mirror of
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134 lines
3.9 KiB
C++
134 lines
3.9 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_SyncRunnable_h
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#define mozilla_SyncRunnable_h
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#include <utility>
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#include "mozilla/AbstractThread.h"
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#include "mozilla/Monitor.h"
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#include "mozilla/dom/JSExecutionManager.h"
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#include "nsThreadUtils.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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public:
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explicit SyncRunnable(nsIRunnable* aRunnable)
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: Runnable("SyncRunnable"),
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mRunnable(aRunnable),
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mMonitor("SyncRunnable"),
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mDone(false) {}
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explicit SyncRunnable(already_AddRefed<nsIRunnable> aRunnable)
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: Runnable("SyncRunnable"),
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mRunnable(std::move(aRunnable)),
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mMonitor("SyncRunnable"),
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mDone(false) {}
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nsresult DispatchToThread(nsIEventTarget* aThread,
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bool aForceDispatch = false) {
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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 NS_OK;
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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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// This could be synchronously dispatching to a thread currently waiting
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// for JS execution clearance. Yield JS execution.
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dom::AutoYieldJSThreadExecution yield;
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while (!mDone) {
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lock.Wait();
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}
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}
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return rv;
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}
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nsresult DispatchToThread(AbstractThread* aThread,
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bool aForceDispatch = false) {
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if (!aForceDispatch && aThread->IsCurrentThreadIn()) {
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mRunnable->Run();
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return NS_OK;
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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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nsresult rv = aThread->Dispatch(RefPtr<nsIRunnable>(this).forget());
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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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return rv;
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}
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static nsresult DispatchToThread(nsIEventTarget* aThread,
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nsIRunnable* aRunnable,
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bool aForceDispatch = false) {
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RefPtr<SyncRunnable> s(new SyncRunnable(aRunnable));
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return s->DispatchToThread(aThread, aForceDispatch);
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}
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static nsresult DispatchToThread(AbstractThread* aThread,
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nsIRunnable* aRunnable,
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bool aForceDispatch = false) {
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RefPtr<SyncRunnable> s(new SyncRunnable(aRunnable));
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return 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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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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