dom/media/MediaShutdownManager.h
author Mike Hommey <mh+mozilla@glandium.org>
Fri, 11 Jan 2019 16:01:15 +0000
changeset 453570 daf50f25895db073e44d50fecf2e4f6fe873865d
parent 446960 0ceae9db9ec0be18daa1a279511ad305723185d4
child 454520 5f4630838d46dd81dadb13220a4af0da9e23a619
permissions -rw-r--r--
Bug 1519307 - Add a new project to build useful parts of breakpad independently. r=froydnj With `ac_add_options --enable-project=tools/crashreporter` in a mozconfig, `./mach build` builds minidump_stackwalk, dump_syms and fileid. One caveat is that due to limitation in how the build system works currently, it's cumbersome to keep dump_syms as a host program for Gecko, and to make it a target program for this project. For now, keep it as a host program. We're not going to use it on automation, but it's still convenient to have for quick local builds (I've had to resort to awful hacks downstream). Differential Revision: https://phabricator.services.mozilla.com/D16299

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* 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/. */

#if !defined(MediaShutdownManager_h_)
#define MediaShutdownManager_h_

#include "mozilla/Monitor.h"
#include "mozilla/RefPtr.h"
#include "mozilla/StaticPtr.h"
#include "nsCOMPtr.h"
#include "nsIAsyncShutdown.h"
#include "nsIThread.h"
#include "nsHashKeys.h"
#include "nsTHashtable.h"

namespace mozilla {

class MediaDecoder;

// The MediaShutdownManager manages shutting down the MediaDecoder
// infrastructure in response to an xpcom-shutdown notification.
// This happens when Gecko is shutting down in the middle of operation.
// This is tricky, as there are a number of moving parts that must
// be shutdown in a particular order. The MediaShutdownManager
// encapsulates all these dependencies to ensure that no shutdown
// order dependencies leak out of the MediaDecoder stack.
// The MediaShutdownManager is a singleton.
//
// The MediaShutdownManager ensures that the MediaDecoder stack
// is shutdown before exiting xpcom-shutdown stage by registering
// itself with nsIAsyncShutdownService to receive notification
// when the stage of shutdown has started and then calls Shutdown()
// on every MediaDecoder. Shutdown will not proceed until all
// MediaDecoders finish shutdown and MediaShutdownManager unregisters
// itself from the async shutdown service.
//
// Note that calling the Unregister() functions may result in the singleton
// being deleted, so don't store references to the singleton, always use the
// singleton by derefing the referenced returned by
// MediaShutdownManager::Instance(), which ensures that the singleton is
// created when needed.
// i.e. like this:
//    MediaShutdownManager::Instance()::Unregister(someDecoder);
//    MediaShutdownManager::Instance()::Register(someOtherDecoder);
// Not like this:
//  MediaShutdownManager& instance = MediaShutdownManager::Instance();
//  instance.Unregister(someDecoder); // Warning! May delete instance!
//  instance.Register(someOtherDecoder); // BAD! instance may be dangling!
class MediaShutdownManager : public nsIAsyncShutdownBlocker {
 public:
  NS_DECL_ISUPPORTS
  NS_DECL_NSIASYNCSHUTDOWNBLOCKER

  static void InitStatics();

  // The MediaShutdownManager is a singleton, access its instance with
  // this accessor.
  static MediaShutdownManager& Instance();

  // Notifies the MediaShutdownManager that it needs to track the shutdown
  // of this MediaDecoder.
  nsresult Register(MediaDecoder* aDecoder);

  // Notifies the MediaShutdownManager that a MediaDecoder that it was
  // tracking has shutdown, and it no longer needs to be shutdown in the
  // xpcom-shutdown listener.
  void Unregister(MediaDecoder* aDecoder);

 private:
  enum InitPhase {
    NotInited,
    InitSucceeded,
    InitFailed,
    XPCOMShutdownStarted,
    XPCOMShutdownEnded
  };

  static InitPhase sInitPhase;

  MediaShutdownManager();
  virtual ~MediaShutdownManager();
  void RemoveBlocker();

  static StaticRefPtr<MediaShutdownManager> sInstance;

  // References to the MediaDecoder. The decoders unregister themselves
  // in their Shutdown() method, so we'll drop the reference naturally when
  // we're shutting down (in the non xpcom-shutdown case).
  nsTHashtable<nsRefPtrHashKey<MediaDecoder>> mDecoders;
};

}  // namespace mozilla

#endif