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diff src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp @ 1716:be3f9c242c9d

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6948538: CMS: BOT walkers can fall into object allocation and initialization cracks Summary: GC workers now recognize an intermediate transient state of blocks which are allocated but have not yet completed initialization. blk_start() calls do not attempt to determine the size of a block in the transient state, rather waiting for the block to become initialized so that it is safe to query its size. Audited and ensured the order of initialization of object fields (klass, free bit and size) to respect block state transition protocol. Also included some new assertion checking code enabled in debug mode. Reviewed-by: chrisphi, johnc, poonam
author ysr
date Mon, 16 Aug 2010 15:58:42 -0700
parents e9ff18c4ace7
children f95d63e2154a
line wrap: on
line diff
--- a/src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp	Sat Aug 14 00:47:52 2010 -0700
+++ b/src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp	Mon Aug 16 15:58:42 2010 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2009, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2010, 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
@@ -48,6 +48,8 @@
   size_t    _word_size;
   size_t    _refillSize;
   size_t    _allocation_size_limit;  // largest size that will be allocated
+
+  void print_on(outputStream* st) const;
 };
 
 // Concrete subclass of CompactibleSpace that implements
@@ -249,10 +251,14 @@
   size_t     numFreeBlocksInIndexedFreeLists() const;
   // Accessor
   HeapWord* unallocated_block() const {
-    HeapWord* ub = _bt.unallocated_block();
-    assert(ub >= bottom() &&
-           ub <= end(), "space invariant");
-    return ub;
+    if (BlockOffsetArrayUseUnallocatedBlock) {
+      HeapWord* ub = _bt.unallocated_block();
+      assert(ub >= bottom() &&
+             ub <= end(), "space invariant");
+      return ub;
+    } else {
+      return end();
+    }
   }
   void freed(HeapWord* start, size_t size) {
     _bt.freed(start, size);
@@ -476,6 +482,7 @@
 
   // Debugging support
   void print()                            const;
+  void print_on(outputStream* st)         const;
   void prepare_for_verify();
   void verify(bool allow_dirty)           const;
   void verifyFreeLists()                  const PRODUCT_RETURN;