From 7a24d17f3bdbd3603fd94be69d4cc7711f11d700 Mon Sep 17 00:00:00 2001
From: aph <unknown>
Date: Wed, 4 Nov 2015 13:38:38 +0100
Subject: [PATCH] 8138966: Intermittent SEGV running ParallelGC Summary: Add
 necessary memory fences so that the parallel threads are unable to observe
 partially filled block tables. Reviewed-by: tschatzl

---
 .../parallelScavenge/psParallelCompact.hpp                 | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.hpp b/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.hpp
index 4d835314c..881f380ce 100644
--- a/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.hpp
+++ b/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.hpp
@@ -348,7 +348,7 @@ public:
     HeapWord*            _partial_obj_addr;
     region_sz_t          _partial_obj_size;
     region_sz_t volatile _dc_and_los;
-    bool                 _blocks_filled;
+    bool        volatile _blocks_filled;
 
 #ifdef ASSERT
     size_t               _blocks_filled_count;   // Number of block table fills.
@@ -499,7 +499,9 @@ ParallelCompactData::RegionData::destination_count() const
 inline bool
 ParallelCompactData::RegionData::blocks_filled() const
 {
-  return _blocks_filled;
+  bool result = _blocks_filled;
+  OrderAccess::acquire();
+  return result;
 }
 
 #ifdef ASSERT
@@ -513,6 +515,7 @@ ParallelCompactData::RegionData::blocks_filled_count() const
 inline void
 ParallelCompactData::RegionData::set_blocks_filled()
 {
+  OrderAccess::release();
   _blocks_filled = true;
   // Debug builds count the number of times the table was filled.
   DEBUG_ONLY(Atomic::inc_ptr(&_blocks_filled_count));
-- 
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