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/*
* Copyright (C) 2010 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. 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 INC. 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 <wtf/RunLoop.h>
#include <wtf/NeverDestroyed.h>
#include <wtf/Ref.h>
#include <wtf/StdLibExtras.h>
#include <wtf/threads/BinarySemaphore.h>
namespace WTF {
SUPPRESS_UNCOUNTED_LOCAL static RunLoop* s_mainRunLoop;
#if USE(WEB_THREAD)
SUPPRESS_UNCOUNTED_LOCAL static RunLoop* s_webRunLoop;
#endif
// Helper class for ThreadSpecificData.
class RunLoop::Holder {
WTF_MAKE_FAST_ALLOCATED;
public:
Holder()
: m_runLoop(adoptRef(*new RunLoop))
{
}
~Holder()
{
m_runLoop->threadWillExit();
}
RunLoop& runLoop() { return m_runLoop; }
private:
const Ref<RunLoop> m_runLoop;
};
void RunLoop::initializeMain()
{
RELEASE_ASSERT(!s_mainRunLoop);
s_mainRunLoop = &RunLoop::current();
}
auto RunLoop::runLoopHolder() -> ThreadSpecific<Holder>&
{
static LazyNeverDestroyed<ThreadSpecific<Holder>> runLoopHolder;
static std::once_flag onceKey;
std::call_once(onceKey, [&] {
runLoopHolder.construct();
});
return runLoopHolder;
}
RunLoop& RunLoop::current()
{
return runLoopHolder()->runLoop();
}
RunLoop& RunLoop::main()
{
ASSERT(s_mainRunLoop);
return *s_mainRunLoop;
}
#if USE(WEB_THREAD)
void RunLoop::initializeWeb()
{
RELEASE_ASSERT(!s_webRunLoop);
s_webRunLoop = &RunLoop::current();
}
RunLoop& RunLoop::web()
{
ASSERT(s_webRunLoop);
return *s_webRunLoop;
}
RunLoop* RunLoop::webIfExists()
{
return s_webRunLoop;
}
#endif
Ref<RunLoop> RunLoop::create(ASCIILiteral threadName, ThreadType threadType, Thread::QOS qos)
{
RefPtr<RunLoop> runLoop;
BinarySemaphore semaphore;
Thread::create(threadName, [&] SUPPRESS_UNCOUNTED_LAMBDA_CAPTURE {
runLoop = &RunLoop::current();
semaphore.signal();
runLoop->run();
}, threadType, qos)->detach();
semaphore.wait();
return runLoop.releaseNonNull();
}
bool RunLoop::isCurrent() const
{
// Avoid constructing the RunLoop for the current thread if it has not been created yet.
return runLoopHolder().isSet() && this == &RunLoop::current();
}
void RunLoop::performWork()
{
bool didSuspendFunctions = false;
{
Locker locker { m_nextIterationLock };
// If the RunLoop re-enters or re-schedules, we're expected to execute all functions in order.
while (!m_currentIteration.isEmpty())
m_nextIteration.prepend(m_currentIteration.takeLast());
m_currentIteration = std::exchange(m_nextIteration, { });
}
while (!m_currentIteration.isEmpty()) {
if (m_isFunctionDispatchSuspended) {
didSuspendFunctions = true;
break;
}
auto function = m_currentIteration.takeFirst();
function();
}
// Suspend only for a single cycle.
m_isFunctionDispatchSuspended = false;
m_hasSuspendedFunctions = didSuspendFunctions;
if (m_hasSuspendedFunctions)
wakeUp();
}
void RunLoop::dispatch(Function<void()>&& function)
{
RELEASE_ASSERT(function);
bool needsWakeup = false;
{
Locker locker { m_nextIterationLock };
needsWakeup = m_nextIteration.isEmpty();
m_nextIteration.append(WTFMove(function));
}
if (needsWakeup)
wakeUp();
}
Ref<RunLoop::DispatchTimer> RunLoop::dispatchAfter(Seconds delay, Function<void()>&& function)
{
RELEASE_ASSERT(function);
Ref<DispatchTimer> timer = adoptRef(*new DispatchTimer(*this));
timer->setFunction([timer = timer.copyRef(), function = WTFMove(function)]() mutable {
Ref<DispatchTimer> protectedTimer { WTFMove(timer) };
function();
protectedTimer->stop();
});
timer->startOneShot(delay);
return timer;
}
void RunLoop::suspendFunctionDispatchForCurrentCycle()
{
// Don't suspend if there are already suspended functions to avoid unexecuted function pile-up.
if (m_isFunctionDispatchSuspended || m_hasSuspendedFunctions)
return;
m_isFunctionDispatchSuspended = true;
// Wake up (even if there is nothing to do) to disable suspension.
wakeUp();
}
void RunLoop::threadWillExit()
{
m_currentIteration.clear();
{
Locker locker { m_nextIterationLock };
m_nextIteration.clear();
}
}
} // namespace WTF
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