8040977: G1 crashes when run with -XX:-G1DeferredRSUpdate

When G1 is run with -XX:-G1DeferredRSUpdate, the VM crashes because of wrong initialization order of member variables. The change makes the initalization explicit, not relying on initialization order any more.

Reviewed-by: brutisso, mgerdin

hotspot/src/share/vm/gc_implementation/g1/g1OopClosures.cpp

@@ -25,11 +25,28 @@
 #include "precompiled.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
+#include "gc_implementation/g1/g1ParScanThreadState.hpp"
 
 G1ParCopyHelper::G1ParCopyHelper(G1CollectedHeap* g1,  G1ParScanThreadState* par_scan_state) :
   G1ParClosureSuper(g1, par_scan_state), _scanned_klass(NULL),
   _cm(_g1->concurrent_mark()) {}
 
+G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1) :
+  _g1(g1), _par_scan_state(NULL), _worker_id(UINT_MAX) { }
+
 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, G1ParScanThreadState* par_scan_state) :
-  _g1(g1), _par_scan_state(par_scan_state),
-  _worker_id(par_scan_state->queue_num()) { }
+  _g1(g1), _par_scan_state(NULL),
+  _worker_id(UINT_MAX) {
+  set_par_scan_thread_state(par_scan_state);
+}
+
+void G1ParClosureSuper::set_par_scan_thread_state(G1ParScanThreadState* par_scan_state) {
+  assert(_par_scan_state == NULL, "_par_scan_state must only be set once");
+  assert(par_scan_state != NULL, "Must set par_scan_state to non-NULL.");
+
+  _par_scan_state = par_scan_state;
+  _worker_id = par_scan_state->queue_num();
+
+  assert(_worker_id < MAX2((uint)ParallelGCThreads, 1u),
+         err_msg("The given worker id %u must be less than the number of threads %u", _worker_id, MAX2((uint)ParallelGCThreads, 1u)));
+}

hotspot/src/share/vm/gc_implementation/g1/g1OopClosures.hpp

@@ -51,8 +51,13 @@ protected:
   G1ParScanThreadState* _par_scan_state;
   uint _worker_id;
 public:
+  // Initializes the instance, leaving _par_scan_state uninitialized. Must be done
+  // later using the set_par_scan_thread_state() method.
+  G1ParClosureSuper(G1CollectedHeap* g1);
   G1ParClosureSuper(G1CollectedHeap* g1, G1ParScanThreadState* par_scan_state);
   bool apply_to_weak_ref_discovered_field() { return true; }
+
+  void set_par_scan_thread_state(G1ParScanThreadState* par_scan_state);
 };
 
 class G1ParPushHeapRSClosure : public G1ParClosureSuper {
@@ -68,9 +73,8 @@ public:
 
 class G1ParScanClosure : public G1ParClosureSuper {
 public:
-  G1ParScanClosure(G1CollectedHeap* g1, G1ParScanThreadState* par_scan_state, ReferenceProcessor* rp) :
-    G1ParClosureSuper(g1, par_scan_state)
-  {
+  G1ParScanClosure(G1CollectedHeap* g1, ReferenceProcessor* rp) :
+    G1ParClosureSuper(g1) {
     assert(_ref_processor == NULL, "sanity");
     _ref_processor = rp;
   }

hotspot/src/share/vm/gc_implementation/g1/g1ParScanThreadState.cpp

@@ -30,10 +30,6 @@
 #include "oops/oop.pcgc.inline.hpp"
 #include "runtime/prefetch.inline.hpp"
 
-#ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
-#pragma warning( disable:4355 ) // 'this' : used in base member initializer list
-#endif // _MSC_VER
-
 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num, ReferenceProcessor* rp)
   : _g1h(g1h),
     _refs(g1h->task_queue(queue_num)),
@@ -44,9 +40,10 @@ G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num,
     _term_attempts(0),
     _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
     _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
-    _age_table(false), _scanner(g1h, this, rp),
+    _age_table(false), _scanner(g1h, rp),
     _strong_roots_time(0), _term_time(0),
     _alloc_buffer_waste(0), _undo_waste(0) {
+  _scanner.set_par_scan_thread_state(this);
   // we allocate G1YoungSurvRateNumRegions plus one entries, since
   // we "sacrifice" entry 0 to keep track of surviving bytes for
   // non-young regions (where the age is -1)

hotspot/test/gc/g1/TestDeferredRSUpdate.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test TestDeferredRSUpdate
+ * @bug 8040977
+ * @summary Ensure that running with -XX:-G1DeferredRSUpdate does not crash the VM
+ * @key gc
+ * @library /testlibrary
+ */
+
+import com.oracle.java.testlibrary.ProcessTools;
+import com.oracle.java.testlibrary.OutputAnalyzer;
+
+public class TestDeferredRSUpdate {
+  public static void main(String[] args) throws Exception {
+    GCTest.main(args);
+
+    ProcessBuilder pb = ProcessTools.createJavaProcessBuilder("-XX:+UseG1GC",
+                                                              "-Xmx10M",
+                                                              // G1DeferredRSUpdate is a develop option, but we cannot limit execution of this test to only debug VMs.
+                                                              "-XX:+IgnoreUnrecognizedVMOptions",
+                                                              "-XX:-G1DeferredRSUpdate",
+                                                              GCTest.class.getName());
+
+    OutputAnalyzer output = new OutputAnalyzer(pb.start());
+    output.shouldHaveExitValue(0);
+  }
+
+  static class GCTest {
+    private static Object[] garbage = new Object[32];
+
+    public static void main(String [] args) {
+      System.out.println("Creating garbage");
+      // Create 128MB of garbage. This should result in at least one minor GC, with
+      // some objects copied to old gen. As references from old to young are installed,
+      // the crash due to the use before initialize occurs.
+      Object prev = null;
+      Object prevPrev = null;
+      for (int i = 0; i < 1024; i++) {
+        Object[] next = new Object[32 * 1024];
+        next[0] = prev;
+        next[1] = prevPrev;
+
+        Object[] cur = (Object[]) garbage[i % garbage.length];
+        if (cur != null) {
+          cur[0] = null;
+          cur[1] = null;
+        }
+        garbage[i % garbage.length] = next;
+
+        prevPrev = prev;
+        prev = next;
+      }
+      System.out.println("Done");
+    }
+  }
+}