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/* -*- 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 */
#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 "nsTHashSet.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 {
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);
enum InitPhase {
static InitPhase sInitPhase;
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).
nsTHashSet<RefPtr<MediaDecoder>> mDecoders;
} // namespace mozilla