1/*
2 * Copyright (C) 2016 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
14 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
17 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
18 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23 * THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "config.h"
27#include "GenericTaskQueue.h"
28
29#include <wtf/Lock.h>
30#include <wtf/MainThread.h>
31#include <wtf/NeverDestroyed.h>
32
33namespace WebCore {
34
35TaskDispatcher<Timer>::TaskDispatcher()
36{
37}
38
39void TaskDispatcher<Timer>::postTask(Function<void()>&& function)
40{
41 {
42 auto locker = holdLock(sharedLock());
43 m_pendingTasks.append(WTFMove(function));
44 pendingDispatchers().append(makeWeakPtr(*this));
45 }
46
47 auto startTimer = [] {
48 if (!sharedTimer().isActive())
49 sharedTimer().startOneShot(0_s);
50 };
51 if (isMainThread())
52 startTimer();
53 else
54 callOnMainThread(WTFMove(startTimer));
55}
56
57Timer& TaskDispatcher<Timer>::sharedTimer()
58{
59 ASSERT(isMainThread());
60 static NeverDestroyed<Timer> timer([] { TaskDispatcher<Timer>::sharedTimerFired(); });
61 return timer.get();
62}
63
64Lock& TaskDispatcher<Timer>::sharedLock()
65{
66 static NeverDestroyed<Lock> lock;
67 return lock;
68}
69
70void TaskDispatcher<Timer>::sharedTimerFired()
71{
72 ASSERT(!sharedTimer().isActive());
73
74 // Copy the pending events first because we don't want to process synchronously the new events
75 // queued by the JS events handlers that are executed in the loop below.
76 Deque<WeakPtr<TaskDispatcher<Timer>>> queuedDispatchers;
77 {
78 auto locker = holdLock(sharedLock());
79 queuedDispatchers = WTFMove(pendingDispatchers());
80 }
81 while (!queuedDispatchers.isEmpty()) {
82 WeakPtr<TaskDispatcher<Timer>> dispatcher = queuedDispatchers.takeFirst();
83 if (!dispatcher)
84 continue;
85 dispatcher->dispatchOneTask();
86 }
87}
88
89
90Deque<WeakPtr<TaskDispatcher<Timer>>>& TaskDispatcher<Timer>::pendingDispatchers()
91{
92 static LazyNeverDestroyed<Deque<WeakPtr<TaskDispatcher<Timer>>>> dispatchers;
93
94 static std::once_flag onceFlag;
95 std::call_once(onceFlag, [] {
96 dispatchers.construct();
97 });
98
99 return dispatchers.get();
100}
101
102void TaskDispatcher<Timer>::dispatchOneTask()
103{
104 WTF::Function<void()> task;
105 {
106 auto locker = holdLock(sharedLock());
107 ASSERT(!m_pendingTasks.isEmpty());
108 task = m_pendingTasks.takeFirst();
109 }
110 task();
111}
112
113}
114
115