gecko-dev/ipc/glue/MessageChannel.h

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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/. */
#ifndef ipc_glue_MessageChannel_h
#define ipc_glue_MessageChannel_h 1
#include "base/basictypes.h"
#include "base/message_loop.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/Monitor.h"
#include "mozilla/Vector.h"
#include "mozilla/WeakPtr.h"
#include "mozilla/ipc/Transport.h"
#include "MessageLink.h"
#include "nsAutoPtr.h"
#include <deque>
#include <stack>
#include <math.h>
namespace mozilla {
namespace ipc {
class MessageChannel;
class RefCountedMonitor : public Monitor
{
public:
RefCountedMonitor()
: Monitor("mozilla.ipc.MessageChannel.mMonitor")
{}
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(RefCountedMonitor)
private:
~RefCountedMonitor() {}
};
class MessageChannel : HasResultCodes
{
friend class ProcessLink;
friend class ThreadLink;
class CxxStackFrame;
class InterruptFrame;
typedef mozilla::Monitor Monitor;
public:
static const int32_t kNoTimeout;
typedef IPC::Message Message;
typedef mozilla::ipc::Transport Transport;
explicit MessageChannel(MessageListener *aListener);
~MessageChannel();
// "Open" from the perspective of the transport layer; the underlying
// socketpair/pipe should already be created.
//
// Returns true if the transport layer was successfully connected,
// i.e., mChannelState == ChannelConnected.
bool Open(Transport* aTransport, MessageLoop* aIOLoop=0, Side aSide=UnknownSide);
// "Open" a connection to another thread in the same process.
//
// Returns true if the transport layer was successfully connected,
// i.e., mChannelState == ChannelConnected.
//
// For more details on the process of opening a channel between
// threads, see the extended comment on this function
// in MessageChannel.cpp.
bool Open(MessageChannel *aTargetChan, MessageLoop *aTargetLoop, Side aSide);
// Close the underlying transport channel.
void Close();
// Force the channel to behave as if a channel error occurred. Valid
// for process links only, not thread links.
void CloseWithError();
void SetAbortOnError(bool abort)
{
mAbortOnError = true;
}
// Misc. behavioral traits consumers can request for this channel
enum ChannelFlags {
REQUIRE_DEFAULT = 0,
// Windows: if this channel operates on the UI thread, indicates
// WindowsMessageLoop code should enable deferred native message
// handling to prevent deadlocks. Should only be used for protocols
// that manage child processes which might create native UI, like
// plugins.
REQUIRE_DEFERRED_MESSAGE_PROTECTION = 1 << 0
};
void SetChannelFlags(ChannelFlags aFlags) { mFlags = aFlags; }
ChannelFlags GetChannelFlags() { return mFlags; }
void BlockScripts();
bool ShouldBlockScripts() const
{
return mBlockScripts;
}
// Asynchronously send a message to the other side of the channel
bool Send(Message* aMsg);
// Asynchronously deliver a message back to this side of the
// channel
bool Echo(Message* aMsg);
// Synchronously send |msg| (i.e., wait for |reply|)
bool Send(Message* aMsg, Message* aReply);
// Make an Interrupt call to the other side of the channel
bool Call(Message* aMsg, Message* aReply);
bool CanSend() const;
void SetReplyTimeoutMs(int32_t aTimeoutMs);
bool IsOnCxxStack() const {
return !mCxxStackFrames.empty();
}
void FlushPendingInterruptQueue();
// Unsound_IsClosed and Unsound_NumQueuedMessages are safe to call from any
// thread, but they make no guarantees about whether you'll get an
// up-to-date value; the values are written on one thread and read without
// locking, on potentially different threads. Thus you should only use
// them when you don't particularly care about getting a recent value (e.g.
// in a memory report).
bool Unsound_IsClosed() const {
return mLink ? mLink->Unsound_IsClosed() : true;
}
uint32_t Unsound_NumQueuedMessages() const {
return mLink ? mLink->Unsound_NumQueuedMessages() : 0;
}
static bool IsPumpingMessages() {
return sIsPumpingMessages;
}
static void SetIsPumpingMessages(bool aIsPumping) {
sIsPumpingMessages = aIsPumping;
}
#ifdef OS_WIN
struct MOZ_STACK_CLASS SyncStackFrame
{
SyncStackFrame(MessageChannel* channel, bool interrupt);
~SyncStackFrame();
bool mInterrupt;
bool mSpinNestedEvents;
bool mListenerNotified;
MessageChannel* mChannel;
// The previous stack frame for this channel.
SyncStackFrame* mPrev;
// The previous stack frame on any channel.
SyncStackFrame* mStaticPrev;
};
friend struct MessageChannel::SyncStackFrame;
static bool IsSpinLoopActive() {
for (SyncStackFrame* frame = sStaticTopFrame; frame; frame = frame->mPrev) {
if (frame->mSpinNestedEvents)
return true;
}
return false;
}
protected:
// The deepest sync stack frame for this channel.
SyncStackFrame* mTopFrame;
bool mIsSyncWaitingOnNonMainThread;
// The deepest sync stack frame on any channel.
static SyncStackFrame* sStaticTopFrame;
public:
void ProcessNativeEventsInInterruptCall();
static void NotifyGeckoEventDispatch();
private:
void SpinInternalEventLoop();
#endif
private:
void CommonThreadOpenInit(MessageChannel *aTargetChan, Side aSide);
void OnOpenAsSlave(MessageChannel *aTargetChan, Side aSide);
void PostErrorNotifyTask();
void OnNotifyMaybeChannelError();
void ReportConnectionError(const char* aChannelName) const;
void ReportMessageRouteError(const char* channelName) const;
bool MaybeHandleError(Result code, const Message& aMsg, const char* channelName);
void Clear();
// Send OnChannelConnected notification to listeners.
void DispatchOnChannelConnected();
// Any protocol that requires blocking until a reply arrives, will send its
// outgoing message through this function. Currently, two protocols do this:
//
// sync, which can only initiate messages from child to parent.
// urgent, which can only initiate messages from parent to child.
//
// SendAndWait() expects that the worker thread owns the monitor, and that
// the message has been prepared to be sent over the link. It returns as
// soon as a reply has been received, or an error has occurred.
//
// Note that while the child is blocked waiting for a sync reply, it can wake
// up to process urgent calls from the parent.
bool SendAndWait(Message* aMsg, Message* aReply);
bool InterruptEventOccurred();
bool ProcessPendingRequest(const Message &aUrgent);
void MaybeUndeferIncall();
void EnqueuePendingMessages();
// Executed on the worker thread. Dequeues one pending message.
bool OnMaybeDequeueOne();
bool DequeueOne(Message *recvd);
// Dispatches an incoming message to its appropriate handler.
void DispatchMessage(const Message &aMsg);
// DispatchMessage will route to one of these functions depending on the
// protocol type of the message.
void DispatchSyncMessage(const Message &aMsg);
void DispatchUrgentMessage(const Message &aMsg);
void DispatchAsyncMessage(const Message &aMsg);
void DispatchRPCMessage(const Message &aMsg);
void DispatchInterruptMessage(const Message &aMsg, size_t aStackDepth);
// Return true if the wait ended because a notification was received.
//
// Return false if the time elapsed from when we started the process of
// waiting until afterwards exceeded the currently allotted timeout.
// That *DOES NOT* mean false => "no event" (== timeout); there are many
// circumstances that could cause the measured elapsed time to exceed the
// timeout EVEN WHEN we were notified.
//
// So in sum: true is a meaningful return value; false isn't,
// necessarily.
bool WaitForSyncNotify();
bool WaitForInterruptNotify();
bool WaitResponse(bool aWaitTimedOut);
bool ShouldContinueFromTimeout();
// The "remote view of stack depth" can be different than the
// actual stack depth when there are out-of-turn replies. When we
// receive one, our actual Interrupt stack depth doesn't decrease, but
// the other side (that sent the reply) thinks it has. So, the
// "view" returned here is |stackDepth| minus the number of
// out-of-turn replies.
//
// Only called from the worker thread.
size_t RemoteViewOfStackDepth(size_t stackDepth) const {
AssertWorkerThread();
return stackDepth - mOutOfTurnReplies.size();
}
int32_t NextSeqno() {
AssertWorkerThread();
return (mSide == ChildSide) ? --mNextSeqno : ++mNextSeqno;
}
// This helper class manages mCxxStackDepth on behalf of MessageChannel.
// When the stack depth is incremented from zero to non-zero, it invokes
// a callback, and similarly for when the depth goes from non-zero to zero.
void EnteredCxxStack() {
mListener->OnEnteredCxxStack();
}
void ExitedCxxStack();
void EnteredCall() {
mListener->OnEnteredCall();
}
void ExitedCall() {
mListener->OnExitedCall();
}
MessageListener *Listener() const {
return mListener.get();
}
void DebugAbort(const char* file, int line, const char* cond,
const char* why,
bool reply=false) const;
// This method is only safe to call on the worker thread, or in a
// debugger with all threads paused.
void DumpInterruptStack(const char* const pfx="") const;
private:
// Called from both threads
size_t InterruptStackDepth() const {
mMonitor->AssertCurrentThreadOwns();
return mInterruptStack.size();
}
// Returns true if we're blocking waiting for a reply.
bool AwaitingSyncReply() const {
mMonitor->AssertCurrentThreadOwns();
return mAwaitingSyncReply;
}
int AwaitingSyncReplyPriority() const {
mMonitor->AssertCurrentThreadOwns();
return mAwaitingSyncReplyPriority;
}
bool AwaitingInterruptReply() const {
mMonitor->AssertCurrentThreadOwns();
return !mInterruptStack.empty();
}
// Returns true if we're dispatching a sync message's callback.
bool DispatchingSyncMessage() const {
AssertWorkerThread();
return mDispatchingSyncMessage;
}
int DispatchingSyncMessagePriority() const {
AssertWorkerThread();
return mDispatchingSyncMessagePriority;
}
bool Connected() const;
private:
// Executed on the IO thread.
void NotifyWorkerThread();
// Return true if |aMsg| is a special message targeted at the IO
// thread, in which case it shouldn't be delivered to the worker.
bool MaybeInterceptSpecialIOMessage(const Message& aMsg);
void OnChannelConnected(int32_t peer_id);
// Tell the IO thread to close the channel and wait for it to ACK.
void SynchronouslyClose();
bool ShouldDeferMessage(const Message& aMsg);
void OnMessageReceivedFromLink(const Message& aMsg);
void OnChannelErrorFromLink();
private:
// Run on the not current thread.
void NotifyChannelClosed();
void NotifyMaybeChannelError();
private:
// Can be run on either thread
void AssertWorkerThread() const
{
NS_ABORT_IF_FALSE(mWorkerLoopID == MessageLoop::current()->id(),
"not on worker thread!");
}
// The "link" thread is either the I/O thread (ProcessLink) or the
// other actor's work thread (ThreadLink). In either case, it is
// NOT our worker thread.
void AssertLinkThread() const
{
NS_ABORT_IF_FALSE(mWorkerLoopID != MessageLoop::current()->id(),
"on worker thread but should not be!");
}
private:
typedef IPC::Message::msgid_t msgid_t;
typedef std::deque<Message> MessageQueue;
typedef std::map<size_t, Message> MessageMap;
// All dequeuing tasks require a single point of cancellation,
// which is handled via a reference-counted task.
class RefCountedTask
{
public:
explicit RefCountedTask(CancelableTask* aTask)
: mTask(aTask)
{ }
private:
~RefCountedTask() { delete mTask; }
public:
void Run() { mTask->Run(); }
void Cancel() { mTask->Cancel(); }
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(RefCountedTask)
private:
CancelableTask* mTask;
};
// Wrap an existing task which can be cancelled at any time
// without the wrapper's knowledge.
class DequeueTask : public Task
{
public:
explicit DequeueTask(RefCountedTask* aTask)
: mTask(aTask)
{ }
void Run() { mTask->Run(); }
private:
nsRefPtr<RefCountedTask> mTask;
};
private:
mozilla::WeakPtr<MessageListener> mListener;
ChannelState mChannelState;
nsRefPtr<RefCountedMonitor> mMonitor;
Side mSide;
MessageLink* mLink;
MessageLoop* mWorkerLoop; // thread where work is done
CancelableTask* mChannelErrorTask; // NotifyMaybeChannelError runnable
// id() of mWorkerLoop. This persists even after mWorkerLoop is cleared
// during channel shutdown.
int mWorkerLoopID;
// A task encapsulating dequeuing one pending message.
nsRefPtr<RefCountedTask> mDequeueOneTask;
// Timeout periods are broken up in two to prevent system suspension from
// triggering an abort. This method (called by WaitForEvent with a 'did
// timeout' flag) decides if we should wait again for half of mTimeoutMs
// or give up.
int32_t mTimeoutMs;
bool mInTimeoutSecondHalf;
// Worker-thread only; sequence numbers for messages that require
// synchronous replies.
int32_t mNextSeqno;
static bool sIsPumpingMessages;
template<class T>
class AutoSetValue {
public:
explicit AutoSetValue(T &var, const T &newValue)
: mVar(var), mPrev(var)
{
mVar = newValue;
}
~AutoSetValue() {
mVar = mPrev;
}
private:
T& mVar;
T mPrev;
};
// Worker thread only.
bool mAwaitingSyncReply;
int mAwaitingSyncReplyPriority;
// Set while we are dispatching a synchronous message. Only for use on the
// worker thread.
bool mDispatchingSyncMessage;
int mDispatchingSyncMessagePriority;
// When we send an urgent request from the parent process, we could race
// with an RPC message that was issued by the child beforehand. In this
// case, if the parent were to wake up while waiting for the urgent reply,
// and process the RPC, it could send an additional urgent message. The
// child would wake up to process the urgent message (as it always will),
// then send a reply, which could be received by the parent out-of-order
// with respect to the first urgent reply.
//
// To address this problem, urgent or RPC requests are associated with a
// "transaction". Whenever one side of the channel wishes to start a
// chain of RPC/urgent messages, it allocates a new transaction ID. Any
// messages the parent receives, not apart of this transaction, are
// deferred. When issuing RPC/urgent requests on top of a started
// transaction, the initiating transaction ID is used.
//
// To ensure IDs are unique, we use sequence numbers for transaction IDs,
// which grow in opposite directions from child to parent.
// The current transaction ID.
int32_t mCurrentTransaction;
class AutoEnterTransaction
{
public:
explicit AutoEnterTransaction(MessageChannel *aChan)
: mChan(aChan),
mOldTransaction(mChan->mCurrentTransaction)
{
mChan->mMonitor->AssertCurrentThreadOwns();
if (mChan->mCurrentTransaction == 0)
mChan->mCurrentTransaction = mChan->NextSeqno();
}
explicit AutoEnterTransaction(MessageChannel *aChan, const Message &aMessage)
: mChan(aChan),
mOldTransaction(mChan->mCurrentTransaction)
{
mChan->mMonitor->AssertCurrentThreadOwns();
if (!aMessage.is_sync())
return;
MOZ_ASSERT_IF(mChan->mSide == ParentSide && mOldTransaction != aMessage.transaction_id(),
!mOldTransaction || aMessage.priority() > mChan->AwaitingSyncReplyPriority());
mChan->mCurrentTransaction = aMessage.transaction_id();
}
~AutoEnterTransaction() {
mChan->mMonitor->AssertCurrentThreadOwns();
mChan->mCurrentTransaction = mOldTransaction;
}
private:
MessageChannel *mChan;
int32_t mOldTransaction;
};
// If waiting for the reply to a sync out-message, it will be saved here
// on the I/O thread and then read and cleared by the worker thread.
nsAutoPtr<Message> mRecvd;
// Queue of all incoming messages, except for replies to sync and urgent
// messages, which are delivered directly to mRecvd, and any pending urgent
// incall, which is stored in mPendingUrgentRequest.
//
// If both this side and the other side are functioning correctly, the queue
// can only be in certain configurations. Let
//
// |A<| be an async in-message,
// |S<| be a sync in-message,
// |C<| be an Interrupt in-call,
// |R<| be an Interrupt reply.
//
// The queue can only match this configuration
//
// A<* (S< | C< | R< (?{mStack.size() == 1} A<* (S< | C<)))
//
// The other side can send as many async messages |A<*| as it wants before
// sending us a blocking message.
//
// The first case is |S<|, a sync in-msg. The other side must be blocked,
// and thus can't send us any more messages until we process the sync
// in-msg.
//
// The second case is |C<|, an Interrupt in-call; the other side must be blocked.
// (There's a subtlety here: this in-call might have raced with an
// out-call, but we detect that with the mechanism below,
// |mRemoteStackDepth|, and races don't matter to the queue.)
//
// Final case, the other side replied to our most recent out-call |R<|.
// If that was the *only* out-call on our stack, |?{mStack.size() == 1}|,
// then other side "finished with us," and went back to its own business.
// That business might have included sending any number of async message
// |A<*| until sending a blocking message |(S< | C<)|. If we had more than
// one Interrupt call on our stack, the other side *better* not have sent us
// another blocking message, because it's blocked on a reply from us.
//
MessageQueue mPending;
// Stack of all the out-calls on which this channel is awaiting responses.
// Each stack refers to a different protocol and the stacks are mutually
// exclusive: multiple outcalls of the same kind cannot be initiated while
// another is active.
std::stack<Message> mInterruptStack;
// This is what we think the Interrupt stack depth is on the "other side" of this
// Interrupt channel. We maintain this variable so that we can detect racy Interrupt
// calls. With each Interrupt out-call sent, we send along what *we* think the
// stack depth of the remote side is *before* it will receive the Interrupt call.
//
// After sending the out-call, our stack depth is "incremented" by pushing
// that pending message onto mPending.
//
// Then when processing an in-call |c|, it must be true that
//
// mStack.size() == c.remoteDepth
//
// I.e., my depth is actually the same as what the other side thought it
// was when it sent in-call |c|. If this fails to hold, we have detected
// racy Interrupt calls.
//
// We then increment mRemoteStackDepth *just before* processing the
// in-call, since we know the other side is waiting on it, and decrement
// it *just after* finishing processing that in-call, since our response
// will pop the top of the other side's |mPending|.
//
// One nice aspect of this race detection is that it is symmetric; if one
// side detects a race, then the other side must also detect the same race.
size_t mRemoteStackDepthGuess;
// Approximation of code frames on the C++ stack. It can only be
// interpreted as the implication:
//
// !mCxxStackFrames.empty() => MessageChannel code on C++ stack
//
// This member is only accessed on the worker thread, and so is not
// protected by mMonitor. It is managed exclusively by the helper
// |class CxxStackFrame|.
mozilla::Vector<InterruptFrame> mCxxStackFrames;
// Did we process an Interrupt out-call during this stack? Only meaningful in
// ExitedCxxStack(), from which this variable is reset.
bool mSawInterruptOutMsg;
// Map of replies received "out of turn", because of Interrupt
// in-calls racing with replies to outstanding in-calls. See
// https://bugzilla.mozilla.org/show_bug.cgi?id=521929.
MessageMap mOutOfTurnReplies;
// Stack of Interrupt in-calls that were deferred because of race
// conditions.
std::stack<Message> mDeferred;
#ifdef OS_WIN
HANDLE mEvent;
#endif
// Should the channel abort the process from the I/O thread when
// a channel error occurs?
bool mAbortOnError;
// Should we prevent scripts from running while dispatching urgent messages?
bool mBlockScripts;
// See SetChannelFlags
ChannelFlags mFlags;
// Task and state used to asynchronously notify channel has been connected
// safely. This is necessary to be able to cancel notification if we are
// closed at the same time.
nsRefPtr<RefCountedTask> mOnChannelConnectedTask;
DebugOnly<bool> mPeerPidSet;
int32_t mPeerPid;
};
bool
ParentProcessIsBlocked();
} // namespace ipc
} // namespace mozilla
#endif // ifndef ipc_glue_MessageChannel_h