gecko-dev/ipc/glue/MessageChannel.cpp

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C++

/* -*- 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 "mozilla/dom/ScriptSettings.h"
#include "mozilla/Assertions.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/Move.h"
#include "mozilla/SizePrintfMacros.h"
#include "mozilla/Telemetry.h"
#include "nsDebug.h"
#include "nsISupportsImpl.h"
#include "nsContentUtils.h"
#include "prprf.h"
// Undo the damage done by mozzconf.h
#undef compress
/*
* IPC design:
*
* There are three kinds of messages: async, sync, and intr. Sync and intr
* messages are blocking. Only intr and high-priority sync messages can nest.
*
* Terminology: To dispatch a message Foo is to run the RecvFoo code for
* it. This is also called "handling" the message.
*
* Sync and async messages have priorities while intr messages always have
* normal priority. The three possible priorities are normal, high, and urgent.
* The intended uses of these priorities are:
* NORMAL - most messages.
* HIGH - CPOW-related messages, which can go in either direction.
* URGENT - messages where we don't want to dispatch
* incoming CPOWs while waiting for the response.
* Async messages cannot have HIGH priority.
*
* To avoid jank, the parent process is not allowed to send sync messages of
* normal priority. When a process is waiting for a response to a sync message
* M0, it will dispatch an incoming message M if:
* 1. M has a higher priority than M0, or
* 2. if M has the same priority as M0 and we're in the child, or
* 3. if M has the same priority as M0 and it was sent by the other side
* while dispatching M0 (nesting).
* The idea is that higher priority messages should take precendence, and we
* also want to allow nesting. The purpose of rule 2 is to handle a race where
* both processes send to each other simultaneously. In this case, we resolve
* the race in favor of the parent (so the child dispatches first).
*
* Messages satisfy the following properties:
* A. When waiting for a response to a sync message, we won't dispatch any
* messages of lower priority.
* B. Messages of the same priority will be dispatched roughly in the
* order they were sent. The exception is when the parent and child send
* sync messages to each other simulataneously. In this case, the parent's
* message is dispatched first. While it is dispatched, the child may send
* further nested messages, and these messages may be dispatched before the
* child's original message. We can consider ordering to be preserved here
* because we pretend that the child's original message wasn't sent until
* after the parent's message is finished being dispatched.
*
* When waiting for a sync message reply, we dispatch an async message only if
* it has URGENT priority. Normally URGENT async messages are sent only from the
* child. However, the parent can send URGENT async messages when it is creating
* a bridged protocol.
*
* Intr messages are blocking but not prioritized. While waiting for an intr
* response, all incoming messages are dispatched until a response is
* received. Intr messages also can be nested. When two intr messages race with
* each other, a similar scheme is used to ensure that one side wins. The
* winning side is chosen based on the message type.
*
* Intr messages differ from sync messages in that, while sending an intr
* message, we may dispatch an async message. This causes some additional
* complexity. One issue is that replies can be received out of order. It's also
* more difficult to determine whether one message is nested inside
* another. Consequently, intr handling uses mOutOfTurnReplies and
* mRemoteStackDepthGuess, which are not needed for sync messages.
*/
using namespace mozilla;
using namespace std;
using mozilla::dom::AutoNoJSAPI;
using mozilla::dom::ScriptSettingsInitialized;
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)
static MessageChannel* gParentProcessBlocker;
namespace mozilla {
namespace ipc {
const int32_t MessageChannel::kNoTimeout = INT32_MIN;
// static
bool MessageChannel::sIsPumpingMessages = false;
enum Direction
{
IN_MESSAGE,
OUT_MESSAGE
};
class MessageChannel::InterruptFrame
{
private:
enum Semantics
{
INTR_SEMS,
SYNC_SEMS,
ASYNC_SEMS
};
public:
InterruptFrame(Direction direction, const Message* msg)
: mMessageName(strdup(msg->name())),
mMessageRoutingId(msg->routing_id()),
mMesageSemantics(msg->is_interrupt() ? INTR_SEMS :
msg->is_sync() ? SYNC_SEMS :
ASYNC_SEMS),
mDirection(direction),
mMoved(false)
{
MOZ_ASSERT(mMessageName);
}
InterruptFrame(InterruptFrame&& aOther)
{
MOZ_ASSERT(aOther.mMessageName);
mMessageName = aOther.mMessageName;
aOther.mMessageName = nullptr;
aOther.mMoved = true;
mMessageRoutingId = aOther.mMessageRoutingId;
mMesageSemantics = aOther.mMesageSemantics;
mDirection = aOther.mDirection;
}
~InterruptFrame()
{
MOZ_ASSERT_IF(!mMessageName, mMoved);
if (mMessageName)
free(const_cast<char*>(mMessageName));
}
InterruptFrame& operator=(InterruptFrame&& aOther)
{
MOZ_RELEASE_ASSERT(&aOther != this);
this->~InterruptFrame();
new (this) InterruptFrame(mozilla::Move(aOther));
return *this;
}
bool IsInterruptIncall() const
{
return INTR_SEMS == mMesageSemantics && IN_MESSAGE == mDirection;
}
bool IsInterruptOutcall() const
{
return INTR_SEMS == mMesageSemantics && OUT_MESSAGE == mDirection;
}
bool IsOutgoingSync() const {
return (mMesageSemantics == INTR_SEMS || mMesageSemantics == SYNC_SEMS) &&
mDirection == OUT_MESSAGE;
}
void Describe(int32_t* id, const char** dir, const char** sems,
const char** name) const
{
*id = mMessageRoutingId;
*dir = (IN_MESSAGE == mDirection) ? "in" : "out";
*sems = (INTR_SEMS == mMesageSemantics) ? "intr" :
(SYNC_SEMS == mMesageSemantics) ? "sync" :
"async";
*name = mMessageName;
}
int32_t GetRoutingId() const
{
return mMessageRoutingId;
}
private:
const char* mMessageName;
int32_t mMessageRoutingId;
Semantics mMesageSemantics;
Direction mDirection;
DebugOnly<bool> mMoved;
// Disable harmful methods.
InterruptFrame(const InterruptFrame& aOther) = delete;
InterruptFrame& operator=(const InterruptFrame&) = delete;
};
class MOZ_STACK_CLASS MessageChannel::CxxStackFrame
{
public:
CxxStackFrame(MessageChannel& that, Direction direction, const Message* msg)
: mThat(that)
{
mThat.AssertWorkerThread();
if (mThat.mCxxStackFrames.empty())
mThat.EnteredCxxStack();
mThat.mCxxStackFrames.append(InterruptFrame(direction, msg));
const InterruptFrame& frame = mThat.mCxxStackFrames.back();
if (frame.IsInterruptIncall())
mThat.EnteredCall();
if (frame.IsOutgoingSync())
mThat.EnteredSyncSend();
mThat.mSawInterruptOutMsg |= frame.IsInterruptOutcall();
}
~CxxStackFrame() {
mThat.AssertWorkerThread();
MOZ_ASSERT(!mThat.mCxxStackFrames.empty());
const InterruptFrame& frame = mThat.mCxxStackFrames.back();
bool exitingSync = frame.IsOutgoingSync();
bool exitingCall = frame.IsInterruptIncall();
mThat.mCxxStackFrames.shrinkBy(1);
bool exitingStack = mThat.mCxxStackFrames.empty();
// mListener could have gone away if Close() was called while
// MessageChannel code was still on the stack
if (!mThat.mListener)
return;
if (exitingCall)
mThat.ExitedCall();
if (exitingSync)
mThat.ExitedSyncSend();
if (exitingStack)
mThat.ExitedCxxStack();
}
private:
MessageChannel& mThat;
// Disable harmful methods.
CxxStackFrame() = delete;
CxxStackFrame(const CxxStackFrame&) = delete;
CxxStackFrame& operator=(const CxxStackFrame&) = delete;
};
namespace {
class MOZ_STACK_CLASS MaybeScriptBlocker {
public:
explicit MaybeScriptBlocker(MessageChannel *aChannel, bool aBlock
MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
: mBlocked(aChannel->ShouldBlockScripts() && aBlock)
{
MOZ_GUARD_OBJECT_NOTIFIER_INIT;
if (mBlocked) {
nsContentUtils::AddScriptBlocker();
}
}
~MaybeScriptBlocker() {
if (mBlocked) {
nsContentUtils::RemoveScriptBlocker();
}
}
private:
MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
bool mBlocked;
};
} // namespace
MessageChannel::MessageChannel(MessageListener *aListener)
: mListener(aListener),
mChannelState(ChannelClosed),
mSide(UnknownSide),
mLink(nullptr),
mWorkerLoop(nullptr),
mChannelErrorTask(nullptr),
mWorkerLoopID(-1),
mTimeoutMs(kNoTimeout),
mInTimeoutSecondHalf(false),
mNextSeqno(0),
mAwaitingSyncReply(false),
mAwaitingSyncReplyPriority(0),
mDispatchingSyncMessage(false),
mDispatchingSyncMessagePriority(0),
mDispatchingAsyncMessage(false),
mDispatchingAsyncMessagePriority(0),
mCurrentTransaction(0),
mTimedOutMessageSeqno(0),
mTimedOutMessagePriority(0),
mRecvdErrors(0),
mRemoteStackDepthGuess(false),
mSawInterruptOutMsg(false),
mIsWaitingForIncoming(false),
mAbortOnError(false),
mBlockScripts(false),
mFlags(REQUIRE_DEFAULT),
mPeerPidSet(false),
mPeerPid(-1)
{
MOZ_COUNT_CTOR(ipc::MessageChannel);
#ifdef OS_WIN
mTopFrame = nullptr;
mIsSyncWaitingOnNonMainThread = false;
#endif
mDequeueOneTask = new RefCountedTask(NewRunnableMethod(
this,
&MessageChannel::OnMaybeDequeueOne));
mOnChannelConnectedTask = new RefCountedTask(NewRunnableMethod(
this,
&MessageChannel::DispatchOnChannelConnected));
#ifdef OS_WIN
mEvent = CreateEventW(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
Clear();
}
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);
}
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);
}
bool
MessageChannel::CanSend() const
{
if (!mMonitor) {
return false;
}
MonitorAutoLock lock(*mMonitor);
return Connected();
}
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.
if (gParentProcessBlocker == this) {
gParentProcessBlocker = nullptr;
}
mDequeueOneTask->Cancel();
mWorkerLoop = nullptr;
delete mLink;
mLink = nullptr;
mOnChannelConnectedTask->Cancel();
if (mChannelErrorTask) {
mChannelErrorTask->Cancel();
mChannelErrorTask = nullptr;
}
// Free up any memory used by pending messages.
mPending.clear();
mRecvd = nullptr;
mOutOfTurnReplies.clear();
while (!mDeferred.empty()) {
mDeferred.pop();
}
}
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();
if (MSG_ROUTING_NONE == msg->routing_id()) {
ReportMessageRouteError("MessageChannel::Echo");
return false;
}
MonitorAutoLock lock(*mMonitor);
if (!Connected()) {
ReportConnectionError("MessageChannel", msg);
return false;
}
mLink->EchoMessage(msg.forget());
return true;
}
bool
MessageChannel::Send(Message* aMsg)
{
CxxStackFrame frame(*this, OUT_MESSAGE, aMsg);
nsAutoPtr<Message> msg(aMsg);
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
if (MSG_ROUTING_NONE == msg->routing_id()) {
ReportMessageRouteError("MessageChannel::Send");
return false;
}
MonitorAutoLock lock(*mMonitor);
if (!Connected()) {
ReportConnectionError("MessageChannel", msg);
return false;
}
mLink->SendMessage(msg.forget());
return true;
}
class CancelMessage : public IPC::Message
{
public:
CancelMessage() :
IPC::Message(MSG_ROUTING_NONE, CANCEL_MESSAGE_TYPE, PRIORITY_NORMAL)
{
}
static bool Read(const Message* msg) {
return true;
}
void Log(const std::string& aPrefix, FILE* aOutf) const {
fputs("(special `Cancel' message)", aOutf);
}
};
bool
MessageChannel::MaybeInterceptSpecialIOMessage(const Message& aMsg)
{
AssertLinkThread();
mMonitor->AssertCurrentThreadOwns();
if (MSG_ROUTING_NONE == aMsg.routing_id()) {
if (GOODBYE_MESSAGE_TYPE == aMsg.type()) {
// :TODO: Sort out Close() on this side racing with Close() on the
// other side
mChannelState = ChannelClosing;
if (LoggingEnabled()) {
printf("NOTE: %s process received `Goodbye', closing down\n",
(mSide == ChildSide) ? "child" : "parent");
}
return true;
} else if (CANCEL_MESSAGE_TYPE == aMsg.type()) {
CancelCurrentTransactionInternal();
NotifyWorkerThread();
return true;
}
}
return false;
}
bool
MessageChannel::ShouldDeferMessage(const Message& aMsg)
{
// Never defer messages that have the highest priority, even async
// ones. This is safe because only the child can send these messages, so
// they can never nest.
if (aMsg.priority() == IPC::Message::PRIORITY_URGENT)
return false;
// Unless they're urgent, we always defer async messages.
if (!aMsg.is_sync()) {
MOZ_ASSERT(aMsg.priority() == IPC::Message::PRIORITY_NORMAL);
return true;
}
int msgPrio = aMsg.priority();
int waitingPrio = AwaitingSyncReplyPriority();
// Always defer if the priority of the incoming message is less than the
// priority of the message we're awaiting.
if (msgPrio < waitingPrio)
return true;
// Never defer if the message has strictly greater priority.
if (msgPrio > waitingPrio)
return false;
// When both sides send sync messages of the same priority, we resolve the
// race by dispatching in the child and deferring the incoming message in
// the parent. However, the parent still needs to dispatch nested sync
// messages.
//
// Deferring in the parent only sort of breaks message ordering. When the
// child's message comes in, we can pretend the child hasn't quite
// finished sending it yet. Since the message is sync, we know that the
// child hasn't moved on yet.
return mSide == ParentSide && aMsg.transaction_id() != mCurrentTransaction;
}
// Predicate that is true for messages that should be consolidated if 'compress' is set.
class MatchingKinds {
typedef IPC::Message Message;
Message::msgid_t mType;
int32_t mRoutingId;
public:
MatchingKinds(Message::msgid_t aType, int32_t aRoutingId) :
mType(aType), mRoutingId(aRoutingId) {}
bool operator()(const Message &msg) {
return msg.type() == mType && msg.routing_id() == mRoutingId;
}
};
void
MessageChannel::OnMessageReceivedFromLink(const Message& aMsg)
{
AssertLinkThread();
mMonitor->AssertCurrentThreadOwns();
if (MaybeInterceptSpecialIOMessage(aMsg))
return;
// Regardless of the Interrupt stack, if we're awaiting a sync reply,
// we know that it needs to be immediately handled to unblock us.
if (aMsg.is_sync() && aMsg.is_reply()) {
if (aMsg.seqno() == mTimedOutMessageSeqno) {
// Drop the message, but allow future sync messages to be sent.
mTimedOutMessageSeqno = 0;
return;
}
MOZ_ASSERT(aMsg.transaction_id() == mCurrentTransaction);
MOZ_ASSERT(AwaitingSyncReply());
MOZ_ASSERT(!mRecvd);
// Rather than storing errors in mRecvd, we mark them in
// mRecvdErrors. We need a counter because multiple replies can arrive
// when a timeout happens, as in the following example. Imagine the
// child is running slowly. The parent sends a sync message P1. It times
// out. The child eventually sends a sync message C1. While waiting for
// the C1 response, the child dispatches P1. In doing so, it sends sync
// message C2. At that point, it's valid for the parent to send error
// responses for both C1 and C2.
if (aMsg.is_reply_error()) {
mRecvdErrors++;
NotifyWorkerThread();
return;
}
mRecvd = new Message(aMsg);
NotifyWorkerThread();
return;
}
// Prioritized messages cannot be compressed.
MOZ_ASSERT_IF(aMsg.compress_type() != IPC::Message::COMPRESSION_NONE,
aMsg.priority() == IPC::Message::PRIORITY_NORMAL);
bool compress = false;
if (aMsg.compress_type() == IPC::Message::COMPRESSION_ENABLED) {
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_type() ==
IPC::Message::COMPRESSION_ENABLED);
mPending.pop_back();
}
} else if (aMsg.compress_type() == IPC::Message::COMPRESSION_ALL) {
// Check the message queue for another message with this type/destination.
auto it = std::find_if(mPending.rbegin(), mPending.rend(),
MatchingKinds(aMsg.type(), aMsg.routing_id()));
if (it != mPending.rend()) {
// This message type has compression enabled, and the queue holds
// a message with the same message type and routed to the same destination.
// Erase it. Note that, since we always compress these redundancies, There Can
// Be Only One.
compress = true;
MOZ_ASSERT((*it).compress_type() == IPC::Message::COMPRESSION_ALL);
mPending.erase((++it).base());
}
}
bool shouldWakeUp = AwaitingInterruptReply() ||
(AwaitingSyncReply() && !ShouldDeferMessage(aMsg)) ||
AwaitingIncomingMessage();
// There are three cases we're concerned about, relating to the state of the
// main thread:
//
// (1) We are waiting on a sync 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 depending on ShouldDeferMessage. 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.
mPending.push_back(aMsg);
if (shouldWakeUp) {
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));
}
}
}
void
MessageChannel::ProcessPendingRequests()
{
// Loop until there aren't any more priority messages to process.
for (;;) {
mozilla::Vector<Message> toProcess;
for (MessageQueue::iterator it = mPending.begin(); it != mPending.end(); ) {
Message &msg = *it;
if (!ShouldDeferMessage(msg)) {
toProcess.append(Move(msg));
it = mPending.erase(it);
continue;
}
it++;
}
if (toProcess.empty())
break;
// Processing these messages could result in more messages, so we
// loop around to check for more afterwards.
for (auto it = toProcess.begin(); it != toProcess.end(); it++)
ProcessPendingRequest(*it);
}
}
bool
MessageChannel::WasTransactionCanceled(int transaction, int prio)
{
if (transaction == mCurrentTransaction) {
return false;
}
// This isn't an assert so much as an intentional crash because we're in a
// situation that we don't know how to recover from: The child is awaiting
// a reply to a normal-priority sync message. The transaction that this
// message initiated has now been canceled. That could only happen if a CPOW
// raced with the sync message and was dispatched by the child while the
// child was awaiting the sync reply; at some point while dispatching the
// CPOW, the transaction was canceled.
//
// Notes:
//
// 1. We don't want to cancel the normal-priority sync message along with
// the CPOWs because the browser relies on these messages working
// reliably.
//
// 2. Ideally we would like to avoid dispatching CPOWs while awaiting a sync
// response. This isn't possible though. To avoid deadlock, the parent would
// have to dispatch the sync message while waiting for the CPOW
// response. However, it wouldn't have dispatched async messages at that
// time, so we would have a message ordering bug. Dispatching the async
// messages first causes other hard-to-handle situations (what if they send
// CPOWs?).
//
// 3. We would like to be able to cancel the CPOWs but not the sync
// message. However, that would leave both the parent and the child running
// code at the same time, all while the sync message is still
// outstanding. That can cause a problem where message replies are received
// out of order.
IPC_ASSERT(prio != IPC::Message::PRIORITY_NORMAL,
"Intentional crash: We canceled a CPOW that was racing with a sync message.");
return true;
}
bool
MessageChannel::Send(Message* aMsg, Message* aReply)
{
nsAutoPtr<Message> msg(aMsg);
// See comment in DispatchSyncMessage.
MaybeScriptBlocker scriptBlocker(this, true);
// Sanity checks.
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
if (mCurrentTransaction == 0)
mListener->OnBeginSyncTransaction();
#ifdef OS_WIN
SyncStackFrame frame(this, false);
NeuteredWindowRegion neuteredRgn(mFlags & REQUIRE_DEFERRED_MESSAGE_PROTECTION);
#endif
CxxStackFrame f(*this, OUT_MESSAGE, msg);
MonitorAutoLock lock(*mMonitor);
if (mTimedOutMessageSeqno) {
// Don't bother sending another sync message if a previous one timed out
// and we haven't received a reply for it. Once the original timed-out
// message receives a reply, we'll be able to send more sync messages
// again.
return false;
}
if (mCurrentTransaction &&
DispatchingSyncMessagePriority() == IPC::Message::PRIORITY_NORMAL &&
msg->priority() > IPC::Message::PRIORITY_NORMAL)
{
// Don't allow sending CPOWs while we're dispatching a sync message.
// If you want to do that, use sendRpcMessage instead.
return false;
}
if (mCurrentTransaction &&
(msg->priority() < DispatchingSyncMessagePriority() ||
mAwaitingSyncReplyPriority > msg->priority()))
{
CancelCurrentTransactionInternal();
mLink->SendMessage(new CancelMessage());
}
IPC_ASSERT(msg->is_sync(), "can only Send() sync messages here");
if (mCurrentTransaction) {
IPC_ASSERT(msg->priority() >= DispatchingSyncMessagePriority(),
"can't send sync message of a lesser priority than what's being dispatched");
IPC_ASSERT(AwaitingSyncReplyPriority() <= msg->priority(),
"nested sync message sends must be of increasing priority");
IPC_ASSERT(DispatchingSyncMessagePriority() != IPC::Message::PRIORITY_URGENT,
"not allowed to send messages while dispatching urgent messages");
}
IPC_ASSERT(DispatchingAsyncMessagePriority() != IPC::Message::PRIORITY_URGENT,
"not allowed to send messages while dispatching urgent messages");
if (!Connected()) {
ReportConnectionError("MessageChannel::SendAndWait", msg);
return false;
}
msg->set_seqno(NextSeqno());
int32_t seqno = msg->seqno();
int prio = msg->priority();
DebugOnly<msgid_t> replyType = msg->type() + 1;
AutoSetValue<bool> replies(mAwaitingSyncReply, true);
AutoSetValue<int> prioSet(mAwaitingSyncReplyPriority, prio);
AutoEnterTransaction transact(this, seqno);
int32_t transaction = mCurrentTransaction;
msg->set_transaction_id(transaction);
ProcessPendingRequests();
if (WasTransactionCanceled(transaction, prio)) {
return false;
}
mLink->SendMessage(msg.forget());
while (true) {
ProcessPendingRequests();
if (WasTransactionCanceled(transaction, prio)) {
return false;
}
// See if we've received a reply.
if (mRecvdErrors) {
mRecvdErrors--;
return false;
}
if (mRecvd) {
break;
}
MOZ_ASSERT(!mTimedOutMessageSeqno);
bool maybeTimedOut = !WaitForSyncNotify();
if (!Connected()) {
ReportConnectionError("MessageChannel::SendAndWait");
return false;
}
if (WasTransactionCanceled(transaction, prio)) {
return false;
}
// We only time out a message if it initiated a new transaction (i.e.,
// if neither side has any other message Sends on the stack).
bool canTimeOut = transaction == seqno;
if (maybeTimedOut && canTimeOut && !ShouldContinueFromTimeout()) {
// We might have received a reply during WaitForSyncNotify or inside
// ShouldContinueFromTimeout (which drops the lock). We need to make
// sure not to set mTimedOutMessageSeqno if that happens, since then
// there would be no way to unset it.
if (mRecvdErrors) {
mRecvdErrors--;
return false;
}
if (mRecvd) {
break;
}
mTimedOutMessageSeqno = seqno;
mTimedOutMessagePriority = prio;
return false;
}
}
MOZ_ASSERT(mRecvd);
MOZ_ASSERT(mRecvd->is_reply(), "expected reply");
MOZ_ASSERT(!mRecvd->is_reply_error());
MOZ_ASSERT(mRecvd->type() == replyType, "wrong reply type");
MOZ_ASSERT(mRecvd->seqno() == seqno);
MOZ_ASSERT(mRecvd->is_sync());
*aReply = Move(*mRecvd);
mRecvd = nullptr;
return true;
}
bool
MessageChannel::Call(Message* aMsg, Message* aReply)
{
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
#ifdef OS_WIN
SyncStackFrame frame(this, true);
NeuteredWindowRegion neuteredRgn(mFlags & REQUIRE_DEFERRED_MESSAGE_PROTECTION);
#endif
// This must come before MonitorAutoLock, as its destructor acquires the
// monitor lock.
CxxStackFrame cxxframe(*this, OUT_MESSAGE, aMsg);
MonitorAutoLock lock(*mMonitor);
if (!Connected()) {
ReportConnectionError("MessageChannel::Call", aMsg);
return false;
}
// Sanity checks.
IPC_ASSERT(!AwaitingSyncReply(),
"cannot issue Interrupt call while blocked on sync request");
IPC_ASSERT(!DispatchingSyncMessage(),
"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::Call");
return false;
}
#ifdef OS_WIN
/* We should pump messages at this point to ensure that the IPC peer
does not become deadlocked on a pending inter-thread SendMessage() */
neuteredRgn.PumpOnce();
#endif
// 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 ((it = mOutOfTurnReplies.find(mInterruptStack.top().seqno()))
!= mOutOfTurnReplies.end())
{
recvd = Move(it->second);
mOutOfTurnReplies.erase(it);
} else if (!mPending.empty()) {
recvd = Move(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()) {
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()] = Move(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();
bool is_reply_error = recvd.is_reply_error();
if (!is_reply_error) {
*aReply = Move(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 !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::WaitForIncomingMessage()
{
#ifdef OS_WIN
SyncStackFrame frame(this, true);
NeuteredWindowRegion neuteredRgn(mFlags & REQUIRE_DEFERRED_MESSAGE_PROTECTION);
#endif
{ // Scope for lock
MonitorAutoLock lock(*mMonitor);
AutoEnterWaitForIncoming waitingForIncoming(*this);
if (mChannelState != ChannelConnected) {
return false;
}
if (!HasPendingEvents()) {
return WaitForInterruptNotify();
}
}
return OnMaybeDequeueOne();
}
bool
MessageChannel::HasPendingEvents()
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
return Connected() && !mPending.empty();
}
bool
MessageChannel::InterruptEventOccurred()
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
IPC_ASSERT(InterruptStackDepth() > 0, "not in wait loop");
return (!Connected() ||
!mPending.empty() ||
(!mOutOfTurnReplies.empty() &&
mOutOfTurnReplies.find(mInterruptStack.top().seqno()) !=
mOutOfTurnReplies.end()));
}
bool
MessageChannel::ProcessPendingRequest(const Message &aUrgent)
{
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());
DispatchMessage(aUrgent);
if (!Connected()) {
ReportConnectionError("MessageChannel::ProcessPendingRequest");
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 (!mDeferred.empty())
MaybeUndeferIncall();
if (mPending.empty())
return false;
*recvd = Move(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()] = Move(recvd);
return false;
}
// We should not be in a transaction yet if we're not blocked.
MOZ_ASSERT(mCurrentTransaction == 0);
DispatchMessage(recvd);
return true;
}
void
MessageChannel::DispatchMessage(const Message &aMsg)
{
Maybe<AutoNoJSAPI> nojsapi;
if (ScriptSettingsInitialized() && NS_IsMainThread())
nojsapi.emplace();
nsAutoPtr<Message> reply;
{
AutoEnterTransaction transaction(this, aMsg);
int id = aMsg.transaction_id();
MOZ_ASSERT_IF(aMsg.is_sync(), id == mCurrentTransaction);
{
MonitorAutoUnlock unlock(*mMonitor);
CxxStackFrame frame(*this, IN_MESSAGE, &aMsg);
if (aMsg.is_sync())
DispatchSyncMessage(aMsg, *getter_Transfers(reply));
else if (aMsg.is_interrupt())
DispatchInterruptMessage(aMsg, 0);
else
DispatchAsyncMessage(aMsg);
}
if (mCurrentTransaction != id) {
// The transaction has been canceled. Don't send a reply.
reply = nullptr;
}
}
if (reply && ChannelConnected == mChannelState) {
mLink->SendMessage(reply.forget());
}
}
void
MessageChannel::DispatchSyncMessage(const Message& aMsg, Message*& aReply)
{
AssertWorkerThread();
int prio = aMsg.priority();
// We don't want to run any code that might run a nested event loop here, so
// we avoid running event handlers. Once we've sent the response to the
// urgent message, it's okay to run event handlers again since the parent is
// no longer blocked.
MOZ_ASSERT_IF(prio > IPC::Message::PRIORITY_NORMAL, NS_IsMainThread());
MaybeScriptBlocker scriptBlocker(this, prio > IPC::Message::PRIORITY_NORMAL);
MessageChannel* dummy;
MessageChannel*& blockingVar = ShouldBlockScripts() ? gParentProcessBlocker : dummy;
Result rv;
if (mTimedOutMessageSeqno && mTimedOutMessagePriority >= prio) {
// If the other side sends a message in response to one of our messages
// that we've timed out, then we reply with an error.
//
// We do this because want to avoid a situation where we process an
// incoming message from the child here while it simultaneously starts
// processing our timed-out CPOW. It's very bad for both sides to
// be processing sync messages concurrently.
//
// The only exception is if the incoming message has urgent priority and
// our timed-out message had only high priority. In that case it's safe
// to process the incoming message because we know that the child won't
// process anything (the child will defer incoming messages when waiting
// for a response to its urgent message).
rv = MsgNotAllowed;
} else {
AutoSetValue<MessageChannel*> blocked(blockingVar, this);
AutoSetValue<bool> sync(mDispatchingSyncMessage, true);
AutoSetValue<int> prioSet(mDispatchingSyncMessagePriority, prio);
rv = mListener->OnMessageReceived(aMsg, aReply);
}
if (!MaybeHandleError(rv, aMsg, "DispatchSyncMessage")) {
aReply = new Message();
aReply->set_sync();
aReply->set_priority(aMsg.priority());
aReply->set_reply();
aReply->set_reply_error();
}
aReply->set_seqno(aMsg.seqno());
aReply->set_transaction_id(aMsg.transaction_id());
}
void
MessageChannel::DispatchAsyncMessage(const Message& aMsg)
{
AssertWorkerThread();
MOZ_ASSERT(!aMsg.is_interrupt() && !aMsg.is_sync());
if (aMsg.routing_id() == MSG_ROUTING_NONE) {
NS_RUNTIMEABORT("unhandled special message!");
}
Result rv;
{
int prio = aMsg.priority();
AutoSetValue<bool> async(mDispatchingAsyncMessage, true);
AutoSetValue<int> prioSet(mDispatchingAsyncMessagePriority, prio);
rv = mListener->OnMessageReceived(aMsg);
}
MaybeHandleError(rv, 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;
const Message& parentMsg = (mSide == ChildSide) ? aMsg : mInterruptStack.top();
const Message& childMsg = (mSide == ChildSide) ? mInterruptStack.top() : aMsg;
switch (mListener->MediateInterruptRace(parentMsg, childMsg))
{
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
nsAutoPtr<Message> reply;
++mRemoteStackDepthGuess;
Result rv = mListener->OnCallReceived(aMsg, *getter_Transfers(reply));
--mRemoteStackDepthGuess;
if (!MaybeHandleError(rv, aMsg, "DispatchInterruptMessage")) {
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.forget());
}
}
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");
// 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;
MOZ_ASSERT(call.priority() == IPC::Message::PRIORITY_NORMAL);
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;
}
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)
{
MOZ_ASSERT(!mPeerPidSet);
mPeerPidSet = true;
mPeerPid = peer_id;
mWorkerLoop->PostTask(FROM_HERE, new DequeueTask(mOnChannelConnectedTask));
}
void
MessageChannel::DispatchOnChannelConnected()
{
AssertWorkerThread();
MOZ_ASSERT(mPeerPidSet);
if (mListener)
mListener->OnChannelConnected(mPeerPid);
}
void
MessageChannel::ReportMessageRouteError(const char* channelName) const
{
PrintErrorMessage(mSide, channelName, "Need a route");
mListener->OnProcessingError(MsgRouteError, "MsgRouteError");
}
void
MessageChannel::ReportConnectionError(const char* aChannelName, Message* aMsg) const
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
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");
}
if (aMsg) {
char reason[512];
PR_snprintf(reason, sizeof(reason),
"(msgtype=0x%lX,name=%s) %s",
aMsg->type(), aMsg->name(), errorMsg);
PrintErrorMessage(mSide, aChannelName, reason);
} else {
PrintErrorMessage(mSide, aChannelName, errorMsg);
}
MonitorAutoUnlock unlock(*mMonitor);
mListener->OnProcessingError(MsgDropped, errorMsg);
}
bool
MessageChannel::MaybeHandleError(Result code, const Message& aMsg, 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;
}
char reason[512];
PR_snprintf(reason, sizeof(reason),
"(msgtype=0x%lX,name=%s) %s",
aMsg.type(), aMsg.name(), errorMsg);
PrintErrorMessage(mSide, channelName, reason);
mListener->OnProcessingError(code, reason);
return false;
}
void
MessageChannel::OnChannelErrorFromLink()
{
AssertLinkThread();
mMonitor->AssertCurrentThreadOwns();
if (InterruptStackDepth() > 0)
NotifyWorkerThread();
if (AwaitingSyncReply() || AwaitingIncomingMessage())
NotifyWorkerThread();
if (ChannelClosing != mChannelState) {
if (mAbortOnError) {
NS_RUNTIMEABORT("Aborting on channel error.");
}
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::CloseWithTimeout()
{
AssertWorkerThread();
MonitorAutoLock lock(*mMonitor);
if (ChannelConnected != mChannelState) {
return;
}
SynchronouslyClose();
mChannelState = ChannelTimeout;
}
void
MessageChannel::BlockScripts()
{
MOZ_ASSERT(NS_IsMainThread());
mBlockScripts = true;
}
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 (ChannelOpening == mChannelState) {
// SynchronouslyClose() waits for an ack from the other side, so
// the opening sequence should complete before this returns.
SynchronouslyClose();
mChannelState = ChannelError;
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!");
}
// 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: %" PRIuSIZE "\n",
mRemoteStackDepthGuess);
printf_stderr(" deferred stack size: %" PRIuSIZE "\n",
mDeferred.size());
printf_stderr(" out-of-turn Interrupt replies stack size: %" PRIuSIZE "\n",
mOutOfTurnReplies.size());
printf_stderr(" Pending queue size: %" PRIuSIZE ", 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.length(); ++i) {
int32_t id;
const char* dir;
const char* sems;
const char* name;
mCxxStackFrames[i].Describe(&id, &dir, &sems, &name);
printf_stderr("%s[(%u) %s %s %s(actor=%d) ]\n", pfx,
i, dir, sems, name, id);
}
}
int32_t
MessageChannel::GetTopmostMessageRoutingId() const
{
MOZ_ASSERT(MessageLoop::current() == mWorkerLoop);
if (mCxxStackFrames.empty()) {
return MSG_ROUTING_NONE;
}
const InterruptFrame& frame = mCxxStackFrames.back();
return frame.GetRoutingId();
}
void
MessageChannel::CancelCurrentTransactionInternal()
{
// When we cancel a transaction, we need to behave as if there's no longer
// any IPC on the stack. Anything we were dispatching or sending will get
// canceled. Consequently, we have to update the state variables below.
//
// We also need to ensure that when any IPC functions on the stack return,
// they don't reset these values using an RAII class like AutoSetValue. To
// avoid that, these RAII classes check if the variable they set has been
// tampered with (by us). If so, they don't reset the variable to the old
// value.
MOZ_ASSERT(mCurrentTransaction);
mCurrentTransaction = 0;
mAwaitingSyncReply = false;
mAwaitingSyncReplyPriority = 0;
// We could also zero out mDispatchingSyncMessage here. However, that would
// cause a race because mDispatchingSyncMessage is a worker-thread-only
// field and we can be called on the I/O thread. Luckily, we can check to
// see if mCurrentTransaction is 0 before examining DispatchSyncMessage.
}
void
MessageChannel::CancelCurrentTransaction()
{
MonitorAutoLock lock(*mMonitor);
if (mCurrentTransaction) {
CancelCurrentTransactionInternal();
mLink->SendMessage(new CancelMessage());
}
}
void
CancelCPOWs()
{
if (gParentProcessBlocker) {
mozilla::Telemetry::Accumulate(mozilla::Telemetry::IPC_TRANSACTION_CANCEL, true);
gParentProcessBlocker->CancelCurrentTransaction();
}
}
} // namespace ipc
} // namespace mozilla