1 /*
   2  * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "memory/allocation.hpp"
  27 #include "runtime/init.hpp"
  28 #include "runtime/task.hpp"
  29 #include "runtime/thread.inline.hpp"
  30 #include "runtime/timer.hpp"
  31 
  32 int PeriodicTask::_num_tasks = 0;
  33 PeriodicTask* PeriodicTask::_tasks[PeriodicTask::max_tasks];
  34 #ifndef PRODUCT
  35 elapsedTimer PeriodicTask::_timer;
  36 int PeriodicTask::_intervalHistogram[PeriodicTask::max_interval];
  37 int PeriodicTask::_ticks;
  38 
  39 void PeriodicTask::print_intervals() {
  40   if (ProfilerCheckIntervals) {
  41     for (int i = 0; i < PeriodicTask::max_interval; i++) {
  42       int n = _intervalHistogram[i];
  43       if (n > 0) tty->print_cr("%3d: %5d (%4.1f%%)", i, n, 100.0 * n / _ticks);
  44     }
  45   }
  46 }
  47 #endif
  48 
  49 void PeriodicTask::real_time_tick(int delay_time) {
  50   assert(Thread::current()->is_Watcher_thread(), "must be WatcherThread");
  51 
  52 #ifndef PRODUCT
  53   if (ProfilerCheckIntervals) {
  54     _ticks++;
  55     _timer.stop();
  56     int ms = (int)_timer.milliseconds();
  57     _timer.reset();
  58     _timer.start();
  59     if (ms >= PeriodicTask::max_interval) ms = PeriodicTask::max_interval - 1;
  60     _intervalHistogram[ms]++;
  61   }
  62 #endif
  63 
  64   {
  65     MutexLocker ml(PeriodicTask_lock);


  66     int orig_num_tasks = _num_tasks;
  67 
  68     for(int index = 0; index < _num_tasks; index++) {
  69       _tasks[index]->execute_if_pending(delay_time);
  70       if (_num_tasks < orig_num_tasks) { // task dis-enrolled itself
  71         index--;  // re-do current slot as it has changed
  72         orig_num_tasks = _num_tasks;
  73       }
  74     }
  75   }
  76 }
  77 
  78 int PeriodicTask::time_to_wait() {
  79   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
  80 
  81   if (_num_tasks == 0) {
  82     return 0; // sleep until shutdown or a task is enrolled
  83   }
  84 
  85   int delay = _tasks[0]->time_to_next_interval();
  86   for (int index = 1; index < _num_tasks; index++) {
  87     delay = MIN2(delay, _tasks[index]->time_to_next_interval());
  88   }
  89   return delay;
  90 }
  91 
  92 
  93 PeriodicTask::PeriodicTask(size_t interval_time) :
  94   _counter(0), _interval((int) interval_time) {
  95   // Sanity check the interval time
  96   assert(_interval >= PeriodicTask::min_interval &&
  97          _interval %  PeriodicTask::interval_gran == 0,
  98               "improper PeriodicTask interval time");
  99 }
 100 
 101 PeriodicTask::~PeriodicTask() {
 102   // This PeriodicTask may have already been disenrolled by a call
 103   // to disenroll() before the PeriodicTask was deleted.
 104   disenroll();
 105 }
 106 
 107 // enroll the current PeriodicTask
 108 void PeriodicTask::enroll() {
 109   // Follow normal safepoint aware lock enter protocol if the caller does
 110   // not already own the PeriodicTask_lock. Otherwise, we don't try to
 111   // enter it again because VM internal Mutexes do not support recursion.
 112   //
 113   MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ? NULL
 114                                                       : PeriodicTask_lock);
 115 
 116   if (_num_tasks == PeriodicTask::max_tasks) {
 117     fatal("Overflow in PeriodicTask table");
 118   } else {
 119     _tasks[_num_tasks++] = this;
 120   }
 121 
 122   WatcherThread* thread = WatcherThread::watcher_thread();
 123   if (thread != NULL) {
 124     thread->unpark();
 125   } else {
 126     WatcherThread::start();
 127   }
 128 }
 129 
 130 // disenroll the current PeriodicTask
 131 void PeriodicTask::disenroll() {
 132   // Follow normal safepoint aware lock enter protocol if the caller does
 133   // not already own the PeriodicTask_lock. Otherwise, we don't try to
 134   // enter it again because VM internal Mutexes do not support recursion.
 135   //
 136   MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ? NULL
 137                                                       : PeriodicTask_lock);
 138 
 139   int index;
 140   for(index = 0; index < _num_tasks && _tasks[index] != this; index++)
 141     ;
 142 
 143   if (index == _num_tasks) {
 144     return;
 145   }
 146 
 147   _num_tasks--;
 148 
 149   for (; index < _num_tasks; index++) {
 150     _tasks[index] = _tasks[index+1];
 151   }
 152 }
--- EOF ---