1 /*

     2  * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  *

    23  */

    24 

    25 #include "precompiled.hpp"

    26 #include "classfile/altHashing.hpp"

    27 #include "classfile/javaClasses.hpp"

    28 #include "classfile/stringTable.hpp"

    29 #include "classfile/systemDictionary.hpp"

    30 #include "gc_interface/collectedHeap.inline.hpp"

    31 #include "memory/allocation.inline.hpp"

    32 #include "memory/filemap.hpp"

    33 #include "memory/gcLocker.inline.hpp"

    34 #include "oops/oop.inline.hpp"

    35 #include "oops/oop.inline2.hpp"

    36 #include "runtime/mutexLocker.hpp"

    37 #include "utilities/hashtable.inline.hpp"

    38 #if INCLUDE_ALL_GCS

    39 #include "gc_implementation/g1/g1StringDedup.hpp"

    40 #endif

    41 

    42 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC

    43 

    44 // the number of buckets a thread claims

    45 const int ClaimChunkSize = 32;

    46 

    47 #ifdef ASSERT

    48 class StableMemoryChecker : public StackObj {

    49   enum { _bufsize = wordSize*4 };

    50 

    51   address _region;

    52   jint    _size;

    53   u1      _save_buf[_bufsize];

    54 

    55   int sample(u1* save_buf) {

    56     if (_size <= _bufsize) {

    57       memcpy(save_buf, _region, _size);

    58       return _size;

    59     } else {

    60       // copy head and tail

    61       memcpy(&save_buf[0],          _region,                      _bufsize/2);

    62       memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2);

    63       return (_bufsize/2)*2;

    64     }

    65   }

    66 

    67  public:

    68   StableMemoryChecker(const void* region, jint size) {

    69     _region = (address) region;

    70     _size   = size;

    71     sample(_save_buf);

    72   }

    73 

    74   bool verify() {

    75     u1 check_buf[sizeof(_save_buf)];

    76     int check_size = sample(check_buf);

    77     return (0 == memcmp(_save_buf, check_buf, check_size));

    78   }

    79 

    80   void set_region(const void* region) { _region = (address) region; }

    81 };

    82 #endif

    83 

    84 

    85 // --------------------------------------------------------------------------

    86 StringTable* StringTable::_the_table = NULL;

    87 

    88 bool StringTable::_needs_rehashing = false;

    89 

    90 volatile int StringTable::_parallel_claimed_idx = 0;

    91 

    92 // Pick hashing algorithm

    93 unsigned int StringTable::hash_string(const jchar* s, int len) {

    94   return use_alternate_hashcode() ? AltHashing::murmur3_32(seed(), s, len) :

    95                                     java_lang_String::hash_code(s, len);

    96 }

    97 

    98 oop StringTable::lookup(int index, jchar* name,

    99                         int len, unsigned int hash) {

   100   int count = 0;

   101   for (HashtableEntry<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) {

   102     count++;

   103     if (l->hash() == hash) {

   104       if (java_lang_String::equals(l->literal(), name, len)) {

   105         return l->literal();

   106       }

   107     }

   108   }

   109   // If the bucket size is too deep check if this hash code is insufficient.

   110   if (count >= BasicHashtable<mtSymbol>::rehash_count && !needs_rehashing()) {

   111     _needs_rehashing = check_rehash_table(count);

   112   }

   113   return NULL;

   114 }

   115 

   116 

   117 oop StringTable::basic_add(int index_arg, Handle string, jchar* name,

   118                            int len, unsigned int hashValue_arg, TRAPS) {

   119 

   120   assert(java_lang_String::equals(string(), name, len),

   121          "string must be properly initialized");

   122   // Cannot hit a safepoint in this function because the "this" pointer can move.

   123   No_Safepoint_Verifier nsv;

   124 

   125   // Check if the symbol table has been rehashed, if so, need to recalculate

   126   // the hash value and index before second lookup.

   127   unsigned int hashValue;

   128   int index;

   129   if (use_alternate_hashcode()) {

   130     hashValue = hash_string(name, len);

   131     index = hash_to_index(hashValue);

   132   } else {

   133     hashValue = hashValue_arg;

   134     index = index_arg;

   135   }

   136 

   137   // Since look-up was done lock-free, we need to check if another

   138   // thread beat us in the race to insert the symbol.

   139 

   140   oop test = lookup(index, name, len, hashValue); // calls lookup(u1*, int)

   141   if (test != NULL) {

   142     // Entry already added

   143     return test;

   144   }

   145 

   146   HashtableEntry<oop, mtSymbol>* entry = new_entry(hashValue, string());

   147   add_entry(index, entry);

   148   return string();

   149 }

   150 

   151 

   152 oop StringTable::lookup(Symbol* symbol) {

   153   ResourceMark rm;

   154   int length;

   155   jchar* chars = symbol->as_unicode(length);

   156   return lookup(chars, length);

   157 }

   158 

   159 

   160 oop StringTable::lookup(jchar* name, int len) {

   161   unsigned int hash = hash_string(name, len);

   162   int index = the_table()->hash_to_index(hash);

   163   return the_table()->lookup(index, name, len, hash);

   164 }

   165 

   166 

   167 oop StringTable::intern(Handle string_or_null, jchar* name,

   168                         int len, TRAPS) {

   169   unsigned int hashValue = hash_string(name, len);

   170   int index = the_table()->hash_to_index(hashValue);

   171   oop found_string = the_table()->lookup(index, name, len, hashValue);

   172 

   173   // Found

   174   if (found_string != NULL) return found_string;

   175 

   176   debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));

   177   assert(!Universe::heap()->is_in_reserved(name),

   178          "proposed name of symbol must be stable");

   179 

   180   Handle string;

   181   // try to reuse the string if possible

   182   if (!string_or_null.is_null()) {

   183     string = string_or_null;

   184   } else {

   185     string = java_lang_String::create_from_unicode(name, len, CHECK_NULL);

   186   }

   187 

   188 #if INCLUDE_ALL_GCS

   189   if (G1StringDedup::is_enabled()) {

   190     // Deduplicate the string before it is interned. Note that we should never

   191     // deduplicate a string after it has been interned. Doing so will counteract

   192     // compiler optimizations done on e.g. interned string literals.

   193     G1StringDedup::deduplicate(string());

   194   }

   195 #endif

   196 

   197   // Grab the StringTable_lock before getting the_table() because it could

   198   // change at safepoint.

   199   MutexLocker ml(StringTable_lock, THREAD);

   200 

   201   // Otherwise, add to symbol to table

   202   return the_table()->basic_add(index, string, name, len,

   203                                 hashValue, CHECK_NULL);

   204 }

   205 

   206 oop StringTable::intern(Symbol* symbol, TRAPS) {

   207   if (symbol == NULL) return NULL;

   208   ResourceMark rm(THREAD);

   209   int length;

   210   jchar* chars = symbol->as_unicode(length);

   211   Handle string;

   212   oop result = intern(string, chars, length, CHECK_NULL);

   213   return result;

   214 }

   215 

   216 

   217 oop StringTable::intern(oop string, TRAPS)

   218 {

   219   if (string == NULL) return NULL;

   220   ResourceMark rm(THREAD);

   221   int length;

   222   Handle h_string (THREAD, string);

   223   jchar* chars = java_lang_String::as_unicode_string(string, length, CHECK_NULL);

   224   oop result = intern(h_string, chars, length, CHECK_NULL);

   225   return result;

   226 }

   227 

   228 

   229 oop StringTable::intern(const char* utf8_string, TRAPS) {

   230   if (utf8_string == NULL) return NULL;

   231   ResourceMark rm(THREAD);

   232   int length = UTF8::unicode_length(utf8_string);

   233   jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);

   234   UTF8::convert_to_unicode(utf8_string, chars, length);

   235   Handle string;

   236   oop result = intern(string, chars, length, CHECK_NULL);

   237   return result;

   238 }

   239 

   240 void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {

   241   buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), processed, removed);

   242 }

   243 

   244 void StringTable::possibly_parallel_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {

   245   // Readers of the table are unlocked, so we should only be removing

   246   // entries at a safepoint.

   247   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

   248   const int limit = the_table()->table_size();

   249 

   250   for (;;) {

   251     // Grab next set of buckets to scan

   252     int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;

   253     if (start_idx >= limit) {

   254       // End of table

   255       break;

   256     }

   257 

   258     int end_idx = MIN2(limit, start_idx + ClaimChunkSize);

   259     buckets_unlink_or_oops_do(is_alive, f, start_idx, end_idx, processed, removed);

   260   }

   261 }

   262 

   263 void StringTable::buckets_oops_do(OopClosure* f, int start_idx, int end_idx) {

   264   const int limit = the_table()->table_size();

   265 

   266   assert(0 <= start_idx && start_idx <= limit,

   267          err_msg("start_idx (%d) is out of bounds", start_idx));

   268   assert(0 <= end_idx && end_idx <= limit,

   269          err_msg("end_idx (%d) is out of bounds", end_idx));

   270   assert(start_idx <= end_idx,

   271          err_msg("Index ordering: start_idx=%d, end_idx=%d",

   272                  start_idx, end_idx));

   273 

   274   for (int i = start_idx; i < end_idx; i += 1) {

   275     HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);

   276     while (entry != NULL) {

   277       assert(!entry->is_shared(), "CDS not used for the StringTable");

   278 

   279       f->do_oop((oop*)entry->literal_addr());

   280 

   281       entry = entry->next();

   282     }

   283   }

   284 }

   285 

   286 void StringTable::buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, int* processed, int* removed) {

   287   const int limit = the_table()->table_size();

   288 

   289   assert(0 <= start_idx && start_idx <= limit,

   290          err_msg("start_idx (%d) is out of bounds", start_idx));

   291   assert(0 <= end_idx && end_idx <= limit,

   292          err_msg("end_idx (%d) is out of bounds", end_idx));

   293   assert(start_idx <= end_idx,

   294          err_msg("Index ordering: start_idx=%d, end_idx=%d",

   295                  start_idx, end_idx));

   296 

   297   for (int i = start_idx; i < end_idx; ++i) {

   298     HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i);

   299     HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);

   300     while (entry != NULL) {

   301       assert(!entry->is_shared(), "CDS not used for the StringTable");

   302 

   303       if (is_alive->do_object_b(entry->literal())) {

   304         if (f != NULL) {

   305           f->do_oop((oop*)entry->literal_addr());

   306         }

   307         p = entry->next_addr();

   308       } else {

   309         *p = entry->next();

   310         the_table()->free_entry(entry);

   311         (*removed)++;

   312       }

   313       (*processed)++;

   314       entry = *p;

   315     }

   316   }

   317 }

   318 

   319 void StringTable::oops_do(OopClosure* f) {

   320   buckets_oops_do(f, 0, the_table()->table_size());

   321 }

   322 

   323 void StringTable::possibly_parallel_oops_do(OopClosure* f) {

   324   const int limit = the_table()->table_size();

   325 

   326   for (;;) {

   327     // Grab next set of buckets to scan

   328     int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;

   329     if (start_idx >= limit) {

   330       // End of table

   331       break;

   332     }

   333 

   334     int end_idx = MIN2(limit, start_idx + ClaimChunkSize);

   335     buckets_oops_do(f, start_idx, end_idx);

   336   }

   337 }

   338 

   339 // This verification is part of Universe::verify() and needs to be quick.

   340 // See StringTable::verify_and_compare() below for exhaustive verification.

   341 void StringTable::verify() {

   342   for (int i = 0; i < the_table()->table_size(); ++i) {

   343     HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);

   344     for ( ; p != NULL; p = p->next()) {

   345       oop s = p->literal();

   346       guarantee(s != NULL, "interned string is NULL");

   347       unsigned int h = java_lang_String::hash_string(s);

   348       guarantee(p->hash() == h, "broken hash in string table entry");

   349       guarantee(the_table()->hash_to_index(h) == i,

   350                 "wrong index in string table");

   351     }

   352   }

   353 }

   354 

   355 void StringTable::dump(outputStream* st) {

   356   the_table()->dump_table(st, "StringTable");

   357 }

   358 

   359 StringTable::VerifyRetTypes StringTable::compare_entries(

   360                                       int bkt1, int e_cnt1,

   361                                       HashtableEntry<oop, mtSymbol>* e_ptr1,

   362                                       int bkt2, int e_cnt2,

   363                                       HashtableEntry<oop, mtSymbol>* e_ptr2) {

   364   // These entries are sanity checked by verify_and_compare_entries()

   365   // before this function is called.

   366   oop str1 = e_ptr1->literal();

   367   oop str2 = e_ptr2->literal();

   368 

   369   if (str1 == str2) {

   370     tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") "

   371                   "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]",

   372                   (void *)str1, bkt1, e_cnt1, bkt2, e_cnt2);

   373     return _verify_fail_continue;

   374   }

   375 

   376   if (java_lang_String::equals(str1, str2)) {

   377     tty->print_cr("ERROR: identical String values in entry @ "

   378                   "bucket[%d][%d] and entry @ bucket[%d][%d]",

   379                   bkt1, e_cnt1, bkt2, e_cnt2);

   380     return _verify_fail_continue;

   381   }

   382 

   383   return _verify_pass;

   384 }

   385 

   386 StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt,

   387                                       HashtableEntry<oop, mtSymbol>* e_ptr,

   388                                       StringTable::VerifyMesgModes mesg_mode) {

   389 

   390   VerifyRetTypes ret = _verify_pass;  // be optimistic

   391 

   392   oop str = e_ptr->literal();

   393   if (str == NULL) {

   394     if (mesg_mode == _verify_with_mesgs) {

   395       tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt,

   396                     e_cnt);

   397     }

   398     // NULL oop means no more verifications are possible

   399     return _verify_fail_done;

   400   }

   401 

   402   if (str->klass() != SystemDictionary::String_klass()) {

   403     if (mesg_mode == _verify_with_mesgs) {

   404       tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]",

   405                     bkt, e_cnt);

   406     }

   407     // not a String means no more verifications are possible

   408     return _verify_fail_done;

   409   }

   410 

   411   unsigned int h = java_lang_String::hash_string(str);

   412   if (e_ptr->hash() != h) {

   413     if (mesg_mode == _verify_with_mesgs) {

   414       tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], "

   415                     "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h);

   416     }

   417     ret = _verify_fail_continue;

   418   }

   419 

   420   if (the_table()->hash_to_index(h) != bkt) {

   421     if (mesg_mode == _verify_with_mesgs) {

   422       tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], "

   423                     "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h,

   424                     the_table()->hash_to_index(h));

   425     }

   426     ret = _verify_fail_continue;

   427   }

   428 

   429   return ret;

   430 }

   431 

   432 // See StringTable::verify() above for the quick verification that is

   433 // part of Universe::verify(). This verification is exhaustive and

   434 // reports on every issue that is found. StringTable::verify() only

   435 // reports on the first issue that is found.

   436 //

   437 // StringTable::verify_entry() checks:

   438 // - oop value != NULL (same as verify())

   439 // - oop value is a String

   440 // - hash(String) == hash in entry (same as verify())

   441 // - index for hash == index of entry (same as verify())

   442 //

   443 // StringTable::compare_entries() checks:

   444 // - oops are unique across all entries

   445 // - String values are unique across all entries

   446 //

   447 int StringTable::verify_and_compare_entries() {

   448   assert(StringTable_lock->is_locked(), "sanity check");

   449 

   450   int  fail_cnt = 0;

   451 

   452   // first, verify all the entries individually:

   453   for (int bkt = 0; bkt < the_table()->table_size(); bkt++) {

   454     HashtableEntry<oop, mtSymbol>* e_ptr = the_table()->bucket(bkt);

   455     for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) {

   456       VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs);

   457       if (ret != _verify_pass) {

   458         fail_cnt++;

   459       }

   460     }

   461   }

   462 

   463   // Optimization: if the above check did not find any failures, then

   464   // the comparison loop below does not need to call verify_entry()

   465   // before calling compare_entries(). If there were failures, then we

   466   // have to call verify_entry() to see if the entry can be passed to

   467   // compare_entries() safely. When we call verify_entry() in the loop

   468   // below, we do so quietly to void duplicate messages and we don't

   469   // increment fail_cnt because the failures have already been counted.

   470   bool need_entry_verify = (fail_cnt != 0);

   471 

   472   // second, verify all entries relative to each other:

   473   for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) {

   474     HashtableEntry<oop, mtSymbol>* e_ptr1 = the_table()->bucket(bkt1);

   475     for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) {

   476       if (need_entry_verify) {

   477         VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1,

   478                                           _verify_quietly);

   479         if (ret == _verify_fail_done) {

   480           // cannot use the current entry to compare against other entries

   481           continue;

   482         }

   483       }

   484 

   485       for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) {

   486         HashtableEntry<oop, mtSymbol>* e_ptr2 = the_table()->bucket(bkt2);

   487         int e_cnt2;

   488         for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) {

   489           if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) {

   490             // skip the entries up to and including the one that

   491             // we're comparing against

   492             continue;

   493           }

   494 

   495           if (need_entry_verify) {

   496             VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2,

   497                                               _verify_quietly);

   498             if (ret == _verify_fail_done) {

   499               // cannot compare against this entry

   500               continue;

   501             }

   502           }

   503 

   504           // compare two entries, report and count any failures:

   505           if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2)

   506               != _verify_pass) {

   507             fail_cnt++;

   508           }

   509         }

   510       }

   511     }

   512   }

   513   return fail_cnt;

   514 }

   515 

   516 // Create a new table and using alternate hash code, populate the new table

   517 // with the existing strings.   Set flag to use the alternate hash code afterwards.

   518 void StringTable::rehash_table() {

   519   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

   520   // This should never happen with -Xshare:dump but it might in testing mode.

   521   if (DumpSharedSpaces) return;

   522   StringTable* new_table = new StringTable();

   523 

   524   // Rehash the table

   525   the_table()->move_to(new_table);

   526 

   527   // Delete the table and buckets (entries are reused in new table).

   528   delete _the_table;

   529   // Don't check if we need rehashing until the table gets unbalanced again.

   530   // Then rehash with a new global seed.

   531   _needs_rehashing = false;

   532   _the_table = new_table;

   533 }