xpcom/threads/nsThreadManager.cpp
author Henri Sivonen <hsivonen@hsivonen.fi>
Fri, 06 Jul 2018 10:44:43 +0300
changeset 489140 4ef0f163fdeb9afeddd87b37bfd987298c038542
parent 486623 c31ed05b4863f016b942a387d9767dcf14d8cd75
child 496777 a03a61d6d724503c3b7c5e31fe32ced1f5d1c219
permissions -rw-r--r--
Bug 1402247 - Use encoding_rs for XPCOM string encoding conversions. r=Nika,erahm,froydnj. Correctness improvements: * UTF errors are handled safely per spec instead of dangerously truncating strings. * There are fewer converter implementations. Performance improvements: * The old code did exact buffer length math, which meant doing UTF math twice on each input string (once for length calculation and another time for conversion). Exact length math is more complicated when handling errors properly, which the old code didn't do. The new code does UTF math on the string content only once (when converting) but risks allocating more than once. There are heuristics in place to lower the probability of reallocation in cases where the double math avoidance isn't enough of a saving to absorb an allocation and memcpy. * Previously, in UTF-16 <-> UTF-8 conversions, an ASCII prefix was optimized but a single non-ASCII code point pessimized the rest of the string. The new code tries to get back on the fast ASCII path. * UTF-16 to Latin1 conversion guarantees less about handling of out-of-range input to eliminate an operation from the inner loop on x86/x86_64. * When assigning to a pre-existing string, the new code tries to reuse the old buffer instead of first releasing the old buffer and then allocating a new one. * When reallocating from the new code, the memcpy covers only the data that is part of the logical length of the old string instead of memcpying the whole capacity. (For old callers old excess memcpy behavior is preserved due to bogus callers. See bug 1472113.) * UTF-8 strings in XPConnect that are in the Latin1 range are passed to SpiderMonkey as Latin1. New features: * Conversion between UTF-8 and Latin1 is added in order to enable faster future interop between Rust code (or otherwise UTF-8-using code) and text node and SpiderMonkey code that uses Latin1. MozReview-Commit-ID: JaJuExfILM9

/* -*- 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 "nsThreadManager.h"
#include "nsThread.h"
#include "nsThreadUtils.h"
#include "nsIClassInfoImpl.h"
#include "nsTArray.h"
#include "nsAutoPtr.h"
#include "nsXULAppAPI.h"
#include "LabeledEventQueue.h"
#include "MainThreadQueue.h"
#include "mozilla/AbstractThread.h"
#include "mozilla/ClearOnShutdown.h"
#include "mozilla/EventQueue.h"
#include "mozilla/Preferences.h"
#include "mozilla/Scheduler.h"
#include "mozilla/SystemGroup.h"
#include "mozilla/StaticPtr.h"
#include "mozilla/ThreadEventQueue.h"
#include "mozilla/ThreadLocal.h"
#include "PrioritizedEventQueue.h"
#ifdef MOZ_CANARY
#include <fcntl.h>
#include <unistd.h>
#endif

#include "MainThreadIdlePeriod.h"
#include "InputEventStatistics.h"

using namespace mozilla;

static MOZ_THREAD_LOCAL(bool) sTLSIsMainThread;
static MOZ_THREAD_LOCAL(PRThread*) gTlsCurrentVirtualThread;

bool
NS_IsMainThreadTLSInitialized()
{
  return sTLSIsMainThread.initialized();
}

bool
NS_IsMainThread()
{
  return sTLSIsMainThread.get();
}

void
NS_SetMainThread()
{
  if (!sTLSIsMainThread.init()) {
    MOZ_CRASH();
  }
  sTLSIsMainThread.set(true);
  MOZ_ASSERT(NS_IsMainThread());
}

void
NS_SetMainThread(PRThread* aVirtualThread)
{
  MOZ_ASSERT(Scheduler::IsCooperativeThread());

  MOZ_ASSERT(!gTlsCurrentVirtualThread.get());
  gTlsCurrentVirtualThread.set(aVirtualThread);
  NS_SetMainThread();
}

void
NS_UnsetMainThread()
{
  MOZ_ASSERT(Scheduler::IsCooperativeThread());

  sTLSIsMainThread.set(false);
  MOZ_ASSERT(!NS_IsMainThread());
  gTlsCurrentVirtualThread.set(nullptr);
}

#ifdef DEBUG

namespace mozilla {

void
AssertIsOnMainThread()
{
  MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
}

} // mozilla namespace

#endif

typedef nsTArray<NotNull<RefPtr<nsThread>>> nsThreadArray;

static bool sShutdownComplete;

//-----------------------------------------------------------------------------

/* static */ void
nsThreadManager::ReleaseThread(void* aData)
{
  if (sShutdownComplete) {
    // We've already completed shutdown and released the references to all or
    // our TLS wrappers. Don't try to release them again.
    return;
  }

  auto* thread = static_cast<nsThread*>(aData);

  get().UnregisterCurrentThread(*thread, true);

  if (thread->mHasTLSEntry) {
    thread->mHasTLSEntry = false;
    thread->Release();
  }
}

// statically allocated instance
NS_IMETHODIMP_(MozExternalRefCountType)
nsThreadManager::AddRef()
{
  return 2;
}
NS_IMETHODIMP_(MozExternalRefCountType)
nsThreadManager::Release()
{
  return 1;
}
NS_IMPL_CLASSINFO(nsThreadManager, nullptr,
                  nsIClassInfo::THREADSAFE | nsIClassInfo::SINGLETON,
                  NS_THREADMANAGER_CID)
NS_IMPL_QUERY_INTERFACE_CI(nsThreadManager, nsIThreadManager)
NS_IMPL_CI_INTERFACE_GETTER(nsThreadManager, nsIThreadManager)

namespace {

// Simple observer to monitor the beginning of the shutdown.
class ShutdownObserveHelper final : public nsIObserver
                                  , public nsSupportsWeakReference
{
public:
  NS_DECL_ISUPPORTS

  static nsresult
  Create(ShutdownObserveHelper** aObserver)
  {
    MOZ_ASSERT(aObserver);

    RefPtr<ShutdownObserveHelper> observer = new ShutdownObserveHelper();

    nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
    if (NS_WARN_IF(!obs)) {
      return NS_ERROR_FAILURE;
    }

    nsresult rv = obs->AddObserver(observer, NS_XPCOM_SHUTDOWN_OBSERVER_ID, true);
    if (NS_WARN_IF(NS_FAILED(rv))) {
      return rv;
    }

    rv = obs->AddObserver(observer, "content-child-will-shutdown", true);
    if (NS_WARN_IF(NS_FAILED(rv))) {
      return rv;
    }

    observer.forget(aObserver);
    return NS_OK;
  }

  NS_IMETHOD
  Observe(nsISupports* aSubject, const char* aTopic,
          const char16_t* aData) override
  {
    if (!strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) ||
        !strcmp(aTopic, "content-child-will-shutdown")) {
      mShuttingDown = true;
      return NS_OK;
    }

    return NS_OK;
  }

  bool
  ShuttingDown() const
  {
    return mShuttingDown;
  }

private:
  explicit ShutdownObserveHelper()
    : mShuttingDown(false)
  {}

  ~ShutdownObserveHelper() = default;

  bool mShuttingDown;
};

NS_INTERFACE_MAP_BEGIN(ShutdownObserveHelper)
  NS_INTERFACE_MAP_ENTRY(nsIObserver)
  NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIObserver)
NS_INTERFACE_MAP_END

NS_IMPL_ADDREF(ShutdownObserveHelper)
NS_IMPL_RELEASE(ShutdownObserveHelper)

StaticRefPtr<ShutdownObserveHelper> gShutdownObserveHelper;

} // anonymous

//-----------------------------------------------------------------------------

/*static*/ nsThreadManager&
nsThreadManager::get()
{
  static nsThreadManager sInstance;
  return sInstance;
}

/* static */ void
nsThreadManager::InitializeShutdownObserver()
{
  MOZ_ASSERT(!gShutdownObserveHelper);

  RefPtr<ShutdownObserveHelper> observer;
  nsresult rv = ShutdownObserveHelper::Create(getter_AddRefs(observer));
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return;
  }

  gShutdownObserveHelper = observer;
  ClearOnShutdown(&gShutdownObserveHelper);
}

nsresult
nsThreadManager::Init()
{
  // Child processes need to initialize the thread manager before they
  // initialize XPCOM in order to set up the crash reporter. This leads to
  // situations where we get initialized twice.
  if (mInitialized) {
    return NS_OK;
  }

  if (!gTlsCurrentVirtualThread.init()) {
    return NS_ERROR_UNEXPECTED;
  }

  Scheduler::EventLoopActivation::Init();

  if (PR_NewThreadPrivateIndex(&mCurThreadIndex, ReleaseThread) == PR_FAILURE) {
    return NS_ERROR_FAILURE;
  }


#ifdef MOZ_CANARY
  const int flags = O_WRONLY | O_APPEND | O_CREAT | O_NONBLOCK;
  const mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
  char* env_var_flag = getenv("MOZ_KILL_CANARIES");
  sCanaryOutputFD =
    env_var_flag ? (env_var_flag[0] ? open(env_var_flag, flags, mode) :
                                      STDERR_FILENO) :
                   0;
#endif

  nsCOMPtr<nsIIdlePeriod> idlePeriod = new MainThreadIdlePeriod();

  bool startScheduler = false;
  if (XRE_IsContentProcess() && Scheduler::IsSchedulerEnabled()) {
    mMainThread = Scheduler::Init(idlePeriod);
    startScheduler = true;
  } else {
    if (XRE_IsContentProcess() && Scheduler::UseMultipleQueues()) {
      mMainThread = CreateMainThread<ThreadEventQueue<PrioritizedEventQueue<LabeledEventQueue>>, LabeledEventQueue>(idlePeriod);
    } else {
      mMainThread = CreateMainThread<ThreadEventQueue<PrioritizedEventQueue<EventQueue>>, EventQueue>(idlePeriod);
    }
  }

  nsresult rv = mMainThread->InitCurrentThread();
  if (NS_FAILED(rv)) {
    mMainThread = nullptr;
    return rv;
  }

  // We need to keep a pointer to the current thread, so we can satisfy
  // GetIsMainThread calls that occur post-Shutdown.
  mMainThread->GetPRThread(&mMainPRThread);

  // Init AbstractThread.
  AbstractThread::InitTLS();
  AbstractThread::InitMainThread();

  mInitialized = true;

  if (startScheduler) {
    Scheduler::Start();
  }
  return NS_OK;
}

void
nsThreadManager::Shutdown()
{
  MOZ_ASSERT(NS_IsMainThread(), "shutdown not called from main thread");

  // Prevent further access to the thread manager (no more new threads!)
  //
  // What happens if shutdown happens before NewThread completes?
  // We Shutdown() the new thread, and return error if we've started Shutdown
  // between when NewThread started, and when the thread finished initializing
  // and registering with ThreadManager.
  //
  mInitialized = false;

  // Empty the main thread event queue before we begin shutting down threads.
  NS_ProcessPendingEvents(mMainThread);

  {
    // We gather the threads from the hashtable into a list, so that we avoid
    // holding the hashtable lock while calling nsIThread::Shutdown.
    nsThreadArray threads;
    {
      OffTheBooksMutexAutoLock lock(mLock);
      for (auto iter = mThreadsByPRThread.Iter(); !iter.Done(); iter.Next()) {
        RefPtr<nsThread>& thread = iter.Data();
        threads.AppendElement(WrapNotNull(thread));
        iter.Remove();
      }
    }

    // It's tempting to walk the list of threads here and tell them each to stop
    // accepting new events, but that could lead to badness if one of those
    // threads is stuck waiting for a response from another thread.  To do it
    // right, we'd need some way to interrupt the threads.
    //
    // Instead, we process events on the current thread while waiting for threads
    // to shutdown.  This means that we have to preserve a mostly functioning
    // world until such time as the threads exit.

    // Shutdown all threads that require it (join with threads that we created).
    for (uint32_t i = 0; i < threads.Length(); ++i) {
      NotNull<nsThread*> thread = threads[i];
      if (thread->ShutdownRequired()) {
        thread->Shutdown();
      }
    }
  }

  // NB: It's possible that there are events in the queue that want to *start*
  // an asynchronous shutdown. But we have already shutdown the threads above,
  // so there's no need to worry about them. We only have to wait for all
  // in-flight asynchronous thread shutdowns to complete.
  mMainThread->WaitForAllAsynchronousShutdowns();

  // In case there are any more events somehow...
  NS_ProcessPendingEvents(mMainThread);

  // There are no more background threads at this point.

  // Clear the table of threads.
  {
    OffTheBooksMutexAutoLock lock(mLock);
    mThreadsByPRThread.Clear();
  }

  // Normally thread shutdown clears the observer for the thread, but since the
  // main thread is special we do it manually here after we're sure all events
  // have been processed.
  mMainThread->SetObserver(nullptr);

  // Release main thread object.
  mMainThread = nullptr;

  // Remove the TLS entry for the main thread.
  PR_SetThreadPrivate(mCurThreadIndex, nullptr);

  {
    // Cleanup the last references to any threads which haven't shut down yet.
    nsTArray<RefPtr<nsThread>> threads;
    for (auto* thread : nsThread::Enumerate()) {
      if (thread->mHasTLSEntry) {
        threads.AppendElement(dont_AddRef(thread));
        thread->mHasTLSEntry = false;
      }
    }
  }

  // xpcshell tests sometimes leak the main thread. They don't enable leak
  // checking, so that doesn't cause the test to fail, but leaving the entry in
  // the thread list triggers an assertion, which does.
  nsThread::ClearThreadList();

  sShutdownComplete = true;
}

void
nsThreadManager::RegisterCurrentThread(nsThread& aThread)
{
  MOZ_ASSERT(aThread.GetPRThread() == PR_GetCurrentThread(), "bad aThread");

  OffTheBooksMutexAutoLock lock(mLock);

  ++mCurrentNumberOfThreads;
  if (mCurrentNumberOfThreads > mHighestNumberOfThreads) {
    mHighestNumberOfThreads = mCurrentNumberOfThreads;
  }

  mThreadsByPRThread.Put(aThread.GetPRThread(), &aThread);  // XXX check OOM?

  aThread.AddRef();  // for TLS entry
  aThread.mHasTLSEntry = true;
  PR_SetThreadPrivate(mCurThreadIndex, &aThread);
}

void
nsThreadManager::UnregisterCurrentThread(nsThread& aThread, bool aIfExists)
{
  {
    OffTheBooksMutexAutoLock lock(mLock);

    if (aIfExists && !mThreadsByPRThread.GetWeak(aThread.GetPRThread())) {
      return;
    }

    MOZ_ASSERT(aThread.GetPRThread() == PR_GetCurrentThread(), "bad aThread");

    --mCurrentNumberOfThreads;
    mThreadsByPRThread.Remove(aThread.GetPRThread());
  }

  PR_SetThreadPrivate(mCurThreadIndex, nullptr);
  // Ref-count balanced via ReleaseThread
}

nsThread*
nsThreadManager::CreateCurrentThread(SynchronizedEventQueue* aQueue,
                                     nsThread::MainThreadFlag aMainThread)
{
  // Make sure we don't have an nsThread yet.
  MOZ_ASSERT(!PR_GetThreadPrivate(mCurThreadIndex));

  if (!mInitialized) {
    return nullptr;
  }

  // OK, that's fine.  We'll dynamically create one :-)
  RefPtr<nsThread> thread = new nsThread(WrapNotNull(aQueue), aMainThread, 0);
  if (!thread || NS_FAILED(thread->InitCurrentThread())) {
    return nullptr;
  }

  return thread.get();  // reference held in TLS
}

nsThread*
nsThreadManager::GetCurrentThread()
{
  // read thread local storage
  void* data = PR_GetThreadPrivate(mCurThreadIndex);
  if (data) {
    return static_cast<nsThread*>(data);
  }

  if (!mInitialized) {
    return nullptr;
  }

  // OK, that's fine.  We'll dynamically create one :-)
  RefPtr<ThreadEventQueue<EventQueue>> queue =
    new ThreadEventQueue<EventQueue>(MakeUnique<EventQueue>());
  RefPtr<nsThread> thread = new nsThread(WrapNotNull(queue), nsThread::NOT_MAIN_THREAD, 0);
  if (!thread || NS_FAILED(thread->InitCurrentThread())) {
    return nullptr;
  }

  return thread.get();  // reference held in TLS
}

bool
nsThreadManager::IsNSThread() const
{
  if (!mInitialized) {
    return false;
  }
  if (auto* thread = (nsThread*)PR_GetThreadPrivate(mCurThreadIndex)) {
    return thread->mShutdownRequired;
  }
  return false;
}

NS_IMETHODIMP
nsThreadManager::NewThread(uint32_t aCreationFlags,
                           uint32_t aStackSize,
                           nsIThread** aResult)
{
  return NewNamedThread(NS_LITERAL_CSTRING(""), aStackSize, aResult);
}

NS_IMETHODIMP
nsThreadManager::NewNamedThread(const nsACString& aName,
                                uint32_t aStackSize,
                                nsIThread** aResult)
{
  // Note: can be called from arbitrary threads

  // No new threads during Shutdown
  if (NS_WARN_IF(!mInitialized)) {
    return NS_ERROR_NOT_INITIALIZED;
  }

  RefPtr<ThreadEventQueue<EventQueue>> queue =
    new ThreadEventQueue<EventQueue>(MakeUnique<EventQueue>());
  RefPtr<nsThread> thr = new nsThread(WrapNotNull(queue), nsThread::NOT_MAIN_THREAD, aStackSize);
  nsresult rv = thr->Init(aName);  // Note: blocks until the new thread has been set up
  if (NS_FAILED(rv)) {
    return rv;
  }

  // At this point, we expect that the thread has been registered in mThreadByPRThread;
  // however, it is possible that it could have also been replaced by now, so
  // we cannot really assert that it was added.  Instead, kill it if we entered
  // Shutdown() during/before Init()

  if (NS_WARN_IF(!mInitialized)) {
    if (thr->ShutdownRequired()) {
      thr->Shutdown(); // ok if it happens multiple times
    }
    return NS_ERROR_NOT_INITIALIZED;
  }

  thr.forget(aResult);
  return NS_OK;
}

NS_IMETHODIMP
nsThreadManager::GetThreadFromPRThread(PRThread* aThread, nsIThread** aResult)
{
  // Keep this functioning during Shutdown
  if (NS_WARN_IF(!mMainThread)) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  if (NS_WARN_IF(!aThread)) {
    return NS_ERROR_INVALID_ARG;
  }

  RefPtr<nsThread> temp;
  {
    OffTheBooksMutexAutoLock lock(mLock);
    mThreadsByPRThread.Get(aThread, getter_AddRefs(temp));
  }

  NS_IF_ADDREF(*aResult = temp);
  return NS_OK;
}

NS_IMETHODIMP
nsThreadManager::GetMainThread(nsIThread** aResult)
{
  // Keep this functioning during Shutdown
  if (NS_WARN_IF(!mMainThread)) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  NS_ADDREF(*aResult = mMainThread);
  return NS_OK;
}

NS_IMETHODIMP
nsThreadManager::GetCurrentThread(nsIThread** aResult)
{
  // Keep this functioning during Shutdown
  if (!mMainThread) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  *aResult = GetCurrentThread();
  if (!*aResult) {
    return NS_ERROR_OUT_OF_MEMORY;
  }
  NS_ADDREF(*aResult);
  return NS_OK;
}

NS_IMETHODIMP
nsThreadManager::SpinEventLoopUntil(nsINestedEventLoopCondition* aCondition)
{
  return SpinEventLoopUntilInternal(aCondition, false);
}

NS_IMETHODIMP
nsThreadManager::SpinEventLoopUntilOrShutdown(nsINestedEventLoopCondition* aCondition)
{
  return SpinEventLoopUntilInternal(aCondition, true);
}

nsresult
nsThreadManager::SpinEventLoopUntilInternal(nsINestedEventLoopCondition* aCondition,
                                            bool aCheckingShutdown)
{
  nsCOMPtr<nsINestedEventLoopCondition> condition(aCondition);
  nsresult rv = NS_OK;

  // Nothing to do if already shutting down. Note that gShutdownObserveHelper is
  // nullified on shutdown.
  if (aCheckingShutdown &&
      (!gShutdownObserveHelper || gShutdownObserveHelper->ShuttingDown())) {
    return NS_OK;
  }

  if (!mozilla::SpinEventLoopUntil([&]() -> bool {
        // Shutting down is started.
        if (aCheckingShutdown &&
            (!gShutdownObserveHelper ||
             gShutdownObserveHelper->ShuttingDown())) {
          return true;
        }

        bool isDone = false;
        rv = condition->IsDone(&isDone);
        // JS failure should be unusual, but we need to stop and propagate
        // the error back to the caller.
        if (NS_FAILED(rv)) {
          return true;
        }

        return isDone;
      })) {
    // We stopped early for some reason, which is unexpected.
    return NS_ERROR_UNEXPECTED;
  }

  // If we exited when the condition told us to, we need to return whether
  // the condition encountered failure when executing.
  return rv;
}

NS_IMETHODIMP
nsThreadManager::SpinEventLoopUntilEmpty()
{
  nsIThread* thread = NS_GetCurrentThread();

  while (NS_HasPendingEvents(thread)) {
    (void)NS_ProcessNextEvent(thread, false);
  }

  return NS_OK;
}

NS_IMETHODIMP
nsThreadManager::GetSystemGroupEventTarget(nsIEventTarget** aTarget)
{
  nsCOMPtr<nsIEventTarget> target = SystemGroup::EventTargetFor(TaskCategory::Other);
  target.forget(aTarget);
  return NS_OK;
}

uint32_t
nsThreadManager::GetHighestNumberOfThreads()
{
  OffTheBooksMutexAutoLock lock(mLock);
  return mHighestNumberOfThreads;
}

NS_IMETHODIMP
nsThreadManager::DispatchToMainThread(nsIRunnable *aEvent, uint32_t aPriority)
{
  // Note: C++ callers should instead use NS_DispatchToMainThread.
  MOZ_ASSERT(NS_IsMainThread());

  // Keep this functioning during Shutdown
  if (NS_WARN_IF(!mMainThread)) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  if (aPriority != nsIRunnablePriority::PRIORITY_NORMAL) {
    nsCOMPtr<nsIRunnable> event(aEvent);
    return mMainThread->DispatchFromScript(
             new PrioritizableRunnable(event.forget(), aPriority), 0);
  }
  return mMainThread->DispatchFromScript(aEvent, 0);
}

void
nsThreadManager::EnableMainThreadEventPrioritization()
{
  MOZ_ASSERT(NS_IsMainThread());
  InputEventStatistics::Get().SetEnable(true);
  mMainThread->EnableInputEventPrioritization();
}

void
nsThreadManager::FlushInputEventPrioritization()
{
  MOZ_ASSERT(NS_IsMainThread());
  mMainThread->FlushInputEventPrioritization();
}

void
nsThreadManager::SuspendInputEventPrioritization()
{
  MOZ_ASSERT(NS_IsMainThread());
  mMainThread->SuspendInputEventPrioritization();
}

void
nsThreadManager::ResumeInputEventPrioritization()
{
  MOZ_ASSERT(NS_IsMainThread());
  mMainThread->ResumeInputEventPrioritization();
}

NS_IMETHODIMP
nsThreadManager::IdleDispatchToMainThread(nsIRunnable *aEvent, uint32_t aTimeout)
{
  // Note: C++ callers should instead use NS_IdleDispatchToThread or
  // NS_IdleDispatchToCurrentThread.
  MOZ_ASSERT(NS_IsMainThread());

  nsCOMPtr<nsIRunnable> event(aEvent);
  if (aTimeout) {
    return NS_IdleDispatchToThread(event.forget(), aTimeout, mMainThread);
  }

  return NS_IdleDispatchToThread(event.forget(), mMainThread);
}

namespace mozilla {

PRThread*
GetCurrentVirtualThread()
{
  // We call GetCurrentVirtualThread very early in startup, before the TLS is
  // initialized. Make sure we don't assert in that case.
  if (gTlsCurrentVirtualThread.initialized()) {
    if (gTlsCurrentVirtualThread.get()) {
      return gTlsCurrentVirtualThread.get();
    }
  }
  return PR_GetCurrentThread();
}

PRThread*
GetCurrentPhysicalThread()
{
  return PR_GetCurrentThread();
}

} // namespace mozilla