xpcom/threads/TaskController.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "TaskController.h"
   8 #include "nsIIdleRunnable.h"
   9 #include "nsIRunnable.h"
  10 #include "nsThreadUtils.h"
  11 #include <algorithm>
  12 #include <initializer_list>
  13 #include "GeckoProfiler.h"
  14 #include "mozilla/EventQueue.h"
  15 #include "mozilla/BackgroundHangMonitor.h"
  16 #include "mozilla/InputTaskManager.h"
  17 #include "mozilla/VsyncTaskManager.h"
  18 #include "mozilla/IOInterposer.h"
  19 #include "mozilla/StaticMutex.h"
  20 #include "mozilla/SchedulerGroup.h"
  21 #include "mozilla/ScopeExit.h"
  22 #include "mozilla/Unused.h"
  23 #include "nsIThreadInternal.h"
  24 #include "nsQueryObject.h"
  25 #include "nsThread.h"
  26 #include "prenv.h"
  27 #include "prsystem.h"
  28
  29 namespace mozilla {
  30
  31 std::unique_ptr<TaskController> TaskController::sSingleton;
  32 thread_local size_t mThreadPoolIndex = -1;
  33 std::atomic<uint64_t> Task::sCurrentTaskSeqNo = 0;
  34
  35 const int32_t kMinimumPoolThreadCount = 2;
  36 const int32_t kMaximumPoolThreadCount = 8;
  37
  38 /* static */
  39 int32_t TaskController::GetPoolThreadCount() {
  40   if (PR_GetEnv("MOZ_TASKCONTROLLER_THREADCOUNT")) {
  41     return strtol(PR_GetEnv("MOZ_TASKCONTROLLER_THREADCOUNT"), nullptr, 0);
  42   }
  43
  44   int32_t numCores = std::max<int32_t>(1, PR_GetNumberOfProcessors());
  45
  46   return std::clamp<int32_t>(numCores, kMinimumPoolThreadCount,
  47                              kMaximumPoolThreadCount);
  48 }
  49
  50 #if defined(MOZ_COLLECTING_RUNNABLE_TELEMETRY)
  51
  52 struct TaskMarker {
  53   static constexpr Span<const char> MarkerTypeName() {
  54     return MakeStringSpan("Task");
  55   }
  56   static void StreamJSONMarkerData(baseprofiler::SpliceableJSONWriter& aWriter,
  57                                    const nsCString& aName, uint32_t aPriority) {
  58     aWriter.StringProperty("name", aName);
  59     aWriter.IntProperty("priority", aPriority);
  60
  61 #  define EVENT_PRIORITY(NAME, VALUE)                \
  62     if (aPriority == (VALUE)) {                      \
  63       aWriter.StringProperty("priorityName", #NAME); \
  64     } else
  65     EVENT_QUEUE_PRIORITY_LIST(EVENT_PRIORITY)
  66 #  undef EVENT_PRIORITY
  67     {
  68       aWriter.StringProperty("priorityName", "Invalid Value");
  69     }
  70   }
  71   static MarkerSchema MarkerTypeDisplay() {
  72     using MS = MarkerSchema;
  73     MS schema{MS::Location::MarkerChart, MS::Location::MarkerTable};
  74     schema.SetChartLabel("{marker.data.name}");
  75     schema.SetTableLabel(
  76         "{marker.name} - {marker.data.name} - priority: "
  77         "{marker.data.priorityName} ({marker.data.priority})");
  78     schema.AddKeyLabelFormatSearchable("name", "Task Name", MS::Format::String,
  79                                        MS::Searchable::Searchable);
  80     schema.AddKeyLabelFormat("priorityName", "Priority Name",
  81                              MS::Format::String);
  82     schema.AddKeyLabelFormat("priority", "Priority level", MS::Format::Integer);
  83     return schema;
  84   }
  85 };
  86
  87 class MOZ_RAII AutoProfileTask {
  88  public:
  89   explicit AutoProfileTask(nsACString& aName, uint64_t aPriority)
  90       : mName(aName), mPriority(aPriority) {
  91     if (profiler_is_active()) {
  92       mStartTime = TimeStamp::Now();
  93     }
  94   }
  95
  96   ~AutoProfileTask() {
  97     if (!profiler_thread_is_being_profiled_for_markers()) {
  98       return;
  99     }
 100
 101     AUTO_PROFILER_LABEL("AutoProfileTask", PROFILER);
 102     AUTO_PROFILER_STATS(AUTO_PROFILE_TASK);
 103     profiler_add_marker("Runnable", ::mozilla::baseprofiler::category::OTHER,
 104                         mStartTime.IsNull()
 105                             ? MarkerTiming::IntervalEnd()
 106                             : MarkerTiming::IntervalUntilNowFrom(mStartTime),
 107                         TaskMarker{}, mName, mPriority);
 108   }
 109
 110  private:
 111   TimeStamp mStartTime;
 112   nsAutoCString mName;
 113   uint32_t mPriority;
 114 };
 115
 116 #  define AUTO_PROFILE_FOLLOWING_TASK(task)                                  \
 117     nsAutoCString name;                                                      \
 118     (task)->GetName(name);                                                   \
 119     AUTO_PROFILER_LABEL_DYNAMIC_NSCSTRING_NONSENSITIVE("Task", OTHER, name); \
 120     mozilla::AutoProfileTask PROFILER_RAII(name, (task)->GetPriority());
 121 #else
 122 #  define AUTO_PROFILE_FOLLOWING_TASK(task)
 123 #endif
 124
 125 bool TaskManager::
 126     UpdateCachesForCurrentIterationAndReportPriorityModifierChanged(
 127         const MutexAutoLock& aProofOfLock, IterationType aIterationType) {
 128   mCurrentSuspended = IsSuspended(aProofOfLock);
 129
 130   if (aIterationType == IterationType::EVENT_LOOP_TURN && !mCurrentSuspended) {
 131     int32_t oldModifier = mCurrentPriorityModifier;
 132     mCurrentPriorityModifier =
 133         GetPriorityModifierForEventLoopTurn(aProofOfLock);
 134
 135     if (mCurrentPriorityModifier != oldModifier) {
 136       return true;
 137     }
 138   }
 139   return false;
 140 }
 141
 142 #ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY
 143 class MOZ_RAII AutoSetMainThreadRunnableName {
 144  public:
 145   explicit AutoSetMainThreadRunnableName(const nsCString& aName) {
 146     MOZ_ASSERT(NS_IsMainThread());
 147     // We want to record our current runnable's name in a static so
 148     // that BHR can record it.
 149     mRestoreRunnableName = nsThread::sMainThreadRunnableName;
 150
 151     // Copy the name into sMainThreadRunnableName's buffer, and append a
 152     // terminating null.
 153     uint32_t length = std::min((uint32_t)nsThread::kRunnableNameBufSize - 1,
 154                                (uint32_t)aName.Length());
 155     memcpy(nsThread::sMainThreadRunnableName.begin(), aName.BeginReading(),
 156            length);
 157     nsThread::sMainThreadRunnableName[length] = '\0';
 158   }
 159
 160   ~AutoSetMainThreadRunnableName() {
 161     nsThread::sMainThreadRunnableName = mRestoreRunnableName;
 162   }
 163
 164  private:
 165   Array<char, nsThread::kRunnableNameBufSize> mRestoreRunnableName;
 166 };
 167 #endif
 168
 169 Task* Task::GetHighestPriorityDependency() {
 170   Task* currentTask = this;
 171
 172   while (!currentTask->mDependencies.empty()) {
 173     auto iter = currentTask->mDependencies.begin();
 174
 175     while (iter != currentTask->mDependencies.end()) {
 176       if ((*iter)->mCompleted) {
 177         auto oldIter = iter;
 178         iter++;
 179         // Completed tasks are removed here to prevent needlessly keeping them
 180         // alive or iterating over them in the future.
 181         currentTask->mDependencies.erase(oldIter);
 182         continue;
 183       }
 184
 185       currentTask = iter->get();
 186       break;
 187     }
 188   }
 189
 190   return currentTask == this ? nullptr : currentTask;
 191 }
 192
 193 TaskController* TaskController::Get() {
 194   MOZ_ASSERT(sSingleton.get());
 195   return sSingleton.get();
 196 }
 197
 198 void TaskController::Initialize() {
 199   MOZ_ASSERT(!sSingleton);
 200   sSingleton = std::make_unique<TaskController>();
 201 }
 202
 203 void ThreadFuncPoolThread(void* aIndex) {
 204   mThreadPoolIndex = *reinterpret_cast<int32_t*>(aIndex);
 205   delete reinterpret_cast<int32_t*>(aIndex);
 206   TaskController::Get()->RunPoolThread();
 207 }
 208
 209 TaskController::TaskController()
 210     : mGraphMutex("TaskController::mGraphMutex"),
 211       mThreadPoolCV(mGraphMutex, "TaskController::mThreadPoolCV"),
 212       mMainThreadCV(mGraphMutex, "TaskController::mMainThreadCV"),
 213       mRunOutOfMTTasksCounter(0) {
 214   InputTaskManager::Init();
 215   VsyncTaskManager::Init();
 216   mMTProcessingRunnable = NS_NewRunnableFunction(
 217       "TaskController::ExecutePendingMTTasks()",
 218       []() { TaskController::Get()->ProcessPendingMTTask(); });
 219   mMTBlockingProcessingRunnable = NS_NewRunnableFunction(
 220       "TaskController::ExecutePendingMTTasks()",
 221       []() { TaskController::Get()->ProcessPendingMTTask(true); });
 222 }
 223
 224 // We want our default stack size limit to be approximately 2MB, to be safe for
 225 // JS helper tasks that can use a lot of stack, but expect most threads to use
 226 // much less. On Linux, however, requesting a stack of 2MB or larger risks the
 227 // kernel allocating an entire 2MB huge page for it on first access, which we do
 228 // not want. To avoid this possibility, we subtract 2 standard VM page sizes
 229 // from our default.
 230 constexpr PRUint32 sBaseStackSize = 2048 * 1024 - 2 * 4096;
 231
 232 // TSan enforces a minimum stack size that's just slightly larger than our
 233 // default helper stack size.  It does this to store blobs of TSan-specific data
 234 // on each thread's stack.  Unfortunately, that means that even though we'll
 235 // actually receive a larger stack than we requested, the effective usable space
 236 // of that stack is significantly less than what we expect.  To offset TSan
 237 // stealing our stack space from underneath us, double the default.
 238 //
 239 // Similarly, ASan requires more stack space due to red-zones.
 240 #if defined(MOZ_TSAN) || defined(MOZ_ASAN)
 241 constexpr PRUint32 sStackSize = 2 * sBaseStackSize;
 242 #else
 243 constexpr PRUint32 sStackSize = sBaseStackSize;
 244 #endif
 245
 246 void TaskController::InitializeThreadPool() {
 247   mPoolInitializationMutex.AssertCurrentThreadOwns();
 248   MOZ_ASSERT(!mThreadPoolInitialized);
 249   mThreadPoolInitialized = true;
 250
 251   int32_t poolSize = GetPoolThreadCount();
 252   for (int32_t i = 0; i < poolSize; i++) {
 253     int32_t* index = new int32_t(i);
 254     mPoolThreads.push_back(
 255         {PR_CreateThread(PR_USER_THREAD, ThreadFuncPoolThread, index,
 256                          PR_PRIORITY_NORMAL, PR_GLOBAL_THREAD,
 257                          PR_JOINABLE_THREAD, sStackSize),
 258          nullptr});
 259   }
 260 }
 261
 262 /* static */
 263 size_t TaskController::GetThreadStackSize() { return sStackSize; }
 264
 265 void TaskController::SetPerformanceCounterState(
 266     PerformanceCounterState* aPerformanceCounterState) {
 267   mPerformanceCounterState = aPerformanceCounterState;
 268 }
 269
 270 /* static */
 271 void TaskController::Shutdown() {
 272   InputTaskManager::Cleanup();
 273   VsyncTaskManager::Cleanup();
 274   if (sSingleton) {
 275     sSingleton->ShutdownThreadPoolInternal();
 276     sSingleton->ShutdownInternal();
 277   }
 278   MOZ_ASSERT(!sSingleton);
 279 }
 280
 281 void TaskController::ShutdownThreadPoolInternal() {
 282   {
 283     // Prevent racecondition on mShuttingDown and wait.
 284     MutexAutoLock lock(mGraphMutex);
 285
 286     mShuttingDown = true;
 287     mThreadPoolCV.NotifyAll();
 288   }
 289   for (PoolThread& thread : mPoolThreads) {
 290     PR_JoinThread(thread.mThread);
 291   }
 292 }
 293
 294 void TaskController::ShutdownInternal() { sSingleton = nullptr; }
 295
 296 void TaskController::RunPoolThread() {
 297   IOInterposer::RegisterCurrentThread();
 298
 299   // This is used to hold on to a task to make sure it is released outside the
 300   // lock. This is required since it's perfectly feasible for task destructors
 301   // to post events themselves.
 302   RefPtr<Task> lastTask;
 303
 304   nsAutoCString threadName;
 305   threadName.AppendLiteral("TaskController #");
 306   threadName.AppendInt(static_cast<int64_t>(mThreadPoolIndex));
 307   AUTO_PROFILER_REGISTER_THREAD(threadName.BeginReading());
 308
 309   MutexAutoLock lock(mGraphMutex);
 310   while (true) {
 311     bool ranTask = false;
 312
 313     if (!mThreadableTasks.empty()) {
 314       for (auto iter = mThreadableTasks.begin(); iter != mThreadableTasks.end();
 315            ++iter) {
 316         // Search for the highest priority dependency of the highest priority
 317         // task.
 318
 319         // We work with rawptrs to avoid needless refcounting. All our tasks
 320         // are always kept alive by the graph. If one is removed from the graph
 321         // it is kept alive by mPoolThreads[mThreadPoolIndex].mCurrentTask.
 322         Task* task = iter->get();
 323
 324         MOZ_ASSERT(!task->mTaskManager);
 325
 326         mPoolThreads[mThreadPoolIndex].mEffectiveTaskPriority =
 327             task->GetPriority();
 328
 329         Task* nextTask;
 330         while ((nextTask = task->GetHighestPriorityDependency())) {
 331           task = nextTask;
 332         }
 333
 334         if (task->IsMainThreadOnly() || task->mInProgress) {
 335           continue;
 336         }
 337
 338         mPoolThreads[mThreadPoolIndex].mCurrentTask = task;
 339         mThreadableTasks.erase(task->mIterator);
 340         task->mIterator = mThreadableTasks.end();
 341         task->mInProgress = true;
 342
 343         if (!mThreadableTasks.empty()) {
 344           // Ensure at least one additional thread is woken up if there are
 345           // more threadable tasks to process. Notifying all threads at once
 346           // isn't actually better for performance since they all need the
 347           // GraphMutex to proceed anyway.
 348           mThreadPoolCV.Notify();
 349         }
 350
 351         bool taskCompleted = false;
 352         {
 353           MutexAutoUnlock unlock(mGraphMutex);
 354           lastTask = nullptr;
 355           AUTO_PROFILE_FOLLOWING_TASK(task);
 356           taskCompleted = task->Run();
 357           ranTask = true;
 358         }
 359
 360         task->mInProgress = false;
 361
 362         if (!taskCompleted) {
 363           // Presumably this task was interrupted, leave its dependencies
 364           // unresolved and reinsert into the queue.
 365           auto insertion = mThreadableTasks.insert(
 366               mPoolThreads[mThreadPoolIndex].mCurrentTask);
 367           MOZ_ASSERT(insertion.second);
 368           task->mIterator = insertion.first;
 369         } else {
 370           task->mCompleted = true;
 371 #ifdef DEBUG
 372           task->mIsInGraph = false;
 373 #endif
 374           task->mDependencies.clear();
 375           // This may have unblocked a main thread task. We could do this only
 376           // if there was a main thread task before this one in the dependency
 377           // chain.
 378           mMayHaveMainThreadTask = true;
 379           // Since this could have multiple dependencies thare are restricted
 380           // to the main thread. Let's make sure that's awake.
 381           EnsureMainThreadTasksScheduled();
 382
 383           MaybeInterruptTask(GetHighestPriorityMTTask());
 384         }
 385
 386         // Store last task for release next time we release the lock or enter
 387         // wait state.
 388         lastTask = mPoolThreads[mThreadPoolIndex].mCurrentTask.forget();
 389         break;
 390       }
 391     }
 392
 393     // Ensure the last task is released before we enter the wait state.
 394     if (lastTask) {
 395       MutexAutoUnlock unlock(mGraphMutex);
 396       lastTask = nullptr;
 397
 398       // Run another loop iteration, while we were unlocked there was an
 399       // opportunity for another task to be posted or shutdown to be initiated.
 400       continue;
 401     }
 402
 403     if (!ranTask) {
 404       if (mShuttingDown) {
 405         IOInterposer::UnregisterCurrentThread();
 406         MOZ_ASSERT(mThreadableTasks.empty());
 407         return;
 408       }
 409
 410       AUTO_PROFILER_LABEL("TaskController::RunPoolThread", IDLE);
 411       mThreadPoolCV.Wait();
 412     }
 413   }
 414 }
 415
 416 void TaskController::AddTask(already_AddRefed<Task>&& aTask) {
 417   RefPtr<Task> task(aTask);
 418
 419   if (!task->IsMainThreadOnly()) {
 420     MutexAutoLock lock(mPoolInitializationMutex);
 421     if (!mThreadPoolInitialized) {
 422       InitializeThreadPool();
 423     }
 424   }
 425
 426   MutexAutoLock lock(mGraphMutex);
 427
 428   if (TaskManager* manager = task->GetManager()) {
 429     if (manager->mTaskCount == 0) {
 430       mTaskManagers.insert(manager);
 431     }
 432     manager->DidQueueTask();
 433
 434     // Set this here since if this manager's priority modifier doesn't change
 435     // we will not reprioritize when iterating over the queue.
 436     task->mPriorityModifier = manager->mCurrentPriorityModifier;
 437   }
 438
 439   if (profiler_is_active_and_unpaused()) {
 440     task->mInsertionTime = TimeStamp::Now();
 441   }
 442
 443 #ifdef DEBUG
 444   task->mIsInGraph = true;
 445
 446   for (const RefPtr<Task>& otherTask : task->mDependencies) {
 447     MOZ_ASSERT(!otherTask->mTaskManager ||
 448                otherTask->mTaskManager == task->mTaskManager);
 449   }
 450 #endif
 451
 452   LogTask::LogDispatch(task);
 453
 454   std::pair<std::set<RefPtr<Task>, Task::PriorityCompare>::iterator, bool>
 455       insertion;
 456   if (task->IsMainThreadOnly()) {
 457     insertion = mMainThreadTasks.insert(std::move(task));
 458   } else {
 459     insertion = mThreadableTasks.insert(std::move(task));
 460   }
 461   (*insertion.first)->mIterator = insertion.first;
 462   MOZ_ASSERT(insertion.second);
 463
 464   MaybeInterruptTask(*insertion.first);
 465 }
 466
 467 void TaskController::WaitForTaskOrMessage() {
 468   MutexAutoLock lock(mGraphMutex);
 469   while (!mMayHaveMainThreadTask) {
 470     AUTO_PROFILER_LABEL("TaskController::WaitForTaskOrMessage", IDLE);
 471     mMainThreadCV.Wait();
 472   }
 473 }
 474
 475 void TaskController::ExecuteNextTaskOnlyMainThread() {
 476   MOZ_ASSERT(NS_IsMainThread());
 477   MutexAutoLock lock(mGraphMutex);
 478   ExecuteNextTaskOnlyMainThreadInternal(lock);
 479 }
 480
 481 void TaskController::ProcessPendingMTTask(bool aMayWait) {
 482   MOZ_ASSERT(NS_IsMainThread());
 483   MutexAutoLock lock(mGraphMutex);
 484
 485   for (;;) {
 486     // We only ever process one event here. However we may sometimes
 487     // not actually process a real event because of suspended tasks.
 488     // This loop allows us to wait until we've processed something
 489     // in that scenario.
 490
 491     mMTTaskRunnableProcessedTask = ExecuteNextTaskOnlyMainThreadInternal(lock);
 492
 493     if (mMTTaskRunnableProcessedTask || !aMayWait) {
 494       break;
 495     }
 496
 497 #ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
 498     // Unlock before calling into the BackgroundHangMonitor API as it uses
 499     // the timer API.
 500     {
 501       MutexAutoUnlock unlock(mGraphMutex);
 502       BackgroundHangMonitor().NotifyWait();
 503     }
 504 #endif
 505
 506     {
 507       // ProcessNextEvent will also have attempted to wait, however we may have
 508       // given it a Runnable when all the tasks in our task graph were suspended
 509       // but we weren't able to cheaply determine that.
 510       AUTO_PROFILER_LABEL("TaskController::ProcessPendingMTTask", IDLE);
 511       mMainThreadCV.Wait();
 512     }
 513
 514 #ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
 515     {
 516       MutexAutoUnlock unlock(mGraphMutex);
 517       BackgroundHangMonitor().NotifyActivity();
 518     }
 519 #endif
 520   }
 521
 522   if (mMayHaveMainThreadTask) {
 523     EnsureMainThreadTasksScheduled();
 524   }
 525 }
 526
 527 void TaskController::ReprioritizeTask(Task* aTask, uint32_t aPriority) {
 528   MutexAutoLock lock(mGraphMutex);
 529   std::set<RefPtr<Task>, Task::PriorityCompare>* queue = &mMainThreadTasks;
 530   if (!aTask->IsMainThreadOnly()) {
 531     queue = &mThreadableTasks;
 532   }
 533
 534   MOZ_ASSERT(aTask->mIterator != queue->end());
 535   queue->erase(aTask->mIterator);
 536
 537   aTask->mPriority = aPriority;
 538
 539   auto insertion = queue->insert(aTask);
 540   MOZ_ASSERT(insertion.second);
 541   aTask->mIterator = insertion.first;
 542
 543   MaybeInterruptTask(aTask);
 544 }
 545
 546 // Code supporting runnable compatibility.
 547 // Task that wraps a runnable.
 548 class RunnableTask : public Task {
 549  public:
 550   RunnableTask(already_AddRefed<nsIRunnable>&& aRunnable, int32_t aPriority,
 551                bool aMainThread = true)
 552       : Task(aMainThread, aPriority), mRunnable(aRunnable) {}
 553
 554   virtual bool Run() override {
 555     mRunnable->Run();
 556     mRunnable = nullptr;
 557     return true;
 558   }
 559
 560   void SetIdleDeadline(TimeStamp aDeadline) override {
 561     nsCOMPtr<nsIIdleRunnable> idleRunnable = do_QueryInterface(mRunnable);
 562     if (idleRunnable) {
 563       idleRunnable->SetDeadline(aDeadline);
 564     }
 565   }
 566
 567   virtual bool GetName(nsACString& aName) override {
 568 #ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY
 569     if (nsCOMPtr<nsINamed> named = do_QueryInterface(mRunnable)) {
 570       MOZ_ALWAYS_TRUE(NS_SUCCEEDED(named->GetName(aName)));
 571     } else {
 572       aName.AssignLiteral("non-nsINamed runnable");
 573     }
 574     if (aName.IsEmpty()) {
 575       aName.AssignLiteral("anonymous runnable");
 576     }
 577     return true;
 578 #else
 579     return false;
 580 #endif
 581   }
 582
 583  private:
 584   RefPtr<nsIRunnable> mRunnable;
 585 };
 586
 587 void TaskController::DispatchRunnable(already_AddRefed<nsIRunnable>&& aRunnable,
 588                                       uint32_t aPriority,
 589                                       TaskManager* aManager) {
 590   RefPtr<RunnableTask> task = new RunnableTask(std::move(aRunnable), aPriority);
 591
 592   task->SetManager(aManager);
 593   TaskController::Get()->AddTask(task.forget());
 594 }
 595
 596 nsIRunnable* TaskController::GetRunnableForMTTask(bool aReallyWait) {
 597   MutexAutoLock lock(mGraphMutex);
 598
 599   while (mMainThreadTasks.empty()) {
 600     if (!aReallyWait) {
 601       return nullptr;
 602     }
 603
 604     AUTO_PROFILER_LABEL("TaskController::GetRunnableForMTTask::Wait", IDLE);
 605     mMainThreadCV.Wait();
 606   }
 607
 608   return aReallyWait ? mMTBlockingProcessingRunnable : mMTProcessingRunnable;
 609 }
 610
 611 bool TaskController::HasMainThreadPendingTasks() {
 612   MOZ_ASSERT(NS_IsMainThread());
 613   auto resetIdleState = MakeScopeExit([&idleManager = mIdleTaskManager] {
 614     if (idleManager) {
 615       idleManager->State().ClearCachedIdleDeadline();
 616     }
 617   });
 618
 619   for (bool considerIdle : {false, true}) {
 620     if (considerIdle && !mIdleTaskManager) {
 621       continue;
 622     }
 623
 624     MutexAutoLock lock(mGraphMutex);
 625
 626     if (considerIdle) {
 627       mIdleTaskManager->State().ForgetPendingTaskGuarantee();
 628       // Temporarily unlock so we can peek our idle deadline.
 629       // XXX We could do this _before_ we take the lock if the API would let us.
 630       // We do want to do this before looking at mMainThreadTasks, in case
 631       // someone adds one while we're unlocked.
 632       {
 633         MutexAutoUnlock unlock(mGraphMutex);
 634         mIdleTaskManager->State().CachePeekedIdleDeadline(unlock);
 635       }
 636     }
 637
 638     // Return early if there's no tasks at all.
 639     if (mMainThreadTasks.empty()) {
 640       return false;
 641     }
 642
 643     // We can cheaply count how many tasks are suspended.
 644     uint64_t totalSuspended = 0;
 645     for (TaskManager* manager : mTaskManagers) {
 646       DebugOnly<bool> modifierChanged =
 647           manager
 648               ->UpdateCachesForCurrentIterationAndReportPriorityModifierChanged(
 649                   lock, TaskManager::IterationType::NOT_EVENT_LOOP_TURN);
 650       MOZ_ASSERT(!modifierChanged);
 651
 652       // The idle manager should be suspended unless we're doing the idle pass.
 653       MOZ_ASSERT(manager != mIdleTaskManager || manager->mCurrentSuspended ||
 654                      considerIdle,
 655                  "Why are idle tasks not suspended here?");
 656
 657       if (manager->mCurrentSuspended) {
 658         // XXX - If managers manage off-main-thread tasks this breaks! This
 659         // scenario is explicitly not supported.
 660         //
 661         // This is only incremented inside the lock -or- decremented on the main
 662         // thread so this is safe.
 663         totalSuspended += manager->mTaskCount;
 664       }
 665     }
 666
 667     // This would break down if we have a non-suspended task depending on a
 668     // suspended task. This is why for the moment we do not allow tasks
 669     // to be dependent on tasks managed by another taskmanager.
 670     if (mMainThreadTasks.size() > totalSuspended) {
 671       // If mIdleTaskManager->mTaskCount is 0, we never updated the suspended
 672       // state of mIdleTaskManager above, hence shouldn't even check it here.
 673       // But in that case idle tasks are not contributing to our suspended task
 674       // count anyway.
 675       if (mIdleTaskManager && mIdleTaskManager->mTaskCount &&
 676           !mIdleTaskManager->mCurrentSuspended) {
 677         MOZ_ASSERT(considerIdle, "Why is mIdleTaskManager not suspended?");
 678         // Check whether the idle tasks were really needed to make our "we have
 679         // an unsuspended task" decision.  If they were, we need to force-enable
 680         // idle tasks until we run our next task.
 681         if (mMainThreadTasks.size() - mIdleTaskManager->mTaskCount <=
 682             totalSuspended) {
 683           mIdleTaskManager->State().EnforcePendingTaskGuarantee();
 684         }
 685       }
 686       return true;
 687     }
 688   }
 689   return false;
 690 }
 691
 692 uint64_t TaskController::PendingMainthreadTaskCountIncludingSuspended() {
 693   MutexAutoLock lock(mGraphMutex);
 694   return mMainThreadTasks.size();
 695 }
 696
 697 bool TaskController::ExecuteNextTaskOnlyMainThreadInternal(
 698     const MutexAutoLock& aProofOfLock) {
 699   MOZ_ASSERT(NS_IsMainThread());
 700   mGraphMutex.AssertCurrentThreadOwns();
 701   // Block to make it easier to jump to our cleanup.
 702   bool taskRan = false;
 703   do {
 704     taskRan = DoExecuteNextTaskOnlyMainThreadInternal(aProofOfLock);
 705     if (taskRan) {
 706       if (mIdleTaskManager && mIdleTaskManager->mTaskCount &&
 707           mIdleTaskManager->IsSuspended(aProofOfLock)) {
 708         uint32_t activeTasks = mMainThreadTasks.size();
 709         for (TaskManager* manager : mTaskManagers) {
 710           if (manager->IsSuspended(aProofOfLock)) {
 711             activeTasks -= manager->mTaskCount;
 712           } else {
 713             break;
 714           }
 715         }
 716
 717         if (!activeTasks) {
 718           // We have only idle (and maybe other suspended) tasks left, so need
 719           // to update the idle state. We need to temporarily release the lock
 720           // while we do that.
 721           MutexAutoUnlock unlock(mGraphMutex);
 722           mIdleTaskManager->State().RequestIdleDeadlineIfNeeded(unlock);
 723         }
 724       }
 725       break;
 726     }
 727
 728     if (!mIdleTaskManager) {
 729       break;
 730     }
 731
 732     if (mIdleTaskManager->mTaskCount) {
 733       // We have idle tasks that we may not have gotten above because
 734       // our idle state is not up to date.  We need to update the idle state
 735       // and try again.  We need to temporarily release the lock while we do
 736       // that.
 737       MutexAutoUnlock unlock(mGraphMutex);
 738       mIdleTaskManager->State().UpdateCachedIdleDeadline(unlock);
 739     } else {
 740       MutexAutoUnlock unlock(mGraphMutex);
 741       mIdleTaskManager->State().RanOutOfTasks(unlock);
 742     }
 743
 744     // When we unlocked, someone may have queued a new task on us.  So try to
 745     // see whether we can run things again.
 746     taskRan = DoExecuteNextTaskOnlyMainThreadInternal(aProofOfLock);
 747   } while (false);
 748
 749   if (mIdleTaskManager) {
 750     // The pending task guarantee is not needed anymore, since we just tried
 751     // running a task
 752     mIdleTaskManager->State().ForgetPendingTaskGuarantee();
 753
 754     if (mMainThreadTasks.empty()) {
 755       ++mRunOutOfMTTasksCounter;
 756
 757       // XXX the IdlePeriodState API demands we have a MutexAutoUnlock for it.
 758       // Otherwise we could perhaps just do this after we exit the locked block,
 759       // by pushing the lock down into this method.  Though it's not clear that
 760       // we could check mMainThreadTasks.size() once we unlock, and whether we
 761       // could maybe substitute mMayHaveMainThreadTask for that check.
 762       MutexAutoUnlock unlock(mGraphMutex);
 763       mIdleTaskManager->State().RanOutOfTasks(unlock);
 764     }
 765   }
 766
 767   return taskRan;
 768 }
 769
 770 bool TaskController::DoExecuteNextTaskOnlyMainThreadInternal(
 771     const MutexAutoLock& aProofOfLock) {
 772   mGraphMutex.AssertCurrentThreadOwns();
 773
 774   nsCOMPtr<nsIThread> mainIThread;
 775   NS_GetMainThread(getter_AddRefs(mainIThread));
 776
 777   nsThread* mainThread = static_cast<nsThread*>(mainIThread.get());
 778   if (mainThread) {
 779     mainThread->SetRunningEventDelay(TimeDuration(), TimeStamp());
 780   }
 781
 782   uint32_t totalSuspended = 0;
 783   for (TaskManager* manager : mTaskManagers) {
 784     bool modifierChanged =
 785         manager
 786             ->UpdateCachesForCurrentIterationAndReportPriorityModifierChanged(
 787                 aProofOfLock, TaskManager::IterationType::EVENT_LOOP_TURN);
 788     if (modifierChanged) {
 789       ProcessUpdatedPriorityModifier(manager);
 790     }
 791     if (manager->mCurrentSuspended) {
 792       totalSuspended += manager->mTaskCount;
 793     }
 794   }
 795
 796   MOZ_ASSERT(mMainThreadTasks.size() >= totalSuspended);
 797
 798   // This would break down if we have a non-suspended task depending on a
 799   // suspended task. This is why for the moment we do not allow tasks
 800   // to be dependent on tasks managed by another taskmanager.
 801   if (mMainThreadTasks.size() > totalSuspended) {
 802     for (auto iter = mMainThreadTasks.begin(); iter != mMainThreadTasks.end();
 803          iter++) {
 804       Task* task = iter->get();
 805
 806       if (task->mTaskManager && task->mTaskManager->mCurrentSuspended) {
 807         // Even though we may want to run some dependencies of this task, we
 808         // will run them at their own priority level and not the priority
 809         // level of their dependents.
 810         continue;
 811       }
 812
 813       task = GetFinalDependency(task);
 814
 815       if (!task->IsMainThreadOnly() || task->mInProgress ||
 816           (task->mTaskManager && task->mTaskManager->mCurrentSuspended)) {
 817         continue;
 818       }
 819
 820       mCurrentTasksMT.push(task);
 821       mMainThreadTasks.erase(task->mIterator);
 822       task->mIterator = mMainThreadTasks.end();
 823       task->mInProgress = true;
 824       TaskManager* manager = task->GetManager();
 825       bool result = false;
 826
 827       {
 828         MutexAutoUnlock unlock(mGraphMutex);
 829         if (manager) {
 830           manager->WillRunTask();
 831           if (manager != mIdleTaskManager) {
 832             // Notify the idle period state that we're running a non-idle task.
 833             // This needs to happen while our mutex is not locked!
 834             mIdleTaskManager->State().FlagNotIdle();
 835           } else {
 836             TimeStamp idleDeadline =
 837                 mIdleTaskManager->State().GetCachedIdleDeadline();
 838             MOZ_ASSERT(
 839                 idleDeadline,
 840                 "How can we not have a deadline if our manager is enabled?");
 841             task->SetIdleDeadline(idleDeadline);
 842           }
 843         }
 844         if (mIdleTaskManager) {
 845           // We found a task to run; we can clear the idle deadline on our idle
 846           // task manager.  This _must_ be done before we actually run the task,
 847           // because running the task could reenter via spinning the event loop
 848           // and we want to make sure there's no cached idle deadline at that
 849           // point.  But we have to make sure we do it after out SetIdleDeadline
 850           // call above, in the case when the task is actually an idle task.
 851           mIdleTaskManager->State().ClearCachedIdleDeadline();
 852         }
 853
 854         TimeStamp now = TimeStamp::Now();
 855
 856         if (mainThread) {
 857           if (task->GetPriority() < uint32_t(EventQueuePriority::InputHigh) ||
 858               task->mInsertionTime.IsNull()) {
 859             mainThread->SetRunningEventDelay(TimeDuration(), now);
 860           } else {
 861             mainThread->SetRunningEventDelay(now - task->mInsertionTime, now);
 862           }
 863         }
 864
 865         nsAutoCString name;
 866 #ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY
 867         task->GetName(name);
 868 #endif
 869
 870         PerformanceCounterState::Snapshot snapshot =
 871             mPerformanceCounterState->RunnableWillRun(
 872                 now, manager == mIdleTaskManager);
 873
 874         {
 875           LogTask::Run log(task);
 876 #ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY
 877           AutoSetMainThreadRunnableName nameGuard(name);
 878 #endif
 879           AUTO_PROFILE_FOLLOWING_TASK(task);
 880           result = task->Run();
 881         }
 882
 883         // Task itself should keep manager alive.
 884         if (manager) {
 885           manager->DidRunTask();
 886         }
 887
 888         mPerformanceCounterState->RunnableDidRun(name, std::move(snapshot));
 889       }
 890
 891       // Task itself should keep manager alive.
 892       if (manager && result && manager->mTaskCount == 0) {
 893         mTaskManagers.erase(manager);
 894       }
 895
 896       task->mInProgress = false;
 897
 898       if (!result) {
 899         // Presumably this task was interrupted, leave its dependencies
 900         // unresolved and reinsert into the queue.
 901         auto insertion =
 902             mMainThreadTasks.insert(std::move(mCurrentTasksMT.top()));
 903         MOZ_ASSERT(insertion.second);
 904         task->mIterator = insertion.first;
 905         manager->WillRunTask();
 906       } else {
 907         task->mCompleted = true;
 908 #ifdef DEBUG
 909         task->mIsInGraph = false;
 910 #endif
 911         // Clear dependencies to release references.
 912         task->mDependencies.clear();
 913
 914         if (!mThreadableTasks.empty()) {
 915           // We're going to wake up a single thread in our pool. This thread
 916           // is responsible for waking up additional threads in the situation
 917           // where more than one task became available.
 918           mThreadPoolCV.Notify();
 919         }
 920       }
 921
 922       mCurrentTasksMT.pop();
 923       return true;
 924     }
 925   }
 926
 927   mMayHaveMainThreadTask = false;
 928   if (mIdleTaskManager) {
 929     // We did not find a task to run.  We still need to clear the cached idle
 930     // deadline on our idle state, because that deadline was only relevant to
 931     // the execution of this function.  Had we found a task, we would have
 932     // cleared the deadline before running that task.
 933     mIdleTaskManager->State().ClearCachedIdleDeadline();
 934   }
 935   return false;
 936 }
 937
 938 Task* TaskController::GetFinalDependency(Task* aTask) {
 939   Task* nextTask;
 940
 941   while ((nextTask = aTask->GetHighestPriorityDependency())) {
 942     aTask = nextTask;
 943   }
 944
 945   return aTask;
 946 }
 947
 948 void TaskController::MaybeInterruptTask(Task* aTask) {
 949   mGraphMutex.AssertCurrentThreadOwns();
 950
 951   if (!aTask) {
 952     return;
 953   }
 954
 955   // This optimization prevents many slow lookups in long chains of similar
 956   // priority.
 957   if (!aTask->mDependencies.empty()) {
 958     Task* firstDependency = aTask->mDependencies.begin()->get();
 959     if (aTask->GetPriority() <= firstDependency->GetPriority() &&
 960         !firstDependency->mCompleted &&
 961         aTask->IsMainThreadOnly() == firstDependency->IsMainThreadOnly()) {
 962       // This task has the same or a higher priority as one of its dependencies,
 963       // never any need to interrupt.
 964       return;
 965     }
 966   }
 967
 968   Task* finalDependency = GetFinalDependency(aTask);
 969
 970   if (finalDependency->mInProgress) {
 971     // No need to wake anything, we can't schedule this task right now anyway.
 972     return;
 973   }
 974
 975   if (aTask->IsMainThreadOnly()) {
 976     mMayHaveMainThreadTask = true;
 977
 978     EnsureMainThreadTasksScheduled();
 979
 980     if (mCurrentTasksMT.empty()) {
 981       return;
 982     }
 983
 984     // We could go through the steps above here and interrupt an off main
 985     // thread task in case it has a lower priority.
 986     if (!finalDependency->IsMainThreadOnly()) {
 987       return;
 988     }
 989
 990     if (mCurrentTasksMT.top()->GetPriority() < aTask->GetPriority()) {
 991       mCurrentTasksMT.top()->RequestInterrupt(aTask->GetPriority());
 992     }
 993   } else {
 994     Task* lowestPriorityTask = nullptr;
 995     for (PoolThread& thread : mPoolThreads) {
 996       if (!thread.mCurrentTask) {
 997         mThreadPoolCV.Notify();
 998         // There's a free thread, no need to interrupt anything.
 999         return;
1000       }
1001
1002       if (!lowestPriorityTask) {
1003         lowestPriorityTask = thread.mCurrentTask.get();
1004         continue;
1005       }
1006
1007       // This should possibly select the lowest priority task which was started
1008       // the latest. But for now we ignore that optimization.
1009       // This also doesn't guarantee a task is interruptable, so that's an
1010       // avenue for improvements as well.
1011       if (lowestPriorityTask->GetPriority() > thread.mEffectiveTaskPriority) {
1012         lowestPriorityTask = thread.mCurrentTask.get();
1013       }
1014     }
1015
1016     if (lowestPriorityTask->GetPriority() < aTask->GetPriority()) {
1017       lowestPriorityTask->RequestInterrupt(aTask->GetPriority());
1018     }
1019
1020     // We choose not to interrupt main thread tasks for tasks which may be
1021     // executed off the main thread.
1022   }
1023 }
1024
1025 Task* TaskController::GetHighestPriorityMTTask() {
1026   mGraphMutex.AssertCurrentThreadOwns();
1027
1028   if (!mMainThreadTasks.empty()) {
1029     return mMainThreadTasks.begin()->get();
1030   }
1031   return nullptr;
1032 }
1033
1034 void TaskController::EnsureMainThreadTasksScheduled() {
1035   if (mObserver) {
1036     mObserver->OnDispatchedEvent();
1037   }
1038   if (mExternalCondVar) {
1039     mExternalCondVar->Notify();
1040   }
1041   mMainThreadCV.Notify();
1042 }
1043
1044 void TaskController::ProcessUpdatedPriorityModifier(TaskManager* aManager) {
1045   mGraphMutex.AssertCurrentThreadOwns();
1046
1047   MOZ_ASSERT(NS_IsMainThread());
1048
1049   int32_t modifier = aManager->mCurrentPriorityModifier;
1050
1051   std::vector<RefPtr<Task>> storedTasks;
1052   // Find all relevant tasks.
1053   for (auto iter = mMainThreadTasks.begin(); iter != mMainThreadTasks.end();) {
1054     if ((*iter)->mTaskManager == aManager) {
1055       storedTasks.push_back(*iter);
1056       iter = mMainThreadTasks.erase(iter);
1057     } else {
1058       iter++;
1059     }
1060   }
1061
1062   // Reinsert found tasks with their new priorities.
1063   for (RefPtr<Task>& ref : storedTasks) {
1064     // Kept alive at first by the vector and then by mMainThreadTasks.
1065     Task* task = ref;
1066     task->mPriorityModifier = modifier;
1067     auto insertion = mMainThreadTasks.insert(std::move(ref));
1068     MOZ_ASSERT(insertion.second);
1069     task->mIterator = insertion.first;
1070   }
1071 }
1072
1073 }  // namespace mozilla