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gecko/ipc/glue/MessageChannel.cpp

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: sw=4 ts=4 et :
*/
/* 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/. */
#include "mozilla/ipc/MessageChannel.h"
#include "mozilla/ipc/ProtocolUtils.h"
#include "nsDebug.h"
#include "nsTraceRefcnt.h"
using namespace mozilla;
using namespace std;
using mozilla::MonitorAutoLock;
using mozilla::MonitorAutoUnlock;
template<>
struct RunnableMethodTraits<mozilla::ipc::MessageChannel>
{
static void RetainCallee(mozilla::ipc::MessageChannel* obj) { }
static void ReleaseCallee(mozilla::ipc::MessageChannel* obj) { }
};
#define IPC_ASSERT(_cond, ...) \
do { \
if (!(_cond)) \
DebugAbort(__FILE__, __LINE__, #_cond,## __VA_ARGS__); \
} while (0)
namespace mozilla {
namespace ipc {
const int32_t MessageChannel::kNoTimeout = INT32_MIN;
// static
bool MessageChannel::sIsPumpingMessages = false;
MessageChannel::MessageChannel(MessageListener *aListener)
: mListener(aListener->asWeakPtr()),
mChannelState(ChannelClosed),
mSide(UnknownSide),
mLink(nullptr),
mWorkerLoop(nullptr),
mChannelErrorTask(nullptr),
mWorkerLoopID(-1),
mTimeoutMs(kNoTimeout),
mInTimeoutSecondHalf(false),
mNextSeqno(0),
mPendingSyncReplies(0),
mPendingUrgentReplies(0),
mPendingRPCReplies(0),
mCurrentRPCTransaction(0),
mDispatchingSyncMessage(false),
mRemoteStackDepthGuess(false),
mSawInterruptOutMsg(false)
{
MOZ_COUNT_CTOR(ipc::MessageChannel);
#ifdef OS_WIN
mTopFrame = nullptr;
#endif
mDequeueOneTask = new RefCountedTask(NewRunnableMethod(
this,
&MessageChannel::OnMaybeDequeueOne));
#ifdef OS_WIN
mEvent = CreateEvent(nullptr, TRUE, FALSE, nullptr);
NS_ASSERTION(mEvent, "CreateEvent failed! Nothing is going to work!");
#endif
}
MessageChannel::~MessageChannel()
{
MOZ_COUNT_DTOR(ipc::MessageChannel);
IPC_ASSERT(mCxxStackFrames.empty(), "mismatched CxxStackFrame ctor/dtors");
#ifdef OS_WIN
DebugOnly<BOOL> ok = CloseHandle(mEvent);
MOZ_ASSERT(ok);
#endif
}
bool
MessageChannel::Connected() const
{
mMonitor->AssertCurrentThreadOwns();
// The transport layer allows us to send messages before
// receiving the "connected" ack from the remote side.
return (ChannelOpening == mChannelState || ChannelConnected == mChannelState);
}
void
MessageChannel::Clear()
{
// Don't clear mWorkerLoopID; we use it in AssertLinkThread() and
// AssertWorkerThread().
//
// Also don't clear mListener. If we clear it, then sending a message
// through this channel after it's Clear()'ed can cause this process to
// crash.
//
// In practice, mListener owns the channel, so the channel gets deleted
// before mListener. But just to be safe, mListener is a weak pointer.
mDequeueOneTask->Cancel();
mWorkerLoop = nullptr;
delete mLink;
mLink = nullptr;
if (mChannelErrorTask) {
mChannelErrorTask->Cancel();
mChannelErrorTask = nullptr;
}
}
bool
MessageChannel::Open(Transport* aTransport, MessageLoop* aIOLoop, Side aSide)
{
NS_PRECONDITION(!mLink, "Open() called > once");
mMonitor = new RefCountedMonitor();
mWorkerLoop = MessageLoop::current();
mWorkerLoopID = mWorkerLoop->id();
ProcessLink *link = new ProcessLink(this);
link->Open(aTransport, aIOLoop, aSide); // :TODO: n.b.: sets mChild
mLink = link;
return true;
}
bool
MessageChannel::Open(MessageChannel *aTargetChan, MessageLoop *aTargetLoop, Side aSide)
{
// Opens a connection to another thread in the same process.
// This handshake proceeds as follows:
// - Let A be the thread initiating the process (either child or parent)
// and B be the other thread.
// - A spawns thread for B, obtaining B's message loop
// - A creates ProtocolChild and ProtocolParent instances.
// Let PA be the one appropriate to A and PB the side for B.
// - A invokes PA->Open(PB, ...):
// - set state to mChannelOpening
// - this will place a work item in B's worker loop (see next bullet)
// and then spins until PB->mChannelState becomes mChannelConnected
// - meanwhile, on PB's worker loop, the work item is removed and:
// - invokes PB->SlaveOpen(PA, ...):
// - sets its state and that of PA to Connected
NS_PRECONDITION(aTargetChan, "Need a target channel");
NS_PRECONDITION(ChannelClosed == mChannelState, "Not currently closed");
CommonThreadOpenInit(aTargetChan, aSide);
Side oppSide = UnknownSide;
switch(aSide) {
case ChildSide: oppSide = ParentSide; break;
case ParentSide: oppSide = ChildSide; break;
case UnknownSide: break;
}
mMonitor = new RefCountedMonitor();
MonitorAutoLock lock(*mMonitor);
mChannelState = ChannelOpening;
aTargetLoop->PostTask(
FROM_HERE,
NewRunnableMethod(aTargetChan, &MessageChannel::OnOpenAsSlave, this, oppSide));
while (ChannelOpening == mChannelState)
mMonitor->Wait();
NS_ASSERTION(ChannelConnected == mChannelState, "not connected when awoken");
return (ChannelConnected == mChannelState);
}
void
MessageChannel::OnOpenAsSlave(MessageChannel *aTargetChan, Side aSide)
{
// Invoked when the other side has begun the open.
NS_PRECONDITION(ChannelClosed == mChannelState,
"Not currently closed");
NS_PRECONDITION(ChannelOpening == aTargetChan->mChannelState,
"Target channel not in the process of opening");
CommonThreadOpenInit(aTargetChan, aSide);
mMonitor = aTargetChan->mMonitor;
MonitorAutoLock lock(*mMonitor);
NS_ASSERTION(ChannelOpening == aTargetChan->mChannelState,
"Target channel not in the process of opening");
mChannelState = ChannelConnected;
aTargetChan->mChannelState = ChannelConnected;
aTargetChan->mMonitor->Notify();
}
void
MessageChannel::CommonThreadOpenInit(MessageChannel *aTargetChan, Side aSide)
{
mWorkerLoop = MessageLoop::current();
mWorkerLoopID = mWorkerLoop->id();
mLink = new ThreadLink(this, aTargetChan);
mSide = aSide;
}
bool
MessageChannel::Echo(Message* aMsg)
{
nsAutoPtr<Message> msg(aMsg);
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
IPC_ASSERT(MSG_ROUTING_NONE != msg->routing_id(), "need a route");
MonitorAutoLock lock(*mMonitor);
if (!Connected()) {
ReportConnectionError("MessageChannel");
return false;
}
mLink->EchoMessage(msg.forget());
return true;
}
bool
MessageChannel::Send(Message* aMsg)
{
Message copy = *aMsg;
CxxStackFrame frame(*this, OUT_MESSAGE, &copy);
nsAutoPtr<Message> msg(aMsg);
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
IPC_ASSERT(MSG_ROUTING_NONE != msg->routing_id(), "need a route");
MonitorAutoLock lock(*mMonitor);
if (!Connected()) {
ReportConnectionError("MessageChannel");
return false;
}
mLink->SendMessage(msg.forget());
return true;
}
bool
MessageChannel::MaybeInterceptSpecialIOMessage(const Message& aMsg)
{
AssertLinkThread();
mMonitor->AssertCurrentThreadOwns();
if (MSG_ROUTING_NONE == aMsg.routing_id() &&
GOODBYE_MESSAGE_TYPE == aMsg.type())
{
// :TODO: Sort out Close() on this side racing with Close() on the
// other side
mChannelState = ChannelClosing;
printf("NOTE: %s process received `Goodbye', closing down\n",
(mSide == ChildSide) ? "child" : "parent");
return true;
}
return false;
}
void
MessageChannel::OnMessageReceivedFromLink(const Message& aMsg)
{
AssertLinkThread();
mMonitor->AssertCurrentThreadOwns();
if (MaybeInterceptSpecialIOMessage(aMsg))
return;
// Regardless of the Interrupt stack, if we're awaiting a sync or urgent reply,
// we know that it needs to be immediately handled to unblock us.
if ((AwaitingSyncReply() && aMsg.is_sync()) ||
(AwaitingUrgentReply() && aMsg.is_urgent()) ||
(AwaitingRPCReply() && aMsg.is_rpc()))
{
mRecvd = new Message(aMsg);
NotifyWorkerThread();
return;
}
// Urgent messages cannot be compressed.
MOZ_ASSERT(!aMsg.compress() || !aMsg.is_urgent());
bool compress = (aMsg.compress() && !mPending.empty() &&
mPending.back().type() == aMsg.type() &&
mPending.back().routing_id() == aMsg.routing_id());
if (compress) {
// This message type has compression enabled, and the back of the
// queue was the same message type and routed to the same destination.
// Replace it with the newer message.
MOZ_ASSERT(mPending.back().compress());
mPending.pop_back();
}
bool shouldWakeUp = AwaitingInterruptReply() ||
// Allow incoming RPCs to be processed inside an urgent message.
(AwaitingUrgentReply() && aMsg.is_rpc()) ||
// Always process urgent messages while blocked.
((AwaitingSyncReply() || AwaitingRPCReply()) && aMsg.is_urgent());
// There are four cases we're concerned about, relating to the state of the
// main thread:
//
// (1) We are waiting on a sync|rpc reply - main thread is blocked on the
// IPC monitor.
// - If the message is high priority, we wake up the main thread to
// deliver the message. Otherwise, we leave it in the mPending queue,
// posting a task to the main event loop, where it will be processed
// once the synchronous reply has been received.
//
// (2) We are waiting on an Interrupt reply - main thread is blocked on the
// IPC monitor.
// - Always notify and wake up the main thread.
//
// (3) We are not waiting on a reply.
// - We post a task to the main event loop.
//
// Note that, we may notify the main thread even though the monitor is not
// blocked. This is okay, since we always check for pending events before
// blocking again.
if (shouldWakeUp && (AwaitingUrgentReply() && aMsg.is_rpc())) {
// If we're receiving an RPC message while blocked on an urgent message,
// we must defer any messages that were not sent as part of the child
// answering the urgent message.
//
// We must also be sure that we will not accidentally defer any RPC
// message that was sent while answering an urgent message. Otherwise,
// we will deadlock.
//
// On the parent side, the current transaction can only transition from 0
// to an ID, either by us issuing an urgent request while not blocked, or
// by receiving an RPC request while not blocked. When we unblock, the
// current transaction is reset to 0.
//
// When the child side receives an urgent message, any RPC messages sent
// before issuing the urgent reply will carry the urgent message's
// transaction ID.
//
// Since AwaitingUrgentReply() implies we are blocked, it also implies
// that we are within a transaction that will not change until we are
// completely unblocked (i.e, the transaction has completed).
if (aMsg.transaction_id() != mCurrentRPCTransaction)
shouldWakeUp = false;
}
if (aMsg.is_urgent()) {
MOZ_ASSERT(!mPendingUrgentRequest);
mPendingUrgentRequest = new Message(aMsg);
} else if (aMsg.is_rpc() && shouldWakeUp) {
// Only use this slot if we need to wake up for an RPC call. Otherwise
// we treat it like a normal async or sync message.
MOZ_ASSERT(!mPendingRPCCall);
mPendingRPCCall = new Message(aMsg);
} else {
mPending.push_back(aMsg);
}
if (shouldWakeUp) {
// Always wake up Interrupt waiters, sync waiters for urgent messages,
// RPC waiters for urgent messages, and urgent waiters for RPCs in the
// same transaction.
NotifyWorkerThread();
} else {
// Worker thread is either not blocked on a reply, or this is an
// incoming Interrupt that raced with outgoing sync, and needs to be
// deferred to a later event-loop iteration.
if (!compress) {
// If we compressed away the previous message, we'll re-use
// its pending task.
mWorkerLoop->PostTask(FROM_HERE, new DequeueTask(mDequeueOneTask));
}
}
}
bool
MessageChannel::Send(Message* aMsg, Message* aReply)
{
// Sanity checks.
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
#ifdef OS_WIN
SyncStackFrame frame(this, false);
#endif
Message copy = *aMsg;
CxxStackFrame f(*this, OUT_MESSAGE, &copy);
MonitorAutoLock lock(*mMonitor);
IPC_ASSERT(aMsg->is_sync(), "can only Send() sync messages here");
IPC_ASSERT(!DispatchingSyncMessage(), "violation of sync handler invariant");
IPC_ASSERT(!AwaitingSyncReply(), "nested sync messages are not supported");
AutoEnterPendingReply replies(mPendingSyncReplies);
if (!SendAndWait(aMsg, aReply))
return false;
NS_ABORT_IF_FALSE(aReply->is_sync(), "reply is not sync");
return true;
}
bool
MessageChannel::UrgentCall(Message* aMsg, Message* aReply)
{
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
IPC_ASSERT(mSide == ParentSide, "cannot send urgent requests from child");
#ifdef OS_WIN
SyncStackFrame frame(this, false);
#endif
Message copy = *aMsg;
CxxStackFrame f(*this, OUT_MESSAGE, &copy);
MonitorAutoLock lock(*mMonitor);
IPC_ASSERT(!AwaitingInterruptReply(), "urgent calls cannot be issued within Interrupt calls");
IPC_ASSERT(!AwaitingSyncReply(), "urgent calls cannot be issued within sync sends");
AutoEnterRPCTransaction transact(this);
aMsg->set_transaction_id(mCurrentRPCTransaction);
AutoEnterPendingReply replies(mPendingUrgentReplies);
if (!SendAndWait(aMsg, aReply))
return false;
NS_ABORT_IF_FALSE(aReply->is_urgent(), "reply is not urgent");
return true;
}
bool
MessageChannel::RPCCall(Message* aMsg, Message* aReply)
{
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
IPC_ASSERT(mSide == ChildSide, "cannot send rpc messages from parent");
#ifdef OS_WIN
SyncStackFrame frame(this, false);
#endif
Message copy = *aMsg;
CxxStackFrame f(*this, OUT_MESSAGE, &copy);
MonitorAutoLock lock(*mMonitor);
// RPC calls must be the only thing on the stack.
IPC_ASSERT(!AwaitingInterruptReply(), "rpc calls cannot be issued within interrupts");
AutoEnterRPCTransaction transact(this);
aMsg->set_transaction_id(mCurrentRPCTransaction);
AutoEnterPendingReply replies(mPendingRPCReplies);
if (!SendAndWait(aMsg, aReply))
return false;
NS_ABORT_IF_FALSE(aReply->is_rpc(), "expected rpc reply");
return true;
}
bool
MessageChannel::SendAndWait(Message* aMsg, Message* aReply)
{
mMonitor->AssertCurrentThreadOwns();
nsAutoPtr<Message> msg(aMsg);
if (!Connected()) {
ReportConnectionError("MessageChannel::SendAndWait");
return false;
}
msg->set_seqno(NextSeqno());
DebugOnly<int32_t> replySeqno = msg->seqno();
DebugOnly<msgid_t> replyType = msg->type() + 1;
mLink->SendMessage(msg.forget());
while (true) {
// Wait for an event to occur.
while (true) {
if (mRecvd || mPendingUrgentRequest || mPendingRPCCall)
break;
bool maybeTimedOut = !WaitForSyncNotify();
if (!Connected()) {
ReportConnectionError("MessageChannel::SendAndWait");
return false;
}
if (maybeTimedOut && !ShouldContinueFromTimeout())
return false;
}
if (mPendingUrgentRequest && !ProcessPendingUrgentRequest())
return false;
if (mPendingRPCCall && !ProcessPendingRPCCall())
return false;
if (mRecvd) {
NS_ABORT_IF_FALSE(mRecvd->is_reply(), "expected reply");
if (mRecvd->is_reply_error()) {
mRecvd = nullptr;
return false;
}
NS_ABORT_IF_FALSE(mRecvd->type() == replyType, "wrong reply type");
NS_ABORT_IF_FALSE(mRecvd->seqno() == replySeqno, "wrong sequence number");
*aReply = *mRecvd;
mRecvd = nullptr;
return true;
}
}
return true;
}
bool
MessageChannel::Call(Message* aMsg, Message* aReply)
{
if (aMsg->is_urgent())
return UrgentCall(aMsg, aReply);
if (aMsg->is_rpc())
return RPCCall(aMsg, aReply);
return InterruptCall(aMsg, aReply);
}
bool
MessageChannel::InterruptCall(Message* aMsg, Message* aReply)
{
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
#ifdef OS_WIN
SyncStackFrame frame(this, true);
#endif
// This must come before MonitorAutoLock, as its destructor acquires the
// monitor lock.
Message copy = *aMsg;
CxxStackFrame cxxframe(*this, OUT_MESSAGE, &copy);
MonitorAutoLock lock(*mMonitor);
if (!Connected()) {
ReportConnectionError("MessageChannel::Call");
return false;
}
// Sanity checks.
IPC_ASSERT(!AwaitingSyncReply() && !AwaitingUrgentReply(),
"cannot issue Interrupt call whiel blocked on sync or urgent");
IPC_ASSERT(!DispatchingSyncMessage() || aMsg->priority() == IPC::Message::PRIORITY_HIGH,
"violation of sync handler invariant");
IPC_ASSERT(aMsg->is_interrupt(), "can only Call() Interrupt messages here");
nsAutoPtr<Message> msg(aMsg);
msg->set_seqno(NextSeqno());
msg->set_interrupt_remote_stack_depth_guess(mRemoteStackDepthGuess);
msg->set_interrupt_local_stack_depth(1 + InterruptStackDepth());
mInterruptStack.push(*msg);
mLink->SendMessage(msg.forget());
while (true) {
// 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("MessageChannel::InterruptCall");
return false;
}
// Now might be the time to process a message deferred because of race
// resolution.
MaybeUndeferIncall();
// Wait for an event to occur.
while (!InterruptEventOccurred()) {
bool maybeTimedOut = !WaitForInterruptNotify();
// We might have received a "subtly deferred" message in a nested
// loop that it's now time to process.
if (InterruptEventOccurred() ||
(!maybeTimedOut && (!mDeferred.empty() || !mOutOfTurnReplies.empty())))
{
break;
}
if (maybeTimedOut && !ShouldContinueFromTimeout())
return false;
}
Message recvd;
MessageMap::iterator it;
if (mPendingUrgentRequest) {
recvd = *mPendingUrgentRequest;
mPendingUrgentRequest = nullptr;
} else if (mPendingRPCCall) {
recvd = *mPendingRPCCall;
mPendingRPCCall = nullptr;
} else if ((it = mOutOfTurnReplies.find(mInterruptStack.top().seqno()))
!= mOutOfTurnReplies.end())
{
recvd = it->second;
mOutOfTurnReplies.erase(it);
} 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 the message is not Interrupt, we can dispatch it as normal.
if (!recvd.is_interrupt()) {
// Other side should be blocked.
IPC_ASSERT(!recvd.is_sync() || mPending.empty(), "other side should be blocked");
{
AutoEnterRPCTransaction transaction(this, &recvd);
MonitorAutoUnlock unlock(*mMonitor);
CxxStackFrame frame(*this, IN_MESSAGE, &recvd);
DispatchMessage(recvd);
}
if (!Connected()) {
ReportConnectionError("MessageChannel::DispatchMessage");
return false;
}
continue;
}
// If the message is an Interrupt reply, either process it as a reply to our
// call, or add it to the list of out-of-turn replies we've received.
if (recvd.is_reply()) {
IPC_ASSERT(!mInterruptStack.empty(), "invalid Interrupt stack");
// If this is not a reply the call we've initiated, add it to our
// out-of-turn replies and keep polling for events.
{
const Message &outcall = mInterruptStack.top();
// Note, In the parent, sequence numbers increase from 0, and
// in the child, they decrease from 0.
if ((mSide == ChildSide && recvd.seqno() > outcall.seqno()) ||
(mSide != ChildSide && recvd.seqno() < outcall.seqno()))
{
mOutOfTurnReplies[recvd.seqno()] = recvd;
continue;
}
IPC_ASSERT(recvd.is_reply_error() ||
(recvd.type() == (outcall.type() + 1) &&
recvd.seqno() == outcall.seqno()),
"somebody's misbehavin'", true);
}
// We received a reply to our most recent outstanding call. Pop
// this frame and return the reply.
mInterruptStack.pop();
if (!recvd.is_reply_error()) {
*aReply = recvd;
}
// If we have no more pending out calls waiting on replies, then
// the reply queue should be empty.
IPC_ASSERT(!mInterruptStack.empty() || mOutOfTurnReplies.empty(),
"still have pending replies with no pending out-calls",
true);
return !recvd.is_reply_error();
}
// Dispatch an Interrupt in-call. Snapshot the current stack depth while we
// own the monitor.
size_t stackDepth = InterruptStackDepth();
{
MonitorAutoUnlock unlock(*mMonitor);
CxxStackFrame frame(*this, IN_MESSAGE, &recvd);
DispatchInterruptMessage(recvd, stackDepth);
}
if (!Connected()) {
ReportConnectionError("MessageChannel::DispatchInterruptMessage");
return false;
}
}
return true;
}
bool
MessageChannel::InterruptEventOccurred()
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
IPC_ASSERT(InterruptStackDepth() > 0, "not in wait loop");
return (!Connected() ||
!mPending.empty() ||
mPendingUrgentRequest ||
mPendingRPCCall ||
(!mOutOfTurnReplies.empty() &&
mOutOfTurnReplies.find(mInterruptStack.top().seqno()) !=
mOutOfTurnReplies.end()));
}
bool
MessageChannel::ProcessPendingUrgentRequest()
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
// Note that it is possible we could have sent a sync message at
// the same time the parent process sent an urgent message, and
// therefore mPendingUrgentRequest is set *and* mRecvd is set as
// well, because the link thread received both before the worker
// thread woke up.
//
// In this case, we process the urgent message first, but we need
// to save the reply.
nsAutoPtr<Message> savedReply(mRecvd.forget());
// We're the child process. We should not be receiving RPC calls.
IPC_ASSERT(!mPendingRPCCall, "unexpected RPC call");
nsAutoPtr<Message> recvd(mPendingUrgentRequest.forget());
{
// In order to send the parent RPC messages and guarantee it will
// wake up, we must re-use its transaction.
AutoEnterRPCTransaction transaction(this, recvd);
MonitorAutoUnlock unlock(*mMonitor);
DispatchUrgentMessage(*recvd);
}
if (!Connected()) {
ReportConnectionError("MessageChannel::DispatchUrgentMessage");
return false;
}
// In between having dispatched our reply to the parent process, and
// re-acquiring the monitor, the parent process could have already
// processed that reply and sent the reply to our sync message. If so,
// our saved reply should be empty.
IPC_ASSERT(!mRecvd || !savedReply, "unknown reply");
if (!mRecvd)
mRecvd = savedReply.forget();
return true;
}
bool
MessageChannel::ProcessPendingRPCCall()
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
// See comment above re: mRecvd replies and incoming calls.
nsAutoPtr<Message> savedReply(mRecvd.forget());
IPC_ASSERT(!mPendingUrgentRequest, "unexpected urgent message");
nsAutoPtr<Message> recvd(mPendingRPCCall.forget());
{
// If we are not currently in a transaction, this will begin one,
// and the link thread will not wake us up for any RPC messages not
// apart of this transaction. If we are already in a transaction,
// then this will assert that we're still in the same transaction.
AutoEnterRPCTransaction transaction(this, recvd);
MonitorAutoUnlock unlock(*mMonitor);
DispatchRPCMessage(*recvd);
}
if (!Connected()) {
ReportConnectionError("MessageChannel::DispatchRPCMessage");
return false;
}
// In between having dispatched our reply to the parent process, and
// re-acquiring the monitor, the parent process could have already
// processed that reply and sent the reply to our sync message. If so,
// our saved reply should be empty.
IPC_ASSERT(!mRecvd || !savedReply, "unknown reply");
if (!mRecvd)
mRecvd = savedReply.forget();
return true;
}
bool
MessageChannel::DequeueOne(Message *recvd)
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
if (!Connected()) {
ReportConnectionError("OnMaybeDequeueOne");
return false;
}
if (mPendingUrgentRequest) {
*recvd = *mPendingUrgentRequest;
mPendingUrgentRequest = nullptr;
return true;
}
if (mPendingRPCCall) {
*recvd = *mPendingRPCCall;
mPendingRPCCall = nullptr;
return true;
}
if (!mDeferred.empty())
MaybeUndeferIncall();
if (mPending.empty())
return false;
*recvd = mPending.front();
mPending.pop_front();
return true;
}
bool
MessageChannel::OnMaybeDequeueOne()
{
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
Message recvd;
MonitorAutoLock lock(*mMonitor);
if (!DequeueOne(&recvd))
return false;
if (IsOnCxxStack() && recvd.is_interrupt() && recvd.is_reply()) {
// We probably just received a reply in a nested loop for an
// Interrupt call sent before entering that loop.
mOutOfTurnReplies[recvd.seqno()] = recvd;
return false;
}
{
// We should not be in a transaction yet if we're not blocked.
MOZ_ASSERT(mCurrentRPCTransaction == 0);
AutoEnterRPCTransaction transaction(this, &recvd);
MonitorAutoUnlock unlock(*mMonitor);
CxxStackFrame frame(*this, IN_MESSAGE, &recvd);
DispatchMessage(recvd);
}
return true;
}
void
MessageChannel::DispatchMessage(const Message &aMsg)
{
if (aMsg.is_sync())
DispatchSyncMessage(aMsg);
else if (aMsg.is_urgent())
DispatchUrgentMessage(aMsg);
else if (aMsg.is_interrupt())
DispatchInterruptMessage(aMsg, 0);
else if (aMsg.is_rpc())
DispatchRPCMessage(aMsg);
else
DispatchAsyncMessage(aMsg);
}
void
MessageChannel::DispatchSyncMessage(const Message& aMsg)
{
AssertWorkerThread();
Message *reply = nullptr;
mDispatchingSyncMessage = true;
Result rv = mListener->OnMessageReceived(aMsg, reply);
mDispatchingSyncMessage = false;
if (!MaybeHandleError(rv, "DispatchSyncMessage")) {
delete reply;
reply = new Message();
reply->set_sync();
reply->set_reply();
reply->set_reply_error();
}
reply->set_seqno(aMsg.seqno());
MonitorAutoLock lock(*mMonitor);
if (ChannelConnected == mChannelState)
mLink->SendMessage(reply);
}
void
MessageChannel::DispatchUrgentMessage(const Message& aMsg)
{
AssertWorkerThread();
MOZ_ASSERT(aMsg.is_urgent());
Message *reply = nullptr;
if (!MaybeHandleError(mListener->OnCallReceived(aMsg, reply), "DispatchUrgentMessage")) {
delete reply;
reply = new Message();
reply->set_urgent();
reply->set_reply();
reply->set_reply_error();
}
reply->set_seqno(aMsg.seqno());
MonitorAutoLock lock(*mMonitor);
if (ChannelConnected == mChannelState)
mLink->SendMessage(reply);
}
void
MessageChannel::DispatchRPCMessage(const Message& aMsg)
{
AssertWorkerThread();
MOZ_ASSERT(aMsg.is_rpc());
Message *reply = nullptr;
if (!MaybeHandleError(mListener->OnCallReceived(aMsg, reply), "DispatchRPCMessage")) {
delete reply;
reply = new Message();
reply->set_rpc();
reply->set_reply();
reply->set_reply_error();
}
reply->set_seqno(aMsg.seqno());
MonitorAutoLock lock(*mMonitor);
if (ChannelConnected == mChannelState)
mLink->SendMessage(reply);
}
void
MessageChannel::DispatchAsyncMessage(const Message& aMsg)
{
AssertWorkerThread();
MOZ_ASSERT(!aMsg.is_interrupt() && !aMsg.is_sync() && !aMsg.is_urgent());
if (aMsg.routing_id() == MSG_ROUTING_NONE) {
NS_RUNTIMEABORT("unhandled special message!");
}
MaybeHandleError(mListener->OnMessageReceived(aMsg), "DispatchAsyncMessage");
}
void
MessageChannel::DispatchInterruptMessage(const Message& aMsg, size_t stackDepth)
{
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
IPC_ASSERT(aMsg.is_interrupt() && !aMsg.is_reply(), "wrong message type");
// Race detection: see the long comment near mRemoteStackDepthGuess in
// MessageChannel.h. "Remote" stack depth means our side, and "local" means
// the other side.
if (aMsg.interrupt_remote_stack_depth_guess() != RemoteViewOfStackDepth(stackDepth)) {
// Interrupt 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 (mListener->MediateInterruptRace((mSide == ChildSide) ? aMsg : mInterruptStack.top(),
(mSide != ChildSide) ? mInterruptStack.top() : aMsg))
{
case RIPChildWins:
winner = "child";
defer = (mSide == ChildSide);
break;
case RIPParentWins:
winner = "parent";
defer = (mSide != ChildSide);
break;
case RIPError:
NS_RUNTIMEABORT("NYI: 'Error' Interrupt race policy");
return;
default:
NS_RUNTIMEABORT("not reached");
return;
}
if (LoggingEnabled()) {
printf_stderr(" (%s: %s won, so we're%sdeferring)\n",
(mSide == ChildSide) ? "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(aMsg);
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
Message* reply = nullptr;
++mRemoteStackDepthGuess;
Result rv = mListener->OnCallReceived(aMsg, reply);
--mRemoteStackDepthGuess;
if (!MaybeHandleError(rv, "DispatchInterruptMessage")) {
delete reply;
reply = new Message();
reply->set_interrupt();
reply->set_reply();
reply->set_reply_error();
}
reply->set_seqno(aMsg.seqno());
MonitorAutoLock lock(*mMonitor);
if (ChannelConnected == mChannelState)
mLink->SendMessage(reply);
}
void
MessageChannel::MaybeUndeferIncall()
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
if (mDeferred.empty())
return;
size_t stackDepth = InterruptStackDepth();
// the other side can only *under*-estimate our actual stack depth
IPC_ASSERT(mDeferred.top().interrupt_remote_stack_depth_guess() <= stackDepth,
"fatal logic error");
if (mDeferred.top().interrupt_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
IPC_ASSERT(0 < mRemoteStackDepthGuess, "fatal logic error");
--mRemoteStackDepthGuess;
mPending.push_back(call);
}
void
MessageChannel::FlushPendingInterruptQueue()
{
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
{
MonitorAutoLock lock(*mMonitor);
if (mDeferred.empty()) {
if (mPending.empty())
return;
const Message& last = mPending.back();
if (!last.is_interrupt() || last.is_reply())
return;
}
}
while (OnMaybeDequeueOne());
}
void
MessageChannel::ExitedCxxStack()
{
mListener->OnExitedCxxStack();
if (mSawInterruptOutMsg) {
MonitorAutoLock lock(*mMonitor);
// see long comment in OnMaybeDequeueOne()
EnqueuePendingMessages();
mSawInterruptOutMsg = false;
}
}
void
MessageChannel::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
for (size_t i = 0; i < mPending.size(); ++i) {
mWorkerLoop->PostTask(FROM_HERE, new DequeueTask(mDequeueOneTask));
}
}
static inline bool
IsTimeoutExpired(PRIntervalTime aStart, PRIntervalTime aTimeout)
{
return (aTimeout != PR_INTERVAL_NO_TIMEOUT) &&
(aTimeout <= (PR_IntervalNow() - aStart));
}
bool
MessageChannel::WaitResponse(bool aWaitTimedOut)
{
if (aWaitTimedOut) {
if (mInTimeoutSecondHalf) {
// We've really timed out this time.
return false;
}
// Try a second time.
mInTimeoutSecondHalf = true;
} else {
mInTimeoutSecondHalf = false;
}
return true;
}
#ifndef OS_WIN
bool
MessageChannel::WaitForSyncNotify()
{
PRIntervalTime timeout = (kNoTimeout == mTimeoutMs) ?
PR_INTERVAL_NO_TIMEOUT :
PR_MillisecondsToInterval(mTimeoutMs);
// XXX could optimize away this syscall for "no timeout" case if desired
PRIntervalTime waitStart = PR_IntervalNow();
mMonitor->Wait(timeout);
// If the timeout didn't expire, we know we received an event. The
// converse is not true.
return WaitResponse(IsTimeoutExpired(waitStart, timeout));
}
bool
MessageChannel::WaitForInterruptNotify()
{
return WaitForSyncNotify();
}
void
MessageChannel::NotifyWorkerThread()
{
mMonitor->Notify();
}
#endif
bool
MessageChannel::ShouldContinueFromTimeout()
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
bool cont;
{
MonitorAutoUnlock unlock(*mMonitor);
cont = mListener->OnReplyTimeout();
}
static enum { UNKNOWN, NOT_DEBUGGING, DEBUGGING } sDebuggingChildren = UNKNOWN;
if (sDebuggingChildren == UNKNOWN) {
sDebuggingChildren = getenv("MOZ_DEBUG_CHILD_PROCESS") ? DEBUGGING : NOT_DEBUGGING;
}
if (sDebuggingChildren == DEBUGGING) {
return true;
}
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 interrupt messages to the child,
// and in that case arriving async messages are enqueued to the interrupt
// channel's special queue. They're then ignored because the channel
// state changes to ChannelTimeout (i.e. !Connected).
SynchronouslyClose();
mChannelState = ChannelTimeout;
}
return cont;
}
void
MessageChannel::SetReplyTimeoutMs(int32_t aTimeoutMs)
{
// Set channel timeout value. Since this is broken up into
// two period, the minimum timeout value is 2ms.
AssertWorkerThread();
mTimeoutMs = (aTimeoutMs <= 0)
? kNoTimeout
: (int32_t)ceil((double)aTimeoutMs / 2.0);
}
void
MessageChannel::OnChannelConnected(int32_t peer_id)
{
mWorkerLoop->PostTask(
FROM_HERE,
NewRunnableMethod(this,
&MessageChannel::DispatchOnChannelConnected,
peer_id));
}
void
MessageChannel::DispatchOnChannelConnected(int32_t peer_pid)
{
AssertWorkerThread();
if (mListener)
mListener->OnChannelConnected(peer_pid);
}
static void
PrintErrorMessage(Side side, const char* channelName, const char* msg)
{
const char *from = (side == ChildSide)
? "Child"
: ((side == ParentSide) ? "Parent" : "Unknown");
printf_stderr("\n###!!! [%s][%s] Error: %s\n\n", from, channelName, msg);
}
void
MessageChannel::ReportConnectionError(const char* aChannelName) const
{
const char* errorMsg = nullptr;
switch (mChannelState) {
case ChannelClosed:
errorMsg = "Closed channel: cannot send/recv";
break;
case ChannelOpening:
errorMsg = "Opening channel: not yet ready for send/recv";
break;
case ChannelTimeout:
errorMsg = "Channel timeout: cannot send/recv";
break;
case ChannelClosing:
errorMsg = "Channel closing: too late to send/recv, messages will be lost";
break;
case ChannelError:
errorMsg = "Channel error: cannot send/recv";
break;
default:
NS_RUNTIMEABORT("unreached");
}
PrintErrorMessage(mSide, aChannelName, errorMsg);
mListener->OnProcessingError(MsgDropped);
}
bool
MessageChannel::MaybeHandleError(Result code, const char* channelName)
{
if (MsgProcessed == code)
return true;
const char* errorMsg = nullptr;
switch (code) {
case MsgNotKnown:
errorMsg = "Unknown message: not processed";
break;
case MsgNotAllowed:
errorMsg = "Message not allowed: cannot be sent/recvd in this state";
break;
case MsgPayloadError:
errorMsg = "Payload error: message could not be deserialized";
break;
case MsgProcessingError:
errorMsg = "Processing error: message was deserialized, but the handler returned false (indicating failure)";
break;
case MsgRouteError:
errorMsg = "Route error: message sent to unknown actor ID";
break;
case MsgValueError:
errorMsg = "Value error: message was deserialized, but contained an illegal value";
break;
default:
NS_RUNTIMEABORT("unknown Result code");
return false;
}
PrintErrorMessage(mSide, channelName, errorMsg);
mListener->OnProcessingError(code);
return false;
}
void
MessageChannel::OnChannelErrorFromLink()
{
AssertLinkThread();
mMonitor->AssertCurrentThreadOwns();
if (InterruptStackDepth() > 0)
NotifyWorkerThread();
if (AwaitingSyncReply() || AwaitingRPCReply() || AwaitingUrgentReply())
NotifyWorkerThread();
if (ChannelClosing != mChannelState) {
mChannelState = ChannelError;
mMonitor->Notify();
}
PostErrorNotifyTask();
}
void
MessageChannel::NotifyMaybeChannelError()
{
mMonitor->AssertNotCurrentThreadOwns();
// TODO sort out Close() on this side racing with Close() on the other side
if (ChannelClosing == mChannelState) {
// the channel closed, but we received a "Goodbye" message warning us
// about it. no worries
mChannelState = ChannelClosed;
NotifyChannelClosed();
return;
}
// Oops, error! Let the listener know about it.
mChannelState = ChannelError;
mListener->OnChannelError();
Clear();
}
void
MessageChannel::OnNotifyMaybeChannelError()
{
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
mChannelErrorTask = nullptr;
// 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 (IsOnCxxStack()) {
mChannelErrorTask =
NewRunnableMethod(this, &MessageChannel::OnNotifyMaybeChannelError);
// 10 ms delay is completely arbitrary
mWorkerLoop->PostDelayedTask(FROM_HERE, mChannelErrorTask, 10);
return;
}
NotifyMaybeChannelError();
}
void
MessageChannel::PostErrorNotifyTask()
{
mMonitor->AssertCurrentThreadOwns();
if (mChannelErrorTask)
return;
// This must be the last code that runs on this thread!
mChannelErrorTask =
NewRunnableMethod(this, &MessageChannel::OnNotifyMaybeChannelError);
mWorkerLoop->PostTask(FROM_HERE, mChannelErrorTask);
}
// Special async message.
class GoodbyeMessage : public IPC::Message
{
public:
GoodbyeMessage() :
IPC::Message(MSG_ROUTING_NONE, GOODBYE_MESSAGE_TYPE, PRIORITY_NORMAL)
{
}
static bool Read(const Message* msg) {
return true;
}
void Log(const std::string& aPrefix, FILE* aOutf) const {
fputs("(special `Goodbye' message)", aOutf);
}
};
void
MessageChannel::SynchronouslyClose()
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
mLink->SendClose();
while (ChannelClosed != mChannelState)
mMonitor->Wait();
}
void
MessageChannel::CloseWithError()
{
AssertWorkerThread();
MonitorAutoLock lock(*mMonitor);
if (ChannelConnected != mChannelState) {
return;
}
SynchronouslyClose();
mChannelState = ChannelError;
PostErrorNotifyTask();
}
void
MessageChannel::Close()
{
AssertWorkerThread();
{
MonitorAutoLock lock(*mMonitor);
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(*mMonitor);
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
mLink->SendMessage(new GoodbyeMessage());
SynchronouslyClose();
}
NotifyChannelClosed();
}
void
MessageChannel::NotifyChannelClosed()
{
mMonitor->AssertNotCurrentThreadOwns();
if (ChannelClosed != mChannelState)
NS_RUNTIMEABORT("channel should have been closed!");
// OK, the IO thread just closed the channel normally. Let the
// listener know about it.
mListener->OnChannelClose();
Clear();
}
void
MessageChannel::DebugAbort(const char* file, int line, const char* cond,
const char* why,
bool reply) const
{
printf_stderr("###!!! [MessageChannel][%s][%s:%d] "
"Assertion (%s) failed. %s %s\n",
mSide == ChildSide ? "Child" : "Parent",
file, line, cond,
why,
reply ? "(reply)" : "");
// technically we need the mutex for this, but we're dying anyway
DumpInterruptStack(" ");
printf_stderr(" remote Interrupt stack guess: %lu\n",
mRemoteStackDepthGuess);
printf_stderr(" deferred stack size: %lu\n",
mDeferred.size());
printf_stderr(" out-of-turn Interrupt replies stack size: %lu\n",
mOutOfTurnReplies.size());
printf_stderr(" Pending queue size: %lu, front to back:\n",
mPending.size());
MessageQueue pending = mPending;
while (!pending.empty()) {
printf_stderr(" [ %s%s ]\n",
pending.front().is_interrupt() ? "intr" :
(pending.front().is_sync() ? "sync" : "async"),
pending.front().is_reply() ? "reply" : "");
pending.pop_front();
}
NS_RUNTIMEABORT(why);
}
void
MessageChannel::DumpInterruptStack(const char* const pfx) const
{
NS_WARN_IF_FALSE(MessageLoop::current() != mWorkerLoop,
"The worker thread had better be paused in a debugger!");
printf_stderr("%sMessageChannel 'backtrace':\n", pfx);
// print a python-style backtrace, first frame to last
for (uint32_t i = 0; i < mCxxStackFrames.size(); ++i) {
int32_t id;
const char* dir, *sems, *name;
mCxxStackFrames[i].Describe(&id, &dir, &sems, &name);
printf_stderr("%s[(%u) %s %s %s(actor=%d) ]\n", pfx,
i, dir, sems, name, id);
}
}
} // ipc
} // mozilla
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