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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
#include "MessagePump.h"
#include "nsIThread.h"
#include "nsITimer.h"
#include "nsICancelableRunnable.h"
#include "base/basictypes.h"
#include "base/logging.h"
#include "base/scoped_nsautorelease_pool.h"
#include "mozilla/Assertions.h"
#include "mozilla/DebugOnly.h"
#include "nsComponentManagerUtils.h"
#include "nsDebug.h"
#include "nsServiceManagerUtils.h"
#include "nsString.h"
#include "nsThreadUtils.h"
#include "nsTimerImpl.h"
#include "nsXULAppAPI.h"
#include "prthread.h"
using base::TimeTicks;
using namespace mozilla::ipc;
#ifdef DEBUG
static MessagePump::Delegate* gFirstDelegate;
#endif
namespace mozilla {
namespace ipc {
class DoWorkRunnable final : public CancelableRunnable,
public nsITimerCallback {
public:
explicit DoWorkRunnable(MessagePump* aPump)
: CancelableRunnable("ipc::DoWorkRunnable"), mPump(aPump) {
MOZ_ASSERT(aPump);
}
NS_DECL_ISUPPORTS_INHERITED
NS_DECL_NSIRUNNABLE
NS_DECL_NSITIMERCALLBACK
nsresult Cancel() override;
private:
~DoWorkRunnable() = default;
MessagePump* mPump;
// DoWorkRunnable is designed as a stateless singleton. Do not add stateful
// members here!
};
} /* namespace ipc */
} /* namespace mozilla */
MessagePump::MessagePump(nsISerialEventTarget* aEventTarget)
: mEventTarget(aEventTarget) {
mDoWorkEvent = new DoWorkRunnable(this);
}
MessagePump::~MessagePump() = default;
void MessagePump::Run(MessagePump::Delegate* aDelegate) {
MOZ_ASSERT(keep_running_);
MOZ_RELEASE_ASSERT(NS_IsMainThread(),
"Use mozilla::ipc::MessagePumpForNonMainThreads instead!");
MOZ_RELEASE_ASSERT(!mEventTarget);
nsIThread* thisThread = NS_GetCurrentThread();
MOZ_ASSERT(thisThread);
mDelayedWorkTimer = NS_NewTimer();
MOZ_ASSERT(mDelayedWorkTimer);
base::ScopedNSAutoreleasePool autoReleasePool;
for (;;) {
autoReleasePool.Recycle();
bool did_work = NS_ProcessNextEvent(thisThread, false) ? true : false;
if (!keep_running_) break;
// NB: it is crucial *not* to directly call |aDelegate->DoWork()|
// here. To ensure that MessageLoop tasks and XPCOM events have
// equal priority, we sensitively rely on processing exactly one
// Task per DoWorkRunnable XPCOM event.
did_work |= aDelegate->DoDelayedWork(&delayed_work_time_);
if (did_work && delayed_work_time_.is_null()) mDelayedWorkTimer->Cancel();
if (!keep_running_) break;
if (did_work) continue;
did_work = aDelegate->DoIdleWork();
if (!keep_running_) break;
if (did_work) continue;
// This will either sleep or process an event.
NS_ProcessNextEvent(thisThread, true);
}
mDelayedWorkTimer->Cancel();
keep_running_ = true;
}
void MessagePump::ScheduleWork() {
// Make sure the event loop wakes up.
if (mEventTarget) {
mEventTarget->Dispatch(mDoWorkEvent, NS_DISPATCH_NORMAL);
} else {
// Some things (like xpcshell) don't use the app shell and so Run hasn't
// been called. We still need to wake up the main thread.
NS_DispatchToMainThread(mDoWorkEvent);
}
event_.Signal();
}
void MessagePump::ScheduleWorkForNestedLoop() {
// This method is called when our MessageLoop has just allowed
// nested tasks. In our setup, whenever that happens we know that
// DoWork() will be called "soon", so there's no need to pay the
// cost of what will be a no-op nsThread::Dispatch(mDoWorkEvent).
}
void MessagePump::ScheduleDelayedWork(const base::TimeTicks& aDelayedTime) {
// To avoid racing on mDelayedWorkTimer, we need to be on the same thread as
// ::Run().
MOZ_RELEASE_ASSERT((!mEventTarget && NS_IsMainThread()) ||
mEventTarget->IsOnCurrentThread());
if (!mDelayedWorkTimer) {
mDelayedWorkTimer = NS_NewTimer();
if (!mDelayedWorkTimer) {
// Called before XPCOM has started up? We can't do this correctly.
NS_WARNING("Delayed task might not run!");
delayed_work_time_ = aDelayedTime;
return;
}
}
if (!delayed_work_time_.is_null()) {
mDelayedWorkTimer->Cancel();
}
delayed_work_time_ = aDelayedTime;
// TimeDelta's constructor initializes to 0
base::TimeDelta delay;
if (aDelayedTime > base::TimeTicks::Now())
delay = aDelayedTime - base::TimeTicks::Now();
uint32_t delayMS = uint32_t(delay.InMilliseconds());
mDelayedWorkTimer->InitWithCallback(mDoWorkEvent, delayMS,
nsITimer::TYPE_ONE_SHOT);
}
nsISerialEventTarget* MessagePump::GetXPCOMThread() {
if (mEventTarget) {
return mEventTarget;
}
// Main thread
return GetMainThreadSerialEventTarget();
}
void MessagePump::DoDelayedWork(base::MessagePump::Delegate* aDelegate) {
aDelegate->DoDelayedWork(&delayed_work_time_);
if (!delayed_work_time_.is_null()) {
ScheduleDelayedWork(delayed_work_time_);
}
}
NS_IMPL_ISUPPORTS_INHERITED(DoWorkRunnable, CancelableRunnable,
nsITimerCallback)
NS_IMETHODIMP
DoWorkRunnable::Run() {
MessageLoop* loop = MessageLoop::current();
MOZ_ASSERT(loop);
bool nestableTasksAllowed = loop->NestableTasksAllowed();
// MessageLoop::RunTask() disallows nesting, but our Frankenventloop will
// always dispatch DoWork() below from what looks to MessageLoop like a nested
// context. So we unconditionally allow nesting here.
loop->SetNestableTasksAllowed(true);
loop->DoWork();
loop->SetNestableTasksAllowed(nestableTasksAllowed);
return NS_OK;
}
NS_IMETHODIMP
DoWorkRunnable::Notify(nsITimer* aTimer) {
MessageLoop* loop = MessageLoop::current();
MOZ_ASSERT(loop);
bool nestableTasksAllowed = loop->NestableTasksAllowed();
loop->SetNestableTasksAllowed(true);
mPump->DoDelayedWork(loop);
loop->SetNestableTasksAllowed(nestableTasksAllowed);
return NS_OK;
}
nsresult DoWorkRunnable::Cancel() {
// Workers require cancelable runnables, but we can't really cancel cleanly
// here. If we don't process this runnable then we will leave something
// unprocessed in the message_loop. Therefore, eagerly complete our work
// instead by immediately calling Run(). Run() should be called separately
// after this. Unfortunately we cannot use flags to verify this because
// DoWorkRunnable is a stateless singleton that can be in the event queue
// multiple times simultaneously.
MOZ_ALWAYS_SUCCEEDS(Run());
return NS_OK;
}
void MessagePumpForChildProcess::Run(base::MessagePump::Delegate* aDelegate) {
if (mFirstRun) {
MOZ_ASSERT(aDelegate && !gFirstDelegate);
#ifdef DEBUG
gFirstDelegate = aDelegate;
#endif
mFirstRun = false;
if (NS_FAILED(XRE_RunAppShell())) {
NS_WARNING("Failed to run app shell?!");
}
MOZ_ASSERT(aDelegate && aDelegate == gFirstDelegate);
#ifdef DEBUG
gFirstDelegate = nullptr;
#endif
return;
}
MOZ_ASSERT(aDelegate && aDelegate == gFirstDelegate);
// We can get to this point in startup with Tasks in our loop's
// incoming_queue_ or pending_queue_, but without a matching
// DoWorkRunnable(). In MessagePump::Run() above, we sensitively
// depend on *not* directly calling delegate->DoWork(), because that
// prioritizes Tasks above XPCOM events. However, from this point
// forward, any Task posted to our loop is guaranteed to have a
// DoWorkRunnable enqueued for it.
//
// So we just flush the pending work here and move on.
MessageLoop* loop = MessageLoop::current();
bool nestableTasksAllowed = loop->NestableTasksAllowed();
loop->SetNestableTasksAllowed(true);
while (aDelegate->DoWork())
;
loop->SetNestableTasksAllowed(nestableTasksAllowed);
// Really run.
mozilla::ipc::MessagePump::Run(aDelegate);
}
void MessagePumpForNonMainThreads::Run(base::MessagePump::Delegate* aDelegate) {
MOZ_ASSERT(keep_running_);
MOZ_RELEASE_ASSERT(!NS_IsMainThread(),
"Use mozilla::ipc::MessagePump instead!");
nsIThread* thread = NS_GetCurrentThread();
MOZ_RELEASE_ASSERT(mEventTarget->IsOnCurrentThread());
mDelayedWorkTimer = NS_NewTimer(mEventTarget);
MOZ_ASSERT(mDelayedWorkTimer);
// Chromium event notifications to be processed will be received by this
// event loop as a DoWorkRunnables via ScheduleWork. Chromium events that
// were received before our thread is valid, however, will not generate
// runnable wrappers. We must process any of these before we enter this
// loop, or we will forever have unprocessed chromium messages in our queue.
//
// Note we would like to request a flush of the chromium event queue
// using a runnable on the xpcom side, but some thread implementations
// (dom workers) get cranky if we call ScheduleWork here (ScheduleWork
// calls dispatch on mEventTarget) before the thread processes an event. As
// such, clear the queue manually.
while (aDelegate->DoWork()) {
}
base::ScopedNSAutoreleasePool autoReleasePool;
for (;;) {
autoReleasePool.Recycle();
bool didWork = NS_ProcessNextEvent(thread, false) ? true : false;
if (!keep_running_) {
break;
}
didWork |= aDelegate->DoDelayedWork(&delayed_work_time_);
if (didWork && delayed_work_time_.is_null()) {
mDelayedWorkTimer->Cancel();
}
if (!keep_running_) {
break;
}
if (didWork) {
continue;
}
DebugOnly<bool> didIdleWork = aDelegate->DoIdleWork();
MOZ_ASSERT(!didIdleWork);
if (!keep_running_) {
break;
}
if (didWork) {
continue;
}
// This will either sleep or process an event.
NS_ProcessNextEvent(thread, true);
}
mDelayedWorkTimer->Cancel();
keep_running_ = true;
}