jdk8-mips64-public/hotspot: src/share/vm/utilities/hashtable.hpp@ce9a710b0f63 (annotated)

src/share/vm/utilities/hashtable.hpp@ce9a710b0f63 (annotated)

src/share/vm/utilities/hashtable.hpp

Mon, 15 May 2017 12:20:15 +0200

author: tschatzl
date: Mon, 15 May 2017 12:20:15 +0200
changeset 8766: ce9a710b0f63
parent 7207: 152cf4afc11f
child 8856: ac27a9c85bea
permissions: -rw-r--r--

8180048: Interned string and symbol table leak memory during parallel unlinking
Summary: Make appending found dead BasicHashtableEntrys to the free list atomic.
Reviewed-by: ehelin, shade

 /*
  * Copyright (c) 2003, 2014, 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_UTILITIES_HASHTABLE_HPP
 #define SHARE_VM_UTILITIES_HASHTABLE_HPP
 #include "classfile/classLoaderData.hpp"
 #include "memory/allocation.hpp"
 #include "oops/oop.hpp"
 #include "oops/symbol.hpp"
 #include "runtime/handles.hpp"
 // This is a generic hashtable, designed to be used for the symbol
 // and string tables.
 //
 // It is implemented as an open hash table with a fixed number of buckets.
 //
 // %note:
 //  - TableEntrys are allocated in blocks to reduce the space overhead.
 template <MEMFLAGS F> class BasicHashtableEntry : public CHeapObj<F> {
   friend class VMStructs;
 private:
   unsigned int         _hash;           // 32-bit hash for item
   // Link to next element in the linked list for this bucket.  EXCEPT
   // bit 0 set indicates that this entry is shared and must not be
   // unlinked from the table. Bit 0 is set during the dumping of the
   // archive. Since shared entries are immutable, _next fields in the
   // shared entries will not change.  New entries will always be
   // unshared and since pointers are align, bit 0 will always remain 0
   // with no extra effort.
   BasicHashtableEntry<F>* _next;
   // Windows IA64 compiler requires subclasses to be able to access these
 protected:
   // Entry objects should not be created, they should be taken from the
   // free list with BasicHashtable.new_entry().
   BasicHashtableEntry() { ShouldNotReachHere(); }
   // Entry objects should not be destroyed.  They should be placed on
   // the free list instead with BasicHashtable.free_entry().
   ~BasicHashtableEntry() { ShouldNotReachHere(); }
 public:
   unsigned int hash() const             { return _hash; }
   void set_hash(unsigned int hash)      { _hash = hash; }
   unsigned int* hash_addr()             { return &_hash; }
   static BasicHashtableEntry<F>* make_ptr(BasicHashtableEntry<F>* p) {
     return (BasicHashtableEntry*)((intptr_t)p & -2);
   }
   BasicHashtableEntry<F>* next() const {
     return make_ptr(_next);
   }
   void set_next(BasicHashtableEntry<F>* next) {
     _next = next;
   }
   BasicHashtableEntry<F>** next_addr() {
     return &_next;
   }
   bool is_shared() const {
     return ((intptr_t)_next & 1) != 0;
   }
   void set_shared() {
     _next = (BasicHashtableEntry<F>*)((intptr_t)_next | 1);
   }
 };
 template <class T, MEMFLAGS F> class HashtableEntry : public BasicHashtableEntry<F> {
   friend class VMStructs;
 private:
   T               _literal;          // ref to item in table.
 public:
   // Literal
   T literal() const                   { return _literal; }
   T* literal_addr()                   { return &_literal; }
   void set_literal(T s)               { _literal = s; }
   HashtableEntry* next() const {
     return (HashtableEntry*)BasicHashtableEntry<F>::next();
   }
   HashtableEntry** next_addr() {
     return (HashtableEntry**)BasicHashtableEntry<F>::next_addr();
   }
 };
 template <MEMFLAGS F> class HashtableBucket : public CHeapObj<F> {
   friend class VMStructs;
 private:
   // Instance variable
   BasicHashtableEntry<F>*       _entry;
 public:
   // Accessing
   void clear()                        { _entry = NULL; }
   // The following methods use order access methods to avoid race
   // conditions in multiprocessor systems.
   BasicHashtableEntry<F>* get_entry() const;
   void set_entry(BasicHashtableEntry<F>* l);
   // The following method is not MT-safe and must be done under lock.
   BasicHashtableEntry<F>** entry_addr()  { return &_entry; }
 };
 template <MEMFLAGS F> class BasicHashtable : public CHeapObj<F> {
   friend class VMStructs;
 public:
   BasicHashtable(int table_size, int entry_size);
   BasicHashtable(int table_size, int entry_size,
                  HashtableBucket<F>* buckets, int number_of_entries);
   // Sharing support.
   void copy_buckets(char** top, char* end);
   void copy_table(char** top, char* end);
   // Bucket handling
   int hash_to_index(unsigned int full_hash) {
     int h = full_hash % _table_size;
     assert(h >= 0 && h < _table_size, "Illegal hash value");
     return h;
   }
   // Reverse the order of elements in each of the buckets.
   void reverse();
 private:
   // Instance variables
   int               _table_size;
   HashtableBucket<F>*     _buckets;
   BasicHashtableEntry<F>* volatile _free_list;
   char*             _first_free_entry;
   char*             _end_block;
   int               _entry_size;
   volatile int      _number_of_entries;
 protected:
 #ifdef ASSERT
   int               _lookup_count;
   int               _lookup_length;
   void verify_lookup_length(double load);
 #endif
   void initialize(int table_size, int entry_size, int number_of_entries);
   // Accessor
   int entry_size() const { return _entry_size; }
   // The following method is MT-safe and may be used with caution.
   BasicHashtableEntry<F>* bucket(int i);
   // The following method is not MT-safe and must be done under lock.
   BasicHashtableEntry<F>** bucket_addr(int i) { return _buckets[i].entry_addr(); }
   // Attempt to get an entry from the free list
   BasicHashtableEntry<F>* new_entry_free_list();
   // Table entry management
   BasicHashtableEntry<F>* new_entry(unsigned int hashValue);
   // Used when moving the entry to another table
   // Clean up links, but do not add to free_list
   void unlink_entry(BasicHashtableEntry<F>* entry) {
     entry->set_next(NULL);
     --_number_of_entries;
   }
   // Move over freelist and free block for allocation
   void copy_freelist(BasicHashtable* src) {
     _free_list = src->_free_list;
     src->_free_list = NULL;
     _first_free_entry = src->_first_free_entry;
     src->_first_free_entry = NULL;
     _end_block = src->_end_block;
     src->_end_block = NULL;
   }
   // Free the buckets in this hashtable
   void free_buckets();
   // Helper data structure containing context for the bucket entry unlink process,
   // storing the unlinked buckets in a linked list.
   // Also avoids the need to pass around these four members as parameters everywhere.
   struct BucketUnlinkContext {
     int _num_processed;
     int _num_removed;
     // Head and tail pointers for the linked list of removed entries.
     BasicHashtableEntry<F>* _removed_head;
     BasicHashtableEntry<F>* _removed_tail;
     BucketUnlinkContext() : _num_processed(0), _num_removed(0), _removed_head(NULL), _removed_tail(NULL) {
     }
     void free_entry(BasicHashtableEntry<F>* entry);
   };
   // Add of bucket entries linked together in the given context to the global free list. This method
   // is mt-safe wrt. to other calls of this method.
   void bulk_free_entries(BucketUnlinkContext* context);
 public:
   int table_size() { return _table_size; }
   void set_entry(int index, BasicHashtableEntry<F>* entry);
   void add_entry(int index, BasicHashtableEntry<F>* entry);
   void free_entry(BasicHashtableEntry<F>* entry);
   int number_of_entries() { return _number_of_entries; }
   void verify() PRODUCT_RETURN;
 };
 template <class T, MEMFLAGS F> class Hashtable : public BasicHashtable<F> {
   friend class VMStructs;
 public:
   Hashtable(int table_size, int entry_size)
     : BasicHashtable<F>(table_size, entry_size) { }
   Hashtable(int table_size, int entry_size,
                    HashtableBucket<F>* buckets, int number_of_entries)
     : BasicHashtable<F>(table_size, entry_size, buckets, number_of_entries) { }
   // Debugging
   void print()               PRODUCT_RETURN;
   // Reverse the order of elements in each of the buckets. Hashtable
   // entries which refer to objects at a lower address than 'boundary'
   // are separated from those which refer to objects at higher
   // addresses, and appear first in the list.
   void reverse(void* boundary = NULL);
 protected:
   unsigned int compute_hash(Symbol* name) {
     return (unsigned int) name->identity_hash();
   }
   int index_for(Symbol* name) {
     return this->hash_to_index(compute_hash(name));
   }
   // Table entry management
   HashtableEntry<T, F>* new_entry(unsigned int hashValue, T obj);
   // The following method is MT-safe and may be used with caution.
   HashtableEntry<T, F>* bucket(int i) {
     return (HashtableEntry<T, F>*)BasicHashtable<F>::bucket(i);
   }
   // The following method is not MT-safe and must be done under lock.
   HashtableEntry<T, F>** bucket_addr(int i) {
     return (HashtableEntry<T, F>**)BasicHashtable<F>::bucket_addr(i);
   }
 };
 template <class T, MEMFLAGS F> class RehashableHashtable : public Hashtable<T, F> {
  protected:
   enum {
     rehash_count = 100,
     rehash_multiple = 60
   };
   // Check that the table is unbalanced
   bool check_rehash_table(int count);
  public:
   RehashableHashtable(int table_size, int entry_size)
     : Hashtable<T, F>(table_size, entry_size) { }
   RehashableHashtable(int table_size, int entry_size,
                    HashtableBucket<F>* buckets, int number_of_entries)
     : Hashtable<T, F>(table_size, entry_size, buckets, number_of_entries) { }
   // Function to move these elements into the new table.
   void move_to(RehashableHashtable<T, F>* new_table);
   static bool use_alternate_hashcode()  { return _seed != 0; }
   static juint seed()                    { return _seed; }
   static int literal_size(Symbol *symbol);
   static int literal_size(oop oop);
   // The following two are currently not used, but are needed anyway because some
   // C++ compilers (MacOS and Solaris) force the instantiation of
   // Hashtable<ConstantPool*, mtClass>::dump_table() even though we never call this function
   // in the VM code.
   static int literal_size(ConstantPool *cp) {Unimplemented(); return 0;}
   static int literal_size(Klass *k)         {Unimplemented(); return 0;}
   void dump_table(outputStream* st, const char *table_name);
  private:
   static juint _seed;
 };
 //  Verions of hashtable where two handles are used to compute the index.
 template <class T, MEMFLAGS F> class TwoOopHashtable : public Hashtable<T, F> {
   friend class VMStructs;
 protected:
   TwoOopHashtable(int table_size, int entry_size)
     : Hashtable<T, F>(table_size, entry_size) {}
   TwoOopHashtable(int table_size, int entry_size, HashtableBucket<F>* t,
                   int number_of_entries)
     : Hashtable<T, F>(table_size, entry_size, t, number_of_entries) {}
 public:
   unsigned int compute_hash(Symbol* name, ClassLoaderData* loader_data) {
     unsigned int name_hash = name->identity_hash();
     // loader is null with CDS
     assert(loader_data != NULL || UseSharedSpaces || DumpSharedSpaces,
            "only allowed with shared spaces");
     unsigned int loader_hash = loader_data == NULL ? 0 : loader_data->identity_hash();
     return name_hash ^ loader_hash;
   }
   int index_for(Symbol* name, ClassLoaderData* loader_data) {
     return this->hash_to_index(compute_hash(name, loader_data));
   }
 };
 #endif // SHARE_VM_UTILITIES_HASHTABLE_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/utilities/hashtable.hpp@ce9a710b0f63 (annotated)

src/share/vm/utilities/hashtable.hpp