jdk8-mips64-public/hotspot: src/share/vm/classfile/placeholders.hpp@2c022e432e10 (annotated)

src/share/vm/classfile/placeholders.hpp@2c022e432e10 (annotated)

src/share/vm/classfile/placeholders.hpp

Fri, 20 Sep 2013 10:53:28 +0200

author: stefank
date: Fri, 20 Sep 2013 10:53:28 +0200
changeset 5769: 2c022e432e10
parent 4425: aefb345d3f5e
child 6876: 710a3c8b516e
child 8316: 626f594dffa6
permissions: -rw-r--r--

8024974: Incorrect use of GC_locker::is_active()
Summary: SymbolTable and StringTable can make calls to GC_locker::is_active() outside a safepoint. This isn't safe because the GC_locker active state (lock count) is only updated at a safepoint and only remains valid as long as _needs_gc is true. However, outside a safepoint_needs_gc can change to false at any time, which makes it impossible to do a correct call to is_active() in that context. In this case these calls can just be removed since the input argument to basic_add() should never be on the heap and so there's no need to check the GC_locker state. This change also adjusts the assert() in is_active() to makes sure all calls to this function are always done under a safepoint.
Reviewed-by: brutisso, dcubed
Contributed-by: per.liden@oracle.com

 /*
  * 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
  * questions.
  *
  */
 #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

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/classfile/placeholders.hpp@2c022e432e10 (annotated)

src/share/vm/classfile/placeholders.hpp