jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/g1/sparsePRT.hpp@97ba643ea3ed (annotated)

src/share/vm/gc_implementation/g1/sparsePRT.hpp@97ba643ea3ed (annotated)

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

Tue, 25 Jan 2011 17:58:19 -0500

author: tonyp
date: Tue, 25 Jan 2011 17:58:19 -0500
changeset 2493: 97ba643ea3ed
parent 2314: f95d63e2154a
child 3900: d2a62e0f25eb
permissions: -rw-r--r--

7014261: G1: RSet-related failures
Summary: A race between the concurrent cleanup thread and the VM thread while it is processing the "expanded sparse table list" causes both threads to try to free the same sparse table entry and either causes one of the threads to fail or leaves the entry in an inconsistent state. The solution is purge all entries on the expanded list that correspond go regions that are being cleaned up.
Reviewed-by: brutisso, johnc

 /*
  * 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
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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_SPARSEPRT_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_G1_SPARSEPRT_HPP
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/heapRegion.hpp"
 #include "memory/allocation.hpp"
 #include "memory/cardTableModRefBS.hpp"
 #include "runtime/mutex.hpp"
 #include "utilities/globalDefinitions.hpp"
 // Sparse remembered set for a heap region (the "owning" region).  Maps
 // indices of other regions to short sequences of cards in the other region
 // that might contain pointers into the owner region.
 // These tables only expand while they are accessed in parallel --
 // deletions may be done in single-threaded code.  This allows us to allow
 // unsynchronized reads/iterations, as long as expansions caused by
 // insertions only enqueue old versions for deletions, but do not delete
 // old versions synchronously.
 class SparsePRTEntry: public CHeapObj {
 public:
   enum SomePublicConstants {
     NullEntry     = -1,
     UnrollFactor  =  4
   };
 private:
   RegionIdx_t _region_ind;
   int         _next_index;
   CardIdx_t   _cards[1];
   // WARNING: Don't put any data members beyond this line. Card array has, in fact, variable length.
   // It should always be the last data member.
 public:
   // Returns the size of the entry, used for entry allocation.
   static size_t size() { return sizeof(SparsePRTEntry) + sizeof(CardIdx_t) * (cards_num() - 1); }
   // Returns the size of the card array.
   static int cards_num() {
     // The number of cards should be a multiple of 4, because that's our current
     // unrolling factor.
     static const int s = MAX2<int>(G1RSetSparseRegionEntries & ~(UnrollFactor - 1), UnrollFactor);
     return s;
   }
   // Set the region_ind to the given value, and delete all cards.
   inline void init(RegionIdx_t region_ind);
   RegionIdx_t r_ind() const { return _region_ind; }
   bool valid_entry() const { return r_ind() >= 0; }
   void set_r_ind(RegionIdx_t rind) { _region_ind = rind; }
   int next_index() const { return _next_index; }
   int* next_index_addr() { return &_next_index; }
   void set_next_index(int ni) { _next_index = ni; }
   // Returns "true" iff the entry contains the given card index.
   inline bool contains_card(CardIdx_t card_index) const;
   // Returns the number of non-NULL card entries.
   inline int num_valid_cards() const;
   // Requires that the entry not contain the given card index.  If there is
   // space available, add the given card index to the entry and return
   // "true"; otherwise, return "false" to indicate that the entry is full.
   enum AddCardResult {
     overflow,
     found,
     added
   };
   inline AddCardResult add_card(CardIdx_t card_index);
   // Copy the current entry's cards into "cards".
   inline void copy_cards(CardIdx_t* cards) const;
   // Copy the current entry's cards into the "_card" array of "e."
   inline void copy_cards(SparsePRTEntry* e) const;
   inline CardIdx_t card(int i) const { return _cards[i]; }
 };
 class RSHashTable : public CHeapObj {
   friend class RSHashTableIter;
   enum SomePrivateConstants {
     NullEntry = -1
   };
   size_t _capacity;
   size_t _capacity_mask;
   size_t _occupied_entries;
   size_t _occupied_cards;
   SparsePRTEntry* _entries;
   int* _buckets;
   int  _free_region;
   int  _free_list;
   // Requires that the caller hold a lock preventing parallel modifying
   // operations, and that the the table be less than completely full.  If
   // an entry for "region_ind" is already in the table, finds it and
   // returns its address; otherwise returns "NULL."
   SparsePRTEntry* entry_for_region_ind(RegionIdx_t region_ind) const;
   // Requires that the caller hold a lock preventing parallel modifying
   // operations, and that the the table be less than completely full.  If
   // an entry for "region_ind" is already in the table, finds it and
   // returns its address; otherwise allocates, initializes, inserts and
   // returns a new entry for "region_ind".
   SparsePRTEntry* entry_for_region_ind_create(RegionIdx_t region_ind);
   // Returns the index of the next free entry in "_entries".
   int alloc_entry();
   // Declares the entry "fi" to be free.  (It must have already been
   // deleted from any bucket lists.
   void free_entry(int fi);
 public:
   RSHashTable(size_t capacity);
   ~RSHashTable();
   // Attempts to ensure that the given card_index in the given region is in
   // the sparse table.  If successful (because the card was already
   // present, or because it was successfullly added) returns "true".
   // Otherwise, returns "false" to indicate that the addition would
   // overflow the entry for the region.  The caller must transfer these
   // entries to a larger-capacity representation.
   bool add_card(RegionIdx_t region_id, CardIdx_t card_index);
   bool get_cards(RegionIdx_t region_id, CardIdx_t* cards);
   bool delete_entry(RegionIdx_t region_id);
   bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const;
   void add_entry(SparsePRTEntry* e);
   SparsePRTEntry* get_entry(RegionIdx_t region_id);
   void clear();
   size_t capacity() const      { return _capacity;       }
   size_t capacity_mask() const { return _capacity_mask;  }
   size_t occupied_entries() const { return _occupied_entries; }
   size_t occupied_cards() const   { return _occupied_cards;   }
   size_t mem_size() const;
   SparsePRTEntry* entry(int i) const { return (SparsePRTEntry*)((char*)_entries + SparsePRTEntry::size() * i); }
   void print();
 };
 // ValueObj because will be embedded in HRRS iterator.
 class RSHashTableIter VALUE_OBJ_CLASS_SPEC {
   int _tbl_ind;         // [-1, 0.._rsht->_capacity)
   int _bl_ind;          // [-1, 0.._rsht->_capacity)
   short _card_ind;      // [0..SparsePRTEntry::cards_num())
   RSHashTable* _rsht;
   // If the bucket list pointed to by _bl_ind contains a card, sets
   // _bl_ind to the index of that entry, and returns the card.
   // Otherwise, returns SparseEntry::NullEntry.
   CardIdx_t find_first_card_in_list();
   // Computes the proper card index for the card whose offset in the
   // current region (as indicated by _bl_ind) is "ci".
   // This is subject to errors when there is iteration concurrent with
   // modification, but these errors should be benign.
   size_t compute_card_ind(CardIdx_t ci);
 public:
   RSHashTableIter() :
     _tbl_ind(RSHashTable::NullEntry),
     _bl_ind(RSHashTable::NullEntry),
     _card_ind((SparsePRTEntry::cards_num() - 1)),
     _rsht(NULL) {}
   void init(RSHashTable* rsht) {
     _rsht = rsht;
     _tbl_ind = -1; // So that first increment gets to 0.
     _bl_ind = RSHashTable::NullEntry;
     _card_ind = (SparsePRTEntry::cards_num() - 1);
   }
   bool has_next(size_t& card_index);
 };
 // Concurrent accesss to a SparsePRT must be serialized by some external
 // mutex.
 class SparsePRTIter;
 class SparsePRTCleanupTask;
 class SparsePRT VALUE_OBJ_CLASS_SPEC {
   friend class SparsePRTCleanupTask;
   //  Iterations are done on the _cur hash table, since they only need to
   //  see entries visible at the start of a collection pause.
   //  All other operations are done using the _next hash table.
   RSHashTable* _cur;
   RSHashTable* _next;
   HeapRegion* _hr;
   enum SomeAdditionalPrivateConstants {
     InitialCapacity = 16
   };
   void expand();
   bool _expanded;
   bool expanded() { return _expanded; }
   void set_expanded(bool b) { _expanded = b; }
   SparsePRT* _next_expanded;
   SparsePRT* next_expanded() { return _next_expanded; }
   void set_next_expanded(SparsePRT* nxt) { _next_expanded = nxt; }
   bool should_be_on_expanded_list();
   static SparsePRT* _head_expanded_list;
 public:
   SparsePRT(HeapRegion* hr);
   ~SparsePRT();
   size_t occupied() const { return _next->occupied_cards(); }
   size_t mem_size() const;
   // Attempts to ensure that the given card_index in the given region is in
   // the sparse table.  If successful (because the card was already
   // present, or because it was successfullly added) returns "true".
   // Otherwise, returns "false" to indicate that the addition would
   // overflow the entry for the region.  The caller must transfer these
   // entries to a larger-capacity representation.
   bool add_card(RegionIdx_t region_id, CardIdx_t card_index);
   // If the table hold an entry for "region_ind",  Copies its
   // cards into "cards", which must be an array of length at least
   // "SparePRTEntry::cards_num()", and returns "true"; otherwise,
   // returns "false".
   bool get_cards(RegionIdx_t region_ind, CardIdx_t* cards);
   // Return the pointer to the entry associated with the given region.
   SparsePRTEntry* get_entry(RegionIdx_t region_ind);
   // If there is an entry for "region_ind", removes it and return "true";
   // otherwise returns "false."
   bool delete_entry(RegionIdx_t region_ind);
   // Clear the table, and reinitialize to initial capacity.
   void clear();
   // Ensure that "_cur" and "_next" point to the same table.
   void cleanup();
   // Clean up all tables on the expanded list.  Called single threaded.
   static void cleanup_all();
   RSHashTable* cur() const { return _cur; }
   void init_iterator(SparsePRTIter* sprt_iter);
   static void add_to_expanded_list(SparsePRT* sprt);
   static SparsePRT* get_from_expanded_list();
   // The purpose of these three methods is to help the GC workers
   // during the cleanup pause to recreate the expanded list, purging
   // any tables from it that belong to regions that are freed during
   // cleanup (if we don't purge those tables, there is a race that
   // causes various crashes; see CR 7014261).
   //
   // We chose to recreate the expanded list, instead of purging
   // entries from it by iterating over it, to avoid this serial phase
   // at the end of the cleanup pause.
   //
   // The three methods below work as follows:
   // * reset_for_cleanup_tasks() : Nulls the expanded list head at the
   //   start of the cleanup pause.
   // * do_cleanup_work() : Called by the cleanup workers for every
   //   region that is not free / is being freed by the cleanup
   //   pause. It creates a list of expanded tables whose head / tail
   //   are on the thread-local SparsePRTCleanupTask object.
   // * finish_cleanup_task() : Called by the cleanup workers after
   //   they complete their cleanup task. It adds the local list into
   //   the global expanded list. It assumes that the
   //   ParGCRareEvent_lock is being held to ensure MT-safety.
   static void reset_for_cleanup_tasks();
   void do_cleanup_work(SparsePRTCleanupTask* sprt_cleanup_task);
   static void finish_cleanup_task(SparsePRTCleanupTask* sprt_cleanup_task);
   bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const {
     return _next->contains_card(region_id, card_index);
   }
 };
 class SparsePRTIter: public RSHashTableIter {
 public:
   void init(const SparsePRT* sprt) {
     RSHashTableIter::init(sprt->cur());
   }
   bool has_next(size_t& card_index) {
     return RSHashTableIter::has_next(card_index);
   }
 };
 // This allows each worker during a cleanup pause to create a
 // thread-local list of sparse tables that have been expanded and need
 // to be processed at the beginning of the next GC pause. This lists
 // are concatenated into the single expanded list at the end of the
 // cleanup pause.
 class SparsePRTCleanupTask VALUE_OBJ_CLASS_SPEC {
 private:
   SparsePRT* _head;
   SparsePRT* _tail;
 public:
   SparsePRTCleanupTask() : _head(NULL), _tail(NULL) { }
   void add(SparsePRT* sprt);
   SparsePRT* head() { return _head; }
   SparsePRT* tail() { return _tail; }
 };
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_SPARSEPRT_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/g1/sparsePRT.hpp@97ba643ea3ed (annotated)

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