gecko-dev/dom/ipc/ProcessHangMonitor.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/ProcessHangMonitor.h"
#include "mozilla/ProcessHangMonitorIPC.h"

#include "jsapi.h"

#include "mozilla/Atomics.h"
#include "mozilla/BackgroundHangMonitor.h"
#include "mozilla/dom/ContentParent.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/ScriptSettings.h"
#include "mozilla/dom/TabChild.h"
#include "mozilla/dom/TabParent.h"
#include "mozilla/ipc/TaskFactory.h"
#include "mozilla/Monitor.h"
#include "mozilla/plugins/PluginBridge.h"
#include "mozilla/Preferences.h"
#include "mozilla/Unused.h"
#include "mozilla/WeakPtr.h"

#include "nsExceptionHandler.h"
#include "nsFrameLoader.h"
#include "nsIHangReport.h"
#include "nsITabParent.h"
#include "nsQueryObject.h"
#include "nsPluginHost.h"
#include "nsThreadUtils.h"

#include "base/task.h"
#include "base/thread.h"

#ifdef XP_WIN
// For IsDebuggerPresent()
#  include <windows.h>
#endif

using namespace mozilla;
using namespace mozilla::dom;
using namespace mozilla::ipc;

/*
 * Basic architecture:
 *
 * Each process has its own ProcessHangMonitor singleton. This singleton exists
 * as long as there is at least one content process in the system. Each content
 * process has a HangMonitorChild and the chrome process has one
 * HangMonitorParent per process. Each process (including the chrome process)
 * runs a hang monitoring thread. The PHangMonitor actors are bound to this
 * thread so that they never block on the main thread.
 *
 * When the content process detects a hang, it posts a task to its hang thread,
 * which sends an IPC message to the hang thread in the parent. The parent
 * cancels any ongoing CPOW requests and then posts a runnable to the main
 * thread that notifies Firefox frontend code of the hang. The frontend code is
 * passed an nsIHangReport, which can be used to terminate the hang.
 *
 * If the user chooses to terminate a script, a task is posted to the chrome
 * process's hang monitoring thread, which sends an IPC message to the hang
 * thread in the content process. That thread sets a flag to indicate that JS
 * execution should be terminated the next time it hits the interrupt
 * callback. A similar scheme is used for debugging slow scripts. If a content
 * process or plug-in needs to be terminated, the chrome process does so
 * directly, without messaging the content process.
 */

namespace {

/* Child process objects */

class HangMonitorChild : public PProcessHangMonitorChild,
                         public BackgroundHangAnnotator {
 public:
  explicit HangMonitorChild(ProcessHangMonitor* aMonitor);
  ~HangMonitorChild() override;

  void Bind(Endpoint<PProcessHangMonitorChild>&& aEndpoint);

  typedef ProcessHangMonitor::SlowScriptAction SlowScriptAction;
  SlowScriptAction NotifySlowScript(nsITabChild* aTabChild,
                                    const char* aFileName,
                                    const nsString& aAddonId);
  void NotifySlowScriptAsync(TabId aTabId, const nsCString& aFileName,
                             const nsString& aAddonId);

  bool IsDebuggerStartupComplete();

  void NotifyPluginHang(uint32_t aPluginId);
  void NotifyPluginHangAsync(uint32_t aPluginId);

  void ClearHang();
  void ClearHangAsync();
  void ClearPaintWhileInterruptingJS(const LayersObserverEpoch& aEpoch);

  // MaybeStartPaintWhileInterruptingJS will notify the background hang monitor
  // of activity if this is the first time calling it since
  // ClearPaintWhileInterruptingJS. It should be callable from any thread, but
  // you must be holding mMonitor if using it off the main thread, since it
  // could race with ClearPaintWhileInterruptingJS.
  void MaybeStartPaintWhileInterruptingJS();

  mozilla::ipc::IPCResult RecvTerminateScript(
      const bool& aTerminateGlobal) override;
  mozilla::ipc::IPCResult RecvBeginStartingDebugger() override;
  mozilla::ipc::IPCResult RecvEndStartingDebugger() override;

  mozilla::ipc::IPCResult RecvPaintWhileInterruptingJS(
      const TabId& aTabId, const bool& aForceRepaint,
      const LayersObserverEpoch& aEpoch) override;

  void ActorDestroy(ActorDestroyReason aWhy) override;

  void InterruptCallback();
  void Shutdown();

  static HangMonitorChild* Get() { return sInstance; }

  void Dispatch(already_AddRefed<nsIRunnable> aRunnable) {
    mHangMonitor->Dispatch(std::move(aRunnable));
  }
  bool IsOnThread() { return mHangMonitor->IsOnThread(); }

  void AnnotateHang(BackgroundHangAnnotations& aAnnotations) override;

 private:
  void ShutdownOnThread();

  // Ordering of this atomic is not preserved while recording/replaying, as it
  // may be accessed during the JS interrupt callback.
  static Atomic<HangMonitorChild*, SequentiallyConsistent,
                recordreplay::Behavior::DontPreserve>
      sInstance;

  const RefPtr<ProcessHangMonitor> mHangMonitor;
  Monitor mMonitor;

  // Main thread-only.
  bool mSentReport;

  // These fields must be accessed with mMonitor held.
  bool mTerminateScript;
  bool mTerminateGlobal;
  bool mStartDebugger;
  bool mFinishedStartingDebugger;
  bool mPaintWhileInterruptingJS;
  bool mPaintWhileInterruptingJSForce;
  TabId mPaintWhileInterruptingJSTab;
  MOZ_INIT_OUTSIDE_CTOR LayersObserverEpoch mPaintWhileInterruptingJSEpoch;
  JSContext* mContext;
  bool mShutdownDone;

  // This field is only accessed on the hang thread.
  bool mIPCOpen;

  // Allows us to ensure we NotifyActivity only once, allowing
  // either thread to do so.
  Atomic<bool> mPaintWhileInterruptingJSActive;
};

Atomic<HangMonitorChild*, SequentiallyConsistent,
       recordreplay::Behavior::DontPreserve>
    HangMonitorChild::sInstance;

/* Parent process objects */

class HangMonitorParent;

class HangMonitoredProcess final : public nsIHangReport {
 public:
  NS_DECL_THREADSAFE_ISUPPORTS

  HangMonitoredProcess(HangMonitorParent* aActor, ContentParent* aContentParent)
      : mActor(aActor), mContentParent(aContentParent) {}

  NS_DECL_NSIHANGREPORT

  // Called when a content process shuts down.
  void Clear() {
    mContentParent = nullptr;
    mActor = nullptr;
  }

  /**
   * Sets the information associated with this hang: this includes the ID of
   * the plugin which caused the hang as well as the content PID. The ID of
   * a minidump taken during the hang can also be provided.
   *
   * @param aHangData The hang information
   * @param aDumpId The ID of a minidump taken when the hang occurred
   */
  void SetHangData(const HangData& aHangData, const nsAString& aDumpId) {
    mHangData = aHangData;
    mDumpId = aDumpId;
  }

  void ClearHang() {
    mHangData = HangData();
    mDumpId.Truncate();
  }

 private:
  ~HangMonitoredProcess() = default;

  // Everything here is main thread-only.
  HangMonitorParent* mActor;
  ContentParent* mContentParent;
  HangData mHangData;
  nsAutoString mDumpId;
};

class HangMonitorParent : public PProcessHangMonitorParent,
                          public SupportsWeakPtr<HangMonitorParent> {
 public:
  explicit HangMonitorParent(ProcessHangMonitor* aMonitor);
  ~HangMonitorParent() override;

  MOZ_DECLARE_WEAKREFERENCE_TYPENAME(HangMonitorParent)

  void Bind(Endpoint<PProcessHangMonitorParent>&& aEndpoint);

  mozilla::ipc::IPCResult RecvHangEvidence(const HangData& aHangData) override;
  mozilla::ipc::IPCResult RecvClearHang() override;

  void ActorDestroy(ActorDestroyReason aWhy) override;

  void SetProcess(HangMonitoredProcess* aProcess) { mProcess = aProcess; }

  void Shutdown();

  void PaintWhileInterruptingJS(dom::TabParent* aTabParent, bool aForceRepaint,
                                const LayersObserverEpoch& aEpoch);

  void TerminateScript(bool aTerminateGlobal);
  void BeginStartingDebugger();
  void EndStartingDebugger();
  void CleanupPluginHang(uint32_t aPluginId, bool aRemoveFiles);

  /**
   * Update the dump for the specified plugin. This method is thread-safe and
   * is used to replace a browser minidump with a full minidump. If aDumpId is
   * empty this is a no-op.
   */
  void UpdateMinidump(uint32_t aPluginId, const nsString& aDumpId);

  void Dispatch(already_AddRefed<nsIRunnable> aRunnable) {
    mHangMonitor->Dispatch(std::move(aRunnable));
  }
  bool IsOnThread() { return mHangMonitor->IsOnThread(); }

 private:
  bool TakeBrowserMinidump(const PluginHangData& aPhd, nsString& aCrashId);

  void SendHangNotification(const HangData& aHangData,
                            const nsString& aBrowserDumpId, bool aTakeMinidump);

  void ClearHangNotification();

  void PaintWhileInterruptingJSOnThread(TabId aTabId, bool aForceRepaint,
                                        const LayersObserverEpoch& aEpoch);

  void ShutdownOnThread();

  const RefPtr<ProcessHangMonitor> mHangMonitor;

  // This field is read-only after construction.
  bool mReportHangs;

  // This field is only accessed on the hang thread.
  bool mIPCOpen;

  Monitor mMonitor;

  // Must be accessed with mMonitor held.
  RefPtr<HangMonitoredProcess> mProcess;
  bool mShutdownDone;
  // Map from plugin ID to crash dump ID. Protected by
  // mBrowserCrashDumpHashLock.
  nsDataHashtable<nsUint32HashKey, nsString> mBrowserCrashDumpIds;
  Mutex mBrowserCrashDumpHashLock;
  mozilla::ipc::TaskFactory<HangMonitorParent> mMainThreadTaskFactory;

  static bool sShouldPaintWhileInterruptingJS;
};

bool HangMonitorParent::sShouldPaintWhileInterruptingJS = true;

}  // namespace

/* HangMonitorChild implementation */

HangMonitorChild::HangMonitorChild(ProcessHangMonitor* aMonitor)
    : mHangMonitor(aMonitor),
      // Ordering of this atomic is not preserved while recording/replaying, as
      // it may be accessed during the JS interrupt callback.
      mMonitor("HangMonitorChild lock", recordreplay::Behavior::DontPreserve),
      mSentReport(false),
      mTerminateScript(false),
      mTerminateGlobal(false),
      mStartDebugger(false),
      mFinishedStartingDebugger(false),
      mPaintWhileInterruptingJS(false),
      mPaintWhileInterruptingJSForce(false),
      mShutdownDone(false),
      mIPCOpen(true),
      mPaintWhileInterruptingJSActive(false) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  mContext = danger::GetJSContext();

  BackgroundHangMonitor::RegisterAnnotator(*this);
}

HangMonitorChild::~HangMonitorChild() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(sInstance == this);
  sInstance = nullptr;
}

void HangMonitorChild::InterruptCallback() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  bool paintWhileInterruptingJS;
  bool paintWhileInterruptingJSForce;
  TabId paintWhileInterruptingJSTab;
  LayersObserverEpoch paintWhileInterruptingJSEpoch;

  {
    MonitorAutoLock lock(mMonitor);
    paintWhileInterruptingJS = mPaintWhileInterruptingJS;
    paintWhileInterruptingJSForce = mPaintWhileInterruptingJSForce;
    paintWhileInterruptingJSTab = mPaintWhileInterruptingJSTab;
    paintWhileInterruptingJSEpoch = mPaintWhileInterruptingJSEpoch;

    mPaintWhileInterruptingJS = false;
  }

  // Don't paint from the interrupt callback when recording or replaying, as
  // the interrupt callback is triggered non-deterministically.
  if (paintWhileInterruptingJS && !recordreplay::IsRecordingOrReplaying()) {
    RefPtr<TabChild> tabChild =
        TabChild::FindTabChild(paintWhileInterruptingJSTab);
    if (tabChild) {
      js::AutoAssertNoContentJS nojs(mContext);
      tabChild->PaintWhileInterruptingJS(paintWhileInterruptingJSEpoch,
                                         paintWhileInterruptingJSForce);
    }
  }
}

void HangMonitorChild::AnnotateHang(BackgroundHangAnnotations& aAnnotations) {
  if (mPaintWhileInterruptingJSActive) {
    aAnnotations.AddAnnotation(NS_LITERAL_STRING("PaintWhileInterruptingJS"),
                               true);
  }
}

void HangMonitorChild::Shutdown() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  BackgroundHangMonitor::UnregisterAnnotator(*this);

  MonitorAutoLock lock(mMonitor);
  while (!mShutdownDone) {
    mMonitor.Wait();
  }
}

void HangMonitorChild::ShutdownOnThread() {
  MOZ_RELEASE_ASSERT(IsOnThread());

  MonitorAutoLock lock(mMonitor);
  mShutdownDone = true;
  mMonitor.Notify();
}

void HangMonitorChild::ActorDestroy(ActorDestroyReason aWhy) {
  MOZ_RELEASE_ASSERT(IsOnThread());

  mIPCOpen = false;

  // We use a task here to ensure that IPDL is finished with this
  // HangMonitorChild before it gets deleted on the main thread.
  Dispatch(NewNonOwningRunnableMethod("HangMonitorChild::ShutdownOnThread",
                                      this,
                                      &HangMonitorChild::ShutdownOnThread));
}

mozilla::ipc::IPCResult HangMonitorChild::RecvTerminateScript(
    const bool& aTerminateGlobal) {
  MOZ_RELEASE_ASSERT(IsOnThread());

  MonitorAutoLock lock(mMonitor);
  if (aTerminateGlobal) {
    mTerminateGlobal = true;
  } else {
    mTerminateScript = true;
  }
  return IPC_OK();
}

mozilla::ipc::IPCResult HangMonitorChild::RecvBeginStartingDebugger() {
  MOZ_RELEASE_ASSERT(IsOnThread());

  MonitorAutoLock lock(mMonitor);
  mStartDebugger = true;
  return IPC_OK();
}

mozilla::ipc::IPCResult HangMonitorChild::RecvEndStartingDebugger() {
  MOZ_RELEASE_ASSERT(IsOnThread());

  MonitorAutoLock lock(mMonitor);
  mFinishedStartingDebugger = true;
  return IPC_OK();
}

mozilla::ipc::IPCResult HangMonitorChild::RecvPaintWhileInterruptingJS(
    const TabId& aTabId, const bool& aForceRepaint,
    const LayersObserverEpoch& aEpoch) {
  MOZ_RELEASE_ASSERT(IsOnThread());

  {
    MonitorAutoLock lock(mMonitor);
    MaybeStartPaintWhileInterruptingJS();
    mPaintWhileInterruptingJS = true;
    mPaintWhileInterruptingJSForce = aForceRepaint;
    mPaintWhileInterruptingJSTab = aTabId;
    mPaintWhileInterruptingJSEpoch = aEpoch;
  }

  JS_RequestInterruptCallback(mContext);

  return IPC_OK();
}

void HangMonitorChild::MaybeStartPaintWhileInterruptingJS() {
  mPaintWhileInterruptingJSActive = true;
}

void HangMonitorChild::ClearPaintWhileInterruptingJS(
    const LayersObserverEpoch& aEpoch) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  MOZ_RELEASE_ASSERT(XRE_IsContentProcess());
  mPaintWhileInterruptingJSActive = false;
}

void HangMonitorChild::Bind(Endpoint<PProcessHangMonitorChild>&& aEndpoint) {
  MOZ_RELEASE_ASSERT(IsOnThread());

  MOZ_ASSERT(!sInstance);
  sInstance = this;

  DebugOnly<bool> ok = aEndpoint.Bind(this);
  MOZ_ASSERT(ok);
}

void HangMonitorChild::NotifySlowScriptAsync(TabId aTabId,
                                             const nsCString& aFileName,
                                             const nsString& aAddonId) {
  if (mIPCOpen) {
    Unused << SendHangEvidence(SlowScriptData(aTabId, aFileName, aAddonId));
  }
}

HangMonitorChild::SlowScriptAction HangMonitorChild::NotifySlowScript(
    nsITabChild* aTabChild, const char* aFileName, const nsString& aAddonId) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  mSentReport = true;

  {
    MonitorAutoLock lock(mMonitor);

    if (mTerminateScript) {
      mTerminateScript = false;
      return SlowScriptAction::Terminate;
    }

    if (mTerminateGlobal) {
      mTerminateGlobal = false;
      return SlowScriptAction::TerminateGlobal;
    }

    if (mStartDebugger) {
      mStartDebugger = false;
      return SlowScriptAction::StartDebugger;
    }
  }

  TabId id;
  if (aTabChild) {
    RefPtr<TabChild> tabChild = static_cast<TabChild*>(aTabChild);
    id = tabChild->GetTabId();
  }
  nsAutoCString filename(aFileName);

  Dispatch(NewNonOwningRunnableMethod<TabId, nsCString, nsString>(
      "HangMonitorChild::NotifySlowScriptAsync", this,
      &HangMonitorChild::NotifySlowScriptAsync, id, filename, aAddonId));
  return SlowScriptAction::Continue;
}

bool HangMonitorChild::IsDebuggerStartupComplete() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  MonitorAutoLock lock(mMonitor);

  if (mFinishedStartingDebugger) {
    mFinishedStartingDebugger = false;
    return true;
  }

  return false;
}

void HangMonitorChild::NotifyPluginHang(uint32_t aPluginId) {
  // main thread in the child
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  mSentReport = true;

  // bounce to background thread
  Dispatch(NewNonOwningRunnableMethod<uint32_t>(
      "HangMonitorChild::NotifyPluginHangAsync", this,
      &HangMonitorChild::NotifyPluginHangAsync, aPluginId));
}

void HangMonitorChild::NotifyPluginHangAsync(uint32_t aPluginId) {
  MOZ_RELEASE_ASSERT(IsOnThread());

  // bounce back to parent on background thread
  if (mIPCOpen) {
    Unused << SendHangEvidence(
        PluginHangData(aPluginId, base::GetCurrentProcId()));
  }
}

void HangMonitorChild::ClearHang() {
  MOZ_ASSERT(NS_IsMainThread());

  if (mSentReport) {
    // bounce to background thread
    Dispatch(NewNonOwningRunnableMethod("HangMonitorChild::ClearHangAsync",
                                        this,
                                        &HangMonitorChild::ClearHangAsync));

    MonitorAutoLock lock(mMonitor);
    mSentReport = false;
    mTerminateScript = false;
    mTerminateGlobal = false;
    mStartDebugger = false;
    mFinishedStartingDebugger = false;
  }
}

void HangMonitorChild::ClearHangAsync() {
  MOZ_RELEASE_ASSERT(IsOnThread());

  // bounce back to parent on background thread
  if (mIPCOpen) {
    Unused << SendClearHang();
  }
}

/* HangMonitorParent implementation */

HangMonitorParent::HangMonitorParent(ProcessHangMonitor* aMonitor)
    : mHangMonitor(aMonitor),
      mIPCOpen(true),
      mMonitor("HangMonitorParent lock"),
      mShutdownDone(false),
      mBrowserCrashDumpHashLock("mBrowserCrashDumpIds lock"),
      mMainThreadTaskFactory(this) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  mReportHangs =
      mozilla::Preferences::GetBool("dom.ipc.reportProcessHangs", false);

  static bool sInited = false;
  if (!sInited) {
    sInited = true;
    Preferences::AddBoolVarCache(&sShouldPaintWhileInterruptingJS,
                                 "browser.tabs.remote.force-paint", true);
  }
}

HangMonitorParent::~HangMonitorParent() {
  MutexAutoLock lock(mBrowserCrashDumpHashLock);

  for (auto iter = mBrowserCrashDumpIds.Iter(); !iter.Done(); iter.Next()) {
    nsString crashId = iter.UserData();
    if (!crashId.IsEmpty()) {
      CrashReporter::DeleteMinidumpFilesForID(crashId);
    }
  }
}

void HangMonitorParent::Shutdown() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  MonitorAutoLock lock(mMonitor);

  if (mProcess) {
    mProcess->Clear();
    mProcess = nullptr;
  }

  Dispatch(NewNonOwningRunnableMethod("HangMonitorParent::ShutdownOnThread",
                                      this,
                                      &HangMonitorParent::ShutdownOnThread));

  while (!mShutdownDone) {
    mMonitor.Wait();
  }
}

void HangMonitorParent::ShutdownOnThread() {
  MOZ_RELEASE_ASSERT(IsOnThread());

  // mIPCOpen is only written from this thread, so need need to take the lock
  // here. We'd be shooting ourselves in the foot, because ActorDestroy takes
  // it.
  if (mIPCOpen) {
    Close();
  }

  MonitorAutoLock lock(mMonitor);
  mShutdownDone = true;
  mMonitor.Notify();
}

void HangMonitorParent::PaintWhileInterruptingJS(
    dom::TabParent* aTab, bool aForceRepaint,
    const LayersObserverEpoch& aEpoch) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (sShouldPaintWhileInterruptingJS) {
    TabId id = aTab->GetTabId();
    Dispatch(NewNonOwningRunnableMethod<TabId, bool, LayersObserverEpoch>(
        "HangMonitorParent::PaintWhileInterruptingJSOnThread", this,
        &HangMonitorParent::PaintWhileInterruptingJSOnThread, id, aForceRepaint,
        aEpoch));
  }
}

void HangMonitorParent::PaintWhileInterruptingJSOnThread(
    TabId aTabId, bool aForceRepaint, const LayersObserverEpoch& aEpoch) {
  MOZ_RELEASE_ASSERT(IsOnThread());

  if (mIPCOpen) {
    Unused << SendPaintWhileInterruptingJS(aTabId, aForceRepaint, aEpoch);
  }
}

void HangMonitorParent::ActorDestroy(ActorDestroyReason aWhy) {
  MOZ_RELEASE_ASSERT(IsOnThread());
  mIPCOpen = false;
}

void HangMonitorParent::Bind(Endpoint<PProcessHangMonitorParent>&& aEndpoint) {
  MOZ_RELEASE_ASSERT(IsOnThread());

  DebugOnly<bool> ok = aEndpoint.Bind(this);
  MOZ_ASSERT(ok);
}

void HangMonitorParent::SendHangNotification(const HangData& aHangData,
                                             const nsString& aBrowserDumpId,
                                             bool aTakeMinidump) {
  // chrome process, main thread
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  nsString dumpId;
  if ((aHangData.type() == HangData::TPluginHangData) && aTakeMinidump) {
    // We've been handed a partial minidump; complete it with plugin and
    // content process dumps.
    const PluginHangData& phd = aHangData.get_PluginHangData();

    plugins::TakeFullMinidump(phd.pluginId(), phd.contentProcessId(),
                              aBrowserDumpId, dumpId);
    UpdateMinidump(phd.pluginId(), dumpId);
  } else {
    // We already have a full minidump; go ahead and use it.
    dumpId = aBrowserDumpId;
  }

  mProcess->SetHangData(aHangData, dumpId);

  nsCOMPtr<nsIObserverService> observerService =
      mozilla::services::GetObserverService();
  observerService->NotifyObservers(mProcess, "process-hang-report", nullptr);
}

void HangMonitorParent::ClearHangNotification() {
  // chrome process, main thread
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  mProcess->ClearHang();

  nsCOMPtr<nsIObserverService> observerService =
      mozilla::services::GetObserverService();
  observerService->NotifyObservers(mProcess, "clear-hang-report", nullptr);
}

// Take a minidump of the browser process if one wasn't already taken for the
// plugin that caused the hang. Return false if a dump was already available or
// true if new one has been taken.
bool HangMonitorParent::TakeBrowserMinidump(const PluginHangData& aPhd,
                                            nsString& aCrashId) {
  MutexAutoLock lock(mBrowserCrashDumpHashLock);
  if (!mBrowserCrashDumpIds.Get(aPhd.pluginId(), &aCrashId)) {
    nsCOMPtr<nsIFile> browserDump;
    if (CrashReporter::TakeMinidump(getter_AddRefs(browserDump), true)) {
      if (!CrashReporter::GetIDFromMinidump(browserDump, aCrashId) ||
          aCrashId.IsEmpty()) {
        browserDump->Remove(false);
        NS_WARNING(
            "Failed to generate timely browser stack, "
            "this is bad for plugin hang analysis!");
      } else {
        mBrowserCrashDumpIds.Put(aPhd.pluginId(), aCrashId);
        return true;
      }
    }
  }

  return false;
}

mozilla::ipc::IPCResult HangMonitorParent::RecvHangEvidence(
    const HangData& aHangData) {
  // chrome process, background thread
  MOZ_RELEASE_ASSERT(IsOnThread());

  if (!mReportHangs) {
    return IPC_OK();
  }

#ifdef XP_WIN
  // Don't report hangs if we're debugging the process. You can comment this
  // line out for testing purposes.
  if (IsDebuggerPresent()) {
    return IPC_OK();
  }
#endif

  // Before we wake up the browser main thread we want to take a
  // browser minidump.
  nsAutoString crashId;
  bool takeMinidump = false;
  if (aHangData.type() == HangData::TPluginHangData) {
    takeMinidump = TakeBrowserMinidump(aHangData.get_PluginHangData(), crashId);
  }

  mHangMonitor->InitiateCPOWTimeout();

  MonitorAutoLock lock(mMonitor);

  NS_DispatchToMainThread(mMainThreadTaskFactory.NewRunnableMethod(
      &HangMonitorParent::SendHangNotification, aHangData, crashId,
      takeMinidump));

  return IPC_OK();
}

mozilla::ipc::IPCResult HangMonitorParent::RecvClearHang() {
  // chrome process, background thread
  MOZ_RELEASE_ASSERT(IsOnThread());

  if (!mReportHangs) {
    return IPC_OK();
  }

  mHangMonitor->InitiateCPOWTimeout();

  MonitorAutoLock lock(mMonitor);

  NS_DispatchToMainThread(mMainThreadTaskFactory.NewRunnableMethod(
      &HangMonitorParent::ClearHangNotification));

  return IPC_OK();
}

void HangMonitorParent::TerminateScript(bool aTerminateGlobal) {
  MOZ_RELEASE_ASSERT(IsOnThread());

  if (mIPCOpen) {
    Unused << SendTerminateScript(aTerminateGlobal);
  }
}

void HangMonitorParent::BeginStartingDebugger() {
  MOZ_RELEASE_ASSERT(IsOnThread());

  if (mIPCOpen) {
    Unused << SendBeginStartingDebugger();
  }
}

void HangMonitorParent::EndStartingDebugger() {
  MOZ_RELEASE_ASSERT(IsOnThread());

  if (mIPCOpen) {
    Unused << SendEndStartingDebugger();
  }
}

void HangMonitorParent::CleanupPluginHang(uint32_t aPluginId,
                                          bool aRemoveFiles) {
  MutexAutoLock lock(mBrowserCrashDumpHashLock);
  nsAutoString crashId;
  if (!mBrowserCrashDumpIds.Get(aPluginId, &crashId)) {
    return;
  }
  mBrowserCrashDumpIds.Remove(aPluginId);

  if (aRemoveFiles && !crashId.IsEmpty()) {
    CrashReporter::DeleteMinidumpFilesForID(crashId);
  }
}

void HangMonitorParent::UpdateMinidump(uint32_t aPluginId,
                                       const nsString& aDumpId) {
  if (aDumpId.IsEmpty()) {
    return;
  }

  MutexAutoLock lock(mBrowserCrashDumpHashLock);
  mBrowserCrashDumpIds.Put(aPluginId, aDumpId);
}

/* HangMonitoredProcess implementation */

NS_IMPL_ISUPPORTS(HangMonitoredProcess, nsIHangReport)

NS_IMETHODIMP
HangMonitoredProcess::GetHangType(uint32_t* aHangType) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  switch (mHangData.type()) {
    case HangData::TSlowScriptData:
      *aHangType = SLOW_SCRIPT;
      break;
    case HangData::TPluginHangData:
      *aHangType = PLUGIN_HANG;
      break;
    default:
      MOZ_ASSERT_UNREACHABLE("Unexpected HangData type");
      return NS_ERROR_UNEXPECTED;
  }

  return NS_OK;
}

NS_IMETHODIMP
HangMonitoredProcess::GetScriptBrowser(Element** aBrowser) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (mHangData.type() != HangData::TSlowScriptData) {
    return NS_ERROR_NOT_AVAILABLE;
  }

  TabId tabId = mHangData.get_SlowScriptData().tabId();
  if (!mContentParent) {
    return NS_ERROR_NOT_AVAILABLE;
  }

  nsTArray<PBrowserParent*> tabs;
  mContentParent->ManagedPBrowserParent(tabs);
  for (size_t i = 0; i < tabs.Length(); i++) {
    TabParent* tp = TabParent::GetFrom(tabs[i]);
    if (tp->GetTabId() == tabId) {
      RefPtr<Element> node = tp->GetOwnerElement();
      node.forget(aBrowser);
      return NS_OK;
    }
  }

  *aBrowser = nullptr;
  return NS_OK;
}

NS_IMETHODIMP
HangMonitoredProcess::GetScriptFileName(nsACString& aFileName) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (mHangData.type() != HangData::TSlowScriptData) {
    return NS_ERROR_NOT_AVAILABLE;
  }

  aFileName = mHangData.get_SlowScriptData().filename();
  return NS_OK;
}

NS_IMETHODIMP
HangMonitoredProcess::GetAddonId(nsAString& aAddonId) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (mHangData.type() != HangData::TSlowScriptData) {
    return NS_ERROR_NOT_AVAILABLE;
  }

  aAddonId = mHangData.get_SlowScriptData().addonId();
  return NS_OK;
}

NS_IMETHODIMP
HangMonitoredProcess::GetPluginName(nsACString& aPluginName) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (mHangData.type() != HangData::TPluginHangData) {
    return NS_ERROR_NOT_AVAILABLE;
  }

  uint32_t id = mHangData.get_PluginHangData().pluginId();

  RefPtr<nsPluginHost> host = nsPluginHost::GetInst();
  nsPluginTag* tag = host->PluginWithId(id);
  if (!tag) {
    return NS_ERROR_UNEXPECTED;
  }

  aPluginName = tag->Name();
  return NS_OK;
}

NS_IMETHODIMP
HangMonitoredProcess::TerminateScript() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (mHangData.type() != HangData::TSlowScriptData) {
    return NS_ERROR_UNEXPECTED;
  }

  if (!mActor) {
    return NS_ERROR_UNEXPECTED;
  }

  ProcessHangMonitor::Get()->Dispatch(NewNonOwningRunnableMethod<bool>(
      "HangMonitorParent::TerminateScript", mActor,
      &HangMonitorParent::TerminateScript, false));
  return NS_OK;
}

NS_IMETHODIMP
HangMonitoredProcess::TerminateGlobal() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (mHangData.type() != HangData::TSlowScriptData) {
    return NS_ERROR_UNEXPECTED;
  }

  if (!mActor) {
    return NS_ERROR_UNEXPECTED;
  }

  ProcessHangMonitor::Get()->Dispatch(NewNonOwningRunnableMethod<bool>(
      "HangMonitorParent::TerminateScript", mActor,
      &HangMonitorParent::TerminateScript, true));
  return NS_OK;
}

NS_IMETHODIMP
HangMonitoredProcess::BeginStartingDebugger() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (mHangData.type() != HangData::TSlowScriptData) {
    return NS_ERROR_UNEXPECTED;
  }

  if (!mActor) {
    return NS_ERROR_UNEXPECTED;
  }

  ProcessHangMonitor::Get()->Dispatch(NewNonOwningRunnableMethod(
      "HangMonitorParent::BeginStartingDebugger", mActor,
      &HangMonitorParent::BeginStartingDebugger));
  return NS_OK;
}

NS_IMETHODIMP
HangMonitoredProcess::EndStartingDebugger() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (mHangData.type() != HangData::TSlowScriptData) {
    return NS_ERROR_UNEXPECTED;
  }

  if (!mActor) {
    return NS_ERROR_UNEXPECTED;
  }

  ProcessHangMonitor::Get()->Dispatch(NewNonOwningRunnableMethod(
      "HangMonitorParent::EndStartingDebugger", mActor,
      &HangMonitorParent::EndStartingDebugger));
  return NS_OK;
}

NS_IMETHODIMP
HangMonitoredProcess::TerminatePlugin() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (mHangData.type() != HangData::TPluginHangData) {
    return NS_ERROR_UNEXPECTED;
  }

  // Use the multi-process crash report generated earlier.
  uint32_t id = mHangData.get_PluginHangData().pluginId();
  base::ProcessId contentPid =
      mHangData.get_PluginHangData().contentProcessId();
  plugins::TerminatePlugin(id, contentPid, NS_LITERAL_CSTRING("HangMonitor"),
                           mDumpId);

  if (mActor) {
    mActor->CleanupPluginHang(id, false);
  }
  return NS_OK;
}

NS_IMETHODIMP
HangMonitoredProcess::IsReportForBrowser(nsFrameLoader* aFrameLoader,
                                         bool* aResult) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  if (!mActor) {
    *aResult = false;
    return NS_OK;
  }

  NS_ENSURE_STATE(aFrameLoader);

  TabParent* tp = TabParent::GetFrom(aFrameLoader);
  if (!tp) {
    *aResult = false;
    return NS_OK;
  }

  *aResult = mContentParent == tp->Manager();
  return NS_OK;
}

NS_IMETHODIMP
HangMonitoredProcess::UserCanceled() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (mHangData.type() != HangData::TPluginHangData) {
    return NS_OK;
  }

  if (mActor) {
    uint32_t id = mHangData.get_PluginHangData().pluginId();
    mActor->CleanupPluginHang(id, true);
  }
  return NS_OK;
}

static bool InterruptCallback(JSContext* cx) {
  if (HangMonitorChild* child = HangMonitorChild::Get()) {
    child->InterruptCallback();
  }

  return true;
}

ProcessHangMonitor* ProcessHangMonitor::sInstance;

ProcessHangMonitor::ProcessHangMonitor() : mCPOWTimeout(false) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  if (XRE_IsContentProcess()) {
    nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
    obs->AddObserver(this, "xpcom-shutdown", false);
  }

  if (NS_FAILED(NS_NewNamedThread("ProcessHangMon", getter_AddRefs(mThread)))) {
    mThread = nullptr;
  }
}

ProcessHangMonitor::~ProcessHangMonitor() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  MOZ_ASSERT(sInstance == this);
  sInstance = nullptr;

  mThread->Shutdown();
  mThread = nullptr;
}

ProcessHangMonitor* ProcessHangMonitor::GetOrCreate() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (!sInstance) {
    sInstance = new ProcessHangMonitor();
  }
  return sInstance;
}

NS_IMPL_ISUPPORTS(ProcessHangMonitor, nsIObserver)

NS_IMETHODIMP
ProcessHangMonitor::Observe(nsISupports* aSubject, const char* aTopic,
                            const char16_t* aData) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (!strcmp(aTopic, "xpcom-shutdown")) {
    if (HangMonitorChild* child = HangMonitorChild::Get()) {
      child->Shutdown();
      delete child;
    }

    nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
    if (obs) {
      obs->RemoveObserver(this, "xpcom-shutdown");
    }
  }
  return NS_OK;
}

ProcessHangMonitor::SlowScriptAction ProcessHangMonitor::NotifySlowScript(
    nsITabChild* aTabChild, const char* aFileName, const nsString& aAddonId) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  return HangMonitorChild::Get()->NotifySlowScript(aTabChild, aFileName,
                                                   aAddonId);
}

bool ProcessHangMonitor::IsDebuggerStartupComplete() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  return HangMonitorChild::Get()->IsDebuggerStartupComplete();
}

bool ProcessHangMonitor::ShouldTimeOutCPOWs() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  if (mCPOWTimeout) {
    mCPOWTimeout = false;
    return true;
  }
  return false;
}

void ProcessHangMonitor::InitiateCPOWTimeout() {
  MOZ_RELEASE_ASSERT(IsOnThread());
  mCPOWTimeout = true;
}

void ProcessHangMonitor::NotifyPluginHang(uint32_t aPluginId) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  return HangMonitorChild::Get()->NotifyPluginHang(aPluginId);
}

static PProcessHangMonitorParent* CreateHangMonitorParent(
    ContentParent* aContentParent,
    Endpoint<PProcessHangMonitorParent>&& aEndpoint) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  ProcessHangMonitor* monitor = ProcessHangMonitor::GetOrCreate();
  auto* parent = new HangMonitorParent(monitor);

  auto* process = new HangMonitoredProcess(parent, aContentParent);
  parent->SetProcess(process);

  monitor->Dispatch(
      NewNonOwningRunnableMethod<Endpoint<PProcessHangMonitorParent>&&>(
          "HangMonitorParent::Bind", parent, &HangMonitorParent::Bind,
          std::move(aEndpoint)));

  return parent;
}

void mozilla::CreateHangMonitorChild(
    Endpoint<PProcessHangMonitorChild>&& aEndpoint) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  JSContext* cx = danger::GetJSContext();
  JS_AddInterruptCallback(cx, InterruptCallback);

  ProcessHangMonitor* monitor = ProcessHangMonitor::GetOrCreate();
  auto* child = new HangMonitorChild(monitor);

  monitor->Dispatch(
      NewNonOwningRunnableMethod<Endpoint<PProcessHangMonitorChild>&&>(
          "HangMonitorChild::Bind", child, &HangMonitorChild::Bind,
          std::move(aEndpoint)));
}

void ProcessHangMonitor::Dispatch(already_AddRefed<nsIRunnable> aRunnable) {
  mThread->Dispatch(std::move(aRunnable), nsIEventTarget::NS_DISPATCH_NORMAL);
}

bool ProcessHangMonitor::IsOnThread() {
  bool on;
  return NS_SUCCEEDED(mThread->IsOnCurrentThread(&on)) && on;
}

/* static */
PProcessHangMonitorParent* ProcessHangMonitor::AddProcess(
    ContentParent* aContentParent) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  if (!mozilla::Preferences::GetBool("dom.ipc.processHangMonitor", false)) {
    return nullptr;
  }

  Endpoint<PProcessHangMonitorParent> parent;
  Endpoint<PProcessHangMonitorChild> child;
  nsresult rv;
  rv = PProcessHangMonitor::CreateEndpoints(
      base::GetCurrentProcId(), aContentParent->OtherPid(), &parent, &child);
  if (NS_FAILED(rv)) {
    MOZ_ASSERT(false, "PProcessHangMonitor::CreateEndpoints failed");
    return nullptr;
  }

  if (!aContentParent->SendInitProcessHangMonitor(std::move(child))) {
    MOZ_ASSERT(false);
    return nullptr;
  }

  return CreateHangMonitorParent(aContentParent, std::move(parent));
}

/* static */
void ProcessHangMonitor::RemoveProcess(PProcessHangMonitorParent* aParent) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  auto parent = static_cast<HangMonitorParent*>(aParent);
  parent->Shutdown();
  delete parent;
}

/* static */
void ProcessHangMonitor::ClearHang() {
  MOZ_ASSERT(NS_IsMainThread());
  if (HangMonitorChild* child = HangMonitorChild::Get()) {
    child->ClearHang();
  }
}

/* static */
void ProcessHangMonitor::PaintWhileInterruptingJS(
    PProcessHangMonitorParent* aParent, dom::TabParent* aTabParent,
    bool aForceRepaint, const layers::LayersObserverEpoch& aEpoch) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  auto parent = static_cast<HangMonitorParent*>(aParent);
  parent->PaintWhileInterruptingJS(aTabParent, aForceRepaint, aEpoch);
}

/* static */
void ProcessHangMonitor::ClearPaintWhileInterruptingJS(
    const layers::LayersObserverEpoch& aEpoch) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  MOZ_RELEASE_ASSERT(XRE_IsContentProcess());

  if (HangMonitorChild* child = HangMonitorChild::Get()) {
    child->ClearPaintWhileInterruptingJS(aEpoch);
  }
}

/* static */
void ProcessHangMonitor::MaybeStartPaintWhileInterruptingJS() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  MOZ_RELEASE_ASSERT(XRE_IsContentProcess());

  if (HangMonitorChild* child = HangMonitorChild::Get()) {
    child->MaybeStartPaintWhileInterruptingJS();
  }
}