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 /*

  * Copyright (c) 2003, 2013, 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_CLASSFILE_PLACEHOLDERS_HPP

 #define SHARE_VM_CLASSFILE_PLACEHOLDERS_HPP

 #include "runtime/thread.hpp"

 #include "utilities/hashtable.hpp"

 class PlaceholderEntry;

 // Placeholder objects. These represent classes currently

 // being loaded, as well as arrays of primitives.

 //

 class PlaceholderTable : public TwoOopHashtable<Symbol*, mtClass> {

   friend class VMStructs;

 public:

   PlaceholderTable(int table_size);

   PlaceholderEntry* new_entry(int hash, Symbol* name, ClassLoaderData* loader_data, bool havesupername, Symbol* supername);

   void free_entry(PlaceholderEntry* entry);

   PlaceholderEntry* bucket(int i) {

     return (PlaceholderEntry*)Hashtable<Symbol*, mtClass>::bucket(i);

   }

   PlaceholderEntry** bucket_addr(int i) {

     return (PlaceholderEntry**)Hashtable<Symbol*, mtClass>::bucket_addr(i);

   }

   void add_entry(int index, PlaceholderEntry* new_entry) {

     Hashtable<Symbol*, mtClass>::add_entry(index, (HashtableEntry<Symbol*, mtClass>*)new_entry);

   }

   void add_entry(int index, unsigned int hash, Symbol* name,

                 ClassLoaderData* loader_data, bool havesupername, Symbol* supername);

   // This returns a Symbol* to match type for SystemDictionary

   Symbol* find_entry(int index, unsigned int hash,

                        Symbol* name, ClassLoaderData* loader_data);

   PlaceholderEntry* get_entry(int index, unsigned int hash,

                        Symbol* name, ClassLoaderData* loader_data);

 // caller to create a placeholder entry must enumerate an action

 // caller claims ownership of that action

 // For parallel classloading:

 // multiple LOAD_INSTANCE threads can proceed in parallel

 // multiple LOAD_SUPER threads can proceed in parallel

 // LOAD_SUPER needed to check for class circularity

 // DEFINE_CLASS: ultimately define class must be single threaded

 // on a class/classloader basis

 // so the head of that queue owns the token

 // and the rest of the threads return the result the first thread gets

  enum classloadAction {

     LOAD_INSTANCE = 1,             // calling load_instance_class

     LOAD_SUPER = 2,                // loading superclass for this class

     DEFINE_CLASS = 3               // find_or_define class

  };

   // find_and_add returns probe pointer - old or new

   // If no entry exists, add a placeholder entry and push SeenThread for classloadAction

   // If entry exists, reuse entry and push SeenThread for classloadAction

   PlaceholderEntry* find_and_add(int index, unsigned int hash,

                                  Symbol* name, ClassLoaderData* loader_data,

                                  classloadAction action, Symbol* supername,

                                  Thread* thread);

   void remove_entry(int index, unsigned int hash,

                     Symbol* name, ClassLoaderData* loader_data);

   // find_and_remove first removes SeenThread for classloadAction

   // If all queues are empty and definer is null, remove the PlacheholderEntry completely

   void find_and_remove(int index, unsigned int hash,

                        Symbol* name, ClassLoaderData* loader_data,

                        classloadAction action, Thread* thread);

   // GC support.

   void classes_do(KlassClosure* f);

   // JVMTI support

   void entries_do(void f(Symbol*));

 #ifndef PRODUCT

   void print();

 #endif

   void verify();

 };

 // SeenThread objects represent list of threads that are

 // currently performing a load action on a class.

 // For class circularity, set before loading a superclass.

 // For bootclasssearchpath, set before calling load_instance_class.

 // Defining must be single threaded on a class/classloader basis

 // For DEFINE_CLASS, the head of the queue owns the

 // define token and the rest of the threads wait to return the

 // result the first thread gets.

 class SeenThread: public CHeapObj<mtInternal> {

 private:

    Thread *_thread;

    SeenThread* _stnext;

    SeenThread* _stprev;

 public:

    SeenThread(Thread *thread) {

        _thread = thread;

        _stnext = NULL;

        _stprev = NULL;

    }

    Thread* thread()                const { return _thread;}

    void set_thread(Thread *thread) { _thread = thread; }

    SeenThread* next()              const { return _stnext;}

    void set_next(SeenThread *seen) { _stnext = seen; }

    void set_prev(SeenThread *seen) { _stprev = seen; }

 #ifndef PRODUCT

   void printActionQ() {

     SeenThread* seen = this;

     while (seen != NULL) {

       seen->thread()->print_value();

       tty->print(", ");

       seen = seen->next();

     }

   }

 #endif // PRODUCT

 };

 // Placeholder objects represent classes currently being loaded.

 // All threads examining the placeholder table must hold the

 // SystemDictionary_lock, so we don't need special precautions

 // on store ordering here.

 // The system dictionary is the only user of this class.

 class PlaceholderEntry : public HashtableEntry<Symbol*, mtClass> {

   friend class VMStructs;

  private:

   ClassLoaderData*  _loader_data;   // initiating loader

   bool              _havesupername; // distinguish between null supername, and unknown

   Symbol*           _supername;

   Thread*           _definer;       // owner of define token

   Klass*            _instanceKlass; // InstanceKlass from successful define

   SeenThread*       _superThreadQ;  // doubly-linked queue of Threads loading a superclass for this class

   SeenThread*       _loadInstanceThreadQ;  // loadInstance thread

                                     // can be multiple threads if classloader object lock broken by application

                                     // or if classloader supports parallel classloading

   SeenThread*       _defineThreadQ; // queue of Threads trying to define this class

                                     // including _definer

                                     // _definer owns token

                                     // queue waits for and returns results from _definer

  public:

   // Simple accessors, used only by SystemDictionary

   Symbol*            klassname()           const { return literal(); }

   ClassLoaderData*   loader_data()         const { return _loader_data; }

   void               set_loader_data(ClassLoaderData* loader_data) { _loader_data = loader_data; }

   bool               havesupername()       const { return _havesupername; }

   void               set_havesupername(bool havesupername) { _havesupername = havesupername; }

   Symbol*            supername()           const { return _supername; }

   void               set_supername(Symbol* supername) {

     _supername = supername;

     if (_supername != NULL) _supername->increment_refcount();

   }

   Thread*            definer()             const {return _definer; }

   void               set_definer(Thread* definer) { _definer = definer; }

   Klass*             instance_klass()      const {return _instanceKlass; }

   void               set_instance_klass(Klass* ik) { _instanceKlass = ik; }

   SeenThread*        superThreadQ()        const { return _superThreadQ; }

   void               set_superThreadQ(SeenThread* SeenThread) { _superThreadQ = SeenThread; }

   SeenThread*        loadInstanceThreadQ() const { return _loadInstanceThreadQ; }

   void               set_loadInstanceThreadQ(SeenThread* SeenThread) { _loadInstanceThreadQ = SeenThread; }

   SeenThread*        defineThreadQ()        const { return _defineThreadQ; }

   void               set_defineThreadQ(SeenThread* SeenThread) { _defineThreadQ = SeenThread; }

   PlaceholderEntry* next() const {

     return (PlaceholderEntry*)HashtableEntry<Symbol*, mtClass>::next();

   }

   PlaceholderEntry** next_addr() {

     return (PlaceholderEntry**)HashtableEntry<Symbol*, mtClass>::next_addr();

   }

   // Test for equality

   // Entries are unique for class/classloader name pair

   bool equals(Symbol* class_name, ClassLoaderData* loader) const {

     return (klassname() == class_name && loader_data() == loader);

   }

   SeenThread* actionToQueue(PlaceholderTable::classloadAction action) {

     SeenThread* queuehead;

     switch (action) {

       case PlaceholderTable::LOAD_INSTANCE:

          queuehead = _loadInstanceThreadQ;

          break;

       case PlaceholderTable::LOAD_SUPER:

          queuehead = _superThreadQ;

          break;

       case PlaceholderTable::DEFINE_CLASS:

          queuehead = _defineThreadQ;

          break;

       default: Unimplemented();

     }

     return queuehead;

   }

   void set_threadQ(SeenThread* seenthread, PlaceholderTable::classloadAction action) {

     switch (action) {

       case PlaceholderTable::LOAD_INSTANCE:

          _loadInstanceThreadQ = seenthread;

          break;

       case PlaceholderTable::LOAD_SUPER:

          _superThreadQ = seenthread;

          break;

       case PlaceholderTable::DEFINE_CLASS:

          _defineThreadQ = seenthread;

          break;

       default: Unimplemented();

     }

     return;

   }

   bool super_load_in_progress() {

      return (_superThreadQ != NULL);

   }

   bool instance_load_in_progress() {

     return (_loadInstanceThreadQ != NULL);

   }

   bool define_class_in_progress() {

     return (_defineThreadQ != NULL);

   }

 // Doubly-linked list of Threads per action for class/classloader pair

 // Class circularity support: links in thread before loading superclass

 // bootstrapsearchpath support: links in a thread before load_instance_class

 // definers: use as queue of define requestors, including owner of

 // define token. Appends for debugging of requestor order

   void add_seen_thread(Thread* thread, PlaceholderTable::classloadAction action) {

     assert_lock_strong(SystemDictionary_lock);

     SeenThread* threadEntry = new SeenThread(thread);

     SeenThread* seen = actionToQueue(action);

     if (seen == NULL) {

       set_threadQ(threadEntry, action);

       return;

     }

     SeenThread* next;

     while ((next = seen->next()) != NULL) {

       seen = next;

     }

     seen->set_next(threadEntry);

     threadEntry->set_prev(seen);

     return;

   }

   bool check_seen_thread(Thread* thread, PlaceholderTable::classloadAction action) {

     assert_lock_strong(SystemDictionary_lock);

     SeenThread* threadQ = actionToQueue(action);

     SeenThread* seen = threadQ;

     while (seen) {

       if (thread == seen->thread()) {

         return true;

       }

       seen = seen->next();

     }

     return false;

   }

   // returns true if seenthreadQ is now empty

   // Note, caller must ensure probe still exists while holding

   // SystemDictionary_lock

   // ignores if cleanup has already been done

   // if found, deletes SeenThread

   bool remove_seen_thread(Thread* thread, PlaceholderTable::classloadAction action) {

     assert_lock_strong(SystemDictionary_lock);

     SeenThread* threadQ = actionToQueue(action);

     SeenThread* seen = threadQ;

     SeenThread* prev = NULL;

     while (seen) {

       if (thread == seen->thread()) {

         if (prev) {

           prev->set_next(seen->next());

         } else {

           set_threadQ(seen->next(), action);

         }

         if (seen->next()) {

           seen->next()->set_prev(prev);

         }

         delete seen;

         break;

       }

       prev = seen;

       seen = seen->next();

     }

     return (actionToQueue(action) == NULL);

   }

   // GC support

   // Applies "f->do_oop" to all root oops in the placeholder table.

   void classes_do(KlassClosure* closure);

   // Print method doesn't append a cr

   void print() const  PRODUCT_RETURN;

   void verify() const;

 };

 #endif // SHARE_VM_CLASSFILE_PLACEHOLDERS_HPP