jdk8-mips64-public/hotspot: src/share/vm/memory/genRemSet.hpp@2c022e432e10 (annotated)

src/share/vm/memory/genRemSet.hpp@2c022e432e10 (annotated)

src/share/vm/memory/genRemSet.hpp

Fri, 20 Sep 2013 10:53:28 +0200

author: stefank
date: Fri, 20 Sep 2013 10:53:28 +0200
changeset 5769: 2c022e432e10
parent 5519: bd902affe102
child 6198: 55fb97c4c58d
permissions: -rw-r--r--

8024974: Incorrect use of GC_locker::is_active()
Summary: SymbolTable and StringTable can make calls to GC_locker::is_active() outside a safepoint. This isn't safe because the GC_locker active state (lock count) is only updated at a safepoint and only remains valid as long as _needs_gc is true. However, outside a safepoint_needs_gc can change to false at any time, which makes it impossible to do a correct call to is_active() in that context. In this case these calls can just be removed since the input argument to basic_add() should never be on the heap and so there's no need to check the GC_locker state. This change also adjusts the assert() in is_active() to makes sure all calls to this function are always done under a safepoint.
Reviewed-by: brutisso, dcubed
Contributed-by: per.liden@oracle.com

 /*
  * Copyright (c) 2001, 2012, 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
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 #ifndef SHARE_VM_MEMORY_GENREMSET_HPP
 #define SHARE_VM_MEMORY_GENREMSET_HPP
 #include "oops/oop.hpp"
 // A GenRemSet provides ways of iterating over pointers accross generations.
 // (This is especially useful for older-to-younger.)
 class Generation;
 class BarrierSet;
 class OopsInGenClosure;
 class CardTableRS;
 // Helper to remember modified oops in all klasses.
 class KlassRemSet {
   bool _accumulate_modified_oops;
  public:
   KlassRemSet() : _accumulate_modified_oops(false) {}
   void set_accumulate_modified_oops(bool value) { _accumulate_modified_oops = value; }
   bool accumulate_modified_oops() { return _accumulate_modified_oops; }
   bool mod_union_is_clear();
   void clear_mod_union();
 };
 class GenRemSet: public CHeapObj<mtGC> {
   friend class Generation;
   BarrierSet* _bs;
   KlassRemSet _klass_rem_set;
 public:
   enum Name {
     CardTable,
     Other
   };
   GenRemSet(BarrierSet * bs) : _bs(bs) {}
   GenRemSet() : _bs(NULL) {}
   virtual Name rs_kind() = 0;
   // These are for dynamic downcasts.  Unfortunately that it names the
   // possible subtypes (but not that they are subtypes!)  Return NULL if
   // the cast is invalide.
   virtual CardTableRS* as_CardTableRS() { return NULL; }
   // Return the barrier set associated with "this."
   BarrierSet* bs() { return _bs; }
   // Set the barrier set.
   void set_bs(BarrierSet* bs) { _bs = bs; }
   KlassRemSet* klass_rem_set() { return &_klass_rem_set; }
   // Do any (sequential) processing necessary to prepare for (possibly
   // "parallel", if that arg is true) calls to younger_refs_iterate.
   virtual void prepare_for_younger_refs_iterate(bool parallel) = 0;
   // Apply the "do_oop" method of "blk" to (exactly) all oop locations
   //  1) that are in objects allocated in "g" at the time of the last call
   //     to "save_Marks", and
   //  2) that point to objects in younger generations.
   virtual void younger_refs_iterate(Generation* g, OopsInGenClosure* blk) = 0;
   virtual void younger_refs_in_space_iterate(Space* sp,
                                              OopsInGenClosure* cl) = 0;
   // This method is used to notify the remembered set that "new_val" has
   // been written into "field" by the garbage collector.
   void write_ref_field_gc(void* field, oop new_val);
 protected:
   virtual void write_ref_field_gc_work(void* field, oop new_val) = 0;
 public:
   // A version of the above suitable for use by parallel collectors.
   virtual void write_ref_field_gc_par(void* field, oop new_val) = 0;
   // Resize one of the regions covered by the remembered set.
   virtual void resize_covered_region(MemRegion new_region) = 0;
   // If the rem set imposes any alignment restrictions on boundaries
   // within the heap, this function tells whether they are met.
   virtual bool is_aligned(HeapWord* addr) = 0;
   // If the RS (or BS) imposes an aligment constraint on maximum heap size.
   // (This must be static, and dispatch on "nm", because it is called
   // before an RS is created.)
   static uintx max_alignment_constraint(Name nm);
   virtual void verify() = 0;
   // Verify that the remembered set has no entries for
   // the heap interval denoted by mr.  If there are any
   // alignment constraints on the remembered set, only the
   // part of the region that is aligned is checked.
   //
   //   alignment boundaries
   //   +--------+-------+--------+-------+
   //         [ region mr              )
   //            [ part checked   )
   virtual void verify_aligned_region_empty(MemRegion mr) = 0;
   // If appropriate, print some information about the remset on "tty".
   virtual void print() {}
   // Informs the RS that the given memregion contains no references to
   // younger generations.
   virtual void clear(MemRegion mr) = 0;
   // Informs the RS that there are no references to generations
   // younger than gen from generations gen and older.
   // The parameter clear_perm indicates if the perm_gen's
   // remembered set should also be processed/cleared.
   virtual void clear_into_younger(Generation* old_gen) = 0;
   // Informs the RS that refs in the given "mr" may have changed
   // arbitrarily, and therefore may contain old-to-young pointers.
   // If "whole heap" is true, then this invalidation is part of an
   // invalidation of the whole heap, which an implementation might
   // handle differently than that of a sub-part of the heap.
   virtual void invalidate(MemRegion mr, bool whole_heap = false) = 0;
   // Informs the RS that refs in this generation
   // may have changed arbitrarily, and therefore may contain
   // old-to-young pointers in arbitrary locations.
   virtual void invalidate_or_clear(Generation* old_gen) = 0;
 };
 #endif // SHARE_VM_MEMORY_GENREMSET_HPP

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src/share/vm/memory/genRemSet.hpp@2c022e432e10 (annotated)

src/share/vm/memory/genRemSet.hpp