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3c25c690a7
XPCOM when shutting down expects all tasks to be run synchronously. As such, we must ensure that the remaining MediaDecoder are shut down before continuing on the next task. In particular destroying gfxPlatforms must only ever happen after, as it is possible for the MediaDecoderReader to make use of gfx resources during shutdown.
110 lines
4.3 KiB
C++
110 lines
4.3 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim:set ts=2 sw=2 sts=2 et cindent: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#if !defined(MediaShutdownManager_h_)
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#define MediaShutdownManager_h_
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#include "nsIObserver.h"
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#include "mozilla/Monitor.h"
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#include "mozilla/RefPtr.h"
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#include "mozilla/StaticPtr.h"
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#include "nsIThread.h"
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#include "nsCOMPtr.h"
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#include "nsTHashtable.h"
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#include "nsHashKeys.h"
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namespace mozilla {
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class MediaDecoder;
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// The MediaShutdownManager manages shutting down the MediaDecoder
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// infrastructure in response to an xpcom-shutdown notification. This happens
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// when Gecko is shutting down in the middle of operation. This is tricky, as
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// there are a number of moving parts that must be shutdown in a particular
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// order. Additionally the xpcom-shutdown observer *must* block until all
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// threads are shutdown, which is tricky since we have a number of threads
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// here and their shutdown is asynchronous. We can't have each element of
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// our pipeline listening for xpcom-shutdown, as if each observer blocks
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// waiting for its threads to shutdown it will block other xpcom-shutdown
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// notifications from firing, and shutdown of one part of the media pipeline
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// (say the State Machine thread) may depend another part to be shutdown
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// first (the MediaDecoder threads). The MediaShutdownManager encapsulates
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// all these dependencies, and provides a single xpcom-shutdown listener
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// for the MediaDecoder infrastructure, to ensure that no shutdown order
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// dependencies leak out of the MediaDecoder stack. The MediaShutdownManager
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// is a singleton.
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//
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// The MediaShutdownManager ensures that the MediaDecoder stack is shutdown
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// before returning from its xpcom-shutdown observer by keeping track of all
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// the active MediaDecoders, and upon xpcom-shutdown calling Shutdown() on
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// every MediaDecoder and then spinning the main thread event loop until all
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// SharedThreadPools have shutdown. Once the SharedThreadPools are shutdown,
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// all the state machines and their threads have been shutdown, the
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// xpcom-shutdown observer returns.
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//
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// Note that calling the Unregister() functions may result in the singleton
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// being deleted, so don't store references to the singleton, always use the
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// singleton by derefing the referenced returned by
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// MediaShutdownManager::Instance(), which ensures that the singleton is
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// created when needed.
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// i.e. like this:
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// MediaShutdownManager::Instance()::Unregister(someDecoder);
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// MediaShutdownManager::Instance()::Register(someOtherDecoder);
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// Not like this:
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// MediaShutdownManager& instance = MediaShutdownManager::Instance();
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// instance.Unregister(someDecoder); // Warning! May delete instance!
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// instance.Register(someOtherDecoder); // BAD! instance may be dangling!
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class MediaShutdownManager : public nsIObserver {
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public:
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NS_DECL_ISUPPORTS
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NS_DECL_NSIOBSERVER
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// The MediaShutdownManager is a singleton, access its instance with
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// this accessor.
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static MediaShutdownManager& Instance();
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// Notifies the MediaShutdownManager that it needs to track the shutdown
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// of this MediaDecoder.
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void Register(MediaDecoder* aDecoder);
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// Notifies the MediaShutdownManager that a MediaDecoder that it was
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// tracking has shutdown, and it no longer needs to be shutdown in the
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// xpcom-shutdown listener.
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void Unregister(MediaDecoder* aDecoder);
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private:
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MediaShutdownManager();
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virtual ~MediaShutdownManager();
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void Shutdown();
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void FinishShutdown();
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// Ensures we have a shutdown listener if we need one, and removes the
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// listener and destroys the singleton if we don't.
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void EnsureCorrectShutdownObserverState();
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static StaticRefPtr<MediaShutdownManager> sInstance;
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// References to the MediaDecoder. The decoders unregister themselves
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// in their Shutdown() method, so we'll drop the reference naturally when
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// we're shutting down (in the non xpcom-shutdown case).
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nsTHashtable<nsRefPtrHashKey<MediaDecoder>> mDecoders;
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// True if we have an XPCOM shutdown observer.
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bool mIsObservingShutdown;
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bool mIsDoingXPCOMShutDown;
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// Will be set to true once all registered MediaDecoders have completed their
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// shutdown.
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bool mCompletedShutdown;
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};
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} // namespace mozilla
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#endif
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