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hotspot/src/share/vm/runtime/vmThread.hpp

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+/*
+ * Copyright 1998-2006 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.
+ *
+ */
+
+//
+// Prioritized queue of VM operations.
+//
+// Encapsulates both queue management and
+// and priority policy
+//
+class VMOperationQueue : public CHeapObj {
+ 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 Thread {
+ 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; }
+
+  char* name() const { return (char*)"VM Thread"; }
+
+  // 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);
+
+  // 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;
+};