1/*
2 * Copyright (C) 2007-2019 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/RunLoop.h>
39#include <wtf/StdLibExtras.h>
40#include <wtf/ThreadSpecific.h>
41#include <wtf/Threading.h>
42
43namespace WTF {
44
45static bool callbacksPaused; // This global variable is only accessed from main thread.
46static Lock mainThreadFunctionQueueMutex;
47
48static Deque<Function<void ()>>& functionQueue()
49{
50 static NeverDestroyed<Deque<Function<void ()>>> functionQueue;
51 return functionQueue;
52}
53
54// Share this initializeKey with initializeMainThread and initializeMainThreadToProcessMainThread.
55static std::once_flag initializeKey;
56void initializeMainThread()
57{
58 std::call_once(initializeKey, [] {
59 initializeThreading();
60 initializeMainThreadPlatform();
61 });
62}
63
64#if !USE(WEB_THREAD)
65bool canCurrentThreadAccessThreadLocalData(Thread& thread)
66{
67 return &thread == &Thread::current();
68}
69#endif
70
71// 0.1 sec delays in UI is approximate threshold when they become noticeable. Have a limit that's half of that.
72static constexpr auto maxRunLoopSuspensionTime = 50_ms;
73
74void dispatchFunctionsFromMainThread()
75{
76 ASSERT(isMainThread());
77
78 if (callbacksPaused)
79 return;
80
81 auto startTime = MonotonicTime::now();
82
83 Function<void ()> function;
84
85 while (true) {
86 {
87 std::lock_guard<Lock> lock(mainThreadFunctionQueueMutex);
88 if (!functionQueue().size())
89 break;
90
91 function = functionQueue().takeFirst();
92 }
93
94 function();
95
96 // Clearing the function can have side effects, so do so outside of the lock above.
97 function = nullptr;
98
99 // If we are running accumulated functions for too long so UI may become unresponsive, we need to
100 // yield so the user input can be processed. Otherwise user may not be able to even close the window.
101 // This code has effect only in case the scheduleDispatchFunctionsOnMainThread() is implemented in a way that
102 // allows input events to be processed before we are back here.
103 if (MonotonicTime::now() - startTime > maxRunLoopSuspensionTime) {
104 scheduleDispatchFunctionsOnMainThread();
105 break;
106 }
107 }
108}
109
110bool isMainRunLoop()
111{
112 return RunLoop::isMain();
113}
114
115void callOnMainRunLoop(Function<void()>&& function)
116{
117 RunLoop::main().dispatch(WTFMove(function));
118}
119
120void callOnMainThread(Function<void()>&& function)
121{
122 ASSERT(function);
123
124 bool needToSchedule = false;
125
126 {
127 std::lock_guard<Lock> lock(mainThreadFunctionQueueMutex);
128 needToSchedule = functionQueue().size() == 0;
129 functionQueue().append(WTFMove(function));
130 }
131
132 if (needToSchedule)
133 scheduleDispatchFunctionsOnMainThread();
134}
135
136void setMainThreadCallbacksPaused(bool paused)
137{
138 ASSERT(isMainThread());
139
140 if (callbacksPaused == paused)
141 return;
142
143 callbacksPaused = paused;
144
145 if (!callbacksPaused)
146 scheduleDispatchFunctionsOnMainThread();
147}
148
149bool isMainThreadOrGCThread()
150{
151 if (Thread::mayBeGCThread())
152 return true;
153
154 return isMainThread();
155}
156
157enum class MainStyle : bool {
158 Thread,
159 RunLoop
160};
161
162static void callOnMainAndWait(WTF::Function<void()>&& function, MainStyle mainStyle)
163{
164
165 if (mainStyle == MainStyle::Thread ? isMainThread() : isMainRunLoop()) {
166 function();
167 return;
168 }
169
170 Lock mutex;
171 Condition conditionVariable;
172
173 bool isFinished = false;
174
175 auto functionImpl = [&, function = WTFMove(function)] {
176 function();
177
178 std::lock_guard<Lock> lock(mutex);
179 isFinished = true;
180 conditionVariable.notifyOne();
181 };
182
183 switch (mainStyle) {
184 case MainStyle::Thread:
185 callOnMainThread(WTFMove(functionImpl));
186 break;
187 case MainStyle::RunLoop:
188 callOnMainRunLoop(WTFMove(functionImpl));
189 };
190
191 std::unique_lock<Lock> lock(mutex);
192 conditionVariable.wait(lock, [&] {
193 return isFinished;
194 });
195}
196
197void callOnMainRunLoopAndWait(WTF::Function<void()>&& function)
198{
199 callOnMainAndWait(WTFMove(function), MainStyle::RunLoop);
200}
201
202void callOnMainThreadAndWait(WTF::Function<void()>&& function)
203{
204 callOnMainAndWait(WTFMove(function), MainStyle::Thread);
205}
206
207} // namespace WTF
208