129 lines
3.3 KiB
C++
129 lines
3.3 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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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_SyncRunnable_h
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#define mozilla_SyncRunnable_h
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#include "nsThreadUtils.h"
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#include "mozilla/AbstractThread.h"
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#include "mozilla/Monitor.h"
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#include "mozilla/Move.h"
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namespace mozilla {
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/**
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* This class will wrap a nsIRunnable and dispatch it to the main thread
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* synchronously. This is different from nsIEventTarget.DISPATCH_SYNC:
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* this class does not spin the event loop waiting for the event to be
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* dispatched. This means that you don't risk reentrance from pending
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* messages, but you must be sure that the target thread does not ever block
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* on this thread, or else you will deadlock.
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*
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* Typical usage:
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* RefPtr<SyncRunnable> sr = new SyncRunnable(new myrunnable...());
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* sr->DispatchToThread(t);
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*
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* We also provide a convenience wrapper:
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* SyncRunnable::DispatchToThread(new myrunnable...());
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*
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*/
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class SyncRunnable : public Runnable
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{
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public:
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explicit SyncRunnable(nsIRunnable* aRunnable)
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: mRunnable(aRunnable)
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, mMonitor("SyncRunnable")
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, mDone(false)
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{
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}
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explicit SyncRunnable(already_AddRefed<nsIRunnable> aRunnable)
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: mRunnable(Move(aRunnable))
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, mMonitor("SyncRunnable")
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, mDone(false)
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{
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}
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void DispatchToThread(nsIEventTarget* aThread, bool aForceDispatch = false)
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{
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nsresult rv;
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bool on;
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if (!aForceDispatch) {
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rv = aThread->IsOnCurrentThread(&on);
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MOZ_ASSERT(NS_SUCCEEDED(rv));
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if (NS_SUCCEEDED(rv) && on) {
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mRunnable->Run();
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return;
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}
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}
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rv = aThread->Dispatch(this, NS_DISPATCH_NORMAL);
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if (NS_SUCCEEDED(rv)) {
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mozilla::MonitorAutoLock lock(mMonitor);
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while (!mDone) {
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lock.Wait();
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}
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}
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}
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void DispatchToThread(AbstractThread* aThread, bool aForceDispatch = false)
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{
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if (!aForceDispatch && aThread->IsCurrentThreadIn()) {
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mRunnable->Run();
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return;
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}
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// Check we don't have tail dispatching here. Otherwise we will deadlock
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// ourself when spinning the loop below.
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MOZ_ASSERT(!aThread->RequiresTailDispatchFromCurrentThread());
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aThread->Dispatch(RefPtr<nsIRunnable>(this).forget());
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mozilla::MonitorAutoLock lock(mMonitor);
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while (!mDone) {
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lock.Wait();
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}
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}
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static void DispatchToThread(nsIEventTarget* aThread,
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nsIRunnable* aRunnable,
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bool aForceDispatch = false)
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{
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RefPtr<SyncRunnable> s(new SyncRunnable(aRunnable));
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s->DispatchToThread(aThread, aForceDispatch);
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}
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static void DispatchToThread(AbstractThread* aThread,
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nsIRunnable* aRunnable,
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bool aForceDispatch = false)
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{
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RefPtr<SyncRunnable> s(new SyncRunnable(aRunnable));
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s->DispatchToThread(aThread, aForceDispatch);
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}
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protected:
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NS_IMETHOD Run() override
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{
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mRunnable->Run();
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mozilla::MonitorAutoLock lock(mMonitor);
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MOZ_ASSERT(!mDone);
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mDone = true;
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mMonitor.Notify();
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return NS_OK;
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}
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private:
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nsCOMPtr<nsIRunnable> mRunnable;
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mozilla::Monitor mMonitor;
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bool mDone;
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};
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} // namespace mozilla
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#endif // mozilla_SyncRunnable_h
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