gecko-dev/xpcom/threads/SchedulerGroup.cpp

/* -*- 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 "mozilla/SchedulerGroup.h"

#include "jsfriendapi.h"
#include "mozilla/AbstractThread.h"
#include "mozilla/Atomics.h"
#include "mozilla/Move.h"
#include "mozilla/Unused.h"
#include "mozilla/dom/DocGroup.h"
#include "nsINamed.h"
#include "nsQueryObject.h"
#include "mozilla/dom/ScriptSettings.h"
#include "nsThreadUtils.h"

#include "mozilla/Telemetry.h"

using namespace mozilla;

/* SchedulerEventTarget */

namespace {

#define NS_DISPATCHEREVENTTARGET_IID                 \
  {                                                  \
    0xbf4e36c8, 0x7d04, 0x4ef4, {                    \
      0xbb, 0xd8, 0x11, 0x09, 0x0a, 0xdb, 0x4d, 0xf7 \
    }                                                \
  }

class SchedulerEventTarget final : public nsISerialEventTarget {
  RefPtr<SchedulerGroup> mDispatcher;
  TaskCategory mCategory;

 public:
  NS_DECLARE_STATIC_IID_ACCESSOR(NS_DISPATCHEREVENTTARGET_IID)

  SchedulerEventTarget(SchedulerGroup* aDispatcher, TaskCategory aCategory)
      : mDispatcher(aDispatcher), mCategory(aCategory) {}

  NS_DECL_THREADSAFE_ISUPPORTS
  NS_DECL_NSIEVENTTARGET_FULL

  SchedulerGroup* Dispatcher() const { return mDispatcher; }

 private:
  ~SchedulerEventTarget() {}
};

NS_DEFINE_STATIC_IID_ACCESSOR(SchedulerEventTarget,
                              NS_DISPATCHEREVENTTARGET_IID)

static Atomic<uint64_t> gEarliestUnprocessedVsync(0);

}  // namespace

NS_IMPL_ISUPPORTS(SchedulerEventTarget, SchedulerEventTarget, nsIEventTarget,
                  nsISerialEventTarget)

NS_IMETHODIMP
SchedulerEventTarget::DispatchFromScript(nsIRunnable* aRunnable,
                                         uint32_t aFlags) {
  return Dispatch(do_AddRef(aRunnable), aFlags);
}

NS_IMETHODIMP
SchedulerEventTarget::Dispatch(already_AddRefed<nsIRunnable> aRunnable,
                               uint32_t aFlags) {
  if (NS_WARN_IF(aFlags != NS_DISPATCH_NORMAL)) {
    return NS_ERROR_UNEXPECTED;
  }
  return mDispatcher->Dispatch(mCategory, std::move(aRunnable));
}

NS_IMETHODIMP
SchedulerEventTarget::DelayedDispatch(already_AddRefed<nsIRunnable>, uint32_t) {
  return NS_ERROR_NOT_IMPLEMENTED;
}

NS_IMETHODIMP
SchedulerEventTarget::IsOnCurrentThread(bool* aIsOnCurrentThread) {
  *aIsOnCurrentThread = NS_IsMainThread();
  return NS_OK;
}

NS_IMETHODIMP_(bool)
SchedulerEventTarget::IsOnCurrentThreadInfallible() {
  return NS_IsMainThread();
}

/* static */
nsresult SchedulerGroup::UnlabeledDispatch(
    TaskCategory aCategory, already_AddRefed<nsIRunnable>&& aRunnable) {
  if (NS_IsMainThread()) {
    return NS_DispatchToCurrentThread(std::move(aRunnable));
  } else {
    return NS_DispatchToMainThread(std::move(aRunnable));
  }
}

/* static */
void SchedulerGroup::MarkVsyncReceived() {
  if (gEarliestUnprocessedVsync) {
    // If we've seen a vsync already, but haven't handled it, keep the
    // older one.
    return;
  }

  MOZ_ASSERT(!NS_IsMainThread());
  bool inconsistent = false;
  TimeStamp creation = TimeStamp::ProcessCreation(&inconsistent);
  if (inconsistent) {
    return;
  }

  gEarliestUnprocessedVsync = (TimeStamp::Now() - creation).ToMicroseconds();
}

/* static */
void SchedulerGroup::MarkVsyncRan() { gEarliestUnprocessedVsync = 0; }

MOZ_THREAD_LOCAL(bool) SchedulerGroup::sTlsValidatingAccess;

SchedulerGroup::SchedulerGroup() : mIsRunning(false) {
  if (NS_IsMainThread()) {
    sTlsValidatingAccess.infallibleInit();
  }
}

nsresult SchedulerGroup::DispatchWithDocGroup(
    TaskCategory aCategory, already_AddRefed<nsIRunnable>&& aRunnable,
    dom::DocGroup* aDocGroup) {
  return LabeledDispatch(aCategory, std::move(aRunnable), aDocGroup);
}

nsresult SchedulerGroup::Dispatch(TaskCategory aCategory,
                                  already_AddRefed<nsIRunnable>&& aRunnable) {
  return LabeledDispatch(aCategory, std::move(aRunnable), nullptr);
}

nsISerialEventTarget* SchedulerGroup::EventTargetFor(
    TaskCategory aCategory) const {
  MOZ_ASSERT(aCategory != TaskCategory::Count);
  MOZ_ASSERT(mEventTargets[size_t(aCategory)]);
  return mEventTargets[size_t(aCategory)];
}

AbstractThread* SchedulerGroup::AbstractMainThreadFor(TaskCategory aCategory) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  return AbstractMainThreadForImpl(aCategory);
}

AbstractThread* SchedulerGroup::AbstractMainThreadForImpl(
    TaskCategory aCategory) {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(aCategory != TaskCategory::Count);
  MOZ_ASSERT(mEventTargets[size_t(aCategory)]);

  if (!mAbstractThreads[size_t(aCategory)]) {
    mAbstractThreads[size_t(aCategory)] =
        AbstractThread::CreateEventTargetWrapper(
            mEventTargets[size_t(aCategory)],
            /* aDrainDirectTasks = */ true);
  }

  return mAbstractThreads[size_t(aCategory)];
}

void SchedulerGroup::CreateEventTargets(bool aNeedValidation) {
  for (size_t i = 0; i < size_t(TaskCategory::Count); i++) {
    TaskCategory category = static_cast<TaskCategory>(i);
    if (!aNeedValidation) {
      // The chrome TabGroup dispatches directly to the main thread. This means
      // that we don't have to worry about cyclical references when cleaning up
      // the chrome TabGroup.
      mEventTargets[i] = GetMainThreadSerialEventTarget();
    } else {
      mEventTargets[i] = CreateEventTargetFor(category);
    }
  }
}

void SchedulerGroup::Shutdown(bool aXPCOMShutdown) {
  // There is a RefPtr cycle TabGroup -> SchedulerEventTarget -> TabGroup. To
  // avoid leaks, we need to break the chain somewhere. We shouldn't be using
  // the ThrottledEventQueue for this TabGroup when no windows belong to it,
  // so it's safe to null out the queue here.
  for (size_t i = 0; i < size_t(TaskCategory::Count); i++) {
    mEventTargets[i] =
        aXPCOMShutdown ? nullptr : GetMainThreadSerialEventTarget();
    mAbstractThreads[i] = nullptr;
  }
}

already_AddRefed<nsISerialEventTarget> SchedulerGroup::CreateEventTargetFor(
    TaskCategory aCategory) {
  RefPtr<SchedulerEventTarget> target =
      new SchedulerEventTarget(this, aCategory);
  return target.forget();
}

/* static */
SchedulerGroup* SchedulerGroup::FromEventTarget(nsIEventTarget* aEventTarget) {
  RefPtr<SchedulerEventTarget> target = do_QueryObject(aEventTarget);
  if (!target) {
    return nullptr;
  }
  return target->Dispatcher();
}

nsresult SchedulerGroup::LabeledDispatch(
    TaskCategory aCategory, already_AddRefed<nsIRunnable>&& aRunnable,
    dom::DocGroup* aDocGroup) {
  nsCOMPtr<nsIRunnable> runnable(aRunnable);
  if (XRE_IsContentProcess()) {
    RefPtr<Runnable> internalRunnable =
        new Runnable(runnable.forget(), this, aDocGroup);
    return InternalUnlabeledDispatch(aCategory, internalRunnable.forget());
  }
  return UnlabeledDispatch(aCategory, runnable.forget());
}

/*static*/
nsresult SchedulerGroup::InternalUnlabeledDispatch(
    TaskCategory aCategory, already_AddRefed<Runnable>&& aRunnable) {
  if (NS_IsMainThread()) {
    // NS_DispatchToCurrentThread will not leak the passed in runnable
    // when it fails, so we don't need to do anything special.
    return NS_DispatchToCurrentThread(std::move(aRunnable));
  }

  RefPtr<Runnable> runnable(aRunnable);
  nsresult rv = NS_DispatchToMainThread(do_AddRef(runnable));
  if (NS_FAILED(rv)) {
    // Dispatch failed.  This is a situation where we would have used
    // NS_DispatchToMainThread rather than calling into the SchedulerGroup
    // machinery, and the caller would be expecting to leak the nsIRunnable
    // originally passed in.  But because we've had to wrap things up
    // internally, we were going to leak the nsIRunnable *and* our Runnable
    // wrapper.  But there's no reason that we have to leak our Runnable
    // wrapper; we can just leak the wrapped nsIRunnable, and let the caller
    // take care of unleaking it if they need to.
    Unused << runnable->mRunnable.forget().take();
    nsrefcnt refcnt = runnable.get()->Release();
    MOZ_RELEASE_ASSERT(refcnt == 1, "still holding an unexpected reference!");
  }

  return rv;
}

/* static */
void SchedulerGroup::SetValidatingAccess(ValidationType aType) {
  bool validating = aType == StartValidation;
  sTlsValidatingAccess.set(validating);

  dom::AutoJSAPI jsapi;
  jsapi.Init();
  js::EnableAccessValidation(jsapi.cx(), validating);
}

SchedulerGroup::Runnable::Runnable(already_AddRefed<nsIRunnable>&& aRunnable,
                                   SchedulerGroup* aGroup,
                                   dom::DocGroup* aDocGroup)
    : mozilla::Runnable("SchedulerGroup::Runnable"),
      mRunnable(std::move(aRunnable)),
      mGroup(aGroup),
      mDocGroup(aDocGroup) {}

dom::DocGroup* SchedulerGroup::Runnable::DocGroup() const { return mDocGroup; }

#ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY
NS_IMETHODIMP
SchedulerGroup::Runnable::GetName(nsACString& aName) {
  // Try to get a name from the underlying runnable.
  nsCOMPtr<nsINamed> named = do_QueryInterface(mRunnable);
  if (named) {
    named->GetName(aName);
  }
  if (aName.IsEmpty()) {
    aName.AssignLiteral("anonymous");
  }

  return NS_OK;
}
#endif

NS_IMETHODIMP
SchedulerGroup::Runnable::Run() {
  MOZ_RELEASE_ASSERT(NS_IsMainThread());

  nsresult result = mRunnable->Run();

  // The runnable's destructor can have side effects, so try to execute it in
  // the scope of the TabGroup.
  mRunnable = nullptr;

  mGroup->SetValidatingAccess(EndValidation);
  return result;
}

NS_IMETHODIMP
SchedulerGroup::Runnable::GetPriority(uint32_t* aPriority) {
  *aPriority = nsIRunnablePriority::PRIORITY_NORMAL;
  nsCOMPtr<nsIRunnablePriority> runnablePrio = do_QueryInterface(mRunnable);
  return runnablePrio ? runnablePrio->GetPriority(aPriority) : NS_OK;
}

NS_IMPL_ISUPPORTS_INHERITED(SchedulerGroup::Runnable, mozilla::Runnable,
                            nsIRunnablePriority, SchedulerGroup::Runnable)