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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_dom_RemoteWorkerService_h
#define mozilla_dom_RemoteWorkerService_h
#include "mozilla/AlreadyAddRefed.h"
#include "mozilla/DataMutex.h"
#include "nsCOMPtr.h"
#include "nsIObserver.h"
#include "nsISupportsImpl.h"
class nsIThread;
namespace mozilla::dom {
class RemoteWorkerService;
class RemoteWorkerServiceChild;
class RemoteWorkerServiceShutdownBlocker;
/**
* Refcounted lifecycle helper; when its refcount goes to zero its destructor
* will call RemoteWorkerService::Shutdown() which will remove the shutdown
* blocker and shutdown the "Worker Launcher" thread.
*
* The RemoteWorkerService itself will hold a reference to this singleton which
* it will use to hand out additional refcounts to RemoteWorkerChild instances.
* When the shutdown blocker is notified that it's time to shutdown, the
* RemoteWorkerService's reference will be dropped.
*/
class RemoteWorkerServiceKeepAlive {
public:
explicit RemoteWorkerServiceKeepAlive(
RemoteWorkerServiceShutdownBlocker* aBlocker);
private:
~RemoteWorkerServiceKeepAlive();
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(RemoteWorkerServiceKeepAlive);
RefPtr<RemoteWorkerServiceShutdownBlocker> mBlocker;
};
/**
* Every process has a RemoteWorkerService which does the actual spawning of
* RemoteWorkerChild instances. The RemoteWorkerService creates a "Worker
* Launcher" thread at initialization on which it creates a
* RemoteWorkerServiceChild to service spawn requests. The thread is exposed as
* RemoteWorkerService::Thread(). A new/distinct thread is used because we
* (eventually) don't want to deal with main-thread contention, content
* processes have no equivalent of a PBackground thread, and actors are bound to
* specific threads.
*
* (Disclaimer: currently most RemoteWorkerOps need to happen on the main thread
* because the main-thread ends up as the owner of the worker and all
* manipulation of the worker must happen from the owning thread.)
*/
class RemoteWorkerService final : public nsIObserver {
friend class RemoteWorkerServiceShutdownBlocker;
friend class RemoteWorkerServiceKeepAlive;
public:
NS_DECL_THREADSAFE_ISUPPORTS
NS_DECL_NSIOBSERVER
// To be called when a process is initialized on main-thread.
static void Initialize();
static nsIThread* Thread();
// Called by RemoteWorkerChild instances on the "Worker Launcher" thread at
// their creation to assist in tracking when it's safe to shutdown the
// RemoteWorkerService and "Worker Launcher" thread. This method will return
// a null pointer if the RemoteWorkerService has already begun shutdown.
//
// This is somewhat awkwardly a static method because the RemoteWorkerChild
// instances are not managed by RemoteWorkerServiceChild, but instead are
// managed by PBackground(Child). So we either need to find the
// RemoteWorkerService via the hidden singleton or by having the
// RemoteWorkerChild use PBackgroundChild::ManagedPRemoteWorkerServiceChild()
// to locate the instance. We are choosing to use the singleton because we
// already need to acquire a mutex in the call regardless and the upcoming
// refactorings may want to start using new toplevel protocols and this will
// avoid requiring a change when that happens.
static already_AddRefed<RemoteWorkerServiceKeepAlive> MaybeGetKeepAlive();
private:
RemoteWorkerService();
~RemoteWorkerService();
nsresult InitializeOnMainThread();
void InitializeOnTargetThread();
void CloseActorOnTargetThread();
// Called by RemoteWorkerServiceShutdownBlocker when it's time to drop the
// RemoteWorkerServiceKeepAlive reference.
void BeginShutdown();
// Called by RemoteWorkerServiceShutdownBlocker when the blocker has been
// removed and it's safe to shutdown the "Worker Launcher" thread.
void FinishShutdown();
nsCOMPtr<nsIThread> mThread;
RefPtr<RemoteWorkerServiceChild> mActor;
// The keep-alive is set and cleared on the main thread but we will hand out
// additional references to it from the "Worker Launcher" thread, so it's
// appropriate to use a mutex. (Alternately we could have used a ThreadBound
// and set and cleared on the "Worker Launcher" thread, but that would
// involve more moving parts and could have complicated edge cases.)
DataMutex<RefPtr<RemoteWorkerServiceKeepAlive>> mKeepAlive;
// In order to poll the blocker to know when we can stop spinning the event
// loop at shutdown, we retain a reference to the blocker.
RefPtr<RemoteWorkerServiceShutdownBlocker> mShutdownBlocker;
};
} // namespace mozilla::dom
#endif // mozilla_dom_RemoteWorkerService_h
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