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