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5b2ada26c5
Tasks registered with shutdown tasks are called when the target nsISerialEventTarget is about to be destroyed. Differential Revision: https://phabricator.services.mozilla.com/D129840
131 lines
5.3 KiB
C++
131 lines
5.3 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_SynchronizedEventQueue_h
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#define mozilla_SynchronizedEventQueue_h
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#include "mozilla/AlreadyAddRefed.h"
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#include "mozilla/EventQueue.h"
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#include "mozilla/MemoryReporting.h"
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#include "mozilla/Mutex.h"
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#include "nsIThreadInternal.h"
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#include "nsCOMPtr.h"
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#include "nsTObserverArray.h"
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class nsIEventTarget;
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class nsISerialEventTarget;
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class nsIThreadObserver;
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namespace mozilla {
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// A SynchronizedEventQueue is an abstract class for event queues that can be
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// used across threads. A SynchronizedEventQueue implementation will typically
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// use locks and condition variables to guarantee consistency. The methods of
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// SynchronizedEventQueue are split between ThreadTargetSink (which contains
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// methods for posting events) and SynchronizedEventQueue (which contains
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// methods for getting events). This split allows event targets (specifically
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// ThreadEventTarget) to use a narrow interface, since they only need to post
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// events.
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//
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// ThreadEventQueue is the canonical implementation of
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// SynchronizedEventQueue. When Quantum DOM is implemented, we will use a
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// different synchronized queue on the main thread, SchedulerEventQueue, which
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// will handle the cooperative threading model.
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class ThreadTargetSink {
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public:
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NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ThreadTargetSink)
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virtual bool PutEvent(already_AddRefed<nsIRunnable>&& aEvent,
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EventQueuePriority aPriority) = 0;
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// After this method is called, no more events can be posted.
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virtual void Disconnect(const MutexAutoLock& aProofOfLock) = 0;
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virtual nsresult RegisterShutdownTask(nsITargetShutdownTask* aTask) = 0;
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virtual nsresult UnregisterShutdownTask(nsITargetShutdownTask* aTask) = 0;
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size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) {
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return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
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}
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// Not const because overrides may need to take a lock
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virtual size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) = 0;
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protected:
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virtual ~ThreadTargetSink() = default;
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};
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class SynchronizedEventQueue : public ThreadTargetSink {
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public:
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virtual already_AddRefed<nsIRunnable> GetEvent(
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bool aMayWait, mozilla::TimeDuration* aLastEventDelay = nullptr) = 0;
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virtual bool HasPendingEvent() = 0;
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// This method atomically checks if there are pending events and, if there are
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// none, forbids future events from being posted. It returns true if there
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// were no pending events.
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virtual bool ShutdownIfNoPendingEvents() = 0;
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// These methods provide access to an nsIThreadObserver, whose methods are
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// called when posting and processing events. SetObserver should only be
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// called on the thread that processes events. GetObserver can be called from
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// any thread. GetObserverOnThread must be used from the thread that processes
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// events; it does not acquire a lock.
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virtual already_AddRefed<nsIThreadObserver> GetObserver() = 0;
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virtual already_AddRefed<nsIThreadObserver> GetObserverOnThread() = 0;
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virtual void SetObserver(nsIThreadObserver* aObserver) = 0;
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void AddObserver(nsIThreadObserver* aObserver);
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void RemoveObserver(nsIThreadObserver* aObserver);
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const nsTObserverArray<nsCOMPtr<nsIThreadObserver>>& EventObservers();
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size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) override {
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// Normally we'd return
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// mEventObservers.ShallowSizeOfExcludingThis(aMallocSizeOf); However,
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// mEventObservers may be being mutated on another thread, and we don't lock
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// around access, so locking here wouldn't help. They're small, so
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return 0;
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}
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/**
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* This method causes any events currently enqueued on the thread to be
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* suppressed until PopEventQueue is called, and any event dispatched to this
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* thread's nsIEventTarget will queue as well. Calls to PushEventQueue may be
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* nested and must each be paired with a call to PopEventQueue in order to
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* restore the original state of the thread. The returned nsIEventTarget may
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* be used to push events onto the nested queue. Dispatching will be disabled
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* once the event queue is popped. The thread will only ever process pending
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* events for the innermost event queue. Must only be called on the target
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* thread.
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*/
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virtual already_AddRefed<nsISerialEventTarget> PushEventQueue() = 0;
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/**
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* Revert a call to PushEventQueue. When an event queue is popped, any events
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* remaining in the queue are appended to the elder queue. This also causes
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* the nsIEventTarget returned from PushEventQueue to stop dispatching events.
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* Must only be called on the target thread, and with the innermost event
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* queue.
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*/
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virtual void PopEventQueue(nsIEventTarget* aTarget) = 0;
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/**
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* Flush the list of shutdown tasks which were previously registered. After
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* this is called, new shutdown tasks cannot be registered.
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*/
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virtual void RunShutdownTasks() = 0;
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protected:
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virtual ~SynchronizedEventQueue() = default;
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private:
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nsTObserverArray<nsCOMPtr<nsIThreadObserver>> mEventObservers;
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};
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} // namespace mozilla
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#endif // mozilla_SynchronizedEventQueue_h
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