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/*
* Copyright (C) 2007-2017 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Apple Inc. ("Apple") nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "MainThread.h"
#include "Deque.h"
#include "MonotonicTime.h"
#include "StdLibExtras.h"
#include "Threading.h"
#include <mutex>
#include <wtf/Condition.h>
#include <wtf/Lock.h>
#include <wtf/NeverDestroyed.h>
#include <wtf/ThreadSpecific.h>
namespace WTF {
static bool callbacksPaused; // This global variable is only accessed from main thread.
#if !PLATFORM(COCOA)
static Thread* mainThread { nullptr };
#endif
static Lock mainThreadFunctionQueueMutex;
static Deque<Function<void ()>>& functionQueue()
{
static NeverDestroyed<Deque<Function<void ()>>> functionQueue;
return functionQueue;
}
// Share this initializeKey with initializeMainThread and initializeMainThreadToProcessMainThread.
static std::once_flag initializeKey;
void initializeMainThread()
{
std::call_once(initializeKey, [] {
initializeThreading();
#if !PLATFORM(COCOA)
mainThread = &Thread::current();
#endif
initializeMainThreadPlatform();
initializeGCThreads();
});
}
#if !PLATFORM(COCOA)
bool isMainThread()
{
return mainThread == &Thread::current();
}
#endif
#if PLATFORM(COCOA)
#if !USE(WEB_THREAD)
void initializeMainThreadToProcessMainThread()
{
std::call_once(initializeKey, [] {
initializeThreading();
initializeMainThreadToProcessMainThreadPlatform();
initializeGCThreads();
});
}
#else
void initializeWebThread()
{
static std::once_flag initializeKey;
std::call_once(initializeKey, [] {
initializeWebThreadPlatform();
});
}
#endif // !USE(WEB_THREAD)
#endif // PLATFORM(COCOA)
#if !USE(WEB_THREAD)
bool canAccessThreadLocalDataForThread(Thread& thread)
{
return &thread == &Thread::current();
}
#endif
// 0.1 sec delays in UI is approximate threshold when they become noticeable. Have a limit that's half of that.
static const auto maxRunLoopSuspensionTime = 50_ms;
void dispatchFunctionsFromMainThread()
{
ASSERT(isMainThread());
if (callbacksPaused)
return;
auto startTime = MonotonicTime::now();
Function<void ()> function;
while (true) {
{
std::lock_guard<Lock> lock(mainThreadFunctionQueueMutex);
if (!functionQueue().size())
break;
function = functionQueue().takeFirst();
}
function();
// Clearing the function can have side effects, so do so outside of the lock above.
function = nullptr;
// If we are running accumulated functions for too long so UI may become unresponsive, we need to
// yield so the user input can be processed. Otherwise user may not be able to even close the window.
// This code has effect only in case the scheduleDispatchFunctionsOnMainThread() is implemented in a way that
// allows input events to be processed before we are back here.
if (MonotonicTime::now() - startTime > maxRunLoopSuspensionTime) {
scheduleDispatchFunctionsOnMainThread();
break;
}
}
}
void callOnMainThread(Function<void()>&& function)
{
ASSERT(function);
bool needToSchedule = false;
{
std::lock_guard<Lock> lock(mainThreadFunctionQueueMutex);
needToSchedule = functionQueue().size() == 0;
functionQueue().append(WTFMove(function));
}
if (needToSchedule)
scheduleDispatchFunctionsOnMainThread();
}
void setMainThreadCallbacksPaused(bool paused)
{
ASSERT(isMainThread());
if (callbacksPaused == paused)
return;
callbacksPaused = paused;
if (!callbacksPaused)
scheduleDispatchFunctionsOnMainThread();
}
static ThreadSpecific<std::optional<GCThreadType>, CanBeGCThread::True>* isGCThread;
void initializeGCThreads()
{
static std::once_flag flag;
std::call_once(
flag,
[] {
isGCThread = new ThreadSpecific<std::optional<GCThreadType>, CanBeGCThread::True>();
});
}
void registerGCThread(GCThreadType type)
{
if (!isGCThread) {
// This happens if we're running in a process that doesn't care about
// MainThread.
return;
}
**isGCThread = type;
}
bool isMainThreadOrGCThread()
{
if (mayBeGCThread())
return true;
return isMainThread();
}
std::optional<GCThreadType> mayBeGCThread()
{
if (!isGCThread)
return std::nullopt;
if (!isGCThread->isSet())
return std::nullopt;
return **isGCThread;
}
void callOnMainThreadAndWait(WTF::Function<void()>&& function)
{
if (isMainThread()) {
function();
return;
}
Lock mutex;
Condition conditionVariable;
bool isFinished = false;
callOnMainThread([&, function = WTFMove(function)] {
function();
std::lock_guard<Lock> lock(mutex);
isFinished = true;
conditionVariable.notifyOne();
});
std::unique_lock<Lock> lock(mutex);
conditionVariable.wait(lock, [&] {
return isFinished;
});
}
} // namespace WTF