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