void
RPCChannel::Incall(const Message& call, size_t stackDepth)
{
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
RPC_ASSERT(call.is_rpc() && !call.is_reply(), "wrong message type");
// Race detection: see the long comment near
// mRemoteStackDepthGuess in RPCChannel.h. "Remote" stack depth
// means our side, and "local" means other side.
if (call.rpc_remote_stack_depth_guess() != RemoteViewOfStackDepth(stackDepth)) {
// RPC in-calls have raced.
// the "winner", if there is one, gets to defer processing of
// the other side's in-call
bool defer;
const char* winner;
switch (Listener()->MediateRPCRace(mChild ? call : mStack.top(),
mChild ? mStack.top() : call)) {
case RRPChildWins:
winner = "child";
defer = mChild;
break;
case RRPParentWins:
winner = "parent";
defer = !mChild;
break;
case RRPError:
NS_RUNTIMEABORT("NYI: 'Error' RPC race policy");
return;
default:
NS_RUNTIMEABORT("not reached");
return;
}
if (LoggingEnabled()) {
printf_stderr(" (%s: %s won, so we're%sdeferring)\n",
mChild ? "child" : "parent", winner,
defer ? " " : " not ");
}
if (defer) {
// we now know the other side's stack has one more frame
// than we thought
++mRemoteStackDepthGuess; // decremented in MaybeProcessDeferred()
mDeferred.push(call);
return;
}
// we "lost" and need to process the other side's in-call.
// don't need to fix up the mRemoteStackDepthGuess here,
// because we're just about to increment it in DispatchCall(),
// which will make it correct again
}
#ifdef OS_WIN
SyncStackFrame frame(this, true);
#endif
DispatchIncall(call);
}
void
AsyncChannel::DispatchOnChannelConnected(int32 peer_pid)
{
AssertWorkerThread();
if (mListener)
mListener->OnChannelConnected(peer_pid);
}
void
RPCChannel::DispatchIncall(const Message& call)
{
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
RPC_ASSERT(call.is_rpc() && !call.is_reply(),
"wrong message type");
Message* reply = nullptr;
++mRemoteStackDepthGuess;
Result rv = Listener()->OnCallReceived(call, reply);
--mRemoteStackDepthGuess;
if (!MaybeHandleError(rv, "RPCChannel")) {
delete reply;
reply = new Message();
reply->set_rpc();
reply->set_reply();
reply->set_reply_error();
}
reply->set_seqno(call.seqno());
{
MonitorAutoLock lock(*mMonitor);
if (ChannelConnected == mChannelState)
mLink->SendMessage(reply);
}
}
void
SyncChannel::OnDispatchMessage(const Message& msg)
{
AssertWorkerThread();
NS_ABORT_IF_FALSE(msg.is_sync(), "only sync messages here");
NS_ABORT_IF_FALSE(!msg.is_reply(), "wasn't awaiting reply");
Message* reply = 0;
mProcessingSyncMessage = true;
Result rv =
static_cast<SyncListener*>(mListener)->OnMessageReceived(msg, reply);
mProcessingSyncMessage = false;
if (!MaybeHandleError(rv, "SyncChannel")) {
// FIXME/cjones: error handling; OnError()?
delete reply;
reply = new Message();
reply->set_sync();
reply->set_reply();
reply->set_reply_error();
}
reply->set_seqno(msg.seqno());
{
MonitorAutoLock lock(mMonitor);
if (ChannelConnected == mChannelState)
SendThroughTransport(reply);
}
}
void
RPCChannel::MaybeUndeferIncall()
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
if (mDeferred.empty())
return;
size_t stackDepth = StackDepth();
// the other side can only *under*-estimate our actual stack depth
RPC_ASSERT(mDeferred.top().rpc_remote_stack_depth_guess() <= stackDepth,
"fatal logic error");
if (mDeferred.top().rpc_remote_stack_depth_guess() < RemoteViewOfStackDepth(stackDepth))
return;
// maybe time to process this message
Message call = mDeferred.top();
mDeferred.pop();
// fix up fudge factor we added to account for race
RPC_ASSERT(0 < mRemoteStackDepthGuess, "fatal logic error");
--mRemoteStackDepthGuess;
mPending.push_back(call);
}
bool
SyncChannel::ShouldContinueFromTimeout()
{
AssertWorkerThread();
mMonitor.AssertCurrentThreadOwns();
bool cont;
{
MonitorAutoUnlock unlock(mMonitor);
cont = static_cast<SyncListener*>(mListener)->OnReplyTimeout();
}
if (!cont) {
// NB: there's a sublety here. If parents were allowed to
// send sync messages to children, then it would be possible
// for this synchronous close-on-timeout to race with async
// |OnMessageReceived| tasks arriving from the child, posted
// to the worker thread's event loop. This would complicate
// cleanup of the *Channel. But since IPDL forbids this (and
// since it doesn't support children timing out on parents),
// the parent can only block on RPC messages to the child, and
// in that case arriving async messages are enqueued to the
// RPC channel's special queue. They're then ignored because
// the channel state changes to ChannelTimeout
// (i.e. !Connected).
SynchronouslyClose();
mChannelState = ChannelTimeout;
}
return cont;
}
void
AsyncChannel::OnNotifyMaybeChannelError()
{
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
// OnChannelError holds mMonitor when it posts this task and this
// task cannot be allowed to run until OnChannelError has
// exited. We enforce that order by grabbing the mutex here which
// should only continue once OnChannelError has completed.
{
MonitorAutoLock lock(*mMonitor);
// nothing to do here
}
if (ShouldDeferNotifyMaybeError()) {
mChannelErrorTask =
NewRunnableMethod(this, &AsyncChannel::OnNotifyMaybeChannelError);
// 10 ms delay is completely arbitrary
mWorkerLoop->PostDelayedTask(FROM_HERE, mChannelErrorTask, 10);
return;
}
NotifyMaybeChannelError();
}
bool
SyncChannel::Send(Message* msg, Message* reply)
{
AssertWorkerThread();
mMonitor.AssertNotCurrentThreadOwns();
NS_ABORT_IF_FALSE(!ProcessingSyncMessage(),
"violation of sync handler invariant");
NS_ABORT_IF_FALSE(msg->is_sync(), "can only Send() sync messages here");
#ifdef OS_WIN
SyncStackFrame frame(this, false);
#endif
msg->set_seqno(NextSeqno());
MonitorAutoLock lock(mMonitor);
if (!Connected()) {
ReportConnectionError("SyncChannel");
return false;
}
mPendingReply = msg->type() + 1;
int32 msgSeqno = msg->seqno();
SendThroughTransport(msg);
while (1) {
bool maybeTimedOut = !SyncChannel::WaitForNotify();
if (EventOccurred())
break;
if (maybeTimedOut && !ShouldContinueFromTimeout())
return false;
}
if (!Connected()) {
ReportConnectionError("SyncChannel");
return false;
}
// we just received a synchronous message from the other side.
// If it's not the reply we were awaiting, there's a serious
// error: either a mistimed/malformed message or a sync in-message
// that raced with our sync out-message.
// (NB: IPDL prevents the latter from occuring in actor code)
// FIXME/cjones: real error handling
NS_ABORT_IF_FALSE(mRecvd.is_sync() && mRecvd.is_reply() &&
(mRecvd.is_reply_error() ||
(mPendingReply == mRecvd.type() &&
msgSeqno == mRecvd.seqno())),
"unexpected sync message");
mPendingReply = 0;
*reply = mRecvd;
mRecvd = Message();
return true;
}
void
AsyncChannel::SynchronouslyClose()
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
mLink->SendClose();
while (ChannelClosed != mChannelState)
mMonitor->Wait();
}
bool
SyncChannel::EventOccurred()
{
AssertWorkerThread();
mMonitor.AssertCurrentThreadOwns();
NS_ABORT_IF_FALSE(AwaitingSyncReply(), "not in wait loop");
return (!Connected() || 0 != mRecvd.type());
}
void
AsyncChannel::Close()
{
AssertWorkerThread();
{
// n.b.: We increase the ref count of monitor temporarily
// for the duration of this block. Otherwise, the
// function NotifyMaybeChannelError() will call
// ::Clear() which can free the monitor.
nsRefPtr<RefCountedMonitor> monitor(mMonitor);
MonitorAutoLock lock(*monitor);
if (ChannelError == mChannelState ||
ChannelTimeout == mChannelState) {
// See bug 538586: if the listener gets deleted while the
// IO thread's NotifyChannelError event is still enqueued
// and subsequently deletes us, then the error event will
// also be deleted and the listener will never be notified
// of the channel error.
if (mListener) {
MonitorAutoUnlock unlock(*monitor);
NotifyMaybeChannelError();
}
return;
}
if (ChannelConnected != mChannelState)
// XXX be strict about this until there's a compelling reason
// to relax
NS_RUNTIMEABORT("Close() called on closed channel!");
AssertWorkerThread();
// notify the other side that we're about to close our socket
SendSpecialMessage(new GoodbyeMessage());
SynchronouslyClose();
}
NotifyChannelClosed();
}
void
AsyncChannel::CloseWithError()
{
AssertWorkerThread();
MonitorAutoLock lock(*mMonitor);
if (ChannelConnected != mChannelState) {
return;
}
SynchronouslyClose();
mChannelState = ChannelError;
PostErrorNotifyTask();
}
bool
RPCChannel::OnMaybeDequeueOne()
{
// XXX performance tuning knob: could process all or k pending
// messages here
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
Message recvd;
{
MonitorAutoLock lock(*mMonitor);
if (!Connected()) {
ReportConnectionError("RPCChannel");
return false;
}
if (!mDeferred.empty())
MaybeUndeferIncall();
MessageQueue *queue = mUrgent.empty()
? mNonUrgentDeferred.empty()
? &mPending
: &mNonUrgentDeferred
: &mUrgent;
if (queue->empty())
return false;
recvd = queue->front();
queue->pop_front();
}
if (IsOnCxxStack() && recvd.is_rpc() && recvd.is_reply()) {
// We probably just received a reply in a nested loop for an
// RPC call sent before entering that loop.
mOutOfTurnReplies[recvd.seqno()] = recvd;
return false;
}
CxxStackFrame f(*this, IN_MESSAGE, &recvd);
if (recvd.is_rpc())
Incall(recvd, 0);
else if (recvd.is_sync())
SyncChannel::OnDispatchMessage(recvd);
else
AsyncChannel::OnDispatchMessage(recvd);
return true;
}
bool
RPCChannel::EventOccurred() const
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
RPC_ASSERT(StackDepth() > 0, "not in wait loop");
return (!Connected() ||
!mPending.empty() ||
!mUrgent.empty() ||
(!mOutOfTurnReplies.empty() &&
mOutOfTurnReplies.find(mStack.top().seqno())
!= mOutOfTurnReplies.end()));
}
void
AsyncChannel::OnDispatchMessage(const Message& msg)
{
AssertWorkerThread();
NS_ASSERTION(!msg.is_reply(), "can't process replies here");
NS_ASSERTION(!(msg.is_sync() || msg.is_rpc()), "async dispatch only");
if (MSG_ROUTING_NONE == msg.routing_id()) {
if (!OnSpecialMessage(msg.type(), msg))
// XXX real error handling
NS_RUNTIMEABORT("unhandled special message!");
return;
}
// it's OK to dispatch messages if the channel is closed/error'd,
// since we don't have a reply to send back
(void)MaybeHandleError(mListener->OnMessageReceived(msg), "AsyncChannel");
}
void
RPCChannel::EnqueuePendingMessages()
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
MaybeUndeferIncall();
for (size_t i = 0; i < mDeferred.size(); ++i) {
mWorkerLoop->PostTask(FROM_HERE, new DequeueTask(mDequeueOneTask));
}
// XXX performance tuning knob: could process all or k pending
// messages here, rather than enqueuing for later processing
size_t total = mPending.size() + mUrgent.size() + mNonUrgentDeferred.size();
for (size_t i = 0; i < total; ++i) {
mWorkerLoop->PostTask(FROM_HERE, new DequeueTask(mDequeueOneTask));
}
}
bool
AsyncChannel::Echo(Message* _msg)
{
nsAutoPtr<Message> msg(_msg);
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
NS_ABORT_IF_FALSE(MSG_ROUTING_NONE != msg->routing_id(), "need a route");
{
MonitorAutoLock lock(*mMonitor);
if (!Connected()) {
ReportConnectionError("AsyncChannel");
return false;
}
mLink->EchoMessage(msg.forget());
}
return true;
}
void
RPCChannel::FlushPendingRPCQueue()
{
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
{
MonitorAutoLock lock(*mMonitor);
if (mDeferred.empty()) {
if (mPending.empty())
return;
const Message& last = mPending.back();
if (!last.is_rpc() || last.is_reply())
return;
}
}
while (OnMaybeDequeueOne());
}
void
AsyncChannel::SendSpecialMessage(Message* msg) const
{
AssertWorkerThread();
mLink->SendMessage(msg);
}
bool
RPCChannel::Call(Message* _msg, Message* reply)
{
RPC_ASSERT(!mPendingReply, "should not be waiting for a reply");
nsAutoPtr<Message> msg(_msg);
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
RPC_ASSERT(!ProcessingSyncMessage() || msg->priority() == IPC::Message::PRIORITY_HIGH,
"violation of sync handler invariant");
RPC_ASSERT(msg->is_rpc(), "can only Call() RPC messages here");
#ifdef OS_WIN
SyncStackFrame frame(this, true);
#endif
Message copy = *msg;
CxxStackFrame f(*this, OUT_MESSAGE, ©);
MonitorAutoLock lock(*mMonitor);
if (!Connected()) {
ReportConnectionError("RPCChannel");
return false;
}
bool urgent = (copy.priority() == IPC::Message::PRIORITY_HIGH);
msg->set_seqno(NextSeqno());
msg->set_rpc_remote_stack_depth_guess(mRemoteStackDepthGuess);
msg->set_rpc_local_stack_depth(1 + StackDepth());
mStack.push(*msg);
mLink->SendMessage(msg.forget());
while (1) {
// if a handler invoked by *Dispatch*() spun a nested event
// loop, and the connection was broken during that loop, we
// might have already processed the OnError event. if so,
// trying another loop iteration will be futile because
// channel state will have been cleared
if (!Connected()) {
ReportConnectionError("RPCChannel");
return false;
}
// now might be the time to process a message deferred because
// of race resolution
MaybeUndeferIncall();
// here we're waiting for something to happen. see long
// comment about the queue in RPCChannel.h
while (!EventOccurred()) {
bool maybeTimedOut = !RPCChannel::WaitForNotify();
if (EventOccurred() ||
// we might have received a "subtly deferred" message
// in a nested loop that it's now time to process
(!maybeTimedOut &&
(!mDeferred.empty() || !mOutOfTurnReplies.empty())))
break;
if (maybeTimedOut && !ShouldContinueFromTimeout())
return false;
}
if (!Connected()) {
ReportConnectionError("RPCChannel");
return false;
}
Message recvd;
MessageMap::iterator it;
if (!mOutOfTurnReplies.empty() &&
((it = mOutOfTurnReplies.find(mStack.top().seqno())) !=
mOutOfTurnReplies.end())) {
recvd = it->second;
mOutOfTurnReplies.erase(it);
}
else if (!mUrgent.empty()) {
recvd = mUrgent.front();
mUrgent.pop_front();
}
else if (!mPending.empty()) {
recvd = mPending.front();
mPending.pop_front();
}
else {
// because of subtleties with nested event loops, it's
// possible that we got here and nothing happened. or, we
// might have a deferred in-call that needs to be
// processed. either way, we won't break the inner while
// loop again until something new happens.
continue;
}
if (!recvd.is_rpc()) {
if (urgent && recvd.priority() != IPC::Message::PRIORITY_HIGH) {
// If we're waiting for an urgent reply, don't process any
// messages yet.
mNonUrgentDeferred.push_back(recvd);
} else if (recvd.is_sync()) {
RPC_ASSERT(mPending.empty(),
"other side should have been blocked");
MonitorAutoUnlock unlock(*mMonitor);
CxxStackFrame f(*this, IN_MESSAGE, &recvd);
SyncChannel::OnDispatchMessage(recvd);
} else {
MonitorAutoUnlock unlock(*mMonitor);
CxxStackFrame f(*this, IN_MESSAGE, &recvd);
AsyncChannel::OnDispatchMessage(recvd);
}
continue;
}
RPC_ASSERT(recvd.is_rpc(), "wtf???");
if (recvd.is_reply()) {
RPC_ASSERT(0 < mStack.size(), "invalid RPC stack");
const Message& outcall = mStack.top();
// in the parent, seqno's increase from 0, and in the
// child, they decrease from 0
if ((!mChild && recvd.seqno() < outcall.seqno()) ||
(mChild && recvd.seqno() > outcall.seqno())) {
mOutOfTurnReplies[recvd.seqno()] = recvd;
continue;
}
// FIXME/cjones: handle error
RPC_ASSERT(
recvd.is_reply_error() ||
(recvd.type() == (outcall.type()+1) &&
recvd.seqno() == outcall.seqno()),
"somebody's misbehavin'", "rpc", true);
// we received a reply to our most recent outstanding
// call. pop this frame and return the reply
mStack.pop();
bool isError = recvd.is_reply_error();
if (!isError) {
*reply = recvd;
}
if (0 == StackDepth()) {
RPC_ASSERT(
mOutOfTurnReplies.empty(),
"still have pending replies with no pending out-calls",
"rpc", true);
}
// finished with this RPC stack frame
return !isError;
}
// in-call. process in a new stack frame.
// "snapshot" the current stack depth while we own the Monitor
size_t stackDepth = StackDepth();
{
MonitorAutoUnlock unlock(*mMonitor);
// someone called in to us from the other side. handle the call
CxxStackFrame f(*this, IN_MESSAGE, &recvd);
Incall(recvd, stackDepth);
// FIXME/cjones: error handling
}
}
return true;
}
size_t
RPCChannel::RemoteViewOfStackDepth(size_t stackDepth) const
{
AssertWorkerThread();
return stackDepth - mOutOfTurnReplies.size();
}
