1 /*

     2  * Copyright 2003-2007 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    20  * CA 95054 USA or visit www.sun.com if you need additional information or

    21  * have any questions.

    22  *

    23  */

    24 

    25 # include "incls/_precompiled.incl"

    26 # include "incls/_dictionary.cpp.incl"

    27 

    28 

    29 DictionaryEntry*  Dictionary::_current_class_entry = NULL;

    30 int               Dictionary::_current_class_index =    0;

    31 

    32 

    33 Dictionary::Dictionary(int table_size)

    34   : TwoOopHashtable(table_size, sizeof(DictionaryEntry)) {

    35   _current_class_index = 0;

    36   _current_class_entry = NULL;

    37 };

    38 

    39 

    40 

    41 Dictionary::Dictionary(int table_size, HashtableBucket* t,

    42                        int number_of_entries)

    43   : TwoOopHashtable(table_size, sizeof(DictionaryEntry), t, number_of_entries) {

    44   _current_class_index = 0;

    45   _current_class_entry = NULL;

    46 };

    47 

    48 

    49 DictionaryEntry* Dictionary::new_entry(unsigned int hash, klassOop klass,

    50                                        oop loader) {

    51   DictionaryEntry* entry;

    52   entry = (DictionaryEntry*)Hashtable::new_entry(hash, klass);

    53   entry->set_loader(loader);

    54   entry->set_pd_set(NULL);

    55   return entry;

    56 }

    57 

    58 

    59 DictionaryEntry* Dictionary::new_entry() {

    60   DictionaryEntry* entry = (DictionaryEntry*)Hashtable::new_entry(0L, NULL);

    61   entry->set_loader(NULL);

    62   entry->set_pd_set(NULL);

    63   return entry;

    64 }

    65 

    66 

    67 void Dictionary::free_entry(DictionaryEntry* entry) {

    68   // avoid recursion when deleting linked list

    69   while (entry->pd_set() != NULL) {

    70     ProtectionDomainEntry* to_delete = entry->pd_set();

    71     entry->set_pd_set(to_delete->next());

    72     delete to_delete;

    73   }

    74   Hashtable::free_entry(entry);

    75 }

    76 

    77 

    78 bool DictionaryEntry::contains_protection_domain(oop protection_domain) const {

    79 #ifdef ASSERT

    80   if (protection_domain == instanceKlass::cast(klass())->protection_domain()) {

    81     // Ensure this doesn't show up in the pd_set (invariant)

    82     bool in_pd_set = false;

    83     for (ProtectionDomainEntry* current = _pd_set;

    84                                 current != NULL;

    85                                 current = current->next()) {

    86       if (current->protection_domain() == protection_domain) {

    87         in_pd_set = true;

    88         break;

    89       }

    90     }

    91     if (in_pd_set) {

    92       assert(false, "A klass's protection domain should not show up "

    93                     "in its sys. dict. PD set");

    94     }

    95   }

    96 #endif /* ASSERT */

    97 

    98   if (protection_domain == instanceKlass::cast(klass())->protection_domain()) {

    99     // Succeeds trivially

   100     return true;

   101   }

   102 

   103   for (ProtectionDomainEntry* current = _pd_set;

   104                               current != NULL;

   105                               current = current->next()) {

   106     if (current->protection_domain() == protection_domain) return true;

   107   }

   108   return false;

   109 }

   110 

   111 

   112 void DictionaryEntry::add_protection_domain(oop protection_domain) {

   113   assert_locked_or_safepoint(SystemDictionary_lock);

   114   if (!contains_protection_domain(protection_domain)) {

   115     ProtectionDomainEntry* new_head =

   116                 new ProtectionDomainEntry(protection_domain, _pd_set);

   117     // Warning: Preserve store ordering.  The SystemDictionary is read

   118     //          without locks.  The new ProtectionDomainEntry must be

   119     //          complete before other threads can be allowed to see it

   120     //          via a store to _pd_set.

   121     OrderAccess::release_store_ptr(&_pd_set, new_head);

   122   }

   123   if (TraceProtectionDomainVerification && WizardMode) {

   124     print();

   125   }

   126 }

   127 

   128 

   129 bool Dictionary::do_unloading(BoolObjectClosure* is_alive) {

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

   131   bool class_was_unloaded = false;

   132   int  index = 0; // Defined here for portability! Do not move

   133 

   134   // Remove unloadable entries and classes from system dictionary

   135   // The placeholder array has been handled in always_strong_oops_do.

   136   DictionaryEntry* probe = NULL;

   137   for (index = 0; index < table_size(); index++) {

   138     for (DictionaryEntry** p = bucket_addr(index); *p != NULL; ) {

   139       probe = *p;

   140       klassOop e = probe->klass();

   141       oop class_loader = probe->loader();

   142 

   143       instanceKlass* ik = instanceKlass::cast(e);

   144       if (ik->previous_versions() != NULL) {

   145         // This klass has previous versions so see what we can cleanup

   146         // while it is safe to do so.

   147 

   148         int gc_count = 0;    // leave debugging breadcrumbs

   149         int live_count = 0;

   150 

   151         // RC_TRACE macro has an embedded ResourceMark

   152         RC_TRACE(0x00000200, ("unload: %s: previous version length=%d",

   153           ik->external_name(), ik->previous_versions()->length()));

   154 

   155         for (int i = ik->previous_versions()->length() - 1; i >= 0; i--) {

   156           // check the previous versions array for GC'ed weak refs

   157           PreviousVersionNode * pv_node = ik->previous_versions()->at(i);

   158           jweak cp_ref = pv_node->prev_constant_pool();

   159           assert(cp_ref != NULL, "weak cp ref was unexpectedly cleared");

   160           if (cp_ref == NULL) {

   161             delete pv_node;

   162             ik->previous_versions()->remove_at(i);

   163             // Since we are traversing the array backwards, we don't have to

   164             // do anything special with the index.

   165             continue;  // robustness

   166           }

   167 

   168           constantPoolOop pvcp = (constantPoolOop)JNIHandles::resolve(cp_ref);

   169           if (pvcp == NULL) {

   170             // this entry has been GC'ed so remove it

   171             delete pv_node;

   172             ik->previous_versions()->remove_at(i);

   173             // Since we are traversing the array backwards, we don't have to

   174             // do anything special with the index.

   175             gc_count++;

   176             continue;

   177           } else {

   178             RC_TRACE(0x00000200, ("unload: previous version @%d is alive", i));

   179             if (is_alive->do_object_b(pvcp)) {

   180               live_count++;

   181             } else {

   182               guarantee(false, "sanity check");

   183             }

   184           }

   185 

   186           GrowableArray<jweak>* method_refs = pv_node->prev_EMCP_methods();

   187           if (method_refs != NULL) {

   188             RC_TRACE(0x00000200, ("unload: previous methods length=%d",

   189               method_refs->length()));

   190             for (int j = method_refs->length() - 1; j >= 0; j--) {

   191               jweak method_ref = method_refs->at(j);

   192               assert(method_ref != NULL, "weak method ref was unexpectedly cleared");

   193               if (method_ref == NULL) {

   194                 method_refs->remove_at(j);

   195                 // Since we are traversing the array backwards, we don't have to

   196                 // do anything special with the index.

   197                 continue;  // robustness

   198               }

   199 

   200               methodOop method = (methodOop)JNIHandles::resolve(method_ref);

   201               if (method == NULL) {

   202                 // this method entry has been GC'ed so remove it

   203                 JNIHandles::destroy_weak_global(method_ref);

   204                 method_refs->remove_at(j);

   205               } else {

   206                 // RC_TRACE macro has an embedded ResourceMark

   207                 RC_TRACE(0x00000200,

   208                   ("unload: %s(%s): prev method @%d in version @%d is alive",

   209                   method->name()->as_C_string(),

   210                   method->signature()->as_C_string(), j, i));

   211               }

   212             }

   213           }

   214         }

   215         assert(ik->previous_versions()->length() == live_count, "sanity check");

   216         RC_TRACE(0x00000200,

   217           ("unload: previous version stats: live=%d, GC'ed=%d", live_count,

   218           gc_count));

   219       }

   220 

   221       // Non-unloadable classes were handled in always_strong_oops_do

   222       if (!is_strongly_reachable(class_loader, e)) {

   223         // Entry was not visited in phase1 (negated test from phase1)

   224         assert(class_loader != NULL, "unloading entry with null class loader");

   225         oop k_def_class_loader = ik->class_loader();

   226 

   227         // Do we need to delete this system dictionary entry?

   228         bool purge_entry = false;

   229 

   230         // Do we need to delete this system dictionary entry?

   231         if (!is_alive->do_object_b(class_loader)) {

   232           // If the loader is not live this entry should always be

   233           // removed (will never be looked up again). Note that this is

   234           // not the same as unloading the referred class.

   235           if (k_def_class_loader == class_loader) {

   236             // This is the defining entry, so the referred class is about

   237             // to be unloaded.

   238             // Notify the debugger and clean up the class.

   239             guarantee(!is_alive->do_object_b(e),

   240                       "klass should not be live if defining loader is not");

   241             class_was_unloaded = true;

   242             // notify the debugger

   243             if (JvmtiExport::should_post_class_unload()) {

   244               JvmtiExport::post_class_unload(ik->as_klassOop());

   245             }

   246 

   247             // notify ClassLoadingService of class unload

   248             ClassLoadingService::notify_class_unloaded(ik);

   249 

   250             // Clean up C heap

   251             ik->release_C_heap_structures();

   252           }

   253           // Also remove this system dictionary entry.

   254           purge_entry = true;

   255 

   256         } else {

   257           // The loader in this entry is alive. If the klass is dead,

   258           // the loader must be an initiating loader (rather than the

   259           // defining loader). Remove this entry.

   260           if (!is_alive->do_object_b(e)) {

   261             guarantee(!is_alive->do_object_b(k_def_class_loader),

   262                       "defining loader should not be live if klass is not");

   263             // If we get here, the class_loader must not be the defining

   264             // loader, it must be an initiating one.

   265             assert(k_def_class_loader != class_loader,

   266                    "cannot have live defining loader and unreachable klass");

   267 

   268             // Loader is live, but class and its defining loader are dead.

   269             // Remove the entry. The class is going away.

   270             purge_entry = true;

   271           }

   272         }

   273 

   274         if (purge_entry) {

   275           *p = probe->next();

   276           if (probe == _current_class_entry) {

   277             _current_class_entry = NULL;

   278           }

   279           free_entry(probe);

   280           continue;

   281         }

   282       }

   283       p = probe->next_addr();

   284     }

   285   }

   286   return class_was_unloaded;

   287 }

   288 

   289 

   290 void Dictionary::always_strong_classes_do(OopClosure* blk) {

   291   // Follow all system classes and temporary placeholders in dictionary

   292   for (int index = 0; index < table_size(); index++) {

   293     for (DictionaryEntry *probe = bucket(index);

   294                           probe != NULL;

   295                           probe = probe->next()) {

   296       oop e = probe->klass();

   297       oop class_loader = probe->loader();

   298       if (is_strongly_reachable(class_loader, e)) {

   299         blk->do_oop((oop*)probe->klass_addr());

   300         if (class_loader != NULL) {

   301           blk->do_oop(probe->loader_addr());

   302         }

   303         probe->protection_domain_set_oops_do(blk);

   304       }

   305     }

   306   }

   307 }

   308 

   309 

   310 //   Just the classes from defining class loaders

   311 void Dictionary::classes_do(void f(klassOop)) {

   312   for (int index = 0; index < table_size(); index++) {

   313     for (DictionaryEntry* probe = bucket(index);

   314                           probe != NULL;

   315                           probe = probe->next()) {

   316       klassOop k = probe->klass();

   317       if (probe->loader() == instanceKlass::cast(k)->class_loader()) {

   318         f(k);

   319       }

   320     }

   321   }

   322 }

   323 

   324 // Added for initialize_itable_for_klass to handle exceptions

   325 //   Just the classes from defining class loaders

   326 void Dictionary::classes_do(void f(klassOop, TRAPS), TRAPS) {

   327   for (int index = 0; index < table_size(); index++) {

   328     for (DictionaryEntry* probe = bucket(index);

   329                           probe != NULL;

   330                           probe = probe->next()) {

   331       klassOop k = probe->klass();

   332       if (probe->loader() == instanceKlass::cast(k)->class_loader()) {

   333         f(k, CHECK);

   334       }

   335     }

   336   }

   337 }

   338 

   339 

   340 //   All classes, and their class loaders

   341 //   (added for helpers that use HandleMarks and ResourceMarks)

   342 // Don't iterate over placeholders

   343 void Dictionary::classes_do(void f(klassOop, oop, TRAPS), TRAPS) {

   344   for (int index = 0; index < table_size(); index++) {

   345     for (DictionaryEntry* probe = bucket(index);

   346                           probe != NULL;

   347                           probe = probe->next()) {

   348       klassOop k = probe->klass();

   349       f(k, probe->loader(), CHECK);

   350     }

   351   }

   352 }

   353 

   354 

   355 //   All classes, and their class loaders

   356 // Don't iterate over placeholders

   357 void Dictionary::classes_do(void f(klassOop, oop)) {

   358   for (int index = 0; index < table_size(); index++) {

   359     for (DictionaryEntry* probe = bucket(index);

   360                           probe != NULL;

   361                           probe = probe->next()) {

   362       klassOop k = probe->klass();

   363       f(k, probe->loader());

   364     }

   365   }

   366 }

   367 

   368 

   369 void Dictionary::oops_do(OopClosure* f) {

   370   for (int index = 0; index < table_size(); index++) {

   371     for (DictionaryEntry* probe = bucket(index);

   372                           probe != NULL;

   373                           probe = probe->next()) {

   374       f->do_oop((oop*)probe->klass_addr());

   375       if (probe->loader() != NULL) {

   376         f->do_oop(probe->loader_addr());

   377       }

   378       probe->protection_domain_set_oops_do(f);

   379     }

   380   }

   381 }

   382 

   383 

   384 void Dictionary::methods_do(void f(methodOop)) {

   385   for (int index = 0; index < table_size(); index++) {

   386     for (DictionaryEntry* probe = bucket(index);

   387                           probe != NULL;

   388                           probe = probe->next()) {

   389       klassOop k = probe->klass();

   390       if (probe->loader() == instanceKlass::cast(k)->class_loader()) {

   391         // only take klass is we have the entry with the defining class loader

   392         instanceKlass::cast(k)->methods_do(f);

   393       }

   394     }

   395   }

   396 }

   397 

   398 

   399 klassOop Dictionary::try_get_next_class() {

   400   while (true) {

   401     if (_current_class_entry != NULL) {

   402       klassOop k = _current_class_entry->klass();

   403       _current_class_entry = _current_class_entry->next();

   404       return k;

   405     }

   406     _current_class_index = (_current_class_index + 1) % table_size();

   407     _current_class_entry = bucket(_current_class_index);

   408   }

   409   // never reached

   410 }

   411 

   412 

   413 // Add a loaded class to the system dictionary.

   414 // Readers of the SystemDictionary aren't always locked, so _buckets

   415 // is volatile. The store of the next field in the constructor is

   416 // also cast to volatile;  we do this to ensure store order is maintained

   417 // by the compilers.

   418 

   419 void Dictionary::add_klass(symbolHandle class_name, Handle class_loader,

   420                            KlassHandle obj) {

   421   assert_locked_or_safepoint(SystemDictionary_lock);

   422   assert(obj() != NULL, "adding NULL obj");

   423   assert(Klass::cast(obj())->name() == class_name(), "sanity check on name");

   424 

   425   unsigned int hash = compute_hash(class_name, class_loader);

   426   int index = hash_to_index(hash);

   427   DictionaryEntry* entry = new_entry(hash, obj(), class_loader());

   428   add_entry(index, entry);

   429 }

   430 

   431 

   432 // This routine does not lock the system dictionary.

   433 //

   434 // Since readers don't hold a lock, we must make sure that system

   435 // dictionary entries are only removed at a safepoint (when only one

   436 // thread is running), and are added to in a safe way (all links must

   437 // be updated in an MT-safe manner).

   438 //

   439 // Callers should be aware that an entry could be added just after

   440 // _buckets[index] is read here, so the caller will not see the new entry.

   441 DictionaryEntry* Dictionary::get_entry(int index, unsigned int hash,

   442                                        symbolHandle class_name,

   443                                        Handle class_loader) {

   444   symbolOop name_ = class_name();

   445   oop loader_ = class_loader();

   446   debug_only(_lookup_count++);

   447   for (DictionaryEntry* entry = bucket(index);

   448                         entry != NULL;

   449                         entry = entry->next()) {

   450     if (entry->hash() == hash && entry->equals(name_, loader_)) {

   451       return entry;

   452     }

   453     debug_only(_lookup_length++);

   454   }

   455   return NULL;

   456 }

   457 

   458 

   459 klassOop Dictionary::find(int index, unsigned int hash, symbolHandle name,

   460                           Handle loader, Handle protection_domain, TRAPS) {

   461   DictionaryEntry* entry = get_entry(index, hash, name, loader);

   462   if (entry != NULL && entry->is_valid_protection_domain(protection_domain)) {

   463     return entry->klass();

   464   } else {

   465     return NULL;

   466   }

   467 }

   468 

   469 

   470 klassOop Dictionary::find_class(int index, unsigned int hash,

   471                                 symbolHandle name, Handle loader) {

   472   assert_locked_or_safepoint(SystemDictionary_lock);

   473   assert (index == index_for(name, loader), "incorrect index?");

   474 

   475   DictionaryEntry* entry = get_entry(index, hash, name, loader);

   476   return (entry != NULL) ? entry->klass() : (klassOop)NULL;

   477 }

   478 

   479 

   480 // Variant of find_class for shared classes.  No locking required, as

   481 // that table is static.

   482 

   483 klassOop Dictionary::find_shared_class(int index, unsigned int hash,

   484                                        symbolHandle name) {

   485   assert (index == index_for(name, Handle()), "incorrect index?");

   486 

   487   DictionaryEntry* entry = get_entry(index, hash, name, Handle());

   488   return (entry != NULL) ? entry->klass() : (klassOop)NULL;

   489 }

   490 

   491 

   492 void Dictionary::add_protection_domain(int index, unsigned int hash,

   493                                        instanceKlassHandle klass,

   494                                        Handle loader, Handle protection_domain,

   495                                        TRAPS) {

   496   symbolHandle klass_name(THREAD, klass->name());

   497   DictionaryEntry* entry = get_entry(index, hash, klass_name, loader);

   498 

   499   assert(entry != NULL,"entry must be present, we just created it");

   500   assert(protection_domain() != NULL,

   501          "real protection domain should be present");

   502 

   503   entry->add_protection_domain(protection_domain());

   504 

   505   assert(entry->contains_protection_domain(protection_domain()),

   506          "now protection domain should be present");

   507 }

   508 

   509 

   510 bool Dictionary::is_valid_protection_domain(int index, unsigned int hash,

   511                                             symbolHandle name,

   512                                             Handle loader,

   513                                             Handle protection_domain) {

   514   DictionaryEntry* entry = get_entry(index, hash, name, loader);

   515   return entry->is_valid_protection_domain(protection_domain);

   516 }

   517 

   518 

   519 void Dictionary::reorder_dictionary() {

   520 

   521   // Copy all the dictionary entries into a single master list.

   522 

   523   DictionaryEntry* master_list = NULL;

   524   for (int i = 0; i < table_size(); ++i) {

   525     DictionaryEntry* p = bucket(i);

   526     while (p != NULL) {

   527       DictionaryEntry* tmp;

   528       tmp = p->next();

   529       p->set_next(master_list);

   530       master_list = p;

   531       p = tmp;

   532     }

   533     set_entry(i, NULL);

   534   }

   535 

   536   // Add the dictionary entries back to the list in the correct buckets.

   537   Thread *thread = Thread::current();

   538 

   539   while (master_list != NULL) {

   540     DictionaryEntry* p = master_list;

   541     master_list = master_list->next();

   542     p->set_next(NULL);

   543     symbolHandle class_name (thread, instanceKlass::cast((klassOop)(p->klass()))->name());

   544     unsigned int hash = compute_hash(class_name, Handle(thread, p->loader()));

   545     int index = hash_to_index(hash);

   546     p->set_hash(hash);

   547     p->set_next(bucket(index));

   548     set_entry(index, p);

   549   }

   550 }

   551 

   552 

   553 // ----------------------------------------------------------------------------

   554 #ifndef PRODUCT

   555 

   556 void Dictionary::print() {

   557   ResourceMark rm;

   558   HandleMark   hm;

   559 

   560   tty->print_cr("Java system dictionary (classes=%d)", number_of_entries());

   561   tty->print_cr("^ indicates that initiating loader is different from "

   562                 "defining loader");

   563 

   564   for (int index = 0; index < table_size(); index++) {

   565     for (DictionaryEntry* probe = bucket(index);

   566                           probe != NULL;

   567                           probe = probe->next()) {

   568       if (Verbose) tty->print("%4d: ", index);

   569       klassOop e = probe->klass();

   570       oop class_loader =  probe->loader();

   571       bool is_defining_class =

   572          (class_loader == instanceKlass::cast(e)->class_loader());

   573       tty->print("%s%s", is_defining_class ? " " : "^",

   574                    Klass::cast(e)->external_name());

   575       if (class_loader != NULL) {

   576         tty->print(", loader ");

   577         class_loader->print_value();

   578       }

   579       tty->cr();

   580     }

   581   }

   582 }

   583 

   584 #endif

   585 

   586 void Dictionary::verify() {

   587   guarantee(number_of_entries() >= 0, "Verify of system dictionary failed");

   588   int element_count = 0;

   589   for (int index = 0; index < table_size(); index++) {

   590     for (DictionaryEntry* probe = bucket(index);

   591                           probe != NULL;

   592                           probe = probe->next()) {

   593       klassOop e = probe->klass();

   594       oop class_loader = probe->loader();

   595       guarantee(Klass::cast(e)->oop_is_instance(),

   596                               "Verify of system dictionary failed");

   597       // class loader must be present;  a null class loader is the

   598       // boostrap loader

   599       guarantee(class_loader == NULL || class_loader->is_instance(),

   600                 "checking type of class_loader");

   601       e->verify();

   602       probe->verify_protection_domain_set();

   603       element_count++;

   604     }

   605   }

   606   guarantee(number_of_entries() == element_count,

   607             "Verify of system dictionary failed");

   608   debug_only(verify_lookup_length((double)number_of_entries() / table_size()));

   609 }