1/*
2 * Copyright (C) 2007-2017 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 *
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 * 3. Neither the name of Apple Inc. ("Apple") nor the names of
14 * its contributors may be used to endorse or promote products derived
15 * from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include "config.h"
30#include <wtf/MainThread.h>
31
32#include <mutex>
33#include <wtf/Condition.h>
34#include <wtf/Deque.h>
35#include <wtf/Lock.h>
36#include <wtf/MonotonicTime.h>
37#include <wtf/NeverDestroyed.h>
38#include <wtf/StdLibExtras.h>
39#include <wtf/ThreadSpecific.h>
40#include <wtf/Threading.h>
41
42namespace WTF {
43
44static bool callbacksPaused; // This global variable is only accessed from main thread.
45static Lock mainThreadFunctionQueueMutex;
46
47static Deque<Function<void ()>>& functionQueue()
48{
49 static NeverDestroyed<Deque<Function<void ()>>> functionQueue;
50 return functionQueue;
51}
52
53// Share this initializeKey with initializeMainThread and initializeMainThreadToProcessMainThread.
54static std::once_flag initializeKey;
55void initializeMainThread()
56{
57 std::call_once(initializeKey, [] {
58 initializeThreading();
59 initializeMainThreadPlatform();
60 });
61}
62
63#if PLATFORM(COCOA)
64#if !USE(WEB_THREAD)
65void initializeMainThreadToProcessMainThread()
66{
67 std::call_once(initializeKey, [] {
68 initializeThreading();
69 initializeMainThreadToProcessMainThreadPlatform();
70 });
71}
72#else
73void initializeWebThread()
74{
75 static std::once_flag initializeKey;
76 std::call_once(initializeKey, [] {
77 initializeWebThreadPlatform();
78 });
79}
80#endif // !USE(WEB_THREAD)
81#endif // PLATFORM(COCOA)
82
83#if !USE(WEB_THREAD)
84bool canAccessThreadLocalDataForThread(Thread& thread)
85{
86 return &thread == &Thread::current();
87}
88#endif
89
90// 0.1 sec delays in UI is approximate threshold when they become noticeable. Have a limit that's half of that.
91static const auto maxRunLoopSuspensionTime = 50_ms;
92
93void dispatchFunctionsFromMainThread()
94{
95 ASSERT(isMainThread());
96
97 if (callbacksPaused)
98 return;
99
100 auto startTime = MonotonicTime::now();
101
102 Function<void ()> function;
103
104 while (true) {
105 {
106 std::lock_guard<Lock> lock(mainThreadFunctionQueueMutex);
107 if (!functionQueue().size())
108 break;
109
110 function = functionQueue().takeFirst();
111 }
112
113 function();
114
115 // Clearing the function can have side effects, so do so outside of the lock above.
116 function = nullptr;
117
118 // If we are running accumulated functions for too long so UI may become unresponsive, we need to
119 // yield so the user input can be processed. Otherwise user may not be able to even close the window.
120 // This code has effect only in case the scheduleDispatchFunctionsOnMainThread() is implemented in a way that
121 // allows input events to be processed before we are back here.
122 if (MonotonicTime::now() - startTime > maxRunLoopSuspensionTime) {
123 scheduleDispatchFunctionsOnMainThread();
124 break;
125 }
126 }
127}
128
129void callOnMainThread(Function<void()>&& function)
130{
131 ASSERT(function);
132
133 bool needToSchedule = false;
134
135 {
136 std::lock_guard<Lock> lock(mainThreadFunctionQueueMutex);
137 needToSchedule = functionQueue().size() == 0;
138 functionQueue().append(WTFMove(function));
139 }
140
141 if (needToSchedule)
142 scheduleDispatchFunctionsOnMainThread();
143}
144
145void setMainThreadCallbacksPaused(bool paused)
146{
147 ASSERT(isMainThread());
148
149 if (callbacksPaused == paused)
150 return;
151
152 callbacksPaused = paused;
153
154 if (!callbacksPaused)
155 scheduleDispatchFunctionsOnMainThread();
156}
157
158bool isMainThreadOrGCThread()
159{
160 if (Thread::mayBeGCThread())
161 return true;
162
163 return isMainThread();
164}
165
166void callOnMainThreadAndWait(WTF::Function<void()>&& function)
167{
168 if (isMainThread()) {
169 function();
170 return;
171 }
172
173 Lock mutex;
174 Condition conditionVariable;
175
176 bool isFinished = false;
177
178 callOnMainThread([&, function = WTFMove(function)] {
179 function();
180
181 std::lock_guard<Lock> lock(mutex);
182 isFinished = true;
183 conditionVariable.notifyOne();
184 });
185
186 std::unique_lock<Lock> lock(mutex);
187 conditionVariable.wait(lock, [&] {
188 return isFinished;
189 });
190}
191
192} // namespace WTF
193