xpcom/threads/nsThread.cpp
author Henri Sivonen <hsivonen@hsivonen.fi>
Fri, 06 Jul 2018 10:44:43 +0300
changeset 489140 4ef0f163fdeb9afeddd87b37bfd987298c038542
parent 487677 966b020f6c63ac55b84a5c510a77b84db3f92397
child 490211 c2422757c912799714b0dd9238748585aa3d575a
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 "nsThread.h"

#include "base/message_loop.h"
#include "base/platform_thread.h"

// Chromium's logging can sometimes leak through...
#ifdef LOG
#undef LOG
#endif

#include "mozilla/ReentrantMonitor.h"
#include "nsMemoryPressure.h"
#include "nsThreadManager.h"
#include "nsIClassInfoImpl.h"
#include "nsAutoPtr.h"
#include "nsCOMPtr.h"
#include "nsQueryObject.h"
#include "pratom.h"
#include "mozilla/BackgroundHangMonitor.h"
#include "mozilla/CycleCollectedJSContext.h"
#include "mozilla/Logging.h"
#include "nsIObserverService.h"
#include "mozilla/IOInterposer.h"
#include "mozilla/ipc/MessageChannel.h"
#include "mozilla/ipc/BackgroundChild.h"
#include "mozilla/Preferences.h"
#include "mozilla/Scheduler.h"
#include "mozilla/SchedulerGroup.h"
#include "mozilla/Services.h"
#include "mozilla/StaticPrefs.h"
#include "mozilla/SystemGroup.h"
#include "nsXPCOMPrivate.h"
#include "mozilla/ChaosMode.h"
#include "mozilla/Telemetry.h"
#include "mozilla/TimeStamp.h"
#include "mozilla/Unused.h"
#include "mozilla/dom/ScriptSettings.h"
#include "nsICrashReporter.h"
#include "nsThreadSyncDispatch.h"
#include "nsServiceManagerUtils.h"
#include "GeckoProfiler.h"
#include "InputEventStatistics.h"
#include "ThreadEventTarget.h"

#include "mozilla/dom/ContentChild.h"

#ifdef XP_LINUX
#ifdef __GLIBC__
#include <gnu/libc-version.h>
#endif
#include <sys/mman.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sched.h>
#include <stdio.h>
#endif

#ifdef XP_WIN
#include "mozilla/DynamicallyLinkedFunctionPtr.h"

#include <winbase.h>

using GetCurrentThreadStackLimitsFn = void (WINAPI*)(
  PULONG_PTR LowLimit, PULONG_PTR HighLimit);
#endif

#define HAVE_UALARM _BSD_SOURCE || (_XOPEN_SOURCE >= 500 ||                 \
                      _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&           \
                      !(_POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700)

#if defined(XP_LINUX) && !defined(ANDROID) && defined(_GNU_SOURCE)
#define HAVE_SCHED_SETAFFINITY
#endif

#ifdef XP_MACOSX
#include <mach/mach.h>
#include <mach/thread_policy.h>
#endif

#ifdef MOZ_CANARY
# include <unistd.h>
# include <execinfo.h>
# include <signal.h>
# include <fcntl.h>
# include "nsXULAppAPI.h"
#endif

#if defined(NS_FUNCTION_TIMER) && defined(_MSC_VER)
#include "nsTimerImpl.h"
#include "mozilla/StackWalk.h"
#endif
#ifdef NS_FUNCTION_TIMER
#include "nsCRT.h"
#endif

#ifdef MOZ_TASK_TRACER
#include "GeckoTaskTracer.h"
#include "TracedTaskCommon.h"
using namespace mozilla::tasktracer;
#endif

using namespace mozilla;

static LazyLogModule sThreadLog("nsThread");
#ifdef LOG
#undef LOG
#endif
#define LOG(args) MOZ_LOG(sThreadLog, mozilla::LogLevel::Debug, args)

NS_DECL_CI_INTERFACE_GETTER(nsThread)

Array<char, nsThread::kRunnableNameBufSize> nsThread::sMainThreadRunnableName;

//-----------------------------------------------------------------------------
// Because we do not have our own nsIFactory, we have to implement nsIClassInfo
// somewhat manually.

class nsThreadClassInfo : public nsIClassInfo
{
public:
  NS_DECL_ISUPPORTS_INHERITED  // no mRefCnt
  NS_DECL_NSICLASSINFO

  nsThreadClassInfo()
  {
  }
};

NS_IMETHODIMP_(MozExternalRefCountType)
nsThreadClassInfo::AddRef()
{
  return 2;
}
NS_IMETHODIMP_(MozExternalRefCountType)
nsThreadClassInfo::Release()
{
  return 1;
}
NS_IMPL_QUERY_INTERFACE(nsThreadClassInfo, nsIClassInfo)

NS_IMETHODIMP
nsThreadClassInfo::GetInterfaces(uint32_t* aCount, nsIID*** aArray)
{
  return NS_CI_INTERFACE_GETTER_NAME(nsThread)(aCount, aArray);
}

NS_IMETHODIMP
nsThreadClassInfo::GetScriptableHelper(nsIXPCScriptable** aResult)
{
  *aResult = nullptr;
  return NS_OK;
}

NS_IMETHODIMP
nsThreadClassInfo::GetContractID(nsACString& aResult)
{
  aResult.SetIsVoid(true);
  return NS_OK;
}

NS_IMETHODIMP
nsThreadClassInfo::GetClassDescription(nsACString& aResult)
{
  aResult.SetIsVoid(true);
  return NS_OK;
}

NS_IMETHODIMP
nsThreadClassInfo::GetClassID(nsCID** aResult)
{
  *aResult = nullptr;
  return NS_OK;
}

NS_IMETHODIMP
nsThreadClassInfo::GetFlags(uint32_t* aResult)
{
  *aResult = THREADSAFE;
  return NS_OK;
}

NS_IMETHODIMP
nsThreadClassInfo::GetClassIDNoAlloc(nsCID* aResult)
{
  return NS_ERROR_NOT_AVAILABLE;
}

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

NS_IMPL_ADDREF(nsThread)
NS_IMPL_RELEASE(nsThread)
NS_INTERFACE_MAP_BEGIN(nsThread)
  NS_INTERFACE_MAP_ENTRY(nsIThread)
  NS_INTERFACE_MAP_ENTRY(nsIThreadInternal)
  NS_INTERFACE_MAP_ENTRY(nsIEventTarget)
  NS_INTERFACE_MAP_ENTRY(nsISerialEventTarget)
  NS_INTERFACE_MAP_ENTRY(nsISupportsPriority)
  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIThread)
  if (aIID.Equals(NS_GET_IID(nsIClassInfo))) {
    static nsThreadClassInfo sThreadClassInfo;
    foundInterface = static_cast<nsIClassInfo*>(&sThreadClassInfo);
  } else
NS_INTERFACE_MAP_END
NS_IMPL_CI_INTERFACE_GETTER(nsThread, nsIThread, nsIThreadInternal,
                            nsIEventTarget, nsISupportsPriority)

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

class nsThreadStartupEvent final : public Runnable
{
public:
  nsThreadStartupEvent()
    : Runnable("nsThreadStartupEvent")
    , mMon("nsThreadStartupEvent.mMon")
    , mInitialized(false)
  {
  }

  // This method does not return until the thread startup object is in the
  // completion state.
  void Wait()
  {
    ReentrantMonitorAutoEnter mon(mMon);
    while (!mInitialized) {
      mon.Wait();
    }
  }

private:
  ~nsThreadStartupEvent() = default;

  NS_IMETHOD Run() override
  {
    ReentrantMonitorAutoEnter mon(mMon);
    mInitialized = true;
    mon.Notify();
    return NS_OK;
  }

  ReentrantMonitor mMon;
  bool mInitialized;
};
//-----------------------------------------------------------------------------

struct nsThreadShutdownContext
{
  nsThreadShutdownContext(NotNull<nsThread*> aTerminatingThread,
                          NotNull<nsThread*> aJoiningThread,
                          bool      aAwaitingShutdownAck)
    : mTerminatingThread(aTerminatingThread)
    , mJoiningThread(aJoiningThread)
    , mAwaitingShutdownAck(aAwaitingShutdownAck)
    , mIsMainThreadJoining(NS_IsMainThread())
  {
    MOZ_COUNT_CTOR(nsThreadShutdownContext);
  }
  ~nsThreadShutdownContext()
  {
    MOZ_COUNT_DTOR(nsThreadShutdownContext);
  }

  // NB: This will be the last reference.
  NotNull<RefPtr<nsThread>> mTerminatingThread;
  NotNull<nsThread*> MOZ_UNSAFE_REF("Thread manager is holding reference to joining thread")
    mJoiningThread;
  bool mAwaitingShutdownAck;
  bool mIsMainThreadJoining;
};

// This event is responsible for notifying nsThread::Shutdown that it is time
// to call PR_JoinThread. It implements nsICancelableRunnable so that it can
// run on a DOM Worker thread (where all events must implement
// nsICancelableRunnable.)
class nsThreadShutdownAckEvent : public CancelableRunnable
{
public:
  explicit nsThreadShutdownAckEvent(NotNull<nsThreadShutdownContext*> aCtx)
    : CancelableRunnable("nsThreadShutdownAckEvent")
    , mShutdownContext(aCtx)
  {
  }
  NS_IMETHOD Run() override
  {
    mShutdownContext->mTerminatingThread->ShutdownComplete(mShutdownContext);
    return NS_OK;
  }
  nsresult Cancel() override
  {
    return Run();
  }
private:
  virtual ~nsThreadShutdownAckEvent() { }

  NotNull<nsThreadShutdownContext*> mShutdownContext;
};

// This event is responsible for setting mShutdownContext
class nsThreadShutdownEvent : public Runnable
{
public:
  nsThreadShutdownEvent(NotNull<nsThread*> aThr,
                        NotNull<nsThreadShutdownContext*> aCtx)
    : Runnable("nsThreadShutdownEvent")
    , mThread(aThr)
    , mShutdownContext(aCtx)
  {
  }
  NS_IMETHOD Run() override
  {
    mThread->mShutdownContext = mShutdownContext;
    MessageLoop::current()->Quit();
    return NS_OK;
  }
private:
  NotNull<RefPtr<nsThread>> mThread;
  NotNull<nsThreadShutdownContext*> mShutdownContext;
};

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

static void
SetThreadAffinity(unsigned int cpu)
{
#ifdef HAVE_SCHED_SETAFFINITY
  cpu_set_t cpus;
  CPU_ZERO(&cpus);
  CPU_SET(cpu, &cpus);
  sched_setaffinity(0, sizeof(cpus), &cpus);
  // Don't assert sched_setaffinity's return value because it intermittently (?)
  // fails with EINVAL on Linux x64 try runs.
#elif defined(XP_MACOSX)
  // OS X does not provide APIs to pin threads to specific processors, but you
  // can tag threads as belonging to the same "affinity set" and the OS will try
  // to run them on the same processor. To run threads on different processors,
  // tag them as belonging to different affinity sets. Tag 0, the default, means
  // "no affinity" so let's pretend each CPU has its own tag `cpu+1`.
  thread_affinity_policy_data_t policy;
  policy.affinity_tag = cpu + 1;
  MOZ_ALWAYS_TRUE(thread_policy_set(mach_thread_self(), THREAD_AFFINITY_POLICY,
                                    &policy.affinity_tag, 1) == KERN_SUCCESS);
#elif defined(XP_WIN)
  MOZ_ALWAYS_TRUE(SetThreadIdealProcessor(GetCurrentThread(), cpu) != (DWORD)-1);
#endif
}

static void
SetupCurrentThreadForChaosMode()
{
  if (!ChaosMode::isActive(ChaosFeature::ThreadScheduling)) {
    return;
  }

#ifdef XP_LINUX
  // PR_SetThreadPriority doesn't really work since priorities >
  // PR_PRIORITY_NORMAL can't be set by non-root users. Instead we'll just use
  // setpriority(2) to set random 'nice values'. In regular Linux this is only
  // a dynamic adjustment so it still doesn't really do what we want, but tools
  // like 'rr' can be more aggressive about honoring these values.
  // Some of these calls may fail due to trying to lower the priority
  // (e.g. something may have already called setpriority() for this thread).
  // This makes it hard to have non-main threads with higher priority than the
  // main thread, but that's hard to fix. Tools like rr can choose to honor the
  // requested values anyway.
  // Use just 4 priorities so there's a reasonable chance of any two threads
  // having equal priority.
  setpriority(PRIO_PROCESS, 0, ChaosMode::randomUint32LessThan(4));
#else
  // We should set the affinity here but NSPR doesn't provide a way to expose it.
  uint32_t priority = ChaosMode::randomUint32LessThan(PR_PRIORITY_LAST + 1);
  PR_SetThreadPriority(PR_GetCurrentThread(), PRThreadPriority(priority));
#endif

  // Force half the threads to CPU 0 so they compete for CPU
  if (ChaosMode::randomUint32LessThan(2)) {
    SetThreadAffinity(0);
  }
}

namespace {

struct ThreadInitData {
  nsThread* thread;
  const nsACString& name;
};

}

/* static */ mozilla::OffTheBooksMutex&
nsThread::ThreadListMutex()
{
  static OffTheBooksMutex sMutex("nsThread::ThreadListMutex");
  return sMutex;
}

/* static */ LinkedList<nsThread>&
nsThread::ThreadList()
{
  static LinkedList<nsThread> sList;
  return sList;
}

/* static */ void
nsThread::ClearThreadList()
{
  OffTheBooksMutexAutoLock mal(ThreadListMutex());
  while (ThreadList().popFirst()) {}
}

/* static */ nsThreadEnumerator
nsThread::Enumerate()
{
  return {};
}

/*static*/ void
nsThread::ThreadFunc(void* aArg)
{
  using mozilla::ipc::BackgroundChild;

  ThreadInitData* initData = static_cast<ThreadInitData*>(aArg);
  nsThread* self = initData->thread;  // strong reference

  self->mThread = PR_GetCurrentThread();
  self->mVirtualThread = GetCurrentVirtualThread();
  self->mEventTarget->SetCurrentThread();
  SetupCurrentThreadForChaosMode();

  if (!initData->name.IsEmpty()) {
    NS_SetCurrentThreadName(initData->name.BeginReading());
  }

  self->InitCommon();

  // Inform the ThreadManager
  nsThreadManager::get().RegisterCurrentThread(*self);

  mozilla::IOInterposer::RegisterCurrentThread();

  // This must come after the call to nsThreadManager::RegisterCurrentThread(),
  // because that call is needed to properly set up this thread as an nsThread,
  // which profiler_register_thread() requires. See bug 1347007.
  if (!initData->name.IsEmpty()) {
    PROFILER_REGISTER_THREAD(initData->name.BeginReading());
  }

  // Wait for and process startup event
  nsCOMPtr<nsIRunnable> event = self->mEvents->GetEvent(true, nullptr);
  MOZ_ASSERT(event);

  initData = nullptr; // clear before unblocking nsThread::Init

  event->Run();  // unblocks nsThread::Init
  event = nullptr;

  {
    // Scope for MessageLoop.
    nsAutoPtr<MessageLoop> loop(
      new MessageLoop(MessageLoop::TYPE_MOZILLA_NONMAINTHREAD, self));

    // Now, process incoming events...
    loop->Run();

    BackgroundChild::CloseForCurrentThread();

    // NB: The main thread does not shut down here!  It shuts down via
    // nsThreadManager::Shutdown.

    // Do NS_ProcessPendingEvents but with special handling to set
    // mEventsAreDoomed atomically with the removal of the last event. The key
    // invariant here is that we will never permit PutEvent to succeed if the
    // event would be left in the queue after our final call to
    // NS_ProcessPendingEvents. We also have to keep processing events as long
    // as we have outstanding mRequestedShutdownContexts.
    while (true) {
      // Check and see if we're waiting on any threads.
      self->WaitForAllAsynchronousShutdowns();

      if (self->mEvents->ShutdownIfNoPendingEvents()) {
        break;
      }
      NS_ProcessPendingEvents(self);
    }
  }

  mozilla::IOInterposer::UnregisterCurrentThread();

  // Inform the threadmanager that this thread is going away
  nsThreadManager::get().UnregisterCurrentThread(*self);

  PROFILER_UNREGISTER_THREAD();

  // Dispatch shutdown ACK
  NotNull<nsThreadShutdownContext*> context =
    WrapNotNull(self->mShutdownContext);
  MOZ_ASSERT(context->mTerminatingThread == self);
  event = do_QueryObject(new nsThreadShutdownAckEvent(context));
  if (context->mIsMainThreadJoining) {
    SystemGroup::Dispatch(TaskCategory::Other, event.forget());
  } else {
    context->mJoiningThread->Dispatch(event, NS_DISPATCH_NORMAL);
  }

  // Release any observer of the thread here.
  self->SetObserver(nullptr);

#ifdef MOZ_TASK_TRACER
  FreeTraceInfo();
#endif

  NS_RELEASE(self);
}

void
nsThread::InitCommon()
{
  mThreadId = uint32_t(PlatformThread::CurrentId());

  {
#if defined(XP_LINUX)
    pthread_attr_t attr;
    pthread_attr_init(&attr);
    pthread_getattr_np(pthread_self(), &attr);

    size_t stackSize;
    pthread_attr_getstack(&attr, &mStackBase, &stackSize);

    // Glibc prior to 2.27 reports the stack size and base including the guard
    // region, so we need to compensate for it to get accurate accounting.
    // Also, this behavior difference isn't guarded by a versioned symbol, so we
    // actually need to check the runtime glibc version, not the version we were
    // compiled against.
    static bool sAdjustForGuardSize = ({
#ifdef __GLIBC__
      unsigned major, minor;
      sscanf(gnu_get_libc_version(), "%u.%u", &major, &minor) < 2 ||
        major < 2 || (major == 2 && minor < 27);
#else
      false;
#endif
    });
    if (sAdjustForGuardSize) {
      size_t guardSize;
      pthread_attr_getguardsize(&attr, &guardSize);

      // Note: This assumes that the stack grows down, as is the case on all of
      // our tier 1 platforms. On platforms where the stack grows up, the
      // mStackBase adjustment is unnecessary, but doesn't cause any harm other
      // than under-counting stack memory usage by one page.
      mStackBase = reinterpret_cast<char*>(mStackBase) + guardSize;
      stackSize -= guardSize;
    }

    mStackSize = stackSize;

    // This is a bit of a hack.
    //
    // We really do want the NOHUGEPAGE flag on our thread stacks, since we
    // don't expect any of them to need anywhere near 2MB of space. But setting
    // it here is too late to have an effect, since the first stack page has
    // already been faulted in existence, and NSPR doesn't give us a way to set
    // it beforehand.
    //
    // What this does get us, however, is a different set of VM flags on our
    // thread stacks compared to normal heap memory. Which makes the Linux
    // kernel report them as separate regions, even when they are adjacent to
    // heap memory. This allows us to accurately track the actual memory
    // consumption of our allocated stacks.
    madvise(mStackBase, stackSize, MADV_NOHUGEPAGE);

    pthread_attr_destroy(&attr);
#elif defined(XP_WIN)
    static const DynamicallyLinkedFunctionPtr<GetCurrentThreadStackLimitsFn>
      sGetStackLimits(L"kernel32.dll", "GetCurrentThreadStackLimits");

    if (sGetStackLimits) {
      ULONG_PTR stackBottom, stackTop;
      sGetStackLimits(&stackBottom, &stackTop);
      mStackBase = reinterpret_cast<void*>(stackBottom);
      mStackSize = stackTop - stackBottom;
    }
#endif
  }

  OffTheBooksMutexAutoLock mal(ThreadListMutex());
  ThreadList().insertBack(this);
}

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

// Tell the crash reporter to save a memory report if our heuristics determine
// that an OOM failure is likely to occur soon.
// Memory usage will not be checked more than every 30 seconds or saved more
// than every 3 minutes
// If |aShouldSave == kForceReport|, a report will be saved regardless of
// whether the process is low on memory or not. However, it will still not be
// saved if a report was saved less than 3 minutes ago.
bool
nsThread::SaveMemoryReportNearOOM(ShouldSaveMemoryReport aShouldSave)
{
  // Keep an eye on memory usage (cheap, ~7ms) somewhat frequently,
  // but save memory reports (expensive, ~75ms) less frequently.
  const size_t kLowMemoryCheckSeconds = 30;
  const size_t kLowMemorySaveSeconds = 3 * 60;

  static TimeStamp nextCheck = TimeStamp::NowLoRes()
    + TimeDuration::FromSeconds(kLowMemoryCheckSeconds);
  static bool recentlySavedReport = false; // Keeps track of whether a report
                                           // was saved last time we checked

  // Are we checking again too soon?
  TimeStamp now = TimeStamp::NowLoRes();
  if ((aShouldSave == ShouldSaveMemoryReport::kMaybeReport ||
      recentlySavedReport) && now < nextCheck) {
    return false;
  }

  bool needMemoryReport = (aShouldSave == ShouldSaveMemoryReport::kForceReport);
#ifdef XP_WIN // XXX implement on other platforms as needed
  // If the report is forced there is no need to check whether it is necessary
  if (aShouldSave != ShouldSaveMemoryReport::kForceReport) {
    const size_t LOWMEM_THRESHOLD_VIRTUAL = 200 * 1024 * 1024;
    MEMORYSTATUSEX statex;
    statex.dwLength = sizeof(statex);
    if (GlobalMemoryStatusEx(&statex)) {
      if (statex.ullAvailVirtual < LOWMEM_THRESHOLD_VIRTUAL) {
        needMemoryReport = true;
      }
    }
  }
#endif

  if (needMemoryReport) {
    if (XRE_IsContentProcess()) {
      dom::ContentChild* cc = dom::ContentChild::GetSingleton();
      if (cc) {
        cc->SendNotifyLowMemory();
      }
    } else {
      nsCOMPtr<nsICrashReporter> cr =
        do_GetService("@mozilla.org/toolkit/crash-reporter;1");
      if (cr) {
        cr->SaveMemoryReport();
      }
    }
    recentlySavedReport = true;
    nextCheck = now + TimeDuration::FromSeconds(kLowMemorySaveSeconds);
  } else {
    recentlySavedReport = false;
    nextCheck = now + TimeDuration::FromSeconds(kLowMemoryCheckSeconds);
  }

  return recentlySavedReport;
}

#ifdef MOZ_CANARY
int sCanaryOutputFD = -1;
#endif

nsThread::nsThread(NotNull<SynchronizedEventQueue*> aQueue,
                   MainThreadFlag aMainThread,
                   uint32_t aStackSize)
  : mEvents(aQueue.get())
  , mEventTarget(new ThreadEventTarget(mEvents.get(), aMainThread == MAIN_THREAD))
  , mShutdownContext(nullptr)
  , mScriptObserver(nullptr)
  , mThread(nullptr)
  , mStackSize(aStackSize)
  , mNestedEventLoopDepth(0)
  , mCurrentEventLoopDepth(-1)
  , mShutdownRequired(false)
  , mPriority(PRIORITY_NORMAL)
  , mIsMainThread(uint8_t(aMainThread))
  , mCanInvokeJS(false)
  , mCurrentEvent(nullptr)
  , mCurrentEventStart(TimeStamp::Now())
  , mCurrentPerformanceCounter(nullptr)
{
}

nsThread::~nsThread()
{
  NS_ASSERTION(mRequestedShutdownContexts.IsEmpty(),
               "shouldn't be waiting on other threads to shutdown");

  // We shouldn't need to lock before checking isInList at this point. We're
  // destroying the last reference to this object, so there's no way for anyone
  // else to remove it in the middle of our check. And the not-in-list state is
  // determined the element's next and previous members pointing to itself, so a
  // non-atomic update to an adjacent member won't affect the outcome either.
  if (isInList()) {
    OffTheBooksMutexAutoLock mal(ThreadListMutex());
    removeFrom(ThreadList());
  }

#ifdef DEBUG
  // We deliberately leak these so they can be tracked by the leak checker.
  // If you're having nsThreadShutdownContext leaks, you can set:
  //   XPCOM_MEM_LOG_CLASSES=nsThreadShutdownContext
  // during a test run and that will at least tell you what thread is
  // requesting shutdown on another, which can be helpful for diagnosing
  // the leak.
  for (size_t i = 0; i < mRequestedShutdownContexts.Length(); ++i) {
    Unused << mRequestedShutdownContexts[i].forget();
  }
#endif
}

nsresult
nsThread::Init(const nsACString& aName)
{
  // spawn thread and wait until it is fully setup
  RefPtr<nsThreadStartupEvent> startup = new nsThreadStartupEvent();

  NS_ADDREF_THIS();

  mShutdownRequired = true;

  ThreadInitData initData = { this, aName };

  // ThreadFunc is responsible for setting mThread
  if (!PR_CreateThread(PR_USER_THREAD, ThreadFunc, &initData,
                       PR_PRIORITY_NORMAL, PR_GLOBAL_THREAD,
                       PR_JOINABLE_THREAD, mStackSize)) {
    NS_RELEASE_THIS();
    return NS_ERROR_OUT_OF_MEMORY;
  }

  // ThreadFunc will wait for this event to be run before it tries to access
  // mThread.  By delaying insertion of this event into the queue, we ensure
  // that mThread is set properly.
  {
    mEvents->PutEvent(do_AddRef(startup), EventPriority::Normal); // retain a reference
  }

  // Wait for thread to call ThreadManager::SetupCurrentThread, which completes
  // initialization of ThreadFunc.
  startup->Wait();
  return NS_OK;
}

nsresult
nsThread::InitCurrentThread()
{
  mThread = PR_GetCurrentThread();
  mVirtualThread = GetCurrentVirtualThread();
  SetupCurrentThreadForChaosMode();
  InitCommon();

  nsThreadManager::get().RegisterCurrentThread(*this);
  return NS_OK;
}

//-----------------------------------------------------------------------------
// nsIEventTarget

NS_IMETHODIMP
nsThread::DispatchFromScript(nsIRunnable* aEvent, uint32_t aFlags)
{
  nsCOMPtr<nsIRunnable> event(aEvent);
  return mEventTarget->Dispatch(event.forget(), aFlags);
}

NS_IMETHODIMP
nsThread::Dispatch(already_AddRefed<nsIRunnable> aEvent, uint32_t aFlags)
{
  LOG(("THRD(%p) Dispatch [%p %x]\n", this, /* XXX aEvent */nullptr, aFlags));

  return mEventTarget->Dispatch(std::move(aEvent), aFlags);
}

NS_IMETHODIMP
nsThread::DelayedDispatch(already_AddRefed<nsIRunnable> aEvent, uint32_t aDelayMs)
{
  return mEventTarget->DelayedDispatch(std::move(aEvent), aDelayMs);
}

NS_IMETHODIMP
nsThread::IsOnCurrentThread(bool* aResult)
{
  return mEventTarget->IsOnCurrentThread(aResult);
}

NS_IMETHODIMP_(bool)
nsThread::IsOnCurrentThreadInfallible()
{
  // Rely on mVirtualThread being correct.
  MOZ_CRASH("IsOnCurrentThreadInfallible should never be called on nsIThread");
}

//-----------------------------------------------------------------------------
// nsIThread

NS_IMETHODIMP
nsThread::GetPRThread(PRThread** aResult)
{
  *aResult = mThread;
  return NS_OK;
}

NS_IMETHODIMP
nsThread::GetCanInvokeJS(bool* aResult)
{
  *aResult = mCanInvokeJS;
  return NS_OK;
}

NS_IMETHODIMP
nsThread::SetCanInvokeJS(bool aCanInvokeJS)
{
  mCanInvokeJS = aCanInvokeJS;
  return NS_OK;
}

NS_IMETHODIMP
nsThread::AsyncShutdown()
{
  LOG(("THRD(%p) async shutdown\n", this));

  // XXX If we make this warn, then we hit that warning at xpcom shutdown while
  //     shutting down a thread in a thread pool.  That happens b/c the thread
  //     in the thread pool is already shutdown by the thread manager.
  if (!mThread) {
    return NS_OK;
  }

  return !!ShutdownInternal(/* aSync = */ false) ? NS_OK : NS_ERROR_UNEXPECTED;
}

nsThreadShutdownContext*
nsThread::ShutdownInternal(bool aSync)
{
  MOZ_ASSERT(mThread);
  MOZ_ASSERT(mThread != PR_GetCurrentThread());
  if (NS_WARN_IF(mThread == PR_GetCurrentThread())) {
    return nullptr;
  }

  // Prevent multiple calls to this method
  if (!mShutdownRequired.compareExchange(true, false)) {
    return nullptr;
  }

  {
    OffTheBooksMutexAutoLock mal(ThreadListMutex());
    if (isInList()) {
      removeFrom(ThreadList());
    }
  }

  NotNull<nsThread*> currentThread =
    WrapNotNull(nsThreadManager::get().GetCurrentThread());

  nsAutoPtr<nsThreadShutdownContext>& context =
    *currentThread->mRequestedShutdownContexts.AppendElement();
  context = new nsThreadShutdownContext(WrapNotNull(this), currentThread, aSync);

  // Set mShutdownContext and wake up the thread in case it is waiting for
  // events to process.
  nsCOMPtr<nsIRunnable> event =
    new nsThreadShutdownEvent(WrapNotNull(this), WrapNotNull(context.get()));
  // XXXroc What if posting the event fails due to OOM?
  mEvents->PutEvent(event.forget(), EventPriority::Normal);

  // We could still end up with other events being added after the shutdown
  // task, but that's okay because we process pending events in ThreadFunc
  // after setting mShutdownContext just before exiting.
  return context;
}

void
nsThread::ShutdownComplete(NotNull<nsThreadShutdownContext*> aContext)
{
  MOZ_ASSERT(mThread);
  MOZ_ASSERT(aContext->mTerminatingThread == this);

  {
    OffTheBooksMutexAutoLock mal(ThreadListMutex());
    if (isInList()) {
      removeFrom(ThreadList());
    }
  }

  if (aContext->mAwaitingShutdownAck) {
    // We're in a synchronous shutdown, so tell whatever is up the stack that
    // we're done and unwind the stack so it can call us again.
    aContext->mAwaitingShutdownAck = false;
    return;
  }

  // Now, it should be safe to join without fear of dead-locking.

  PR_JoinThread(mThread);
  mThread = nullptr;

#ifdef DEBUG
  nsCOMPtr<nsIThreadObserver> obs = mEvents->GetObserver();
  MOZ_ASSERT(!obs, "Should have been cleared at shutdown!");
#endif

  // Delete aContext.
  MOZ_ALWAYS_TRUE(
    aContext->mJoiningThread->mRequestedShutdownContexts.RemoveElement(aContext));
}

void
nsThread::WaitForAllAsynchronousShutdowns()
{
  // This is the motivating example for why SpinEventLoop has the template
  // parameter we are providing here.
  SpinEventLoopUntil<ProcessFailureBehavior::IgnoreAndContinue>([&]() {
      return mRequestedShutdownContexts.IsEmpty();
    }, this);
}

NS_IMETHODIMP
nsThread::Shutdown()
{
  LOG(("THRD(%p) sync shutdown\n", this));

  // XXX If we make this warn, then we hit that warning at xpcom shutdown while
  //     shutting down a thread in a thread pool.  That happens b/c the thread
  //     in the thread pool is already shutdown by the thread manager.
  if (!mThread) {
    return NS_OK;
  }

  nsThreadShutdownContext* maybeContext = ShutdownInternal(/* aSync = */ true);
  NS_ENSURE_TRUE(maybeContext, NS_ERROR_UNEXPECTED);
  NotNull<nsThreadShutdownContext*> context = WrapNotNull(maybeContext);

  // Process events on the current thread until we receive a shutdown ACK.
  // Allows waiting; ensure no locks are held that would deadlock us!
  SpinEventLoopUntil([&, context]() {
      return !context->mAwaitingShutdownAck;
    }, context->mJoiningThread);

  ShutdownComplete(context);

  return NS_OK;
}

NS_IMETHODIMP
nsThread::HasPendingEvents(bool* aResult)
{
  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
    return NS_ERROR_NOT_SAME_THREAD;
  }

  *aResult = mEvents->HasPendingEvent();
  return NS_OK;
}

NS_IMETHODIMP
nsThread::IdleDispatch(already_AddRefed<nsIRunnable> aEvent)
{
  nsCOMPtr<nsIRunnable> event = aEvent;

  if (NS_WARN_IF(!event)) {
    return NS_ERROR_INVALID_ARG;
  }

  if (!mEvents->PutEvent(event.forget(), EventPriority::Idle)) {
    NS_WARNING("An idle event was posted to a thread that will never run it (rejected)");
    return NS_ERROR_UNEXPECTED;
  }

  return NS_OK;
}

#ifdef MOZ_CANARY
void canary_alarm_handler(int signum);

class Canary
{
  //XXX ToDo: support nested loops
public:
  Canary()
  {
    if (sCanaryOutputFD > 0 && EventLatencyIsImportant()) {
      signal(SIGALRM, canary_alarm_handler);
      ualarm(15000, 0);
    }
  }

  ~Canary()
  {
    if (sCanaryOutputFD != 0 && EventLatencyIsImportant()) {
      ualarm(0, 0);
    }
  }

  static bool EventLatencyIsImportant()
  {
    return NS_IsMainThread() && XRE_IsParentProcess();
  }
};

void canary_alarm_handler(int signum)
{
  void* array[30];
  const char msg[29] = "event took too long to run:\n";
  // use write to be safe in the signal handler
  write(sCanaryOutputFD, msg, sizeof(msg));
  backtrace_symbols_fd(array, backtrace(array, 30), sCanaryOutputFD);
}

#endif

#define NOTIFY_EVENT_OBSERVERS(observers_, func_, params_)                     \
  do {                                                                         \
    if (!observers_.IsEmpty()) {                                               \
      nsTObserverArray<nsCOMPtr<nsIThreadObserver>>::ForwardIterator           \
        iter_(observers_);                                                     \
      nsCOMPtr<nsIThreadObserver> obs_;                                        \
      while (iter_.HasMore()) {                                                \
        obs_ = iter_.GetNext();                                                \
        obs_ -> func_ params_ ;                                                \
      }                                                                        \
    }                                                                          \
  } while(0)

#ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY
static bool
GetLabeledRunnableName(nsIRunnable* aEvent,
                       nsACString& aName,
                       EventPriority aPriority)
{
  bool labeled = false;
  if (RefPtr<SchedulerGroup::Runnable> groupRunnable = do_QueryObject(aEvent)) {
    labeled = true;
    MOZ_ALWAYS_TRUE(NS_SUCCEEDED(groupRunnable->GetName(aName)));
  } else if (nsCOMPtr<nsINamed> named = do_QueryInterface(aEvent)) {
    MOZ_ALWAYS_TRUE(NS_SUCCEEDED(named->GetName(aName)));
  } else {
    aName.AssignLiteral("non-nsINamed runnable");
  }
  if (aName.IsEmpty()) {
    aName.AssignLiteral("anonymous runnable");
  }

  if (!labeled && aPriority > EventPriority::Input) {
    aName.AppendLiteral("(unlabeled)");
  }

  return labeled;
}
#endif

mozilla::PerformanceCounter*
nsThread::GetPerformanceCounter(nsIRunnable* aEvent)
{
  RefPtr<SchedulerGroup::Runnable> docRunnable = do_QueryObject(aEvent);
  if (docRunnable) {
    mozilla::dom::DocGroup* docGroup = docRunnable->DocGroup();
    if (docGroup) {
      return docGroup->GetPerformanceCounter();
    }
  }
  return nullptr;
}

size_t
nsThread::ShallowSizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
{
  size_t n = 0;
  if (mShutdownContext) {
    n += aMallocSizeOf(mShutdownContext);
  }
  n += mRequestedShutdownContexts.ShallowSizeOfExcludingThis(aMallocSizeOf);
  return aMallocSizeOf(this) + aMallocSizeOf(mThread) + n;
}

size_t
nsThread::SizeOfEventQueues(mozilla::MallocSizeOf aMallocSizeOf) const
{
  size_t n = 0;
  if (mCurrentPerformanceCounter) {
    n += aMallocSizeOf(mCurrentPerformanceCounter);
  }
  if (mEventTarget) {
    // The size of mEvents is reported by mEventTarget.
    n += mEventTarget->SizeOfIncludingThis(aMallocSizeOf);
  }
  return n;
}

size_t
nsThread::SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
{
  return ShallowSizeOfIncludingThis(aMallocSizeOf) + SizeOfEventQueues(aMallocSizeOf);
}

NS_IMETHODIMP
nsThread::ProcessNextEvent(bool aMayWait, bool* aResult)
{
  LOG(("THRD(%p) ProcessNextEvent [%u %u]\n", this, aMayWait,
       mNestedEventLoopDepth));

  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
    return NS_ERROR_NOT_SAME_THREAD;
  }

  // When recording or replaying, execute triggers that were activated
  // non-deterministically at some point since the last turn of the event loop.
  if (recordreplay::IsRecordingOrReplaying()) {
    recordreplay::ExecuteTriggers();

    // Vsync observers are notified whenever processing events on the main
    // thread. Waiting for explicit vsync messages from the UI process can
    // result in paints happening at unexpected times when replaying/rewinding.
    if (mIsMainThread == MAIN_THREAD) {
      recordreplay::child::NotifyVsyncObserver();
    }
  }

  // The toplevel event loop normally blocks waiting for the next event, but
  // if we're trying to shut this thread down, we must exit the event loop when
  // the event queue is empty.
  // This only applys to the toplevel event loop! Nested event loops (e.g.
  // during sync dispatch) are waiting for some state change and must be able
  // to block even if something has requested shutdown of the thread. Otherwise
  // we'll just busywait as we endlessly look for an event, fail to find one,
  // and repeat the nested event loop since its state change hasn't happened yet.
  bool reallyWait = aMayWait && (mNestedEventLoopDepth > 0 || !ShuttingDown());

  Maybe<Scheduler::EventLoopActivation> activation;
  if (IsMainThread()) {
    DoMainThreadSpecificProcessing(reallyWait);
    activation.emplace();
  }

  ++mNestedEventLoopDepth;

  // We only want to create an AutoNoJSAPI on threads that actually do DOM stuff
  // (including workers).  Those are exactly the threads that have an
  // mScriptObserver.
  Maybe<dom::AutoNoJSAPI> noJSAPI;
  bool callScriptObserver = !!mScriptObserver;
  if (callScriptObserver) {
    noJSAPI.emplace();
    mScriptObserver->BeforeProcessTask(reallyWait);
  }

  nsCOMPtr<nsIThreadObserver> obs = mEvents->GetObserverOnThread();
  if (obs) {
    obs->OnProcessNextEvent(this, reallyWait);
  }

  NOTIFY_EVENT_OBSERVERS(EventQueue()->EventObservers(), OnProcessNextEvent, (this, reallyWait));

#ifdef MOZ_CANARY
  Canary canary;
#endif
  nsresult rv = NS_OK;

  {
    // Scope for |event| to make sure that its destructor fires while
    // mNestedEventLoopDepth has been incremented, since that destructor can
    // also do work.
    EventPriority priority;
    nsCOMPtr<nsIRunnable> event = mEvents->GetEvent(reallyWait, &priority);

    if (activation.isSome()) {
      activation.ref().SetEvent(event, priority);
    }

    *aResult = (event.get() != nullptr);

    if (event) {
      LOG(("THRD(%p) running [%p]\n", this, event.get()));

      if (IsMainThread()) {
        BackgroundHangMonitor().NotifyActivity();
      }

      bool schedulerLoggingEnabled = mozilla::StaticPrefs::dom_performance_enable_scheduler_timing();
      if (schedulerLoggingEnabled
          && mNestedEventLoopDepth > mCurrentEventLoopDepth
          && mCurrentPerformanceCounter) {
          // This is a recursive call, we're saving the time
          // spent in the parent event if the runnable is linked to a DocGroup.
          mozilla::TimeDuration duration = TimeStamp::Now() - mCurrentEventStart;
          mCurrentPerformanceCounter->IncrementExecutionDuration(duration.ToMicroseconds());
      }

#ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY
      // If we're on the main thread, we want to record our current runnable's
      // name in a static so that BHR can record it.
      Array<char, kRunnableNameBufSize> restoreRunnableName;
      restoreRunnableName[0] = '\0';
      auto clear = MakeScopeExit([&] {
        if (IsMainThread()) {
          MOZ_ASSERT(NS_IsMainThread());
          sMainThreadRunnableName = restoreRunnableName;
        }
      });
      if (IsMainThread()) {
        nsAutoCString name;
        GetLabeledRunnableName(event, name, priority);

        MOZ_ASSERT(NS_IsMainThread());
        restoreRunnableName = sMainThreadRunnableName;

        // Copy the name into sMainThreadRunnableName's buffer, and append a
        // terminating null.
        uint32_t length = std::min((uint32_t) kRunnableNameBufSize - 1,
                                   (uint32_t) name.Length());
        memcpy(sMainThreadRunnableName.begin(), name.BeginReading(), length);
        sMainThreadRunnableName[length] = '\0';
      }
#endif
      Maybe<AutoTimeDurationHelper> timeDurationHelper;
      if (priority == EventPriority::Input) {
        timeDurationHelper.emplace();
      }

      // The event starts to run, storing the timestamp.
      bool recursiveEvent = false;
      RefPtr<mozilla::PerformanceCounter> currentPerformanceCounter;
      if (schedulerLoggingEnabled) {
        recursiveEvent = mNestedEventLoopDepth > mCurrentEventLoopDepth;
        mCurrentEventStart = mozilla::TimeStamp::Now();
        mCurrentEvent = event;
        mCurrentEventLoopDepth = mNestedEventLoopDepth;
        mCurrentPerformanceCounter = GetPerformanceCounter(event);
        currentPerformanceCounter = mCurrentPerformanceCounter;
      }

      event->Run();

      // End of execution, we can send the duration for the group
      if (schedulerLoggingEnabled) {
       if (recursiveEvent) {
          // If we're in a recursive call, reset the timer,
          // so the parent gets its remaining execution time right.
          mCurrentEventStart = mozilla::TimeStamp::Now();
          mCurrentPerformanceCounter = currentPerformanceCounter;
        } else {
          // We're done with this dispatch
          if (currentPerformanceCounter) {
            mozilla::TimeDuration duration = TimeStamp::Now() - mCurrentEventStart;
            currentPerformanceCounter->IncrementExecutionDuration(duration.ToMicroseconds());
          }
          mCurrentEvent = nullptr;
          mCurrentEventLoopDepth = -1;
          mCurrentPerformanceCounter = nullptr;
        }
      }
    } else if (aMayWait) {
      MOZ_ASSERT(ShuttingDown(),
                 "This should only happen when shutting down");
      rv = NS_ERROR_UNEXPECTED;
    }
  }

  NOTIFY_EVENT_OBSERVERS(EventQueue()->EventObservers(), AfterProcessNextEvent, (this, *aResult));

  if (obs) {
    obs->AfterProcessNextEvent(this, *aResult);
  }

  if (callScriptObserver) {
    if (mScriptObserver) {
      mScriptObserver->AfterProcessTask(mNestedEventLoopDepth);
    }
    noJSAPI.reset();
  }

  --mNestedEventLoopDepth;

  return rv;
}

//-----------------------------------------------------------------------------
// nsISupportsPriority

NS_IMETHODIMP
nsThread::GetPriority(int32_t* aPriority)
{
  *aPriority = mPriority;
  return NS_OK;
}

NS_IMETHODIMP
nsThread::SetPriority(int32_t aPriority)
{
  if (NS_WARN_IF(!mThread)) {
    return NS_ERROR_NOT_INITIALIZED;
  }

  // NSPR defines the following four thread priorities:
  //   PR_PRIORITY_LOW
  //   PR_PRIORITY_NORMAL
  //   PR_PRIORITY_HIGH
  //   PR_PRIORITY_URGENT
  // We map the priority values defined on nsISupportsPriority to these values.

  mPriority = aPriority;

  PRThreadPriority pri;
  if (mPriority <= PRIORITY_HIGHEST) {
    pri = PR_PRIORITY_URGENT;
  } else if (mPriority < PRIORITY_NORMAL) {
    pri = PR_PRIORITY_HIGH;
  } else if (mPriority > PRIORITY_NORMAL) {
    pri = PR_PRIORITY_LOW;
  } else {
    pri = PR_PRIORITY_NORMAL;
  }
  // If chaos mode is active, retain the randomly chosen priority
  if (!ChaosMode::isActive(ChaosFeature::ThreadScheduling)) {
    PR_SetThreadPriority(mThread, pri);
  }

  return NS_OK;
}

NS_IMETHODIMP
nsThread::AdjustPriority(int32_t aDelta)
{
  return SetPriority(mPriority + aDelta);
}

//-----------------------------------------------------------------------------
// nsIThreadInternal

NS_IMETHODIMP
nsThread::GetObserver(nsIThreadObserver** aObs)
{
  nsCOMPtr<nsIThreadObserver> obs = mEvents->GetObserver();
  obs.forget(aObs);
  return NS_OK;
}

NS_IMETHODIMP
nsThread::SetObserver(nsIThreadObserver* aObs)
{
  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
    return NS_ERROR_NOT_SAME_THREAD;
  }

  mEvents->SetObserver(aObs);
  return NS_OK;
}

uint32_t
nsThread::RecursionDepth() const
{
  MOZ_ASSERT(PR_GetCurrentThread() == mThread);
  return mNestedEventLoopDepth;
}

NS_IMETHODIMP
nsThread::AddObserver(nsIThreadObserver* aObserver)
{
  if (NS_WARN_IF(!aObserver)) {
    return NS_ERROR_INVALID_ARG;
  }
  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
    return NS_ERROR_NOT_SAME_THREAD;
  }

  EventQueue()->AddObserver(aObserver);

  return NS_OK;
}

NS_IMETHODIMP
nsThread::RemoveObserver(nsIThreadObserver* aObserver)
{
  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
    return NS_ERROR_NOT_SAME_THREAD;
  }

  EventQueue()->RemoveObserver(aObserver);

  return NS_OK;
}

void
nsThread::SetScriptObserver(mozilla::CycleCollectedJSContext* aScriptObserver)
{
  if (!aScriptObserver) {
    mScriptObserver = nullptr;
    return;
  }

  MOZ_ASSERT(!mScriptObserver);
  mScriptObserver = aScriptObserver;
}

void
nsThread::DoMainThreadSpecificProcessing(bool aReallyWait)
{
  MOZ_ASSERT(IsMainThread());

  ipc::CancelCPOWs();

  if (aReallyWait) {
    BackgroundHangMonitor().NotifyWait();
  }

  // Fire a memory pressure notification, if one is pending.
  if (!ShuttingDown()) {
    MemoryPressureState mpPending = NS_GetPendingMemoryPressure();
    if (mpPending != MemPressure_None) {
      nsCOMPtr<nsIObserverService> os = services::GetObserverService();

      if (os) {
        if (mpPending == MemPressure_Stopping) {
          os->NotifyObservers(nullptr, "memory-pressure-stop", nullptr);
        } else {
          os->NotifyObservers(nullptr, "memory-pressure",
                              mpPending == MemPressure_New ? u"low-memory" :
                              u"low-memory-ongoing");
        }
      } else {
        NS_WARNING("Can't get observer service!");
      }
    }
  }

  if (!ShuttingDown()) {
    SaveMemoryReportNearOOM(ShouldSaveMemoryReport::kMaybeReport);
  }
}

NS_IMETHODIMP
nsThread::GetEventTarget(nsIEventTarget** aEventTarget)
{
  nsCOMPtr<nsIEventTarget> target = this;
  target.forget(aEventTarget);
  return NS_OK;
}

nsIEventTarget*
nsThread::EventTarget()
{
  return this;
}

nsISerialEventTarget*
nsThread::SerialEventTarget()
{
  return this;
}