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 /*

  * Copyright (c) 1998, 2012, 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_RUNTIME_VMTHREAD_HPP

 #define SHARE_VM_RUNTIME_VMTHREAD_HPP

 #include "runtime/perfData.hpp"

 #include "runtime/thread.inline.hpp"

 #include "runtime/vm_operations.hpp"

 //

 // Prioritized queue of VM operations.

 //

 // Encapsulates both queue management and

 // and priority policy

 //

 class VMOperationQueue : public CHeapObj<mtInternal> {

  private:

   enum Priorities {

      SafepointPriority, // Highest priority (operation executed at a safepoint)

      MediumPriority,    // Medium priority

      nof_priorities

   };

   // We maintain a doubled linked list, with explicit count.

   int           _queue_length[nof_priorities];

   int           _queue_counter;

   VM_Operation* _queue       [nof_priorities];

   // we also allow the vmThread to register the ops it has drained so we

   // can scan them from oops_do

   VM_Operation* _drain_list;

   // Double-linked non-empty list insert.

   void insert(VM_Operation* q,VM_Operation* n);

   void unlink(VM_Operation* q);

   // Basic queue manipulation

   bool queue_empty                (int prio);

   void queue_add_front            (int prio, VM_Operation *op);

   void queue_add_back             (int prio, VM_Operation *op);

   VM_Operation* queue_remove_front(int prio);

   void queue_oops_do(int queue, OopClosure* f);

   void drain_list_oops_do(OopClosure* f);

   VM_Operation* queue_drain(int prio);

   // lock-free query: may return the wrong answer but must not break

   bool queue_peek(int prio) { return _queue_length[prio] > 0; }

  public:

   VMOperationQueue();

   // Highlevel operations. Encapsulates policy

   bool add(VM_Operation *op);

   VM_Operation* remove_next();                        // Returns next or null

   VM_Operation* remove_next_at_safepoint_priority()   { return queue_remove_front(SafepointPriority); }

   VM_Operation* drain_at_safepoint_priority() { return queue_drain(SafepointPriority); }

   void set_drain_list(VM_Operation* list) { _drain_list = list; }

   bool peek_at_safepoint_priority() { return queue_peek(SafepointPriority); }

   // GC support

   void oops_do(OopClosure* f);

   void verify_queue(int prio) PRODUCT_RETURN;

 };

 //

 // A single VMThread (the primordial thread) spawns all other threads

 // and is itself used by other threads to offload heavy vm operations

 // like scavenge, garbage_collect etc.

 //

 class VMThread: public NamedThread {

  private:

   static ThreadPriority _current_priority;

   static bool _should_terminate;

   static bool _terminated;

   static Monitor * _terminate_lock;

   static PerfCounter* _perf_accumulated_vm_operation_time;

   void evaluate_operation(VM_Operation* op);

  public:

   // Constructor

   VMThread();

   // Tester

   bool is_VM_thread() const                      { return true; }

   bool is_GC_thread() const                      { return true; }

   // The ever running loop for the VMThread

   void loop();

   // Called to stop the VM thread

   static void wait_for_vm_thread_exit();

   static bool should_terminate()                  { return _should_terminate; }

   static bool is_terminated()                     { return _terminated == true; }

   // Execution of vm operation

   static void execute(VM_Operation* op);

   // Returns the current vm operation if any.

   static VM_Operation* vm_operation()             { return _cur_vm_operation;   }

   // Returns the single instance of VMThread.

   static VMThread* vm_thread()                    { return _vm_thread; }

   // GC support

   void oops_do(OopClosure* f, CLDToOopClosure* cld_f, CodeBlobClosure* cf);

   // Debugging

   void print_on(outputStream* st) const;

   void print() const                              { print_on(tty); }

   void verify();

   // Performance measurement

   static PerfCounter* perf_accumulated_vm_operation_time()               { return _perf_accumulated_vm_operation_time; }

   // Entry for starting vm thread

   virtual void run();

   // Creations/Destructions

   static void create();

   static void destroy();

  private:

   // VM_Operation support

   static VM_Operation*     _cur_vm_operation;   // Current VM operation

   static VMOperationQueue* _vm_queue;           // Queue (w/ policy) of VM operations

   // Pointer to single-instance of VM thread

   static VMThread*     _vm_thread;

 };

 #endif // SHARE_VM_RUNTIME_VMTHREAD_HPP