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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "mozilla/AbstractThread.h"
#include "mozilla/ClearOnShutdown.h"
#include "mozilla/Maybe.h"
#include "mozilla/MozPromise.h" // We initialize the MozPromise logging in this file.
#include "mozilla/StaticPtr.h"
#include "mozilla/StateWatching.h" // We initialize the StateWatching logging in this file.
#include "mozilla/TaskQueue.h"
#include "mozilla/TaskDispatcher.h"
#include "mozilla/Unused.h"
#include "nsThreadUtils.h"
#include "nsContentUtils.h"
#include "nsServiceManagerUtils.h"
namespace mozilla {
LazyLogModule gMozPromiseLog("MozPromise");
LazyLogModule gStateWatchingLog("StateWatching");
StaticRefPtr<AbstractThread> sMainThread;
MOZ_THREAD_LOCAL(AbstractThread*) AbstractThread::sCurrentThreadTLS;
class XPCOMThreadWrapper : public AbstractThread
{
public:
explicit XPCOMThreadWrapper(nsIThread* aTarget, bool aRequireTailDispatch)
: AbstractThread(aRequireTailDispatch)
, mTarget(aTarget)
{
// Our current mechanism of implementing tail dispatch is appshell-specific.
// This is because a very similar mechanism already exists on the main
// thread, and we want to avoid making event dispatch on the main thread
// more complicated than it already is.
//
// If you need to use tail dispatch on other XPCOM threads, you'll need to
// implement an nsIThreadObserver to fire the tail dispatcher at the
// appropriate times.
MOZ_ASSERT_IF(aRequireTailDispatch,
NS_IsMainThread() && NS_GetCurrentThread() == aTarget);
}
virtual void Dispatch(already_AddRefed<nsIRunnable> aRunnable,
DispatchFailureHandling aFailureHandling = AssertDispatchSuccess,
DispatchReason aReason = NormalDispatch) override
{
nsCOMPtr<nsIRunnable> r = aRunnable;
AbstractThread* currentThread;
if (aReason != TailDispatch && (currentThread = GetCurrent()) && RequiresTailDispatch(currentThread)) {
currentThread->TailDispatcher().AddTask(this, r.forget(), aFailureHandling);
return;
}
nsresult rv = mTarget->Dispatch(r, NS_DISPATCH_NORMAL);
MOZ_DIAGNOSTIC_ASSERT(aFailureHandling == DontAssertDispatchSuccess || NS_SUCCEEDED(rv));
Unused << rv;
}
virtual bool IsCurrentThreadIn() override
{
// Compare NSPR threads so that this works after shutdown when
// NS_GetCurrentThread starts returning null.
PRThread* thread = nullptr;
mTarget->GetPRThread(&thread);
bool in = PR_GetCurrentThread() == thread;
return in;
}
void FireTailDispatcher()
{
MOZ_DIAGNOSTIC_ASSERT(mTailDispatcher.isSome());
mTailDispatcher.ref().DrainDirectTasks();
mTailDispatcher.reset();
}
virtual TaskDispatcher& TailDispatcher() override
{
MOZ_ASSERT(this == sMainThread); // See the comment in the constructor.
MOZ_ASSERT(IsCurrentThreadIn());
if (!mTailDispatcher.isSome()) {
mTailDispatcher.emplace(/* aIsTailDispatcher = */ true);
nsCOMPtr<nsIRunnable> event = NewRunnableMethod(this, &XPCOMThreadWrapper::FireTailDispatcher);
nsContentUtils::RunInStableState(event.forget());
}
return mTailDispatcher.ref();
}
virtual bool MightHaveTailTasks() override
{
return mTailDispatcher.isSome();
}
virtual nsIThread* AsXPCOMThread() override { return mTarget; }
private:
RefPtr<nsIThread> mTarget;
Maybe<AutoTaskDispatcher> mTailDispatcher;
};
void
AbstractThread::TailDispatchTasksFor(AbstractThread* aThread)
{
if (MightHaveTailTasks()) {
TailDispatcher().DispatchTasksFor(aThread);
}
}
bool
AbstractThread::HasTailTasksFor(AbstractThread* aThread)
{
if (!MightHaveTailTasks()) {
return false;
}
return TailDispatcher().HasTasksFor(aThread);
}
bool
AbstractThread::RequiresTailDispatch(AbstractThread* aThread) const
{
MOZ_ASSERT(aThread);
// We require tail dispatch if both the source and destination
// threads support it.
return SupportsTailDispatch() && aThread->SupportsTailDispatch();
}
bool
AbstractThread::RequiresTailDispatchFromCurrentThread() const
{
AbstractThread* current = GetCurrent();
return current && RequiresTailDispatch(current);
}
AbstractThread*
AbstractThread::MainThread()
{
MOZ_ASSERT(sMainThread);
return sMainThread;
}
void
AbstractThread::InitStatics()
{
MOZ_ASSERT(NS_IsMainThread());
MOZ_ASSERT(!sMainThread);
nsCOMPtr<nsIThread> mainThread;
NS_GetMainThread(getter_AddRefs(mainThread));
MOZ_DIAGNOSTIC_ASSERT(mainThread);
sMainThread = new XPCOMThreadWrapper(mainThread.get(), /* aRequireTailDispatch = */ true);
ClearOnShutdown(&sMainThread);
if (!sCurrentThreadTLS.init()) {
MOZ_CRASH();
}
sCurrentThreadTLS.set(sMainThread);
}
void
AbstractThread::DispatchStateChange(already_AddRefed<nsIRunnable> aRunnable)
{
GetCurrent()->TailDispatcher().AddStateChangeTask(this, Move(aRunnable));
}
/* static */ void
AbstractThread::DispatchDirectTask(already_AddRefed<nsIRunnable> aRunnable)
{
GetCurrent()->TailDispatcher().AddDirectTask(Move(aRunnable));
}
/* static */
already_AddRefed<AbstractThread>
AbstractThread::CreateXPCOMThreadWrapper(nsIThread* aThread, bool aRequireTailDispatch)
{
RefPtr<XPCOMThreadWrapper> wrapper = new XPCOMThreadWrapper(aThread, aRequireTailDispatch);
// Set the thread-local sCurrentThreadTLS to point to the wrapper on the
// target thread. This ensures that sCurrentThreadTLS is as expected by
// AbstractThread::GetCurrent() on the target thread.
nsCOMPtr<nsIRunnable> r =
NS_NewRunnableFunction([wrapper]() { sCurrentThreadTLS.set(wrapper); });
aThread->Dispatch(r.forget(), NS_DISPATCH_NORMAL);
return wrapper.forget();
}
} // namespace mozilla
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