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.seconds() * 1000.0);
  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     // The WatcherThread is not a JavaThread so we do not honor the
  66     // safepoint protocol for the PeriodicTask_lock.
  67     MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
  68     int orig_num_tasks = _num_tasks;
  69 
  70     for(int index = 0; index < _num_tasks; index++) {
  71       _tasks[index]->execute_if_pending(delay_time);
  72       if (_num_tasks < orig_num_tasks) { // task dis-enrolled itself
  73         index--;  // re-do current slot as it has changed
  74         orig_num_tasks = _num_tasks;
  75       }
  76     }
  77   }
  78 }
  79 
  80 int PeriodicTask::time_to_wait() {
  81   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
  82 
  83   if (_num_tasks == 0) {
  84     return 0; // sleep until shutdown or a task is enrolled
  85   }
  86 
  87   int delay = _tasks[0]->time_to_next_interval();
  88   for (int index = 1; index < _num_tasks; index++) {
  89     delay = MIN2(delay, _tasks[index]->time_to_next_interval());
  90   }
  91   return delay;
  92 }
  93 
  94 
  95 PeriodicTask::PeriodicTask(size_t interval_time) :
  96   _counter(0), _interval((int) interval_time) {
  97   // Sanity check the interval time
  98   assert(_interval >= PeriodicTask::min_interval &&
  99          _interval %  PeriodicTask::interval_gran == 0,
 100               "improper PeriodicTask interval time");
 101 }
 102 
 103 PeriodicTask::~PeriodicTask() {
 104   // This PeriodicTask may have already been disenrolled by a call
 105   // to disenroll() before the PeriodicTask was deleted.
 106   disenroll();
 107 }
 108 
 109 // enroll the current PeriodicTask
 110 void PeriodicTask::enroll() {
 111   // Follow normal safepoint aware lock enter protocol if the caller does
 112   // not already own the PeriodicTask_lock. Otherwise, we don't try to
 113   // enter it again because VM internal Mutexes do not support recursion.
 114   //
 115   MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ? NULL
 116                                                       : PeriodicTask_lock);
 117 
 118   if (_num_tasks == PeriodicTask::max_tasks) {
 119     fatal("Overflow in PeriodicTask table");
 120   }
 121   _tasks[_num_tasks++] = this;
 122 
 123   WatcherThread* thread = WatcherThread::watcher_thread();
 124   if (thread != NULL) {
 125     thread->unpark();
 126   } else {
 127     WatcherThread::start();
 128   }
 129 }
 130 
 131 // disenroll the current PeriodicTask
 132 void PeriodicTask::disenroll() {
 133   // Follow normal safepoint aware lock enter protocol if the caller does
 134   // not already own the PeriodicTask_lock. Otherwise, we don't try to
 135   // enter it again because VM internal Mutexes do not support recursion.
 136   //
 137   MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ? NULL
 138                                                       : PeriodicTask_lock);
 139 
 140   int index;
 141   for(index = 0; index < _num_tasks && _tasks[index] != this; index++)
 142     ;
 143 
 144   if (index == _num_tasks) {
 145     return;
 146   }
 147 
 148   _num_tasks--;
 149 
 150   for (; index < _num_tasks; index++) {
 151     _tasks[index] = _tasks[index+1];
 152   }
 153 }