jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp@e1162778c1c8 (annotated)

src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp@e1162778c1c8 (annotated)

src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp

Thu, 07 Apr 2011 09:53:20 -0700

author: johnc
date: Thu, 07 Apr 2011 09:53:20 -0700
changeset 2781: e1162778c1c8
parent 2453: 2250ee17e258
child 3900: d2a62e0f25eb
permissions: -rw-r--r--

7009266: G1: assert(obj->is_oop_or_null(true )) failed: Error
Summary: A referent object that is only weakly reachable at the start of concurrent marking but is re-attached to the strongly reachable object graph during marking may not be marked as live. This can cause the reference object to be processed prematurely and leave dangling pointers to the referent object. Implement a read barrier for the java.lang.ref.Reference::referent field by intrinsifying the Reference.get() method, and intercepting accesses though JNI, reflection, and Unsafe, so that when a non-null referent object is read it is also logged in an SATB buffer.
Reviewed-by: kvn, iveresov, never, tonyp, dholmes

 /*
  * Copyright (c) 2001, 2011, 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
  * questions.
  *
  */
 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1BLOCKOFFSETTABLE_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1BLOCKOFFSETTABLE_HPP
 #include "memory/memRegion.hpp"
 #include "runtime/virtualspace.hpp"
 #include "utilities/globalDefinitions.hpp"
 // The CollectedHeap type requires subtypes to implement a method
 // "block_start".  For some subtypes, notably generational
 // systems using card-table-based write barriers, the efficiency of this
 // operation may be important.  Implementations of the "BlockOffsetArray"
 // class may be useful in providing such efficient implementations.
 //
 // While generally mirroring the structure of the BOT for GenCollectedHeap,
 // the following types are tailored more towards G1's uses; these should,
 // however, be merged back into a common BOT to avoid code duplication
 // and reduce maintenance overhead.
 //
 //    G1BlockOffsetTable (abstract)
 //    -- G1BlockOffsetArray                (uses G1BlockOffsetSharedArray)
 //       -- G1BlockOffsetArrayContigSpace
 //
 // A main impediment to the consolidation of this code might be the
 // effect of making some of the block_start*() calls non-const as
 // below. Whether that might adversely affect performance optimizations
 // that compilers might normally perform in the case of non-G1
 // collectors needs to be carefully investigated prior to any such
 // consolidation.
 // Forward declarations
 class ContiguousSpace;
 class G1BlockOffsetSharedArray;
 class G1BlockOffsetTable VALUE_OBJ_CLASS_SPEC {
   friend class VMStructs;
 protected:
   // These members describe the region covered by the table.
   // The space this table is covering.
   HeapWord* _bottom;    // == reserved.start
   HeapWord* _end;       // End of currently allocated region.
 public:
   // Initialize the table to cover the given space.
   // The contents of the initial table are undefined.
   G1BlockOffsetTable(HeapWord* bottom, HeapWord* end) :
     _bottom(bottom), _end(end)
     {
       assert(_bottom <= _end, "arguments out of order");
     }
   // Note that the committed size of the covered space may have changed,
   // so the table size might also wish to change.
   virtual void resize(size_t new_word_size) = 0;
   virtual void set_bottom(HeapWord* new_bottom) {
     assert(new_bottom <= _end, "new_bottom > _end");
     _bottom = new_bottom;
     resize(pointer_delta(_end, _bottom));
   }
   // Requires "addr" to be contained by a block, and returns the address of
   // the start of that block.  (May have side effects, namely updating of
   // shared array entries that "point" too far backwards.  This can occur,
   // for example, when LAB allocation is used in a space covered by the
   // table.)
   virtual HeapWord* block_start_unsafe(const void* addr) = 0;
   // Same as above, but does not have any of the possible side effects
   // discussed above.
   virtual HeapWord* block_start_unsafe_const(const void* addr) const = 0;
   // Returns the address of the start of the block containing "addr", or
   // else "null" if it is covered by no block.  (May have side effects,
   // namely updating of shared array entries that "point" too far
   // backwards.  This can occur, for example, when lab allocation is used
   // in a space covered by the table.)
   inline HeapWord* block_start(const void* addr);
   // Same as above, but does not have any of the possible side effects
   // discussed above.
   inline HeapWord* block_start_const(const void* addr) const;
 };
 // This implementation of "G1BlockOffsetTable" divides the covered region
 // into "N"-word subregions (where "N" = 2^"LogN".  An array with an entry
 // for each such subregion indicates how far back one must go to find the
 // start of the chunk that includes the first word of the subregion.
 //
 // Each BlockOffsetArray is owned by a Space.  However, the actual array
 // may be shared by several BlockOffsetArrays; this is useful
 // when a single resizable area (such as a generation) is divided up into
 // several spaces in which contiguous allocation takes place,
 // such as, for example, in G1 or in the train generation.)
 // Here is the shared array type.
 class G1BlockOffsetSharedArray: public CHeapObj {
   friend class G1BlockOffsetArray;
   friend class G1BlockOffsetArrayContigSpace;
   friend class VMStructs;
 private:
   // The reserved region covered by the shared array.
   MemRegion _reserved;
   // End of the current committed region.
   HeapWord* _end;
   // Array for keeping offsets for retrieving object start fast given an
   // address.
   VirtualSpace _vs;
   u_char* _offset_array;          // byte array keeping backwards offsets
   // Bounds checking accessors:
   // For performance these have to devolve to array accesses in product builds.
   u_char offset_array(size_t index) const {
     assert(index < _vs.committed_size(), "index out of range");
     return _offset_array[index];
   }
   void set_offset_array(size_t index, u_char offset) {
     assert(index < _vs.committed_size(), "index out of range");
     assert(offset <= N_words, "offset too large");
     _offset_array[index] = offset;
   }
   void set_offset_array(size_t index, HeapWord* high, HeapWord* low) {
     assert(index < _vs.committed_size(), "index out of range");
     assert(high >= low, "addresses out of order");
     assert(pointer_delta(high, low) <= N_words, "offset too large");
     _offset_array[index] = (u_char) pointer_delta(high, low);
   }
   void set_offset_array(HeapWord* left, HeapWord* right, u_char offset) {
     assert(index_for(right - 1) < _vs.committed_size(),
            "right address out of range");
     assert(left  < right, "Heap addresses out of order");
     size_t num_cards = pointer_delta(right, left) >> LogN_words;
     memset(&_offset_array[index_for(left)], offset, num_cards);
   }
   void set_offset_array(size_t left, size_t right, u_char offset) {
     assert(right < _vs.committed_size(), "right address out of range");
     assert(left  <= right, "indexes out of order");
     size_t num_cards = right - left + 1;
     memset(&_offset_array[left], offset, num_cards);
   }
   void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const {
     assert(index < _vs.committed_size(), "index out of range");
     assert(high >= low, "addresses out of order");
     assert(pointer_delta(high, low) <= N_words, "offset too large");
     assert(_offset_array[index] == pointer_delta(high, low),
            "Wrong offset");
   }
   bool is_card_boundary(HeapWord* p) const;
   // Return the number of slots needed for an offset array
   // that covers mem_region_words words.
   // We always add an extra slot because if an object
   // ends on a card boundary we put a 0 in the next
   // offset array slot, so we want that slot always
   // to be reserved.
   size_t compute_size(size_t mem_region_words) {
     size_t number_of_slots = (mem_region_words / N_words) + 1;
     return ReservedSpace::page_align_size_up(number_of_slots);
   }
 public:
   enum SomePublicConstants {
     LogN = 9,
     LogN_words = LogN - LogHeapWordSize,
     N_bytes = 1 << LogN,
     N_words = 1 << LogN_words
   };
   // Initialize the table to cover from "base" to (at least)
   // "base + init_word_size".  In the future, the table may be expanded
   // (see "resize" below) up to the size of "_reserved" (which must be at
   // least "init_word_size".) The contents of the initial table are
   // undefined; it is the responsibility of the constituent
   // G1BlockOffsetTable(s) to initialize cards.
   G1BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size);
   // Notes a change in the committed size of the region covered by the
   // table.  The "new_word_size" may not be larger than the size of the
   // reserved region this table covers.
   void resize(size_t new_word_size);
   void set_bottom(HeapWord* new_bottom);
   // Updates all the BlockOffsetArray's sharing this shared array to
   // reflect the current "top"'s of their spaces.
   void update_offset_arrays();
   // Return the appropriate index into "_offset_array" for "p".
   inline size_t index_for(const void* p) const;
   // Return the address indicating the start of the region corresponding to
   // "index" in "_offset_array".
   inline HeapWord* address_for_index(size_t index) const;
 };
 // And here is the G1BlockOffsetTable subtype that uses the array.
 class G1BlockOffsetArray: public G1BlockOffsetTable {
   friend class G1BlockOffsetSharedArray;
   friend class G1BlockOffsetArrayContigSpace;
   friend class VMStructs;
 private:
   enum SomePrivateConstants {
     N_words = G1BlockOffsetSharedArray::N_words,
     LogN    = G1BlockOffsetSharedArray::LogN
   };
   // The following enums are used by do_block_helper
   enum Action {
     Action_single,      // BOT records a single block (see single_block())
     Action_mark,        // BOT marks the start of a block (see mark_block())
     Action_check        // Check that BOT records block correctly
                         // (see verify_single_block()).
   };
   // This is the array, which can be shared by several BlockOffsetArray's
   // servicing different
   G1BlockOffsetSharedArray* _array;
   // The space that owns this subregion.
   Space* _sp;
   // If "_sp" is a contiguous space, the field below is the view of "_sp"
   // as a contiguous space, else NULL.
   ContiguousSpace* _csp;
   // If true, array entries are initialized to 0; otherwise, they are
   // initialized to point backwards to the beginning of the covered region.
   bool _init_to_zero;
   // The portion [_unallocated_block, _sp.end()) of the space that
   // is a single block known not to contain any objects.
   // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag.
   HeapWord* _unallocated_block;
   // Sets the entries
   // corresponding to the cards starting at "start" and ending at "end"
   // to point back to the card before "start": the interval [start, end)
   // is right-open.
   void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end);
   // Same as above, except that the args here are a card _index_ interval
   // that is closed: [start_index, end_index]
   void set_remainder_to_point_to_start_incl(size_t start, size_t end);
   // A helper function for BOT adjustment/verification work
   void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action);
 protected:
   ContiguousSpace* csp() const { return _csp; }
   // Returns the address of a block whose start is at most "addr".
   // If "has_max_index" is true, "assumes "max_index" is the last valid one
   // in the array.
   inline HeapWord* block_at_or_preceding(const void* addr,
                                          bool has_max_index,
                                          size_t max_index) const;
   // "q" is a block boundary that is <= "addr"; "n" is the address of the
   // next block (or the end of the space.)  Return the address of the
   // beginning of the block that contains "addr".  Does so without side
   // effects (see, e.g., spec of  block_start.)
   inline HeapWord*
   forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n,
                                          const void* addr) const;
   // "q" is a block boundary that is <= "addr"; return the address of the
   // beginning of the block that contains "addr".  May have side effects
   // on "this", by updating imprecise entries.
   inline HeapWord* forward_to_block_containing_addr(HeapWord* q,
                                                     const void* addr);
   // "q" is a block boundary that is <= "addr"; "n" is the address of the
   // next block (or the end of the space.)  Return the address of the
   // beginning of the block that contains "addr".  May have side effects
   // on "this", by updating imprecise entries.
   HeapWord* forward_to_block_containing_addr_slow(HeapWord* q,
                                                   HeapWord* n,
                                                   const void* addr);
   // Requires that "*threshold_" be the first array entry boundary at or
   // above "blk_start", and that "*index_" be the corresponding array
   // index.  If the block starts at or crosses "*threshold_", records
   // "blk_start" as the appropriate block start for the array index
   // starting at "*threshold_", and for any other indices crossed by the
   // block.  Updates "*threshold_" and "*index_" to correspond to the first
   // index after the block end.
   void alloc_block_work2(HeapWord** threshold_, size_t* index_,
                          HeapWord* blk_start, HeapWord* blk_end);
 public:
   // The space may not have it's bottom and top set yet, which is why the
   // region is passed as a parameter.  If "init_to_zero" is true, the
   // elements of the array are initialized to zero.  Otherwise, they are
   // initialized to point backwards to the beginning.
   G1BlockOffsetArray(G1BlockOffsetSharedArray* array, MemRegion mr,
                      bool init_to_zero);
   // Note: this ought to be part of the constructor, but that would require
   // "this" to be passed as a parameter to a member constructor for
   // the containing concrete subtype of Space.
   // This would be legal C++, but MS VC++ doesn't allow it.
   void set_space(Space* sp);
   // Resets the covered region to the given "mr".
   void set_region(MemRegion mr);
   // Resets the covered region to one with the same _bottom as before but
   // the "new_word_size".
   void resize(size_t new_word_size);
   // These must be guaranteed to work properly (i.e., do nothing)
   // when "blk_start" ("blk" for second version) is "NULL".
   virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
   virtual void alloc_block(HeapWord* blk, size_t size) {
     alloc_block(blk, blk + size);
   }
   // The following methods are useful and optimized for a
   // general, non-contiguous space.
   // Given a block [blk_start, blk_start + full_blk_size), and
   // a left_blk_size < full_blk_size, adjust the BOT to show two
   // blocks [blk_start, blk_start + left_blk_size) and
   // [blk_start + left_blk_size, blk_start + full_blk_size).
   // It is assumed (and verified in the non-product VM) that the
   // BOT was correct for the original block.
   void split_block(HeapWord* blk_start, size_t full_blk_size,
                            size_t left_blk_size);
   // Adjust the BOT to show that it has a single block in the
   // range [blk_start, blk_start + size). All necessary BOT
   // cards are adjusted, but _unallocated_block isn't.
   void single_block(HeapWord* blk_start, HeapWord* blk_end);
   void single_block(HeapWord* blk, size_t size) {
     single_block(blk, blk + size);
   }
   // Adjust BOT to show that it has a block in the range
   // [blk_start, blk_start + size). Only the first card
   // of BOT is touched. It is assumed (and verified in the
   // non-product VM) that the remaining cards of the block
   // are correct.
   void mark_block(HeapWord* blk_start, HeapWord* blk_end);
   void mark_block(HeapWord* blk, size_t size) {
     mark_block(blk, blk + size);
   }
   // Adjust _unallocated_block to indicate that a particular
   // block has been newly allocated or freed. It is assumed (and
   // verified in the non-product VM) that the BOT is correct for
   // the given block.
   inline void allocated(HeapWord* blk_start, HeapWord* blk_end) {
     // Verify that the BOT shows [blk, blk + blk_size) to be one block.
     verify_single_block(blk_start, blk_end);
     if (BlockOffsetArrayUseUnallocatedBlock) {
       _unallocated_block = MAX2(_unallocated_block, blk_end);
     }
   }
   inline void allocated(HeapWord* blk, size_t size) {
     allocated(blk, blk + size);
   }
   inline void freed(HeapWord* blk_start, HeapWord* blk_end);
   inline void freed(HeapWord* blk, size_t size);
   virtual HeapWord* block_start_unsafe(const void* addr);
   virtual HeapWord* block_start_unsafe_const(const void* addr) const;
   // Requires "addr" to be the start of a card and returns the
   // start of the block that contains the given address.
   HeapWord* block_start_careful(const void* addr) const;
   // If true, initialize array slots with no allocated blocks to zero.
   // Otherwise, make them point back to the front.
   bool init_to_zero() { return _init_to_zero; }
   // Verification & debugging - ensure that the offset table reflects the fact
   // that the block [blk_start, blk_end) or [blk, blk + size) is a
   // single block of storage. NOTE: can;t const this because of
   // call to non-const do_block_internal() below.
   inline void verify_single_block(HeapWord* blk_start, HeapWord* blk_end) {
     if (VerifyBlockOffsetArray) {
       do_block_internal(blk_start, blk_end, Action_check);
     }
   }
   inline void verify_single_block(HeapWord* blk, size_t size) {
     verify_single_block(blk, blk + size);
   }
   // Used by region verification. Checks that the contents of the
   // BOT reflect that there's a single object that spans the address
   // range [obj_start, obj_start + word_size); returns true if this is
   // the case, returns false if it's not.
   bool verify_for_object(HeapWord* obj_start, size_t word_size) const;
   // Verify that the given block is before _unallocated_block
   inline void verify_not_unallocated(HeapWord* blk_start,
                                      HeapWord* blk_end) const {
     if (BlockOffsetArrayUseUnallocatedBlock) {
       assert(blk_start < blk_end, "Block inconsistency?");
       assert(blk_end <= _unallocated_block, "_unallocated_block problem");
     }
   }
   inline void verify_not_unallocated(HeapWord* blk, size_t size) const {
     verify_not_unallocated(blk, blk + size);
   }
   void check_all_cards(size_t left_card, size_t right_card) const;
   virtual void print_on(outputStream* out) PRODUCT_RETURN;
 };
 // A subtype of BlockOffsetArray that takes advantage of the fact
 // that its underlying space is a ContiguousSpace, so that its "active"
 // region can be more efficiently tracked (than for a non-contiguous space).
 class G1BlockOffsetArrayContigSpace: public G1BlockOffsetArray {
   friend class VMStructs;
   // allocation boundary at which offset array must be updated
   HeapWord* _next_offset_threshold;
   size_t    _next_offset_index;      // index corresponding to that boundary
   // Work function to be called when allocation start crosses the next
   // threshold in the contig space.
   void alloc_block_work1(HeapWord* blk_start, HeapWord* blk_end) {
     alloc_block_work2(&_next_offset_threshold, &_next_offset_index,
                       blk_start, blk_end);
   }
  public:
   G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array, MemRegion mr);
   // Initialize the threshold to reflect the first boundary after the
   // bottom of the covered region.
   HeapWord* initialize_threshold();
   // Zero out the entry for _bottom (offset will be zero).
   void      zero_bottom_entry();
   // Return the next threshold, the point at which the table should be
   // updated.
   HeapWord* threshold() const { return _next_offset_threshold; }
   // These must be guaranteed to work properly (i.e., do nothing)
   // when "blk_start" ("blk" for second version) is "NULL".  In this
   // implementation, that's true because NULL is represented as 0, and thus
   // never exceeds the "_next_offset_threshold".
   void alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
     if (blk_end > _next_offset_threshold)
       alloc_block_work1(blk_start, blk_end);
   }
   void alloc_block(HeapWord* blk, size_t size) {
      alloc_block(blk, blk+size);
   }
   HeapWord* block_start_unsafe(const void* addr);
   HeapWord* block_start_unsafe_const(const void* addr) const;
   void set_for_starts_humongous(HeapWord* new_top);
   virtual void print_on(outputStream* out) PRODUCT_RETURN;
 };
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1BLOCKOFFSETTABLE_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp@e1162778c1c8 (annotated)

src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp