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 "js/GCAPI.h"

#include "mozilla/Atomics.h"
#include "mozilla/BackgroundHangMonitor.h"
#include "mozilla/dom/ContentChild.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 "nsIFrameLoader.h"
#include "nsIHangReport.h"
#include "nsITabParent.h"
#include "nsPluginHost.h"
#include "nsThreadUtils.h"
#ifdef MOZ_CRASHREPORTER
#include "nsExceptionHandler.h"
#endif

#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:
  explicit HangMonitorChild(ProcessHangMonitor* aMonitor);
  ~HangMonitorChild() override;

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

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

  bool IsDebuggerStartupComplete();

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

  void ClearHang();
  void ClearHangAsync();
  void ClearForcePaint();

  mozilla::ipc::IPCResult RecvTerminateScript() override;
  mozilla::ipc::IPCResult RecvBeginStartingDebugger() override;
  mozilla::ipc::IPCResult RecvEndStartingDebugger() override;

  mozilla::ipc::IPCResult RecvForcePaint(const TabId& aTabId, const uint64_t& aLayerObserverEpoch) override;

  void ActorDestroy(ActorDestroyReason aWhy) override;

  void InterruptCallback();
  void Shutdown();

  static HangMonitorChild* Get() { return sInstance; }

  MessageLoop* MonitorLoop() { return mHangMonitor->MonitorLoop(); }

 private:
  void ShutdownOnThread();

  static Atomic<HangMonitorChild*> sInstance;
  UniquePtr<BackgroundHangMonitor> mForcePaintMonitor;

  const RefPtr<ProcessHangMonitor> mHangMonitor;
  Monitor mMonitor;

  // Main thread-only.
  bool mSentReport;

  // These fields must be accessed with mMonitor held.
  bool mTerminateScript;
  bool mStartDebugger;
  bool mFinishedStartingDebugger;
  bool mForcePaint;
  TabId mForcePaintTab;
  MOZ_INIT_OUTSIDE_CTOR uint64_t mForcePaintEpoch;
  JSContext* mContext;
  bool mShutdownDone;

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

Atomic<HangMonitorChild*> 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_IMETHOD GetHangType(uint32_t* aHangType) override;
  NS_IMETHOD GetScriptBrowser(nsIDOMElement** aBrowser) override;
  NS_IMETHOD GetScriptFileName(nsACString& aFileName) override;
  NS_IMETHOD GetScriptLineNo(uint32_t* aLineNo) override;

  NS_IMETHOD GetPluginName(nsACString& aPluginName) override;

  NS_IMETHOD TerminateScript() override;
  NS_IMETHOD BeginStartingDebugger() override;
  NS_IMETHOD EndStartingDebugger() override;
  NS_IMETHOD TerminatePlugin() override;
  NS_IMETHOD UserCanceled() override;

  NS_IMETHOD IsReportForBrowser(nsIFrameLoader* aFrameLoader, bool* aResult) override;

  // 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();
  }

  void DispatchTabChildNotReady(TabId aTabId);

private:
  ~HangMonitoredProcess() = default;

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

class HangMonitorParent
  : public PProcessHangMonitorParent
{
public:
  explicit HangMonitorParent(ProcessHangMonitor* aMonitor);
  ~HangMonitorParent() override;

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

  mozilla::ipc::IPCResult RecvReady() override;
  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 ForcePaint(dom::TabParent* aTabParent, uint64_t aLayerObserverEpoch);

  void TerminateScript();
  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);

  MessageLoop* MonitorLoop() { return mHangMonitor->MonitorLoop(); }

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

  void DispatchTabChildNotReady(TabId aTabId);

  void ForcePaintOnThread(TabId aTabId, uint64_t aLayerObserverEpoch);

  void ShutdownOnThread();

  const RefPtr<ProcessHangMonitor> mHangMonitor;

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

  // This field is only accessed on the hang thread. Inits to
  // false, and will flip to true once the HangMonitorChild is
  // constructed in the child process, and sends a message saying
  // so.
  bool mReady;

  // 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 sShouldForcePaint;
};

bool HangMonitorParent::sShouldForcePaint = true;

} // namespace

/* HangMonitorChild implementation */

HangMonitorChild::HangMonitorChild(ProcessHangMonitor* aMonitor)
 : mHangMonitor(aMonitor),
   mMonitor("HangMonitorChild lock"),
   mSentReport(false),
   mTerminateScript(false),
   mStartDebugger(false),
   mFinishedStartingDebugger(false),
   mForcePaint(false),
   mShutdownDone(false),
   mIPCOpen(true)
{
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  mContext = danger::GetJSContext();
  mForcePaintMonitor =
    MakeUnique<mozilla::BackgroundHangMonitor>("Gecko_Child_ForcePaint",
                                               128, /* ms timeout for microhangs */
                                               1024, /* ms timeout for permahangs */
                                               BackgroundHangMonitor::THREAD_PRIVATE);
}

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

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

  bool forcePaint;
  TabId forcePaintTab;
  uint64_t forcePaintEpoch;

  {
    MonitorAutoLock lock(mMonitor);
    forcePaint = mForcePaint;
    forcePaintTab = mForcePaintTab;
    forcePaintEpoch = mForcePaintEpoch;

    mForcePaint = false;
  }

  if (forcePaint) {
    RefPtr<TabChild> tabChild = TabChild::FindTabChild(forcePaintTab);
    if (tabChild) {
      js::AutoAssertNoContentJS nojs(mContext);
      tabChild->ForcePaint(forcePaintEpoch);
    } else {
      auto cc = ContentChild::GetSingleton();
      if (cc) {
        cc->SendTabChildNotReady(forcePaintTab);
      }
    }
  }
}

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

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

void
HangMonitorChild::ShutdownOnThread()
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

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

void
HangMonitorChild::ActorDestroy(ActorDestroyReason aWhy)
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

  mIPCOpen = false;

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

mozilla::ipc::IPCResult
HangMonitorChild::RecvTerminateScript()
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

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

mozilla::ipc::IPCResult
HangMonitorChild::RecvBeginStartingDebugger()
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

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

mozilla::ipc::IPCResult
HangMonitorChild::RecvEndStartingDebugger()
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

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

mozilla::ipc::IPCResult
HangMonitorChild::RecvForcePaint(const TabId& aTabId, const uint64_t& aLayerObserverEpoch)
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

  mForcePaintMonitor->NotifyActivity();

  {
    MonitorAutoLock lock(mMonitor);
    mForcePaint = true;
    mForcePaintTab = aTabId;
    mForcePaintEpoch = aLayerObserverEpoch;
  }

  JS_RequestInterruptCallback(mContext);

  return IPC_OK();
}

void
HangMonitorChild::ClearForcePaint()
{
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  MOZ_RELEASE_ASSERT(XRE_IsContentProcess());

  mForcePaintMonitor->NotifyWait();
}

void
HangMonitorChild::Bind(Endpoint<PProcessHangMonitorChild>&& aEndpoint)
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

  MOZ_ASSERT(!sInstance);
  sInstance = this;

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

  Unused << SendReady();
}

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

HangMonitorChild::SlowScriptAction
HangMonitorChild::NotifySlowScript(nsITabChild* aTabChild,
                                   const char* aFileName,
                                   unsigned aLineNo)
{
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  mSentReport = true;

  {
    MonitorAutoLock lock(mMonitor);

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

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

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

  MonitorLoop()->PostTask(NewNonOwningRunnableMethod
                          <TabId, nsCString, unsigned>(this,
                                                       &HangMonitorChild::NotifySlowScriptAsync,
                                                       id, filename, aLineNo));
  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
  MonitorLoop()->PostTask(NewNonOwningRunnableMethod<uint32_t>(this,
                                                               &HangMonitorChild::NotifyPluginHangAsync,
                                                               aPluginId));
}

void
HangMonitorChild::NotifyPluginHangAsync(uint32_t aPluginId)
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

  // 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
    MonitorLoop()->PostTask(NewNonOwningRunnableMethod(this, &HangMonitorChild::ClearHangAsync));

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

void
HangMonitorChild::ClearHangAsync()
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

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

/* HangMonitorParent implementation */

HangMonitorParent::HangMonitorParent(ProcessHangMonitor* aMonitor)
 : mHangMonitor(aMonitor),
   mReady(false),
   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(&sShouldForcePaint,
                                 "browser.tabs.remote.force-paint", true);
  }
}

HangMonitorParent::~HangMonitorParent()
{
#ifdef MOZ_CRASHREPORTER
  MutexAutoLock lock(mBrowserCrashDumpHashLock);

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

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

  MonitorAutoLock lock(mMonitor);

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

  MonitorLoop()->PostTask(NewNonOwningRunnableMethod(this,
                                                     &HangMonitorParent::ShutdownOnThread));

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

void
HangMonitorParent::ShutdownOnThread()
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

  // 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::ForcePaint(dom::TabParent* aTab, uint64_t aLayerObserverEpoch)
{
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (sShouldForcePaint) {
    TabId id = aTab->GetTabId();
    MonitorLoop()->PostTask(NewNonOwningRunnableMethod<TabId, uint64_t>(
                              this, &HangMonitorParent::ForcePaintOnThread, id, aLayerObserverEpoch));
  }
}

void
HangMonitorParent::DispatchTabChildNotReady(TabId aTabId)
{
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (!mProcess) {
    return;
  }

  mProcess->DispatchTabChildNotReady(aTabId);
}

void
HangMonitorParent::ForcePaintOnThread(TabId aTabId, uint64_t aLayerObserverEpoch)
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

  if (mIPCOpen) {
    if (mReady) {
      Unused << SendForcePaint(aTabId, aLayerObserverEpoch);
    } else {
      // We've never heard from the HangMonitorChild before, so
      // it's either not finished setting up, or has only recently
      // finished setting up. In either case, we're dealing with
      // a new content process that probably hasn't had time to
      // get the ContentChild, let alone the TabChild for aTabId,
      // set up, and so attempting to force paint on the non-existant
      // TabChild is not going to work. Instead, we tell the main
      // thread that we're waiting on a TabChild to be created.
      NS_DispatchToMainThread(
        mMainThreadTaskFactory.NewRunnableMethod(
          &HangMonitorParent::DispatchTabChildNotReady, aTabId));
    }
  }
}

void
HangMonitorParent::ActorDestroy(ActorDestroyReason aWhy)
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());
  mIPCOpen = false;
}

void
HangMonitorParent::Bind(Endpoint<PProcessHangMonitorParent>&& aEndpoint)
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

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

class HangObserverNotifier final : public Runnable
{
public:
  HangObserverNotifier(HangMonitoredProcess* aProcess,
                       HangMonitorParent *aParent,
                       const HangData& aHangData,
                       const nsString& aBrowserDumpId,
                       bool aTakeMinidump)
    : mProcess(aProcess),
      mParent(aParent),
      mHangData(aHangData),
      mBrowserDumpId(aBrowserDumpId),
      mTakeMinidump(aTakeMinidump)
  {}

  NS_IMETHOD
  Run() override
  {
    // chrome process, main thread
    MOZ_RELEASE_ASSERT(NS_IsMainThread());

    nsString dumpId;
    if ((mHangData.type() == HangData::TPluginHangData) && mTakeMinidump) {
      // We've been handed a partial minidump; complete it with plugin and
      // content process dumps.
      const PluginHangData& phd = mHangData.get_PluginHangData();
      plugins::TakeFullMinidump(phd.pluginId(), phd.contentProcessId(),
                                mBrowserDumpId, dumpId);
      mParent->UpdateMinidump(phd.pluginId(), dumpId);
    } else {
      // We already have a full minidump; go ahead and use it.
      dumpId = mBrowserDumpId;
    }

    mProcess->SetHangData(mHangData, dumpId);

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

private:
  RefPtr<HangMonitoredProcess> mProcess;
  HangMonitorParent* mParent;
  HangData mHangData;
  nsAutoString mBrowserDumpId;
  bool mTakeMinidump;
};

// 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)
{
#ifdef MOZ_CRASHREPORTER
  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;
      }
    }
  }
#endif // MOZ_CRASHREPORTER

  return false;
}

mozilla::ipc::IPCResult
HangMonitorParent::RecvReady()
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());
  mReady = true;
  return IPC_OK();
}

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

  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);

  nsCOMPtr<nsIRunnable> notifier =
    new HangObserverNotifier(mProcess, this, aHangData, crashId, takeMinidump);
  NS_DispatchToMainThread(notifier);

  return IPC_OK();
}

class ClearHangNotifier final : public Runnable
{
public:
  explicit ClearHangNotifier(HangMonitoredProcess* aProcess)
    : mProcess(aProcess)
  {}

  NS_IMETHOD
  Run() override
  {
    // chrome process, main thread
    MOZ_RELEASE_ASSERT(NS_IsMainThread());
    mProcess->ClearHang();

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

private:
  RefPtr<HangMonitoredProcess> mProcess;
};

mozilla::ipc::IPCResult
HangMonitorParent::RecvClearHang()
{
  // chrome process, background thread
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

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

  mHangMonitor->InitiateCPOWTimeout();

  MonitorAutoLock lock(mMonitor);

  nsCOMPtr<nsIRunnable> notifier =
    new ClearHangNotifier(mProcess);
  NS_DispatchToMainThread(notifier);

  return IPC_OK();
}

void
HangMonitorParent::TerminateScript()
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

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

void
HangMonitorParent::BeginStartingDebugger()
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

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

void
HangMonitorParent::EndStartingDebugger()
{
  MOZ_RELEASE_ASSERT(MessageLoop::current() == MonitorLoop());

  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);
#ifdef MOZ_CRASHREPORTER
  if (aRemoveFiles && !crashId.IsEmpty()) {
    CrashReporter::DeleteMinidumpFilesForID(crashId);
  }
#endif
}

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(nsIDOMElement** 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) {
      nsCOMPtr<nsIDOMElement> node = do_QueryInterface(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::GetScriptLineNo(uint32_t* aLineNo)
{
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (mHangData.type() != HangData::TSlowScriptData) {
    return NS_ERROR_NOT_AVAILABLE;
  }

  *aLineNo = mHangData.get_SlowScriptData().lineno();
  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()->MonitorLoop()->PostTask(NewNonOwningRunnableMethod(mActor,
                                                                                &HangMonitorParent::TerminateScript));
  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()->MonitorLoop()->PostTask(NewNonOwningRunnableMethod(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()->MonitorLoop()->PostTask(NewNonOwningRunnableMethod(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(nsIFrameLoader* aFrameLoader, bool* aResult)
{
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

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

  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;
}

void
HangMonitoredProcess::DispatchTabChildNotReady(TabId aTabId)
{
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  if (!mContentParent) {
    return;
  }

  Unused << mContentParent->RecvTabChildNotReady(aTabId);
}

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);
  }

  mThread = new base::Thread("ProcessHangMonitor");
  if (!mThread->Start()) {
    delete mThread;
    mThread = nullptr;
  }
}

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

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

  delete mThread;
}

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,
                                     unsigned aLineNo)
{
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  return HangMonitorChild::Get()->NotifySlowScript(aTabChild, aFileName, aLineNo);
}

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(MessageLoop::current() == MonitorLoop());
  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->MonitorLoop()->PostTask(NewNonOwningRunnableMethod
                                   <Endpoint<PProcessHangMonitorParent>&&>(parent,
                                                                           &HangMonitorParent::Bind,
                                                                           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->MonitorLoop()->PostTask(NewNonOwningRunnableMethod
                                   <Endpoint<PProcessHangMonitorChild>&&>(child,
                                                                          &HangMonitorChild::Bind,
                                                                          Move(aEndpoint)));
}

MessageLoop*
ProcessHangMonitor::MonitorLoop()
{
  return mThread->message_loop();
}

/* 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(Move(child))) {
    MOZ_ASSERT(false);
    return nullptr;
  }

  return CreateHangMonitorParent(aContentParent, 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::ForcePaint(PProcessHangMonitorParent* aParent,
                               dom::TabParent* aTabParent,
                               uint64_t aLayerObserverEpoch)
{
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  auto parent = static_cast<HangMonitorParent*>(aParent);
  parent->ForcePaint(aTabParent, aLayerObserverEpoch);
}

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

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