--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/classfile/placeholders.hpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,331 @@
+/*
+ * Copyright 2003-2007 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+class PlaceholderEntry;
+
+// Placeholder objects. These represent classes currently
+// being loaded, as well as arrays of primitives.
+//
+
+class PlaceholderTable : public TwoOopHashtable {
+  friend class VMStructs;
+
+public:
+  PlaceholderTable(int table_size);
+
+  PlaceholderEntry* new_entry(int hash, symbolOop name, oop loader, bool havesupername, symbolOop supername);
+
+  PlaceholderEntry* bucket(int i) {
+    return (PlaceholderEntry*)Hashtable::bucket(i);
+  }
+
+  PlaceholderEntry** bucket_addr(int i) {
+    return (PlaceholderEntry**)Hashtable::bucket_addr(i);
+  }
+
+  void add_entry(int index, PlaceholderEntry* new_entry) {
+    Hashtable::add_entry(index, (HashtableEntry*)new_entry);
+  }
+
+  void add_entry(int index, unsigned int hash, symbolHandle name,
+                Handle loader, bool havesupername, symbolHandle supername);
+
+// This returns a symbolOop to match type for SystemDictionary
+  symbolOop find_entry(int index, unsigned int hash,
+                       symbolHandle name, Handle loader);
+
+  PlaceholderEntry* get_entry(int index, unsigned int hash,
+                       symbolHandle name, Handle loader);
+
+// 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
+  // If entry exists, reuse entry and push SeenThread for classloadAction
+  PlaceholderEntry* find_and_add(int index, unsigned int hash,
+                                 symbolHandle name, Handle loader,
+                                 classloadAction action, symbolHandle supername,
+                                 Thread* thread);
+
+  void remove_entry(int index, unsigned int hash,
+                    symbolHandle name, Handle loader);
+
+// Remove placeholder information
+  void find_and_remove(int index, unsigned int hash,
+                       symbolHandle name, Handle loader, Thread* thread);
+
+  // GC support.
+  void oops_do(OopClosure* f);
+
+  // JVMTI support
+  void entries_do(void f(symbolOop, oop));
+
+#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 {
+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 {
+  friend class VMStructs;
+
+
+ private:
+  oop               _loader;        // initiating loader
+  bool              _havesupername; // distinguish between null supername, and unknown
+  symbolOop         _supername;
+  Thread*           _definer;       // owner of define token
+  klassOop          _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
+  symbolOop          klass()               const { return (symbolOop)literal(); }
+  symbolOop*         klass_addr()          { return (symbolOop*)literal_addr(); }
+
+  oop                loader()              const { return _loader; }
+  void               set_loader(oop loader) { _loader = loader; }
+  oop*               loader_addr()         { return &_loader; }
+
+  bool               havesupername()       const { return _havesupername; }
+  void               set_havesupername(bool havesupername) { _havesupername = havesupername; }
+
+  symbolOop          supername()           const { return _supername; }
+  void               set_supername(symbolOop supername) { _supername = supername; }
+  symbolOop*         supername_addr()      { return &_supername; }
+
+  Thread*            definer()             const {return _definer; }
+  void               set_definer(Thread* definer) { _definer = definer; }
+
+  klassOop           instanceKlass()     const {return _instanceKlass; }
+  void               set_instanceKlass(klassOop instanceKlass) { _instanceKlass = instanceKlass; }
+  klassOop*          instanceKlass_addr()   { return &_instanceKlass; }
+
+  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::next();
+  }
+
+  PlaceholderEntry** next_addr() {
+    return (PlaceholderEntry**)HashtableEntry::next_addr();
+  }
+
+  // Test for equality
+  // Entries are unique for class/classloader name pair
+  bool equals(symbolOop class_name, oop class_loader) const {
+    return (klass() == class_name && loader() == class_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 oops_do(OopClosure* blk);
+
+  // Print method doesn't append a cr
+  void print() const  PRODUCT_RETURN;
+  void verify() const;
+};