1 /*
   2  * Copyright (c) 1997, 2019, 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/mutexLocker.inline.hpp"
  29 #include "runtime/task.hpp"
  30 #include "runtime/thread.inline.hpp"
  31 #include "runtime/timer.hpp"
  32 
  33 int PeriodicTask::_num_tasks = 0;
  34 PeriodicTask* PeriodicTask::_tasks[PeriodicTask::max_tasks];
  35 
  36 void PeriodicTask::real_time_tick(int delay_time) {
  37   assert(Thread::current()->is_Watcher_thread(), "must be WatcherThread");
  38 
  39   // The WatcherThread does not participate in the safepoint protocol
  40   // for the PeriodicTask_lock because it is not a JavaThread.
  41   MutexLocker ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
  42   int orig_num_tasks = _num_tasks;
  43 
  44   for(int index = 0; index < _num_tasks; index++) {
  45     _tasks[index]->execute_if_pending(delay_time);
  46     if (_num_tasks < orig_num_tasks) { // task dis-enrolled itself
  47       index--;  // re-do current slot as it has changed
  48       orig_num_tasks = _num_tasks;
  49     }
  50   }
  51 }
  52 
  53 int PeriodicTask::time_to_wait() {
  54   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
  55 
  56   if (_num_tasks == 0) {
  57     return 0; // sleep until shutdown or a task is enrolled
  58   }
  59 
  60   int delay = _tasks[0]->time_to_next_interval();
  61   for (int index = 1; index < _num_tasks; index++) {
  62     delay = MIN2(delay, _tasks[index]->time_to_next_interval());
  63   }
  64   return delay;
  65 }
  66 
  67 
  68 PeriodicTask::PeriodicTask(size_t interval_time) :
  69   _counter(0), _interval((int) interval_time) {
  70   // Sanity check the interval time
  71   assert(_interval >= PeriodicTask::min_interval &&
  72          _interval %  PeriodicTask::interval_gran == 0,
  73               "improper PeriodicTask interval time");
  74 }
  75 
  76 PeriodicTask::~PeriodicTask() {
  77   // This PeriodicTask may have already been disenrolled by a call
  78   // to disenroll() before the PeriodicTask was deleted.
  79   disenroll();
  80 }
  81 
  82 // enroll the current PeriodicTask
  83 void PeriodicTask::enroll() {
  84   // Follow normal safepoint aware lock enter protocol if the caller does
  85   // not already own the PeriodicTask_lock. Otherwise, we don't try to
  86   // enter it again because VM internal Mutexes do not support recursion.
  87   //
  88   MutexLocker ml(PeriodicTask_lock->owned_by_self() ? NULL : PeriodicTask_lock);
  89 
  90   if (_num_tasks == PeriodicTask::max_tasks) {
  91     fatal("Overflow in PeriodicTask table");
  92   } else {
  93     _tasks[_num_tasks++] = this;
  94   }
  95 
  96   WatcherThread* thread = WatcherThread::watcher_thread();
  97   if (thread != NULL) {
  98     thread->unpark();
  99   } else {
 100     WatcherThread::start();
 101   }
 102 }
 103 
 104 // disenroll the current PeriodicTask
 105 void PeriodicTask::disenroll() {
 106   // Follow normal safepoint aware lock enter protocol if the caller does
 107   // not already own the PeriodicTask_lock. Otherwise, we don't try to
 108   // enter it again because VM internal Mutexes do not support recursion.
 109   //
 110   MutexLocker ml(PeriodicTask_lock->owned_by_self() ? NULL : PeriodicTask_lock);
 111 
 112   int index;
 113   for(index = 0; index < _num_tasks && _tasks[index] != this; index++)
 114     ;
 115 
 116   if (index == _num_tasks) {
 117     return;
 118   }
 119 
 120   _num_tasks--;
 121 
 122   for (; index < _num_tasks; index++) {
 123     _tasks[index] = _tasks[index+1];
 124   }
 125 }