EVALUATION

http://hg.openjdk.java.net/jdk7/hotspot-gc/hotspot/rev/60fb9c4db4e6
                                     

SUGGESTED FIX

Subject         hotspot-g1-gc: 6718086: CMS assert: _concurrent_iteration_safe_l...

repo:       /net/jano2/export2/hotspot/hg/hotspot-g1-gc
changeset:  198:60fb9c4db4e6
user:       ysr
date:       Mon Jun 23 16:49:37 2008 -0700
description:
6718086: CMS assert: _concurrent_iteration_safe_limit update missed
Summary: Initialize the field correctly in ContiguousSpace's constructor and initialize() methods, using the latter for the survivor spaces upon initial construction or a subsequent resizing of the yo
ung generation. Add some missing Space sub-class constructors.
Reviewed-by: apetrusenko

files:
src/share/vm/memory/defNewGeneration.cpp src/share/vm/memory/space.cpp src/share/vm/memory/space.hpp


====


data/jprt/archive/2008/06/2008-06-23-235006.ysr.hg_g1_gc_baseline
                                     

SUGGESTED FIX

diff -r bb254e57d2f4 -r 60fb9c4db4e6 src/share/vm/memory/defNewGeneration.cpp
--- a/src/share/vm/memory/defNewGeneration.cpp  Tue Jun 17 08:40:48 2008 -0700
+++ b/src/share/vm/memory/defNewGeneration.cpp  Mon Jun 23 16:49:37 2008 -0700
@@ -227,8 +227,8 @@ void DefNewGeneration::compute_space_bou
       eden()->mangle_unused_area();
     }
   }
-  from()->set_bounds(fromMR); from()->clear();
-    to()->set_bounds(toMR);     to()->clear();
+  from()->initialize(fromMR, true /* clear */);
+    to()->initialize(  toMR, true /* clear */);
   // Make sure we compact eden, then from.
   // The to-space is normally empty before a compaction so need
   // not be considered.  The exception is during promotion
diff -r bb254e57d2f4 -r 60fb9c4db4e6 src/share/vm/memory/space.cpp
--- a/src/share/vm/memory/space.cpp     Tue Jun 17 08:40:48 2008 -0700
+++ b/src/share/vm/memory/space.cpp     Mon Jun 23 16:49:37 2008 -0700
@@ -276,6 +276,7 @@ void ContiguousSpace::initialize(MemRegi
   set_top(bottom());
   set_saved_mark();
   if (clear_space) clear();
+  set_concurrent_iteration_safe_limit(top());
 }

 void ContiguousSpace::clear() {
diff -r bb254e57d2f4 -r 60fb9c4db4e6 src/share/vm/memory/space.hpp
--- a/src/share/vm/memory/space.hpp     Tue Jun 17 08:40:48 2008 -0700
+++ b/src/share/vm/memory/space.hpp     Mon Jun 23 16:49:37 2008 -0700
@@ -373,6 +373,9 @@ private:
   CompactibleSpace* _next_compaction_space;

 public:
+  CompactibleSpace() :
+   _compaction_top(NULL), _next_compaction_space(NULL) {}
+
   virtual void initialize(MemRegion mr, bool clear_space);
   virtual void clear();

@@ -766,6 +769,10 @@ class ContiguousSpace: public Compactibl
   inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);

  public:
+  ContiguousSpace() :
+    _top(NULL),
+    _concurrent_iteration_safe_limit(NULL) {}
+
   virtual void initialize(MemRegion mr, bool clear_space);

   // Accessors
@@ -970,7 +977,8 @@ class EdenSpace : public ContiguousSpace
   HeapWord* _soft_end;

  public:
-  EdenSpace(DefNewGeneration* gen) : _gen(gen) { _soft_end = NULL; }
+  EdenSpace(DefNewGeneration* gen) :
+   _gen(gen), _soft_end(NULL) {}

   // Get/set just the 'soft' limit.
   HeapWord* soft_end()               { return _soft_end; }
                                     

SUGGESTED FIX

See comments section.
                                     

EVALUATION

The field ContiguousSpace::_concurrent_iteration_safe_limit had not
been correctly initialized.

Part of the problem was a merge-o into the G1 workspace from gc_baseline,
and part of the problem was a missing c'tor initializer (the latter will
become part of gc_baseline once G1 integrates).