DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Header

Mercurial (75df7d068a4e)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371
/* -*- 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 "WorkerThread.h"

#include "mozilla/Assertions.h"
#include "mozilla/ipc/BackgroundChild.h"
#include "EventQueue.h"
#include "mozilla/ThreadEventQueue.h"
#include "mozilla/PerformanceCounter.h"
#include "mozilla/StaticPrefs.h"
#include "nsIThreadInternal.h"
#include "WorkerPrivate.h"
#include "WorkerRunnable.h"

#ifdef DEBUG
#  include "nsThreadManager.h"
#endif

namespace mozilla {

using namespace ipc;

namespace dom {

namespace {

// The C stack size. We use the same stack size on all platforms for
// consistency.
//
// Note: Our typical equation of 256 machine words works out to 2MB on 64-bit
// platforms. Since that works out to the size of a VM huge page, that can
// sometimes lead to an OS allocating an entire huge page for the stack at once.
// To avoid this, we subtract the size of 2 pages, to be safe.
const uint32_t kWorkerStackSize = 256 * sizeof(size_t) * 1024 - 8192;

}  // namespace

WorkerThreadFriendKey::WorkerThreadFriendKey() {
  MOZ_COUNT_CTOR(WorkerThreadFriendKey);
}

WorkerThreadFriendKey::~WorkerThreadFriendKey() {
  MOZ_COUNT_DTOR(WorkerThreadFriendKey);
}

class WorkerThread::Observer final : public nsIThreadObserver {
  WorkerPrivate* mWorkerPrivate;

 public:
  explicit Observer(WorkerPrivate* aWorkerPrivate)
      : mWorkerPrivate(aWorkerPrivate) {
    MOZ_ASSERT(aWorkerPrivate);
    aWorkerPrivate->AssertIsOnWorkerThread();
  }

  NS_DECL_THREADSAFE_ISUPPORTS

 private:
  ~Observer() { mWorkerPrivate->AssertIsOnWorkerThread(); }

  NS_DECL_NSITHREADOBSERVER
};

WorkerThread::WorkerThread()
    : nsThread(MakeNotNull<ThreadEventQueue<mozilla::EventQueue>*>(
                   MakeUnique<mozilla::EventQueue>()),
               nsThread::NOT_MAIN_THREAD, kWorkerStackSize),
      mLock("WorkerThread::mLock"),
      mWorkerPrivateCondVar(mLock, "WorkerThread::mWorkerPrivateCondVar"),
      mWorkerPrivate(nullptr),
      mOtherThreadsDispatchingViaEventTarget(0)
#ifdef DEBUG
      ,
      mAcceptingNonWorkerRunnables(true)
#endif
{
}

WorkerThread::~WorkerThread() {
  MOZ_ASSERT(!mWorkerPrivate);
  MOZ_ASSERT(!mOtherThreadsDispatchingViaEventTarget);
  MOZ_ASSERT(mAcceptingNonWorkerRunnables);
}

// static
already_AddRefed<WorkerThread> WorkerThread::Create(
    const WorkerThreadFriendKey& /* aKey */) {
  RefPtr<WorkerThread> thread = new WorkerThread();
  if (NS_FAILED(thread->Init(NS_LITERAL_CSTRING("DOM Worker")))) {
    NS_WARNING("Failed to create new thread!");
    return nullptr;
  }

  return thread.forget();
}

void WorkerThread::SetWorker(const WorkerThreadFriendKey& /* aKey */,
                             WorkerPrivate* aWorkerPrivate) {
  MOZ_ASSERT(PR_GetCurrentThread() == mThread);

  if (aWorkerPrivate) {
    {
      MutexAutoLock lock(mLock);

      MOZ_ASSERT(!mWorkerPrivate);
      MOZ_ASSERT(mAcceptingNonWorkerRunnables);

      mWorkerPrivate = aWorkerPrivate;
#ifdef DEBUG
      mAcceptingNonWorkerRunnables = false;
#endif
    }

    mObserver = new Observer(aWorkerPrivate);
    MOZ_ALWAYS_SUCCEEDS(AddObserver(mObserver));
  } else {
    MOZ_ALWAYS_SUCCEEDS(RemoveObserver(mObserver));
    mObserver = nullptr;

    {
      MutexAutoLock lock(mLock);

      MOZ_ASSERT(mWorkerPrivate);
      MOZ_ASSERT(!mAcceptingNonWorkerRunnables);
      MOZ_ASSERT(!mOtherThreadsDispatchingViaEventTarget,
                 "XPCOM Dispatch hapenning at the same time our thread is "
                 "being unset! This should not be possible!");

      while (mOtherThreadsDispatchingViaEventTarget) {
        mWorkerPrivateCondVar.Wait();
      }

#ifdef DEBUG
      mAcceptingNonWorkerRunnables = true;
#endif
      mWorkerPrivate = nullptr;
    }
  }
}

void WorkerThread::IncrementDispatchCounter() {
  MutexAutoLock lock(mLock);
  if (mWorkerPrivate) {
    PerformanceCounter* performanceCounter =
        mWorkerPrivate->GetPerformanceCounter();
    if (performanceCounter) {
      performanceCounter->IncrementDispatchCounter(DispatchCategory::Worker);
    }
  }
}

nsresult WorkerThread::DispatchPrimaryRunnable(
    const WorkerThreadFriendKey& /* aKey */,
    already_AddRefed<nsIRunnable> aRunnable) {
  nsCOMPtr<nsIRunnable> runnable(aRunnable);

#ifdef DEBUG
  MOZ_ASSERT(PR_GetCurrentThread() != mThread);
  MOZ_ASSERT(runnable);
  {
    MutexAutoLock lock(mLock);

    MOZ_ASSERT(!mWorkerPrivate);
    MOZ_ASSERT(mAcceptingNonWorkerRunnables);
  }
#endif

  nsresult rv = nsThread::Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  return NS_OK;
}

nsresult WorkerThread::DispatchAnyThread(
    const WorkerThreadFriendKey& /* aKey */,
    already_AddRefed<WorkerRunnable> aWorkerRunnable) {
  // May be called on any thread!

#ifdef DEBUG
  {
    const bool onWorkerThread = PR_GetCurrentThread() == mThread;
    {
      MutexAutoLock lock(mLock);

      MOZ_ASSERT(mWorkerPrivate);
      MOZ_ASSERT(!mAcceptingNonWorkerRunnables);

      if (onWorkerThread) {
        mWorkerPrivate->AssertIsOnWorkerThread();
      }
    }
  }
#endif

  // Increment the PerformanceCounter dispatch count
  // to keep track of how many runnables are executed.
  IncrementDispatchCounter();
  nsCOMPtr<nsIRunnable> runnable(aWorkerRunnable);

  nsresult rv = nsThread::Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  // We don't need to notify the worker's condition variable here because we're
  // being called from worker-controlled code and it will make sure to wake up
  // the worker thread if needed.

  return NS_OK;
}

NS_IMETHODIMP
WorkerThread::DispatchFromScript(nsIRunnable* aRunnable, uint32_t aFlags) {
  nsCOMPtr<nsIRunnable> runnable(aRunnable);
  return Dispatch(runnable.forget(), aFlags);
}

NS_IMETHODIMP
WorkerThread::Dispatch(already_AddRefed<nsIRunnable> aRunnable,
                       uint32_t aFlags) {
  // May be called on any thread!
  nsCOMPtr<nsIRunnable> runnable(aRunnable);  // in case we exit early

  // Workers only support asynchronous dispatch.
  if (NS_WARN_IF(aFlags != NS_DISPATCH_NORMAL)) {
    return NS_ERROR_UNEXPECTED;
  }

  const bool onWorkerThread = PR_GetCurrentThread() == mThread;

#ifdef DEBUG
  if (runnable && !onWorkerThread) {
    nsCOMPtr<nsICancelableRunnable> cancelable = do_QueryInterface(runnable);

    {
      MutexAutoLock lock(mLock);

      // Only enforce cancelable runnables after we've started the worker loop.
      if (!mAcceptingNonWorkerRunnables) {
        MOZ_ASSERT(cancelable,
                   "Only nsICancelableRunnable may be dispatched to a worker!");
      }
    }
  }
#endif

  WorkerPrivate* workerPrivate = nullptr;
  if (onWorkerThread) {
    // No need to lock here because it is only modified on this thread.
    MOZ_ASSERT(mWorkerPrivate);
    mWorkerPrivate->AssertIsOnWorkerThread();

    workerPrivate = mWorkerPrivate;
  } else {
    MutexAutoLock lock(mLock);

    MOZ_ASSERT(mOtherThreadsDispatchingViaEventTarget < UINT32_MAX);

    if (mWorkerPrivate) {
      workerPrivate = mWorkerPrivate;

      // Incrementing this counter will make the worker thread sleep if it
      // somehow tries to unset mWorkerPrivate while we're using it.
      mOtherThreadsDispatchingViaEventTarget++;
    }
  }

  // Increment the PerformanceCounter dispatch count
  // to keep track of how many runnables are executed.
  IncrementDispatchCounter();
  nsresult rv;
  if (runnable && onWorkerThread) {
    RefPtr<WorkerRunnable> workerRunnable =
        workerPrivate->MaybeWrapAsWorkerRunnable(runnable.forget());
    rv = nsThread::Dispatch(workerRunnable.forget(), NS_DISPATCH_NORMAL);
  } else {
    rv = nsThread::Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
  }

  if (!onWorkerThread && workerPrivate) {
    // We need to wake the worker thread if we're not already on the right
    // thread and the dispatch succeeded.
    if (NS_SUCCEEDED(rv)) {
      MutexAutoLock workerLock(workerPrivate->mMutex);

      workerPrivate->mCondVar.Notify();
    }

    // Now unset our waiting flag.
    {
      MutexAutoLock lock(mLock);

      MOZ_ASSERT(mOtherThreadsDispatchingViaEventTarget);

      if (!--mOtherThreadsDispatchingViaEventTarget) {
        mWorkerPrivateCondVar.Notify();
      }
    }
  }

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

  return NS_OK;
}

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

uint32_t WorkerThread::RecursionDepth(
    const WorkerThreadFriendKey& /* aKey */) const {
  MOZ_ASSERT(PR_GetCurrentThread() == mThread);

  return mNestedEventLoopDepth;
}

PerformanceCounter* WorkerThread::GetPerformanceCounter(nsIRunnable* aEvent) {
  if (mWorkerPrivate) {
    return mWorkerPrivate->GetPerformanceCounter();
  }
  return nullptr;
}

NS_IMPL_ISUPPORTS(WorkerThread::Observer, nsIThreadObserver)

NS_IMETHODIMP
WorkerThread::Observer::OnDispatchedEvent() {
  MOZ_CRASH("OnDispatchedEvent() should never be called!");
}

NS_IMETHODIMP
WorkerThread::Observer::OnProcessNextEvent(nsIThreadInternal* /* aThread */,
                                           bool aMayWait) {
  mWorkerPrivate->AssertIsOnWorkerThread();

  // If the PBackground child is not created yet, then we must permit
  // blocking event processing to support
  // BackgroundChild::GetOrCreateCreateForCurrentThread(). If this occurs
  // then we are spinning on the event queue at the start of
  // PrimaryWorkerRunnable::Run() and don't want to process the event in
  // mWorkerPrivate yet.
  if (aMayWait) {
    MOZ_ASSERT(CycleCollectedJSContext::Get()->RecursionDepth() == 2);
    MOZ_ASSERT(!BackgroundChild::GetForCurrentThread());
    return NS_OK;
  }

  mWorkerPrivate->OnProcessNextEvent();
  return NS_OK;
}

NS_IMETHODIMP
WorkerThread::Observer::AfterProcessNextEvent(nsIThreadInternal* /* aThread */,
                                              bool /* aEventWasProcessed */) {
  mWorkerPrivate->AssertIsOnWorkerThread();

  mWorkerPrivate->AfterProcessNextEvent();
  return NS_OK;
}

}  // namespace dom
}  // namespace mozilla