author Ehsan Akhgari <ehsan@mozilla.com>
Fri, 02 Jun 2017 20:40:12 -0400
changeset 410718 16798a4167a180349f1c566fad9bc87bcfd0e992
parent 408396 9b7affc8fb26dcd5825770686e68e4b45fa20743
child 410817 e5901d855fafdce064137ab1c72126e43b06c971
permissions -rw-r--r--
Bug 1368286 - Take the idle queue into account in nsThread::HasPendingEvents(); r=smaug

/* -*- 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/. */

#ifndef nsThread_h__
#define nsThread_h__

#include "mozilla/Mutex.h"
#include "nsIIdlePeriod.h"
#include "nsIThreadInternal.h"
#include "nsISupportsPriority.h"
#include "nsEventQueue.h"
#include "nsThreadUtils.h"
#include "nsString.h"
#include "nsTObserverArray.h"
#include "mozilla/Attributes.h"
#include "mozilla/NotNull.h"
#include "mozilla/TimeStamp.h"
#include "nsAutoPtr.h"
#include "mozilla/AlreadyAddRefed.h"
#include "mozilla/UniquePtr.h"

namespace mozilla {
class CycleCollectedJSContext;

using mozilla::NotNull;

// A native thread
class nsThread
  : public nsIThreadInternal
  , public nsISupportsPriority

  enum MainThreadFlag

  nsThread(MainThreadFlag aMainThread, uint32_t aStackSize);

  // Initialize this as a wrapper for a new PRThread, and optionally give it a name.
  nsresult Init(const nsACString& aName = NS_LITERAL_CSTRING(""));

  // Initialize this as a wrapper for the current PRThread.
  nsresult InitCurrentThread();

  // The PRThread corresponding to this thread.
  PRThread* GetPRThread()
    return mThread;

  // If this flag is true, then the nsThread was created using
  // nsIThreadManager::NewThread.
  bool ShutdownRequired()
    return mShutdownRequired;

  // Clear the observer list.
  void ClearObservers()

  SetScriptObserver(mozilla::CycleCollectedJSContext* aScriptObserver);

  RecursionDepth() const;

  void ShutdownComplete(NotNull<struct nsThreadShutdownContext*> aContext);

  void WaitForAllAsynchronousShutdowns();

  enum class ShouldSaveMemoryReport

  static bool SaveMemoryReportNearOOM(ShouldSaveMemoryReport aShouldSave);

  void DoMainThreadSpecificProcessing(bool aReallyWait);

  // Returns a null TimeStamp if we're not in the idle period.
  mozilla::TimeStamp GetIdleDeadline();
  void GetIdleEvent(nsIRunnable** aEvent, mozilla::MutexAutoLock& aProofOfLock);
  void GetEvent(bool aWait, nsIRunnable** aEvent,
                unsigned short* aPriority,
                mozilla::MutexAutoLock& aProofOfLock);

  class nsChainedEventQueue;

  class nsNestedEventTarget;
  friend class nsNestedEventTarget;

  friend class nsThreadShutdownEvent;

  virtual ~nsThread();

  bool ShuttingDown()
    return mShutdownContext != nullptr;

  static void ThreadFunc(void* aArg);

  // Helper
  already_AddRefed<nsIThreadObserver> GetObserver()
    nsIThreadObserver* obs;
    return already_AddRefed<nsIThreadObserver>(obs);

  // Wrappers for event queue methods:
  nsresult PutEvent(nsIRunnable* aEvent, nsNestedEventTarget* aTarget);
  nsresult PutEvent(already_AddRefed<nsIRunnable> aEvent,
                    nsNestedEventTarget* aTarget);

  nsresult DispatchInternal(already_AddRefed<nsIRunnable> aEvent,
                            uint32_t aFlags, nsNestedEventTarget* aTarget);

  struct nsThreadShutdownContext* ShutdownInternal(bool aSync);

  // Wrapper for nsEventQueue that supports chaining.
  class nsChainedEventQueue
    explicit nsChainedEventQueue(mozilla::Mutex& aLock)
      : mNext(nullptr)
      , mEventsAvailable(aLock, "[nsChainedEventQueue.mEventsAvailable]")
      , mProcessSecondaryQueueRunnable(false)
      mNormalQueue =
      // Both queues need to use the same CondVar!
      mSecondaryQueue =

    bool GetEvent(bool aMayWait, nsIRunnable** aEvent,
                  unsigned short* aPriority,
                  mozilla::MutexAutoLock& aProofOfLock);

    void PutEvent(nsIRunnable* aEvent, mozilla::MutexAutoLock& aProofOfLock)
      RefPtr<nsIRunnable> event(aEvent);
      PutEvent(event.forget(), aProofOfLock);

    void PutEvent(already_AddRefed<nsIRunnable> aEvent,
                  mozilla::MutexAutoLock& aProofOfLock)
      RefPtr<nsIRunnable> event(aEvent);
      nsCOMPtr<nsIRunnablePriority> runnablePrio =
      uint32_t prio = nsIRunnablePriority::PRIORITY_NORMAL;
      if (runnablePrio) {
      MOZ_ASSERT(prio == nsIRunnablePriority::PRIORITY_NORMAL ||
                 prio == nsIRunnablePriority::PRIORITY_HIGH);
      if (prio == nsIRunnablePriority::PRIORITY_NORMAL) {
        mNormalQueue->PutEvent(event.forget(), aProofOfLock);
      } else {
        mSecondaryQueue->PutEvent(event.forget(), aProofOfLock);

    bool HasPendingEvent(mozilla::MutexAutoLock& aProofOfLock)
      return mNormalQueue->HasPendingEvent(aProofOfLock) ||

    nsChainedEventQueue* mNext;
    RefPtr<nsNestedEventTarget> mEventTarget;

    mozilla::CondVar mEventsAvailable;
    mozilla::UniquePtr<nsEventQueue> mNormalQueue;
    mozilla::UniquePtr<nsEventQueue> mSecondaryQueue;

    // Try to process one high priority runnable after each normal
    // priority runnable. This gives the processing model HTML spec has for
    // 'Update the rendering' in the case only vsync messages are in the
    // secondary queue and prevents starving the normal queue.
    bool mProcessSecondaryQueueRunnable;

  class nsNestedEventTarget final : public nsIEventTarget

    nsNestedEventTarget(NotNull<nsThread*> aThread,
                        NotNull<nsChainedEventQueue*> aQueue)
      : mThread(aThread)
      , mQueue(aQueue)


    NotNull<RefPtr<nsThread>> mThread;

    // This is protected by mThread->mLock.
    nsChainedEventQueue* mQueue;


  // This lock protects access to mObserver, mEvents, mIdleEvents,
  // mIdlePeriod and mEventsAreDoomed.  All of those fields are only
  // modified on the thread itself (never from another thread).  This
  // means that we can avoid holding the lock while using mObserver
  // and mEvents on the thread itself.  When calling PutEvent on
  // mEvents, we have to hold the lock to synchronize with
  // PopEventQueue.
  mozilla::Mutex mLock;

  nsCOMPtr<nsIThreadObserver> mObserver;
  mozilla::CycleCollectedJSContext* mScriptObserver;

  // Only accessed on the target thread.
  nsAutoTObserverArray<NotNull<nsCOMPtr<nsIThreadObserver>>, 2> mEventObservers;

  NotNull<nsChainedEventQueue*> mEvents;  // never null
  nsChainedEventQueue mEventsRoot;

  // mIdlePeriod keeps track of the current idle period. If at any
  // time the main event queue is empty, calling
  // mIdlePeriod->GetIdlePeriodHint() will give an estimate of when
  // the current idle period will end.
  nsCOMPtr<nsIIdlePeriod> mIdlePeriod;
  mozilla::CondVar mIdleEventsAvailable;
  nsEventQueue mIdleEvents;

  int32_t   mPriority;
  PRThread* mThread;
  uint32_t  mNestedEventLoopDepth;
  uint32_t  mStackSize;

  // The shutdown context for ourselves.
  struct nsThreadShutdownContext* mShutdownContext;
  // The shutdown contexts for any other threads we've asked to shut down.
  nsTArray<nsAutoPtr<struct nsThreadShutdownContext>> mRequestedShutdownContexts;

  bool mShutdownRequired;
  // Set to true when events posted to this thread will never run.
  bool mEventsAreDoomed;
  MainThreadFlag mIsMainThread;

  // The time when we last ran an unlabeled runnable (one not associated with a
  // SchedulerGroup).
  mozilla::TimeStamp mLastUnlabeledRunnable;

  // Set to true if this thread creates a JSRuntime.
  bool mCanInvokeJS;
  // Set to true if HasPendingEvents() has been called and returned true because
  // of a pending idle event.  This is used to remember to return that idle
  // event from GetIdleEvent() to ensure that HasPendingEvents() never lies.
  bool mHasPendingEventsPromisedIdleEvent;

#if defined(XP_UNIX) && !defined(ANDROID) && !defined(DEBUG) && HAVE_UALARM \
  && defined(_GNU_SOURCE)
# define MOZ_CANARY

extern int sCanaryOutputFD;

#endif  // nsThread_h__