d672dce53fbb73037cc2c4dbfe39bca1a9a7 100644 (file)
--- a/mono/sgen/sgen-gc.c
+++ b/mono/sgen/sgen-gc.c
@@ -1074,6 +1074,12 @@ finish_gray_stack (int generation, ScanCopyContext ctx)
        if (sgen_client_bridge_need_processing ())
                sgen_client_bridge_reset_data ();
 
+       /*
+        * Mark all strong toggleref objects. This must be done before we walk ephemerons or finalizers
+        * to ensure they see the full set of live objects.
+        */
+       sgen_client_mark_togglerefs (start_addr, end_addr, ctx);
+
        /*
         * Walk the ephemeron tables marking all values with reachable keys. This must be completely done
         * before processing finalizable objects and non-tracking weak links to avoid finalizing/clearing
@@ -1086,8 +1092,6 @@ finish_gray_stack (int generation, ScanCopyContext ctx)
                ++ephemeron_rounds;
        } while (!done_with_ephemerons);
 
-       sgen_client_mark_togglerefs (start_addr, end_addr, ctx);
-
        if (sgen_client_bridge_need_processing ()) {
                /*Make sure the gray stack is empty before we process bridge objects so we get liveness right*/
                sgen_drain_gray_stack (ctx);

diff --git a/mono/tests/sgen-toggleref.cs b/mono/tests/sgen-toggleref.cs
index d604294fee0884166128bd9687335ba1cd394e03..f4f2df11555816c07308e4935012b020ea486dd1 100644 (file)
--- a/mono/tests/sgen-toggleref.cs
+++ b/mono/tests/sgen-toggleref.cs
@@ -3,6 +3,7 @@ using System.Collections;
 using System.Collections.Generic;
 using System.Threading;
 using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
 
 public class Toggleref {
        public int __test;
@@ -42,23 +43,23 @@ class Driver {
                mono_gc_toggleref_add (Helper.ObjToPtr (obj), true);
        }
 
+       static Toggleref a, b;
+
        static void SetupLinks () {
-               var a = new Toggleref () { id = "root" };
-               var b = new Toggleref () { id = "child" };
-               a.link.Add (b);
-               a.__test = Toggleref.STRONG;
-               b.__test = Toggleref.WEAK;
-               Register (a);
-               Register (b);
-               root = new WeakReference<Toggleref> (a, false);
-               child = new WeakReference<Toggleref> (b, false);
+               var r = new Toggleref () { id = "root" };
+               var c = new Toggleref () { id = "child" };
+               r.link.Add (c);
+               r.__test = Toggleref.STRONG;
+               c.__test = Toggleref.WEAK;
+               Register (r);
+               Register (c);
+               root = new WeakReference<Toggleref> (r, false);
+               child = new WeakReference<Toggleref> (c, false);
        }
 
-       static Toggleref a, b;
-
-       static int Main ()
+       static int test_0_root_keeps_child ()
        {
-               
+               Console.WriteLine ("test_0_root_keeps_child");
                var t = new Thread (SetupLinks);
                t.Start ();
                t.Join ();
@@ -94,6 +95,116 @@ class Driver {
 
 
                return 0;
+       }
+
+       static void SetupLinks2 () {
+               var r = new Toggleref () { id = "root" };
+               var c = new Toggleref () { id = "child" };
+
+               r.__test = Toggleref.STRONG;
+               c.__test = Toggleref.WEAK;
+               Register (r);
+               Register (c);
+               root = new WeakReference<Toggleref> (r, false);
+               child = new WeakReference<Toggleref> (c, false);
+       }
+
+       static int test_0_child_goes_away ()
+       {
+               Console.WriteLine ("test_0_child_goes_away");
+
+               var t = new Thread (SetupLinks2);
+               t.Start ();
+               t.Join ();
+
+               GC.Collect ();
+               GC.WaitForPendingFinalizers ();
+
+               Console.WriteLine ("try get A {0}", root.TryGetTarget (out a));
+               Console.WriteLine ("try get B {0}", child.TryGetTarget (out b));
+               Console.WriteLine ("a is null {0}", a == null);
+               Console.WriteLine ("b is null {0}", b == null);
+               if (a == null || b != null)
+                       return 1;
+               Console.WriteLine ("a test {0}", a.__test);
+
+               return 0;
+       }
+
+       static ConditionalWeakTable<Toggleref, object> cwt = new ConditionalWeakTable<Toggleref, object> ();
+       static WeakReference<object> root_value, child_value;
+       static object a_val, b_val;
+
+
+       static void SetupLinks3 () {
+               var r = new Toggleref () { id = "root" };
+               var c = new Toggleref () { id = "child" };
+
+               r.__test = Toggleref.STRONG;
+               c.__test = Toggleref.WEAK;
+               Register (r);
+               Register (c);
+               root = new WeakReference<Toggleref> (r, false);
+               child = new WeakReference<Toggleref> (c, false);
+
+               var root_val = new object ();
+               var child_val = new object ();
+
+               cwt.Add (r, root_val);
+               cwt.Add (c, child_val);
+
+               root_value = new WeakReference<object> (root_val, false);
+               child_value = new WeakReference<object> (child_val, false);
+       }
+
+       static int test_0_CWT_keep_child_alive ()
+       {
+               Console.WriteLine ("test_0_CWT_keep_child_alive");
+
+               var t = new Thread (SetupLinks3);
+               t.Start ();
+               t.Join ();
+
+               GC.Collect ();
+               GC.WaitForPendingFinalizers ();
+
+               Console.WriteLine ("try get A {0}", root.TryGetTarget (out a));
+               Console.WriteLine ("try get B {0}", child.TryGetTarget (out b));
+               Console.WriteLine ("a is null {0}", a == null);
+               Console.WriteLine ("b is null {0}", b == null);
+               if (a == null || b != null)
+                       return 1;
+               Console.WriteLine ("a test {0}", a.__test);
+
+               Console.WriteLine ("try get a_val {0}", root_value.TryGetTarget (out a_val));
+               Console.WriteLine ("try get v_val {0}", child_value.TryGetTarget (out b_val));
+
+               //the strong toggleref must keep the CWT value to remains alive
+               if (a_val == null)
+                       return 2;
+
+               //the weak toggleref should allow the CWT value to go away
+               if (b_val != null)
+                       return 3;
+
+               object res_value = null;
+               bool res = cwt.TryGetValue (a, out res_value);
+               Console.WriteLine ("CWT result {0} -> {1}", res, res_value == a_val);
+
+               //the strong val is not on the CWT
+               if (!res)
+                       return 4;
+
+               //for some reason the value is not the right one
+               if (res_value != a_val)
+                       return 5;
+
+               return 0;
+       }
 
+       static int Main (string[] args)
+       {
+               return TestDriver.RunTests (typeof (Driver), args);
        }
+
 }
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