1/*
2 * Copyright (C) 2006, 2008 Apple Inc. All rights reserved.
3 * Copyright (C) 2009 Google Inc. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
15 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
17 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
18 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
19 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
20 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
21 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
22 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include "config.h"
28#include "ThreadTimers.h"
29
30#include "SharedTimer.h"
31#include "ThreadGlobalData.h"
32#include "Timer.h"
33#include <wtf/CurrentTime.h>
34#include <wtf/MainThread.h>
35
36#if PLATFORM(IOS)
37#include "WebCoreThread.h"
38#endif
39
40namespace WebCore {
41
42// Fire timers for this length of time, and then quit to let the run loop process user input events.
43// 100ms is about a perceptable delay in UI, so use a half of that as a threshold.
44// This is to prevent UI freeze when there are too many timers or machine performance is low.
45static const double maxDurationOfFiringTimers = 0.050;
46
47// Timers are created, started and fired on the same thread, and each thread has its own ThreadTimers
48// copy to keep the heap and a set of currently firing timers.
49
50static MainThreadSharedTimer* mainThreadSharedTimer()
51{
52    static MainThreadSharedTimer* timer = new MainThreadSharedTimer;
53    return timer;
54}
55
56ThreadTimers::ThreadTimers()
57    : m_sharedTimer(0)
58    , m_firingTimers(false)
59    , m_pendingSharedTimerFireTime(0)
60{
61    if (isUIThread())
62        setSharedTimer(mainThreadSharedTimer());
63}
64
65// A worker thread may initialize SharedTimer after some timers are created.
66// Also, SharedTimer can be replaced with 0 before all timers are destroyed.
67void ThreadTimers::setSharedTimer(SharedTimer* sharedTimer)
68{
69    if (m_sharedTimer) {
70        m_sharedTimer->setFiredFunction(0);
71        m_sharedTimer->stop();
72        m_pendingSharedTimerFireTime = 0;
73    }
74
75    m_sharedTimer = sharedTimer;
76
77    if (sharedTimer) {
78        m_sharedTimer->setFiredFunction(ThreadTimers::sharedTimerFired);
79        updateSharedTimer();
80    }
81}
82
83void ThreadTimers::updateSharedTimer()
84{
85    if (!m_sharedTimer)
86        return;
87
88    if (m_firingTimers || m_timerHeap.isEmpty()) {
89        m_pendingSharedTimerFireTime = 0;
90        m_sharedTimer->stop();
91    } else {
92        double nextFireTime = m_timerHeap.first()->m_nextFireTime;
93        double currentMonotonicTime = monotonicallyIncreasingTime();
94        if (m_pendingSharedTimerFireTime) {
95            // No need to restart the timer if both the pending fire time and the new fire time are in the past.
96            if (m_pendingSharedTimerFireTime <= currentMonotonicTime && nextFireTime <= currentMonotonicTime)
97                return;
98        }
99        m_pendingSharedTimerFireTime = nextFireTime;
100        m_sharedTimer->setFireInterval(std::max(nextFireTime - currentMonotonicTime, 0.0));
101    }
102}
103
104void ThreadTimers::sharedTimerFired()
105{
106    // Redirect to non-static method.
107    threadGlobalData().threadTimers().sharedTimerFiredInternal();
108}
109
110void ThreadTimers::sharedTimerFiredInternal()
111{
112    ASSERT(isMainThread() || (!isWebThread() && !isUIThread()));
113    // Do a re-entrancy check.
114    if (m_firingTimers)
115        return;
116    m_firingTimers = true;
117    m_pendingSharedTimerFireTime = 0;
118
119    double fireTime = monotonicallyIncreasingTime();
120    double timeToQuit = fireTime + maxDurationOfFiringTimers;
121
122    while (!m_timerHeap.isEmpty() && m_timerHeap.first()->m_nextFireTime <= fireTime) {
123        TimerBase* timer = m_timerHeap.first();
124        timer->m_nextFireTime = 0;
125        timer->m_unalignedNextFireTime = 0;
126        timer->heapDeleteMin();
127
128        double interval = timer->repeatInterval();
129        timer->setNextFireTime(interval ? fireTime + interval : 0);
130
131        // Once the timer has been fired, it may be deleted, so do nothing else with it after this point.
132        timer->fired();
133
134        // Catch the case where the timer asked timers to fire in a nested event loop, or we are over time limit.
135        if (!m_firingTimers || timeToQuit < monotonicallyIncreasingTime())
136            break;
137    }
138
139    m_firingTimers = false;
140
141    updateSharedTimer();
142}
143
144void ThreadTimers::fireTimersInNestedEventLoop()
145{
146    // Reset the reentrancy guard so the timers can fire again.
147    m_firingTimers = false;
148    updateSharedTimer();
149}
150
151} // namespace WebCore
152
153