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-rw-r--r--xpcom/threads/SynchronizedEventQueue.h131
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diff --git a/xpcom/threads/SynchronizedEventQueue.h b/xpcom/threads/SynchronizedEventQueue.h
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+/* -*- 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/. */
+
+#ifndef mozilla_SynchronizedEventQueue_h
+#define mozilla_SynchronizedEventQueue_h
+
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/EventQueue.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/Mutex.h"
+#include "nsIThreadInternal.h"
+#include "nsCOMPtr.h"
+#include "nsTObserverArray.h"
+
+class nsIEventTarget;
+class nsISerialEventTarget;
+class nsIThreadObserver;
+
+namespace mozilla {
+
+// A SynchronizedEventQueue is an abstract class for event queues that can be
+// used across threads. A SynchronizedEventQueue implementation will typically
+// use locks and condition variables to guarantee consistency. The methods of
+// SynchronizedEventQueue are split between ThreadTargetSink (which contains
+// methods for posting events) and SynchronizedEventQueue (which contains
+// methods for getting events). This split allows event targets (specifically
+// ThreadEventTarget) to use a narrow interface, since they only need to post
+// events.
+//
+// ThreadEventQueue is the canonical implementation of
+// SynchronizedEventQueue. When Quantum DOM is implemented, we will use a
+// different synchronized queue on the main thread, SchedulerEventQueue, which
+// will handle the cooperative threading model.
+
+class ThreadTargetSink {
+ public:
+ NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ThreadTargetSink)
+
+ virtual bool PutEvent(already_AddRefed<nsIRunnable>&& aEvent,
+ EventQueuePriority aPriority) = 0;
+
+ // After this method is called, no more events can be posted.
+ virtual void Disconnect(const MutexAutoLock& aProofOfLock) = 0;
+
+ virtual nsresult RegisterShutdownTask(nsITargetShutdownTask* aTask) = 0;
+ virtual nsresult UnregisterShutdownTask(nsITargetShutdownTask* aTask) = 0;
+
+ size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) {
+ return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
+ }
+
+ // Not const because overrides may need to take a lock
+ virtual size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) = 0;
+
+ protected:
+ virtual ~ThreadTargetSink() = default;
+};
+
+class SynchronizedEventQueue : public ThreadTargetSink {
+ public:
+ virtual already_AddRefed<nsIRunnable> GetEvent(
+ bool aMayWait, mozilla::TimeDuration* aLastEventDelay = nullptr) = 0;
+ virtual bool HasPendingEvent() = 0;
+
+ // This method atomically checks if there are pending events and, if there are
+ // none, forbids future events from being posted. It returns true if there
+ // were no pending events.
+ virtual bool ShutdownIfNoPendingEvents() = 0;
+
+ // These methods provide access to an nsIThreadObserver, whose methods are
+ // called when posting and processing events. SetObserver should only be
+ // called on the thread that processes events. GetObserver can be called from
+ // any thread. GetObserverOnThread must be used from the thread that processes
+ // events; it does not acquire a lock.
+ virtual already_AddRefed<nsIThreadObserver> GetObserver() = 0;
+ virtual already_AddRefed<nsIThreadObserver> GetObserverOnThread() = 0;
+ virtual void SetObserver(nsIThreadObserver* aObserver) = 0;
+
+ void AddObserver(nsIThreadObserver* aObserver);
+ void RemoveObserver(nsIThreadObserver* aObserver);
+ const nsTObserverArray<nsCOMPtr<nsIThreadObserver>>& EventObservers();
+
+ size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) override {
+ // Normally we'd return
+ // mEventObservers.ShallowSizeOfExcludingThis(aMallocSizeOf); However,
+ // mEventObservers may be being mutated on another thread, and we don't lock
+ // around access, so locking here wouldn't help. They're small, so
+ return 0;
+ }
+
+ /**
+ * This method causes any events currently enqueued on the thread to be
+ * suppressed until PopEventQueue is called, and any event dispatched to this
+ * thread's nsIEventTarget will queue as well. Calls to PushEventQueue may be
+ * nested and must each be paired with a call to PopEventQueue in order to
+ * restore the original state of the thread. The returned nsIEventTarget may
+ * be used to push events onto the nested queue. Dispatching will be disabled
+ * once the event queue is popped. The thread will only ever process pending
+ * events for the innermost event queue. Must only be called on the target
+ * thread.
+ */
+ virtual already_AddRefed<nsISerialEventTarget> PushEventQueue() = 0;
+
+ /**
+ * Revert a call to PushEventQueue. When an event queue is popped, any events
+ * remaining in the queue are appended to the elder queue. This also causes
+ * the nsIEventTarget returned from PushEventQueue to stop dispatching events.
+ * Must only be called on the target thread, and with the innermost event
+ * queue.
+ */
+ virtual void PopEventQueue(nsIEventTarget* aTarget) = 0;
+
+ /**
+ * Flush the list of shutdown tasks which were previously registered. After
+ * this is called, new shutdown tasks cannot be registered.
+ */
+ virtual void RunShutdownTasks() = 0;
+
+ protected:
+ virtual ~SynchronizedEventQueue() = default;
+
+ private:
+ nsTObserverArray<nsCOMPtr<nsIThreadObserver>> mEventObservers;
+};
+
+} // namespace mozilla
+
+#endif // mozilla_SynchronizedEventQueue_h