dom/serviceworkers/ServiceWorkerShutdownBlocker.cpp
author Nika Layzell <nika@thelayzells.com>
Thu, 06 Aug 2020 14:04:13 +0000
changeset 544125 ee09cb88af177571304759bc05c760e3d82fd1ed
parent 538159 3d7ffaefcd5a6c10988a1ecc3b75c3d55e1cd9e2
permissions -rw-r--r--
Bug 1656854 - Part 2: Add a BrowsingContextGroup keepalive to BrowserParent shutdown, r=farre In bug 1652085, I added BrowsingContextGroup keepalives while waiting for replies to the discard message, however that message isn't actually sent to the current owner process. Instead, the BrowsingContext is discarded by the PBrowser being destroyed. This should help ensure we also keep the group alive during normal BrowserParent destruction. Differential Revision: https://phabricator.services.mozilla.com/D85897

/* -*- 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/. */

#include "ServiceWorkerShutdownBlocker.h"

#include <chrono>
#include <utility>

#include "MainThreadUtils.h"
#include "nsDebug.h"
#include "nsError.h"
#include "nsIWritablePropertyBag2.h"
#include "nsThreadUtils.h"

#include "mozilla/Assertions.h"
#include "mozilla/RefPtr.h"

namespace mozilla {
namespace dom {

NS_IMPL_ISUPPORTS(ServiceWorkerShutdownBlocker, nsIAsyncShutdownBlocker)

NS_IMETHODIMP ServiceWorkerShutdownBlocker::GetName(nsAString& aNameOut) {
  aNameOut = nsLiteralString(
      u"ServiceWorkerShutdownBlocker: shutting down Service Workers");
  return NS_OK;
}

NS_IMETHODIMP
ServiceWorkerShutdownBlocker::BlockShutdown(nsIAsyncShutdownClient* aClient) {
  AssertIsOnMainThread();
  MOZ_ASSERT(!mShutdownClient);

  mShutdownClient = aClient;

  MaybeUnblockShutdown();
  MaybeInitUnblockShutdownTimer();

  return NS_OK;
}

NS_IMETHODIMP ServiceWorkerShutdownBlocker::GetState(nsIPropertyBag** aBagOut) {
  AssertIsOnMainThread();
  MOZ_ASSERT(aBagOut);

  nsCOMPtr<nsIWritablePropertyBag2> propertyBag =
      do_CreateInstance("@mozilla.org/hash-property-bag;1");

  if (NS_WARN_IF(!propertyBag)) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  nsresult rv = propertyBag->SetPropertyAsBool(u"acceptingPromises"_ns,
                                               IsAcceptingPromises());

  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  rv = propertyBag->SetPropertyAsUint32(u"pendingPromises"_ns,
                                        GetPendingPromises());

  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  nsAutoCString shutdownStates;

  for (auto iter = mShutdownStates.iter(); !iter.done(); iter.next()) {
    shutdownStates.Append(iter.get().value().GetProgressString());
    shutdownStates.Append(", ");
  }

  rv = propertyBag->SetPropertyAsACString(u"shutdownStates"_ns, shutdownStates);

  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  propertyBag.forget(aBagOut);

  return NS_OK;
}

/* static */ already_AddRefed<ServiceWorkerShutdownBlocker>
ServiceWorkerShutdownBlocker::CreateAndRegisterOn(
    nsIAsyncShutdownClient* aShutdownBarrier) {
  AssertIsOnMainThread();
  MOZ_ASSERT(aShutdownBarrier);

  RefPtr<ServiceWorkerShutdownBlocker> blocker =
      new ServiceWorkerShutdownBlocker();

  nsresult rv = aShutdownBarrier->AddBlocker(
      blocker.get(), NS_LITERAL_STRING_FROM_CSTRING(__FILE__), __LINE__,
      u"Service Workers shutdown"_ns);

  if (NS_WARN_IF(NS_FAILED(rv))) {
    return nullptr;
  }

  return blocker.forget();
}

void ServiceWorkerShutdownBlocker::WaitOnPromise(
    GenericNonExclusivePromise* aPromise, uint32_t aShutdownStateId) {
  AssertIsOnMainThread();
  MOZ_DIAGNOSTIC_ASSERT(IsAcceptingPromises());
  MOZ_ASSERT(aPromise);
  MOZ_ASSERT(mShutdownStates.has(aShutdownStateId));

  ++mState.as<AcceptingPromises>().mPendingPromises;

  RefPtr<ServiceWorkerShutdownBlocker> self = this;

  aPromise->Then(GetCurrentSerialEventTarget(), __func__,
                 [self = std::move(self), shutdownStateId = aShutdownStateId](
                     const GenericNonExclusivePromise::ResolveOrRejectValue&) {
                   // Progress reporting might race with aPromise settling.
                   self->mShutdownStates.remove(shutdownStateId);

                   if (!self->PromiseSettled()) {
                     self->MaybeUnblockShutdown();
                   }
                 });
}

void ServiceWorkerShutdownBlocker::StopAcceptingPromises() {
  AssertIsOnMainThread();
  MOZ_ASSERT(IsAcceptingPromises());

  mState = AsVariant(NotAcceptingPromises(mState.as<AcceptingPromises>()));

  MaybeUnblockShutdown();
  MaybeInitUnblockShutdownTimer();
}

uint32_t ServiceWorkerShutdownBlocker::CreateShutdownState() {
  AssertIsOnMainThread();

  static uint32_t nextShutdownStateId = 1;

  MOZ_ALWAYS_TRUE(mShutdownStates.putNew(nextShutdownStateId,
                                         ServiceWorkerShutdownState()));

  return nextShutdownStateId++;
}

void ServiceWorkerShutdownBlocker::ReportShutdownProgress(
    uint32_t aShutdownStateId, Progress aProgress) {
  AssertIsOnMainThread();
  MOZ_RELEASE_ASSERT(aShutdownStateId != kInvalidShutdownStateId);

  auto lookup = mShutdownStates.lookup(aShutdownStateId);

  // Progress reporting might race with the promise that WaitOnPromise is called
  // with settling.
  if (!lookup) {
    return;
  }

  // This will check for a valid progress transition with assertions.
  lookup->value().SetProgress(aProgress);

  if (aProgress == Progress::ShutdownCompleted) {
    mShutdownStates.remove(lookup);
  }
}

ServiceWorkerShutdownBlocker::ServiceWorkerShutdownBlocker()
    : mState(VariantType<AcceptingPromises>()) {
  AssertIsOnMainThread();
}

ServiceWorkerShutdownBlocker::~ServiceWorkerShutdownBlocker() {
  MOZ_ASSERT(!IsAcceptingPromises());
  MOZ_ASSERT(!GetPendingPromises());
  MOZ_ASSERT(!mShutdownClient);
}

void ServiceWorkerShutdownBlocker::MaybeUnblockShutdown() {
  AssertIsOnMainThread();

  if (!mShutdownClient || IsAcceptingPromises() || GetPendingPromises()) {
    return;
  }

  UnblockShutdown();
}

void ServiceWorkerShutdownBlocker::UnblockShutdown() {
  MOZ_ASSERT(mShutdownClient);

  mShutdownClient->RemoveBlocker(this);
  mShutdownClient = nullptr;

  if (mTimer) {
    mTimer->Cancel();
  }
}

uint32_t ServiceWorkerShutdownBlocker::PromiseSettled() {
  AssertIsOnMainThread();
  MOZ_ASSERT(GetPendingPromises());

  if (IsAcceptingPromises()) {
    return --mState.as<AcceptingPromises>().mPendingPromises;
  }

  return --mState.as<NotAcceptingPromises>().mPendingPromises;
}

bool ServiceWorkerShutdownBlocker::IsAcceptingPromises() const {
  AssertIsOnMainThread();

  return mState.is<AcceptingPromises>();
}

uint32_t ServiceWorkerShutdownBlocker::GetPendingPromises() const {
  AssertIsOnMainThread();

  if (IsAcceptingPromises()) {
    return mState.as<AcceptingPromises>().mPendingPromises;
  }

  return mState.as<NotAcceptingPromises>().mPendingPromises;
}

ServiceWorkerShutdownBlocker::NotAcceptingPromises::NotAcceptingPromises(
    AcceptingPromises aPreviousState)
    : mPendingPromises(aPreviousState.mPendingPromises) {
  AssertIsOnMainThread();
}

NS_IMETHODIMP ServiceWorkerShutdownBlocker::Notify(nsITimer*) {
  // TODO: this method being called indicates that there are ServiceWorkers
  // that did not complete shutdown before the timer expired - there should be
  // a telemetry ping or some other way of recording the state of when this
  // happens (e.g. what's returned by GetState()).
  UnblockShutdown();
  return NS_OK;
}

void ServiceWorkerShutdownBlocker::MaybeInitUnblockShutdownTimer() {
#ifdef RELEASE_OR_BETA
  AssertIsOnMainThread();
  MOZ_ASSERT(!mTimer);

  if (!mShutdownClient || IsAcceptingPromises()) {
    return;
  }

  MOZ_ASSERT(GetPendingPromises(),
             "Shouldn't be blocking shutdown with zero pending promises.");

  using namespace std::chrono_literals;

  static constexpr auto delay =
      std::chrono::duration_cast<std::chrono::milliseconds>(10s);

  mTimer = NS_NewTimer();

  mTimer->InitWithCallback(this, delay.count(), nsITimer::TYPE_ONE_SHOT);
#endif
}

}  // namespace dom
}  // namespace mozilla