| /* |
| * Copyright 1997-2007 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. |
| * |
| */ |
| |
| // A PeriodicTask has the sole purpose of executing its task |
| // function with regular intervals. |
| // Usage: |
| // PeriodicTask pf(10); |
| // pf.enroll(); |
| // ... |
| // pf.disenroll(); |
| |
| class PeriodicTask: public CHeapObj { |
| public: |
| // Useful constants. |
| // The interval constants are used to ensure the declared interval |
| // is appropriate; it must be between min_interval and max_interval, |
| // and have a granularity of interval_gran (all in millis). |
| enum { max_tasks = 10, // Max number of periodic tasks in system |
| interval_gran = 10, |
| min_interval = 10, |
| max_interval = 10000 }; |
| |
| static int num_tasks() { return _num_tasks; } |
| |
| private: |
| size_t _counter; |
| const size_t _interval; |
| |
| static int _num_tasks; |
| static PeriodicTask* _tasks[PeriodicTask::max_tasks]; |
| static void real_time_tick(size_t delay_time); |
| |
| #ifndef PRODUCT |
| static elapsedTimer _timer; // measures time between ticks |
| static int _ticks; // total number of ticks |
| static int _intervalHistogram[max_interval]; // to check spacing of timer interrupts |
| public: |
| static void print_intervals(); |
| #endif |
| // Only the WatcherThread can cause us to execute PeriodicTasks |
| friend class WatcherThread; |
| public: |
| PeriodicTask(size_t interval_time); // interval is in milliseconds of elapsed time |
| ~PeriodicTask(); |
| |
| // Tells whether is enrolled |
| bool is_enrolled() const; |
| |
| // Make the task active |
| // NOTE: this may only be called before the WatcherThread has been started |
| void enroll(); |
| |
| // Make the task deactive |
| // NOTE: this may only be called either while the WatcherThread is |
| // inactive or by a task from within its task() method. One-shot or |
| // several-shot tasks may be implemented this way. |
| void disenroll(); |
| |
| void execute_if_pending(size_t delay_time) { |
| _counter += delay_time; |
| if (_counter >= _interval) { |
| _counter = 0; |
| task(); |
| } |
| } |
| |
| // Returns how long (time in milliseconds) before the next time we should |
| // execute this task. |
| size_t time_to_next_interval() const { |
| assert(_interval > _counter, "task counter greater than interval?"); |
| return _interval - _counter; |
| } |
| |
| // Calculate when the next periodic task will fire. |
| // Called by the WatcherThread's run method. |
| // This assumes that periodic tasks aren't entering the system |
| // dynamically, except for during startup. |
| static size_t time_to_wait() { |
| if (_num_tasks == 0) { |
| // Don't wait any more; shut down the thread since we don't |
| // currently support dynamic enrollment. |
| return 0; |
| } |
| |
| size_t delay = _tasks[0]->time_to_next_interval(); |
| for (int index = 1; index < _num_tasks; index++) { |
| delay = MIN2(delay, _tasks[index]->time_to_next_interval()); |
| } |
| return delay; |
| } |
| |
| // The task to perform at each period |
| virtual void task() = 0; |
| }; |
| |
| class TimeMillisUpdateTask : public PeriodicTask { |
| private: |
| static TimeMillisUpdateTask* _task; |
| public: |
| TimeMillisUpdateTask(int interval) : PeriodicTask(interval) {} |
| void task(); |
| static void engage(); |
| static void disengage(); |
| }; |