From efe21ab92922f535051978fdff2fb4554dc66b92 Mon Sep 17 00:00:00 2001
From: iveresov <unknown>
Date: Thu, 10 Jul 2008 09:29:54 -0700
Subject: [PATCH] 6723570: G1: assertion failure: p == current_top or
 oop(p)->is_oop(),"p is not a block start" (revisited!) Summary: Fixed the
 incorrect assigment to G1OffsetTableContigSpace::_gc_time_stamp. Also added a
 little more paranoia to operations on a global timestamp. Reviewed-by: tonyp

---
 src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp | 3 ++-
 src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp | 8 +++++++-
 src/share/vm/gc_implementation/g1/heapRegion.cpp      | 4 ++--
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp b/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp
index 82db0c37e..bf892425c 100644
--- a/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp
+++ b/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp
@@ -2279,7 +2279,8 @@ G1CollectedHeap::do_collection_pause_at_safepoint(HeapRegion* popular_region) {
   assert(Thread::current() == VMThread::vm_thread(), "should be in vm thread");
   guarantee(!is_gc_active(), "collection is not reentrant");
   assert(regions_accounted_for(), "Region leakage!");
-  ++_gc_time_stamp;
+
+  increment_gc_time_stamp();
 
   if (g1_policy()->in_young_gc_mode()) {
     assert(check_young_list_well_formed(),
diff --git a/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp b/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp
index 4cc1db22d..b47a983d9 100644
--- a/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp
+++ b/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp
@@ -247,7 +247,7 @@ private:
   NumberSeq _pop_obj_rc_at_copy;
   void print_popularity_summary_info() const;
 
-  unsigned _gc_time_stamp;
+  volatile unsigned _gc_time_stamp;
 
   size_t* _surviving_young_words;
 
@@ -653,6 +653,12 @@ public:
 
   void reset_gc_time_stamp() {
     _gc_time_stamp = 0;
+    OrderAccess::fence();
+  }
+
+  void increment_gc_time_stamp() {
+    ++_gc_time_stamp;
+    OrderAccess::fence();
   }
 
   void iterate_dirty_card_closure(bool concurrent, int worker_i);
diff --git a/src/share/vm/gc_implementation/g1/heapRegion.cpp b/src/share/vm/gc_implementation/g1/heapRegion.cpp
index 05435f54c..824adbf87 100644
--- a/src/share/vm/gc_implementation/g1/heapRegion.cpp
+++ b/src/share/vm/gc_implementation/g1/heapRegion.cpp
@@ -793,8 +793,8 @@ void G1OffsetTableContigSpace::set_saved_mark() {
     // will pick up the right saved_mark_word() as the high water mark
     // of the region. Either way, the behaviour will be correct.
     ContiguousSpace::set_saved_mark();
-    OrderAccess::release_store_ptr((volatile intptr_t*) &_gc_time_stamp,
-                                   (intptr_t) curr_gc_time_stamp);
+    _gc_time_stamp = curr_gc_time_stamp;
+    OrderAccess::fence();
   }
 }
 
-- 
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