dom/media/MediaShutdownManager.cpp
author JW Wang <jwwang@mozilla.com>
Fri, 03 Feb 2017 15:16:50 +0800
changeset 479893 d729059d550a71caa819d9dd69470bd5cc669fed
parent 479892 370b66055c098a255d1d6a061b357f932ed70b5f
child 479910 b2d14d738d2c38bd56225340b4dad320fe50bc7d
permissions -rw-r--r--
Bug 1336345. Part 2 - some code cleanup. r=gerald MozReview-Commit-ID: 1XHkvz4aWxB

/* -*- 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/. */

#include "mozilla/Logging.h"
#include "mozilla/StaticPtr.h"
#include "nsContentUtils.h"

#include "MediaDecoder.h"
#include "MediaShutdownManager.h"

namespace mozilla {

extern LazyLogModule gMediaDecoderLog;
#define DECODER_LOG(type, msg) MOZ_LOG(gMediaDecoderLog, type, msg)

NS_IMPL_ISUPPORTS(MediaShutdownManager, nsIAsyncShutdownBlocker)

MediaShutdownManager::MediaShutdownManager()
{
  MOZ_ASSERT(NS_IsMainThread());
}

MediaShutdownManager::~MediaShutdownManager()
{
  MOZ_ASSERT(NS_IsMainThread());
}

// Note that we don't use ClearOnShutdown() on this StaticRefPtr, as that
// may interfere with our shutdown listener.
StaticRefPtr<MediaShutdownManager> MediaShutdownManager::sInstance;

MediaShutdownManager&
MediaShutdownManager::Instance()
{
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_DIAGNOSTIC_ASSERT(sInstance);
  return *sInstance;
}

static nsCOMPtr<nsIAsyncShutdownClient>
GetShutdownBarrier()
{
  nsCOMPtr<nsIAsyncShutdownService> svc = services::GetAsyncShutdown();
  MOZ_RELEASE_ASSERT(svc);

  nsCOMPtr<nsIAsyncShutdownClient> barrier;
  nsresult rv = svc->GetProfileBeforeChange(getter_AddRefs(barrier));
  if (!barrier) {
    // We are probably in a content process. We need to do cleanup at
    // XPCOM shutdown in leakchecking builds.
    rv = svc->GetXpcomWillShutdown(getter_AddRefs(barrier));
  }
  MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv));
  MOZ_RELEASE_ASSERT(barrier);
  return barrier.forget();
}

void
MediaShutdownManager::InitStatics()
{
  MOZ_ASSERT(NS_IsMainThread());
  static bool sInitDone = false;
  if (sInitDone) {
    return;
  }

  sInitDone = true;
  sInstance = new MediaShutdownManager();

  nsresult rv = GetShutdownBarrier()->AddBlocker(
    sInstance, NS_LITERAL_STRING(__FILE__), __LINE__,
    NS_LITERAL_STRING("MediaShutdownManager shutdown"));
  if (NS_FAILED(rv)) {
    // Leak the buffer on the heap to make sure that it lives long enough,
    // as MOZ_CRASH_ANNOTATE expects the pointer passed to it to live to
    // the end of the program.
    const size_t CAPACITY = 256;
    auto buf = new char[CAPACITY];
    snprintf(buf, CAPACITY, "Failed to add shutdown blocker! rv=%x", uint32_t(rv));
    MOZ_CRASH_ANNOTATE(buf);
    MOZ_REALLY_CRASH();
  }
}

void
MediaShutdownManager::RemoveBlocker()
{
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(mIsDoingXPCOMShutDown);
  MOZ_ASSERT(mDecoders.Count() == 0);
  GetShutdownBarrier()->RemoveBlocker(this);
  // Clear our singleton reference. This will probably delete
  // this instance, so don't deref |this| clearing sInstance.
  sInstance = nullptr;
  DECODER_LOG(LogLevel::Debug, ("MediaShutdownManager::BlockShutdown() end."));
}

void
MediaShutdownManager::Register(MediaDecoder* aDecoder)
{
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_RELEASE_ASSERT(!mIsDoingXPCOMShutDown);
  // Don't call Register() after you've Unregistered() all the decoders,
  // that's not going to work.
  MOZ_ASSERT(!mDecoders.Contains(aDecoder));
  mDecoders.PutEntry(aDecoder);
  MOZ_ASSERT(mDecoders.Contains(aDecoder));
  MOZ_ASSERT(mDecoders.Count() > 0);
}

void
MediaShutdownManager::Unregister(MediaDecoder* aDecoder)
{
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(mDecoders.Contains(aDecoder));
  mDecoders.RemoveEntry(aDecoder);
  if (mIsDoingXPCOMShutDown && mDecoders.Count() == 0) {
    RemoveBlocker();
  }
}

NS_IMETHODIMP
MediaShutdownManager::GetName(nsAString& aName)
{
  aName = NS_LITERAL_STRING("MediaShutdownManager: shutdown");
  return NS_OK;
}

NS_IMETHODIMP
MediaShutdownManager::GetState(nsIPropertyBag**)
{
  return NS_OK;
}

NS_IMETHODIMP
MediaShutdownManager::BlockShutdown(nsIAsyncShutdownClient*)
{
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(sInstance);

  DECODER_LOG(LogLevel::Debug, ("MediaShutdownManager::BlockShutdown() start..."));

  // Set this flag to ensure no Register() is allowed when Shutdown() begins.
  mIsDoingXPCOMShutDown = true;

  auto oldCount = mDecoders.Count();
  if (oldCount == 0) {
    RemoveBlocker();
    return NS_OK;
  }

  // Iterate over the decoders and shut them down.
  for (auto iter = mDecoders.Iter(); !iter.Done(); iter.Next()) {
    MediaDecoderOwner* owner = iter.Get()->GetKey()->GetOwner();
    if (owner) {
      // The owner will call MediaDecoder::Shutdown() and
      // drop its reference to the decoder.
      owner->NotifyXPCOMShutdown();
    }
    // Check MediaDecoder::Shutdown doesn't call Unregister() synchronously in
    // order not to corrupt our hashtable traversal.
    MOZ_ASSERT(mDecoders.Count() == oldCount);
  }

  return NS_OK;
}

} // namespace mozilla