xpcom/base/CycleCollectedJSContext.h

   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 #ifndef mozilla_CycleCollectedJSContext_h
   8 #define mozilla_CycleCollectedJSContext_h
   9
  10 #include <deque>
  11
  12 #include "mozilla/Attributes.h"
  13 #include "mozilla/MemoryReporting.h"
  14 #include "mozilla/dom/AtomList.h"
  15 #include "mozilla/dom/Promise.h"
  16 #include "js/GCVector.h"
  17 #include "js/Promise.h"
  18
  19 #include "nsCOMPtr.h"
  20 #include "nsRefPtrHashtable.h"
  21 #include "nsTArray.h"
  22
  23 class nsCycleCollectionNoteRootCallback;
  24 class nsIRunnable;
  25 class nsThread;
  26
  27 namespace mozilla {
  28 class AutoSlowOperation;
  29
  30 class CycleCollectedJSContext;
  31 class CycleCollectedJSRuntime;
  32
  33 namespace dom {
  34 class Exception;
  35 class WorkerJSContext;
  36 class WorkletJSContext;
  37 }  // namespace dom
  38
  39 // Contains various stats about the cycle collection.
  40 struct CycleCollectorResults {
  41   CycleCollectorResults() {
  42     // Initialize here so when we increment mNumSlices the first time we're
  43     // not using uninitialized memory.
  44     Init();
  45   }
  46
  47   void Init() {
  48     mForcedGC = false;
  49     mSuspectedAtCCStart = 0;
  50     mMergedZones = false;
  51     mAnyManual = false;
  52     mVisitedRefCounted = 0;
  53     mVisitedGCed = 0;
  54     mFreedRefCounted = 0;
  55     mFreedGCed = 0;
  56     mFreedJSZones = 0;
  57     mNumSlices = 1;
  58     // mNumSlices is initialized to one, because we call Init() after the
  59     // per-slice increment of mNumSlices has already occurred.
  60   }
  61
  62   bool mForcedGC;
  63   bool mMergedZones;
  64   // mAnyManual is true if any slice was manually triggered, and at shutdown.
  65   bool mAnyManual;
  66   uint32_t mSuspectedAtCCStart;
  67   uint32_t mVisitedRefCounted;
  68   uint32_t mVisitedGCed;
  69   uint32_t mFreedRefCounted;
  70   uint32_t mFreedGCed;
  71   uint32_t mFreedJSZones;
  72   uint32_t mNumSlices;
  73 };
  74
  75 class MicroTaskRunnable {
  76  public:
  77   MicroTaskRunnable() = default;
  78   NS_INLINE_DECL_REFCOUNTING(MicroTaskRunnable)
  79   MOZ_CAN_RUN_SCRIPT virtual void Run(AutoSlowOperation& aAso) = 0;
  80   virtual bool Suppressed() { return false; }
  81
  82  protected:
  83   virtual ~MicroTaskRunnable() = default;
  84 };
  85
  86 // Store the suppressed mictotasks in another microtask so that operations
  87 // for the microtask queue as a whole keep working.
  88 class SuppressedMicroTasks : public MicroTaskRunnable {
  89  public:
  90   explicit SuppressedMicroTasks(CycleCollectedJSContext* aContext);
  91
  92   MOZ_CAN_RUN_SCRIPT_BOUNDARY void Run(AutoSlowOperation& aAso) final {}
  93   virtual bool Suppressed();
  94
  95   CycleCollectedJSContext* mContext;
  96   uint64_t mSuppressionGeneration;
  97   std::deque<RefPtr<MicroTaskRunnable>> mSuppressedMicroTaskRunnables;
  98 };
  99
 100 // Support for JS FinalizationRegistry objects, which allow a JS callback to be
 101 // registered that is called when objects die.
 102 //
 103 // We keep a vector of functions that call back into the JS engine along
 104 // with their associated incumbent globals, one per FinalizationRegistry object
 105 // that has pending cleanup work. These are run in their own task.
 106 class FinalizationRegistryCleanup {
 107  public:
 108   explicit FinalizationRegistryCleanup(CycleCollectedJSContext* aContext);
 109   void Init();
 110   void Destroy();
 111   void QueueCallback(JSFunction* aDoCleanup, JSObject* aIncumbentGlobal);
 112   MOZ_CAN_RUN_SCRIPT void DoCleanup();
 113
 114  private:
 115   static void QueueCallback(JSFunction* aDoCleanup, JSObject* aIncumbentGlobal,
 116                             void* aData);
 117
 118   class CleanupRunnable;
 119
 120   struct Callback {
 121     JSFunction* mCallbackFunction;
 122     JSObject* mIncumbentGlobal;
 123     void trace(JSTracer* trc);
 124   };
 125
 126   // This object is part of CycleCollectedJSContext, so it's safe to have a raw
 127   // pointer to its containing context here.
 128   CycleCollectedJSContext* mContext;
 129
 130   using CallbackVector = JS::GCVector<Callback, 0, InfallibleAllocPolicy>;
 131   JS::PersistentRooted<CallbackVector> mCallbacks;
 132 };
 133
 134 class CycleCollectedJSContext : dom::PerThreadAtomCache, private JS::JobQueue {
 135   friend class CycleCollectedJSRuntime;
 136   friend class SuppressedMicroTasks;
 137
 138  protected:
 139   CycleCollectedJSContext();
 140   virtual ~CycleCollectedJSContext();
 141
 142   MOZ_IS_CLASS_INIT
 143   nsresult Initialize(JSRuntime* aParentRuntime, uint32_t aMaxBytes);
 144
 145   virtual CycleCollectedJSRuntime* CreateRuntime(JSContext* aCx) = 0;
 146
 147   size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
 148
 149  private:
 150   static void PromiseRejectionTrackerCallback(
 151       JSContext* aCx, bool aMutedErrors, JS::Handle<JSObject*> aPromise,
 152       JS::PromiseRejectionHandlingState state, void* aData);
 153
 154   void AfterProcessMicrotasks();
 155
 156  public:
 157   void ProcessStableStateQueue();
 158
 159  private:
 160   void CleanupIDBTransactions(uint32_t aRecursionDepth);
 161
 162  public:
 163   virtual dom::WorkerJSContext* GetAsWorkerJSContext() { return nullptr; }
 164   virtual dom::WorkletJSContext* GetAsWorkletJSContext() { return nullptr; }
 165
 166   CycleCollectedJSRuntime* Runtime() const {
 167     MOZ_ASSERT(mRuntime);
 168     return mRuntime;
 169   }
 170
 171   already_AddRefed<dom::Exception> GetPendingException() const;
 172   void SetPendingException(dom::Exception* aException);
 173
 174   std::deque<RefPtr<MicroTaskRunnable>>& GetMicroTaskQueue();
 175   std::deque<RefPtr<MicroTaskRunnable>>& GetDebuggerMicroTaskQueue();
 176
 177   JSContext* Context() const {
 178     MOZ_ASSERT(mJSContext);
 179     return mJSContext;
 180   }
 181
 182   JS::RootingContext* RootingCx() const {
 183     MOZ_ASSERT(mJSContext);
 184     return JS::RootingContext::get(mJSContext);
 185   }
 186
 187   void SetTargetedMicroTaskRecursionDepth(uint32_t aDepth) {
 188     mTargetedMicroTaskRecursionDepth = aDepth;
 189   }
 190
 191   void UpdateMicroTaskSuppressionGeneration() { ++mSuppressionGeneration; }
 192
 193  protected:
 194   JSContext* MaybeContext() const { return mJSContext; }
 195
 196  public:
 197   // nsThread entrypoints
 198   //
 199   // MOZ_CAN_RUN_SCRIPT_BOUNDARY so we don't need to annotate
 200   // nsThread::ProcessNextEvent and all its callers MOZ_CAN_RUN_SCRIPT for now.
 201   // But we really should!
 202   MOZ_CAN_RUN_SCRIPT_BOUNDARY
 203   virtual void BeforeProcessTask(bool aMightBlock);
 204   // MOZ_CAN_RUN_SCRIPT_BOUNDARY so we don't need to annotate
 205   // nsThread::ProcessNextEvent and all its callers MOZ_CAN_RUN_SCRIPT for now.
 206   // But we really should!
 207   MOZ_CAN_RUN_SCRIPT_BOUNDARY
 208   virtual void AfterProcessTask(uint32_t aRecursionDepth);
 209
 210   // Check whether any eager thresholds have been reached, which would mean
 211   // an idle GC task (minor or major) would be useful.
 212   virtual void MaybePokeGC();
 213
 214   uint32_t RecursionDepth() const;
 215
 216   // Run in stable state (call through nsContentUtils)
 217   void RunInStableState(already_AddRefed<nsIRunnable>&& aRunnable);
 218
 219   void AddPendingIDBTransaction(already_AddRefed<nsIRunnable>&& aTransaction);
 220
 221   // Get the CycleCollectedJSContext for a JSContext.
 222   // Returns null only if Initialize() has not completed on or during
 223   // destruction of the CycleCollectedJSContext.
 224   static CycleCollectedJSContext* GetFor(JSContext* aCx);
 225
 226   // Get the current thread's CycleCollectedJSContext.  Returns null if there
 227   // isn't one.
 228   static CycleCollectedJSContext* Get();
 229
 230   // Queue an async microtask to the current main or worker thread.
 231   virtual void DispatchToMicroTask(
 232       already_AddRefed<MicroTaskRunnable> aRunnable);
 233
 234   // Call EnterMicroTask when you're entering JS execution.
 235   // Usually the best way to do this is to use nsAutoMicroTask.
 236   void EnterMicroTask() { ++mMicroTaskLevel; }
 237
 238   MOZ_CAN_RUN_SCRIPT
 239   void LeaveMicroTask() {
 240     if (--mMicroTaskLevel == 0) {
 241       PerformMicroTaskCheckPoint();
 242     }
 243   }
 244
 245   uint32_t MicroTaskLevel() const { return mMicroTaskLevel; }
 246
 247   void SetMicroTaskLevel(uint32_t aLevel) { mMicroTaskLevel = aLevel; }
 248
 249   MOZ_CAN_RUN_SCRIPT
 250   bool PerformMicroTaskCheckPoint(bool aForce = false);
 251
 252   MOZ_CAN_RUN_SCRIPT
 253   void PerformDebuggerMicroTaskCheckpoint();
 254
 255   bool IsInStableOrMetaStableState() const { return mDoingStableStates; }
 256
 257   // Storage for watching rejected promises waiting for some client to
 258   // consume their rejection.
 259   // Promises in this list have been rejected in the last turn of the
 260   // event loop without the rejection being handled.
 261   // Note that this can contain nullptrs in place of promises removed because
 262   // they're consumed before it'd be reported.
 263   JS::PersistentRooted<JS::GCVector<JSObject*, 0, js::SystemAllocPolicy>>
 264       mUncaughtRejections;
 265
 266   // Promises in this list have previously been reported as rejected
 267   // (because they were in the above list), but the rejection was handled
 268   // in the last turn of the event loop.
 269   JS::PersistentRooted<JS::GCVector<JSObject*, 0, js::SystemAllocPolicy>>
 270       mConsumedRejections;
 271   nsTArray<nsCOMPtr<nsISupports /* UncaughtRejectionObserver */>>
 272       mUncaughtRejectionObservers;
 273
 274   virtual bool IsSystemCaller() const = 0;
 275
 276   // Unused on main thread.  Used by AutoJSAPI on Worker and Worklet threads.
 277   virtual void ReportError(JSErrorReport* aReport,
 278                            JS::ConstUTF8CharsZ aToStringResult) {
 279     MOZ_ASSERT_UNREACHABLE("Not supported");
 280   }
 281
 282   // These two functions control a special flag variable which lets us turn
 283   // tracing on and off from a thread other than this JSContext's main thread.
 284   // This is useful because we want to be able to start tracing many threads
 285   // all at once from the Gecko Profiler in Firefox.
 286   //
 287   // NOTE: the caller must ensure that this CycleCollectedJSContext is not
 288   // being destroyed when this is called. At the time of this API being added,
 289   // the only consumer is the Gecko Profiler, which guarantees this via a mutex
 290   // around unregistering the context, which always occurs before the context
 291   // is destroyed.
 292   void BeginExecutionTracingAsync();
 293   void EndExecutionTracingAsync();
 294
 295  private:
 296   // JS::JobQueue implementation: see js/public/Promise.h.
 297   // SpiderMonkey uses some of these methods to enqueue promise resolution jobs.
 298   // Others protect the debuggee microtask queue from the debugger's
 299   // interruptions; see the comments on JS::AutoDebuggerJobQueueInterruption for
 300   // details.
 301   JSObject* getIncumbentGlobal(JSContext* cx) override;
 302   bool enqueuePromiseJob(JSContext* cx, JS::Handle<JSObject*> promise,
 303                          JS::Handle<JSObject*> job,
 304                          JS::Handle<JSObject*> allocationSite,
 305                          JS::Handle<JSObject*> incumbentGlobal) override;
 306   // MOZ_CAN_RUN_SCRIPT_BOUNDARY for now so we don't have to change SpiderMonkey
 307   // headers.  The caller presumably knows this can run script (like everything
 308   // in SpiderMonkey!) and will deal.
 309   MOZ_CAN_RUN_SCRIPT_BOUNDARY
 310   void runJobs(JSContext* cx) override;
 311   bool empty() const override;
 312   bool isDrainingStopped() const override { return false; }
 313   class SavedMicroTaskQueue;
 314   js::UniquePtr<SavedJobQueue> saveJobQueue(JSContext*) override;
 315
 316  private:
 317   CycleCollectedJSRuntime* mRuntime;
 318
 319   JSContext* mJSContext;
 320
 321   nsCOMPtr<dom::Exception> mPendingException;
 322   nsThread* mOwningThread;  // Manual refcounting to avoid include hell.
 323
 324   struct PendingIDBTransactionData {
 325     nsCOMPtr<nsIRunnable> mTransaction;
 326     uint32_t mRecursionDepth;
 327   };
 328
 329   nsTArray<nsCOMPtr<nsIRunnable>> mStableStateEvents;
 330   nsTArray<PendingIDBTransactionData> mPendingIDBTransactions;
 331   uint32_t mBaseRecursionDepth;
 332   bool mDoingStableStates;
 333
 334   // If set to none 0, microtasks will be processed only when recursion depth
 335   // is the set value.
 336   uint32_t mTargetedMicroTaskRecursionDepth;
 337
 338   uint32_t mMicroTaskLevel;
 339
 340   std::deque<RefPtr<MicroTaskRunnable>> mPendingMicroTaskRunnables;
 341   std::deque<RefPtr<MicroTaskRunnable>> mDebuggerMicroTaskQueue;
 342   RefPtr<SuppressedMicroTasks> mSuppressedMicroTasks;
 343   uint64_t mSuppressionGeneration;
 344
 345   // How many times the debugger has interrupted execution, possibly creating
 346   // microtask checkpoints in places that they would not normally occur.
 347   uint32_t mDebuggerRecursionDepth;
 348
 349   uint32_t mMicroTaskRecursionDepth;
 350
 351   // This implements about-to-be-notified rejected promises list in the spec.
 352   // https://html.spec.whatwg.org/multipage/webappapis.html#about-to-be-notified-rejected-promises-list
 353   typedef nsTArray<RefPtr<dom::Promise>> PromiseArray;
 354   PromiseArray mAboutToBeNotifiedRejectedPromises;
 355
 356   // This is for the "outstanding rejected promises weak set" in the spec,
 357   // https://html.spec.whatwg.org/multipage/webappapis.html#outstanding-rejected-promises-weak-set
 358   // We use different data structure and opposite logic here to achieve the same
 359   // effect. Basically this is used for tracking the rejected promise that does
 360   // NOT need firing a rejectionhandled event. We will check the table to see if
 361   // firing rejectionhandled event is required when a rejected promise is being
 362   // handled.
 363   //
 364   // The rejected promise will be stored in the table if
 365   // - it is unhandled, and
 366   // - The unhandledrejection is not yet fired.
 367   //
 368   // And be removed when
 369   // - it is handled, or
 370   // - A unhandledrejection is fired and it isn't being handled in event
 371   // handler.
 372   typedef nsRefPtrHashtable<nsUint64HashKey, dom::Promise> PromiseHashtable;
 373   PromiseHashtable mPendingUnhandledRejections;
 374
 375   class NotifyUnhandledRejections final : public CancelableRunnable {
 376    public:
 377     explicit NotifyUnhandledRejections(PromiseArray&& aPromises)
 378         : CancelableRunnable("NotifyUnhandledRejections"),
 379           mUnhandledRejections(std::move(aPromises)) {}
 380
 381     NS_IMETHOD Run() final;
 382
 383     nsresult Cancel() final;
 384
 385    private:
 386     PromiseArray mUnhandledRejections;
 387   };
 388
 389   FinalizationRegistryCleanup mFinalizationRegistryCleanup;
 390 };
 391
 392 class MOZ_STACK_CLASS nsAutoMicroTask {
 393  public:
 394   nsAutoMicroTask() {
 395     CycleCollectedJSContext* ccjs = CycleCollectedJSContext::Get();
 396     if (ccjs) {
 397       ccjs->EnterMicroTask();
 398     }
 399   }
 400   MOZ_CAN_RUN_SCRIPT ~nsAutoMicroTask() {
 401     CycleCollectedJSContext* ccjs = CycleCollectedJSContext::Get();
 402     if (ccjs) {
 403       ccjs->LeaveMicroTask();
 404     }
 405   }
 406 };
 407
 408 }  // namespace mozilla
 409
 410 #endif  // mozilla_CycleCollectedJSContext_h