1 files changed, 798 insertions, 0 deletions
diff --git a/xpcom/threads/nsThreadManager.cpp b/xpcom/threads/nsThreadManager.cpp
new file mode 100644
index 0000000000..367b520a54
--- /dev/null
+++ b/xpcom/threads/nsThreadManager.cpp
@@ -0,0 +1,798 @@
+/* -*- 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 "nsThreadPool.h"
+#include "nsThreadUtils.h"
+#include "nsIClassInfoImpl.h"
+#include "nsExceptionHandler.h"
+#include "nsTArray.h"
+#include "nsXULAppAPI.h"
+#include "nsExceptionHandler.h"
+#include "mozilla/AbstractThread.h"
+#include "mozilla/AppShutdown.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/CycleCollectedJSContext.h"  // nsAutoMicroTask
+#include "mozilla/EventQueue.h"
+#include "mozilla/InputTaskManager.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/ProfilerMarkers.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/TaskQueue.h"
+#include "mozilla/ThreadEventQueue.h"
+#include "mozilla/ThreadLocal.h"
+#include "TaskController.h"
+#include "ThreadEventTarget.h"
+#ifdef MOZ_CANARY
+#  include <fcntl.h>
+#  include <unistd.h>
+#endif
+
+#include "MainThreadIdlePeriod.h"
+
+using namespace mozilla;
+
+static MOZ_THREAD_LOCAL(bool) sTLSIsMainThread;
+
+bool NS_IsMainThreadTLSInitialized() { return sTLSIsMainThread.initialized(); }
+
+class BackgroundEventTarget final : public nsIEventTarget,
+                                    public TaskQueueTracker {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIEVENTTARGET_FULL
+
+  BackgroundEventTarget() = default;
+
+  nsresult Init();
+
+  already_AddRefed<nsISerialEventTarget> CreateBackgroundTaskQueue(
+      const char* aName);
+
+  void BeginShutdown(nsTArray<RefPtr<ShutdownPromise>>&);
+  void FinishShutdown();
+
+ private:
+  ~BackgroundEventTarget() = default;
+
+  nsCOMPtr<nsIThreadPool> mPool;
+  nsCOMPtr<nsIThreadPool> mIOPool;
+};
+
+NS_IMPL_ISUPPORTS(BackgroundEventTarget, nsIEventTarget, TaskQueueTracker)
+
+nsresult BackgroundEventTarget::Init() {
+  nsCOMPtr<nsIThreadPool> pool(new nsThreadPool());
+  NS_ENSURE_TRUE(pool, NS_ERROR_FAILURE);
+
+  nsresult rv = pool->SetName("BackgroundThreadPool"_ns);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Use potentially more conservative stack size.
+  rv = pool->SetThreadStackSize(nsIThreadManager::kThreadPoolStackSize);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Thread limit of 2 makes deadlock during synchronous dispatch less likely.
+  rv = pool->SetThreadLimit(2);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = pool->SetIdleThreadLimit(1);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Leave threads alive for up to 5 minutes
+  rv = pool->SetIdleThreadTimeout(300000);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Initialize the background I/O event target.
+  nsCOMPtr<nsIThreadPool> ioPool(new nsThreadPool());
+  NS_ENSURE_TRUE(pool, NS_ERROR_FAILURE);
+
+  // The io pool spends a lot of its time blocking on io, so we want to offload
+  // these jobs on a lower priority if available.
+  rv = ioPool->SetQoSForThreads(nsIThread::QOS_PRIORITY_LOW);
+  NS_ENSURE_SUCCESS(
+      rv, rv);  // note: currently infallible, keeping this for brevity.
+
+  rv = ioPool->SetName("BgIOThreadPool"_ns);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Use potentially more conservative stack size.
+  rv = ioPool->SetThreadStackSize(nsIThreadManager::kThreadPoolStackSize);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Thread limit of 4 makes deadlock during synchronous dispatch less likely.
+  rv = ioPool->SetThreadLimit(4);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = ioPool->SetIdleThreadLimit(1);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Leave threads alive for up to 5 minutes
+  rv = ioPool->SetIdleThreadTimeout(300000);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  pool.swap(mPool);
+  ioPool.swap(mIOPool);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP_(bool)
+BackgroundEventTarget::IsOnCurrentThreadInfallible() {
+  return mPool->IsOnCurrentThread() || mIOPool->IsOnCurrentThread();
+}
+
+NS_IMETHODIMP
+BackgroundEventTarget::IsOnCurrentThread(bool* aValue) {
+  bool value = false;
+  if (NS_SUCCEEDED(mPool->IsOnCurrentThread(&value)) && value) {
+    *aValue = value;
+    return NS_OK;
+  }
+  return mIOPool->IsOnCurrentThread(aValue);
+}
+
+NS_IMETHODIMP
+BackgroundEventTarget::Dispatch(already_AddRefed<nsIRunnable> aRunnable,
+                                uint32_t aFlags) {
+  // We need to be careful here, because if an event is getting dispatched here
+  // from within TaskQueue::Runner::Run, it will be dispatched with
+  // NS_DISPATCH_AT_END, but we might not be running the event on the same
+  // pool, depending on which pool we were on and the dispatch flags.  If we
+  // dispatch an event with NS_DISPATCH_AT_END to the wrong pool, the pool
+  // may not process the event in a timely fashion, which can lead to deadlock.
+  uint32_t flags = aFlags & ~NS_DISPATCH_EVENT_MAY_BLOCK;
+  bool mayBlock = bool(aFlags & NS_DISPATCH_EVENT_MAY_BLOCK);
+  nsCOMPtr<nsIThreadPool>& pool = mayBlock ? mIOPool : mPool;
+
+  // If we're already running on the pool we want to dispatch to, we can
+  // unconditionally add NS_DISPATCH_AT_END to indicate that we shouldn't spin
+  // up a new thread.
+  //
+  // Otherwise, we should remove NS_DISPATCH_AT_END so we don't run into issues
+  // like those in the above comment.
+  if (pool->IsOnCurrentThread()) {
+    flags |= NS_DISPATCH_AT_END;
+  } else {
+    flags &= ~NS_DISPATCH_AT_END;
+  }
+
+  return pool->Dispatch(std::move(aRunnable), flags);
+}
+
+NS_IMETHODIMP
+BackgroundEventTarget::DispatchFromScript(nsIRunnable* aRunnable,
+                                          uint32_t aFlags) {
+  nsCOMPtr<nsIRunnable> runnable(aRunnable);
+  return Dispatch(runnable.forget(), aFlags);
+}
+
+NS_IMETHODIMP
+BackgroundEventTarget::DelayedDispatch(already_AddRefed<nsIRunnable> aRunnable,
+                                       uint32_t) {
+  nsCOMPtr<nsIRunnable> dropRunnable(aRunnable);
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+BackgroundEventTarget::RegisterShutdownTask(nsITargetShutdownTask* aTask) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+BackgroundEventTarget::UnregisterShutdownTask(nsITargetShutdownTask* aTask) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+void BackgroundEventTarget::BeginShutdown(
+    nsTArray<RefPtr<ShutdownPromise>>& promises) {
+  auto queues = GetAllTrackedTaskQueues();
+  for (auto& queue : queues) {
+    promises.AppendElement(queue->BeginShutdown());
+  }
+}
+
+void BackgroundEventTarget::FinishShutdown() {
+  mPool->Shutdown();
+  mIOPool->Shutdown();
+}
+
+already_AddRefed<nsISerialEventTarget>
+BackgroundEventTarget::CreateBackgroundTaskQueue(const char* aName) {
+  return TaskQueue::Create(do_AddRef(this), aName).forget();
+}
+
+extern "C" {
+// This uses the C language linkage because it's exposed to Rust
+// via the xpcom/rust/moz_task crate.
+bool NS_IsMainThread() { return sTLSIsMainThread.get(); }
+}
+
+void NS_SetMainThread() {
+  if (!sTLSIsMainThread.init()) {
+    MOZ_CRASH();
+  }
+  sTLSIsMainThread.set(true);
+  MOZ_ASSERT(NS_IsMainThread());
+  // We initialize the SerialEventTargetGuard's TLS here for simplicity as it
+  // needs to be initialized around the same time you would initialize
+  // sTLSIsMainThread.
+  SerialEventTargetGuard::InitTLS();
+  nsThreadPool::InitTLS();
+}
+
+#ifdef DEBUG
+
+namespace mozilla {
+
+void AssertIsOnMainThread() { MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!"); }
+
+}  // namespace mozilla
+
+#endif
+
+typedef nsTArray<NotNull<RefPtr<nsThread>>> nsThreadArray;
+
+//-----------------------------------------------------------------------------
+
+/* static */
+void nsThreadManager::ReleaseThread(void* aData) {
+  static_cast<nsThread*>(aData)->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)
+
+//-----------------------------------------------------------------------------
+
+/*static*/ nsThreadManager& nsThreadManager::get() {
+  static nsThreadManager sInstance;
+  return sInstance;
+}
+
+nsThreadManager::nsThreadManager()
+    : mCurThreadIndex(0), mMainPRThread(nullptr), mInitialized(false) {}
+
+nsThreadManager::~nsThreadManager() = default;
+
+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 (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
+
+  TaskController::Initialize();
+
+  // Initialize idle handling.
+  nsCOMPtr<nsIIdlePeriod> idlePeriod = new MainThreadIdlePeriod();
+  TaskController::Get()->SetIdleTaskManager(
+      new IdleTaskManager(idlePeriod.forget()));
+
+  // Create main thread queue that forwards events to TaskController and
+  // construct main thread.
+  UniquePtr<EventQueue> queue = MakeUnique<EventQueue>(true);
+
+  RefPtr<ThreadEventQueue> synchronizedQueue =
+      new ThreadEventQueue(std::move(queue), true);
+
+  mMainThread = new nsThread(WrapNotNull(synchronizedQueue),
+                             nsThread::MAIN_THREAD, {.stackSize = 0});
+
+  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();
+
+  // Initialize the background event target.
+  RefPtr<BackgroundEventTarget> target(new BackgroundEventTarget());
+
+  rv = target->Init();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mBackgroundEventTarget = std::move(target);
+
+  mInitialized = true;
+
+  return NS_OK;
+}
+
+void nsThreadManager::ShutdownNonMainThreads() {
+  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);
+
+  mMainThread->mEvents->RunShutdownTasks();
+
+  nsTArray<RefPtr<ShutdownPromise>> promises;
+  mBackgroundEventTarget->BeginShutdown(promises);
+
+  bool taskQueuesShutdown = false;
+  // It's fine to capture everything by reference in the Then handler since it
+  // runs before we exit the nested event loop, thanks to the SpinEventLoopUntil
+  // below.
+  ShutdownPromise::All(mMainThread, promises)->Then(mMainThread, __func__, [&] {
+    mBackgroundEventTarget->FinishShutdown();
+    taskQueuesShutdown = true;
+  });
+
+  // Wait for task queues to shutdown, so we don't shut down the underlying
+  // threads of the background event target in the block below, thereby
+  // preventing the task queues from emptying, preventing the shutdown promises
+  // from resolving, and prevent anything checking `taskQueuesShutdown` from
+  // working.
+  mozilla::SpinEventLoopUntil(
+      "nsThreadManager::Shutdown"_ns, [&]() { return taskQueuesShutdown; },
+      mMainThread);
+
+  {
+    // We gather the threads into a list, so that we avoid holding the
+    // enumerator lock while calling nsIThread::Shutdown.
+    nsTArray<RefPtr<nsThread>> threadsToShutdown;
+    for (auto* thread : nsThread::Enumerate()) {
+      if (thread->ShutdownRequired()) {
+        threadsToShutdown.AppendElement(thread);
+      }
+    }
+
+    // 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 (auto& thread : threadsToShutdown) {
+      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();
+
+  // There are no more background threads at this point.
+}
+
+void nsThreadManager::ShutdownMainThread() {
+  MOZ_ASSERT(!mInitialized, "Must have called BeginShutdown");
+
+  // Do NS_ProcessPendingEvents but with special handling to set
+  // mEventsAreDoomed atomically with the removal of the last event. This means
+  // that PutEvent cannot succeed if the event would be left in the main thread
+  // queue after our final call to NS_ProcessPendingEvents.
+  // See comments in `nsThread::ThreadFunc` for a more detailed explanation.
+  while (true) {
+    if (mMainThread->mEvents->ShutdownIfNoPendingEvents()) {
+      break;
+    }
+    NS_ProcessPendingEvents(mMainThread);
+  }
+
+  // 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);
+
+  mBackgroundEventTarget = nullptr;
+}
+
+void nsThreadManager::ReleaseMainThread() {
+  MOZ_ASSERT(!mInitialized, "Must have called BeginShutdown");
+  MOZ_ASSERT(!mBackgroundEventTarget, "Must have called ShutdownMainThread");
+  MOZ_ASSERT(mMainThread);
+
+  // Release main thread object.
+  mMainThread = nullptr;
+
+  // Remove the TLS entry for the main thread.
+  PR_SetThreadPrivate(mCurThreadIndex, nullptr);
+}
+
+void nsThreadManager::RegisterCurrentThread(nsThread& aThread) {
+  MOZ_ASSERT(aThread.GetPRThread() == PR_GetCurrentThread(), "bad aThread");
+
+  aThread.AddRef();  // for TLS entry
+  PR_SetThreadPrivate(mCurThreadIndex, &aThread);
+}
+
+void nsThreadManager::UnregisterCurrentThread(nsThread& aThread) {
+  MOZ_ASSERT(aThread.GetPRThread() == PR_GetCurrentThread(), "bad aThread");
+
+  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;
+  }
+
+  RefPtr<nsThread> thread =
+      new nsThread(WrapNotNull(aQueue), aMainThread, {.stackSize = 0});
+  if (!thread || NS_FAILED(thread->InitCurrentThread())) {
+    return nullptr;
+  }
+
+  return thread.get();  // reference held in TLS
+}
+
+nsresult nsThreadManager::DispatchToBackgroundThread(nsIRunnable* aEvent,
+                                                     uint32_t aDispatchFlags) {
+  if (!mInitialized) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIEventTarget> backgroundTarget(mBackgroundEventTarget);
+  return backgroundTarget->Dispatch(aEvent, aDispatchFlags);
+}
+
+already_AddRefed<nsISerialEventTarget>
+nsThreadManager::CreateBackgroundTaskQueue(const char* aName) {
+  if (!mInitialized) {
+    return nullptr;
+  }
+
+  return mBackgroundEventTarget->CreateBackgroundTaskQueue(aName);
+}
+
+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 :-)
+  //
+  // We assume that if we're implicitly creating a thread here that it doesn't
+  // want an event queue. Any thread which wants an event queue should
+  // explicitly create its nsThread wrapper.
+  RefPtr<nsThread> thread = new nsThread();
+  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->EventQueue();
+  }
+  return false;
+}
+
+NS_IMETHODIMP
+nsThreadManager::NewNamedThread(
+    const nsACString& aName, nsIThreadManager::ThreadCreationOptions aOptions,
+    nsIThread** aResult) {
+  // Note: can be called from arbitrary threads
+
+  // No new threads during Shutdown
+  if (NS_WARN_IF(!mInitialized)) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  [[maybe_unused]] TimeStamp startTime = TimeStamp::Now();
+
+  RefPtr<ThreadEventQueue> queue =
+      new ThreadEventQueue(MakeUnique<EventQueue>());
+  RefPtr<nsThread> thr =
+      new nsThread(WrapNotNull(queue), nsThread::NOT_MAIN_THREAD, aOptions);
+  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;
+  }
+
+  PROFILER_MARKER_TEXT(
+      "NewThread", OTHER,
+      MarkerOptions(MarkerStack::Capture(),
+                    MarkerTiming::IntervalUntilNowFrom(startTime)),
+      aName);
+  if (!NS_IsMainThread()) {
+    PROFILER_MARKER_TEXT(
+        "NewThread (non-main thread)", OTHER,
+        MarkerOptions(MarkerStack::Capture(), MarkerThreadId::MainThread(),
+                      MarkerTiming::IntervalUntilNowFrom(startTime)),
+        aName);
+  }
+
+  thr.forget(aResult);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadManager::GetMainThread(nsIThread** aResult) {
+  // Keep this functioning during Shutdown
+  if (!mMainThread) {
+    if (!NS_IsMainThread()) {
+      NS_WARNING(
+          "Called GetMainThread but there isn't a main thread and "
+          "we're not the main thread.");
+    }
+    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(const nsACString& aVeryGoodReasonToDoThis,
+                                    nsINestedEventLoopCondition* aCondition) {
+  return SpinEventLoopUntilInternal(aVeryGoodReasonToDoThis, aCondition,
+                                    ShutdownPhase::NotInShutdown);
+}
+
+NS_IMETHODIMP
+nsThreadManager::SpinEventLoopUntilOrQuit(
+    const nsACString& aVeryGoodReasonToDoThis,
+    nsINestedEventLoopCondition* aCondition) {
+  return SpinEventLoopUntilInternal(aVeryGoodReasonToDoThis, aCondition,
+                                    ShutdownPhase::AppShutdownConfirmed);
+}
+
+// statics from SpinEventLoopUntil.h
+AutoNestedEventLoopAnnotation* AutoNestedEventLoopAnnotation::sCurrent =
+    nullptr;
+StaticMutex AutoNestedEventLoopAnnotation::sStackMutex;
+
+// static from SpinEventLoopUntil.h
+void AutoNestedEventLoopAnnotation::AnnotateXPCOMSpinEventLoopStack(
+    const nsACString& aStack) {
+  if (aStack.Length() > 0) {
+    nsCString prefixedStack(XRE_GetProcessTypeString());
+    prefixedStack += ": "_ns + aStack;
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::XPCOMSpinEventLoopStack, prefixedStack);
+  } else {
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::XPCOMSpinEventLoopStack, ""_ns);
+  }
+}
+
+nsresult nsThreadManager::SpinEventLoopUntilInternal(
+    const nsACString& aVeryGoodReasonToDoThis,
+    nsINestedEventLoopCondition* aCondition,
+    ShutdownPhase aShutdownPhaseToCheck) {
+  // XXX: We would want to AssertIsOnMainThread(); but that breaks some GTest.
+  nsCOMPtr<nsINestedEventLoopCondition> condition(aCondition);
+  nsresult rv = NS_OK;
+
+  if (!mozilla::SpinEventLoopUntil(aVeryGoodReasonToDoThis, [&]() -> bool {
+        // Check if an ongoing shutdown reached our limits.
+        if (aShutdownPhaseToCheck > ShutdownPhase::NotInShutdown &&
+            AppShutdown::GetCurrentShutdownPhase() >= aShutdownPhaseToCheck) {
+          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::GetMainThreadEventTarget(nsIEventTarget** aTarget) {
+  nsCOMPtr<nsIEventTarget> target = GetMainThreadSerialEventTarget();
+  target.forget(aTarget);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadManager::DispatchToMainThread(nsIRunnable* aEvent, uint32_t aPriority,
+                                      uint8_t aArgc) {
+  // 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 wasn't explicitly passed, that means it should be treated as
+  // PRIORITY_NORMAL.
+  if (aArgc > 0 && aPriority != nsIRunnablePriority::PRIORITY_NORMAL) {
+    nsCOMPtr<nsIRunnable> event(aEvent);
+    return mMainThread->DispatchFromScript(
+        new PrioritizableRunnable(event.forget(), aPriority), 0);
+  }
+  return mMainThread->DispatchFromScript(aEvent, 0);
+}
+
+class AutoMicroTaskWrapperRunnable final : public Runnable {
+ public:
+  explicit AutoMicroTaskWrapperRunnable(nsIRunnable* aEvent)
+      : Runnable("AutoMicroTaskWrapperRunnable"), mEvent(aEvent) {
+    MOZ_ASSERT(aEvent);
+  }
+
+ private:
+  ~AutoMicroTaskWrapperRunnable() = default;
+
+  NS_IMETHOD Run() override {
+    nsAutoMicroTask mt;
+
+    return mEvent->Run();
+  }
+
+  RefPtr<nsIRunnable> mEvent;
+};
+
+NS_IMETHODIMP
+nsThreadManager::DispatchToMainThreadWithMicroTask(nsIRunnable* aEvent,
+                                                   uint32_t aPriority,
+                                                   uint8_t aArgc) {
+  RefPtr<AutoMicroTaskWrapperRunnable> runnable =
+      new AutoMicroTaskWrapperRunnable(aEvent);
+
+  return DispatchToMainThread(runnable, aPriority, aArgc);
+}
+
+void nsThreadManager::EnableMainThreadEventPrioritization() {
+  MOZ_ASSERT(NS_IsMainThread());
+  InputTaskManager::Get()->EnableInputEventPrioritization();
+}
+
+void nsThreadManager::FlushInputEventPrioritization() {
+  MOZ_ASSERT(NS_IsMainThread());
+  InputTaskManager::Get()->FlushInputEventPrioritization();
+}
+
+void nsThreadManager::SuspendInputEventPrioritization() {
+  MOZ_ASSERT(NS_IsMainThread());
+  InputTaskManager::Get()->SuspendInputEventPrioritization();
+}
+
+void nsThreadManager::ResumeInputEventPrioritization() {
+  MOZ_ASSERT(NS_IsMainThread());
+  InputTaskManager::Get()->ResumeInputEventPrioritization();
+}
+
+// static
+bool nsThreadManager::MainThreadHasPendingHighPriorityEvents() {
+  MOZ_ASSERT(NS_IsMainThread());
+  bool retVal = false;
+  if (get().mMainThread) {
+    get().mMainThread->HasPendingHighPriorityEvents(&retVal);
+  }
+  return retVal;
+}
+
+NS_IMETHODIMP
+nsThreadManager::IdleDispatchToMainThread(nsIRunnable* aEvent,
+                                          uint32_t aTimeout) {
+  // Note: C++ callers should instead use NS_DispatchToThreadQueue or
+  // NS_DispatchToCurrentThreadQueue.
+  MOZ_ASSERT(NS_IsMainThread());
+
+  nsCOMPtr<nsIRunnable> event(aEvent);
+  if (aTimeout) {
+    return NS_DispatchToThreadQueue(event.forget(), aTimeout, mMainThread,
+                                    EventQueuePriority::Idle);
+  }
+
+  return NS_DispatchToThreadQueue(event.forget(), mMainThread,
+                                  EventQueuePriority::Idle);
+}
+
+NS_IMETHODIMP
+nsThreadManager::DispatchDirectTaskToCurrentThread(nsIRunnable* aEvent) {
+  NS_ENSURE_STATE(aEvent);
+  nsCOMPtr<nsIRunnable> runnable = aEvent;
+  return GetCurrentThread()->DispatchDirectTask(runnable.forget());
+}