gecko-dev/ipc/glue/RPCChannel.h

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: sw=4 ts=4 et :
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* 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_RPCChannel_h
#define ipc_glue_RPCChannel_h 1
#include <stdio.h>
#include <deque>
#include <stack>
#include <vector>
#include "base/basictypes.h"
#include "nsAtomicRefcnt.h"
#include "mozilla/ipc/SyncChannel.h"
#include "nsAutoPtr.h"
namespace mozilla {
namespace ipc {
//-----------------------------------------------------------------------------
class RPCChannel : public SyncChannel
{
friend class CxxStackFrame;
public:
// What happens if RPC calls race?
enum RacyRPCPolicy {
RRPError,
RRPChildWins,
RRPParentWins
};
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class /*NS_INTERFACE_CLASS*/ RPCListener :
public SyncChannel::SyncListener
{
public:
virtual ~RPCListener() { }
virtual void OnChannelClose() = 0;
virtual void OnChannelError() = 0;
virtual Result OnMessageReceived(const Message& aMessage) = 0;
virtual void OnProcessingError(Result aError) = 0;
virtual bool OnReplyTimeout() = 0;
virtual Result OnMessageReceived(const Message& aMessage,
Message*& aReply) = 0;
virtual Result OnCallReceived(const Message& aMessage,
Message*& aReply) = 0;
virtual void OnChannelConnected(int32 peer_pid) {};
virtual void OnEnteredCxxStack()
{
NS_RUNTIMEABORT("default impl shouldn't be invoked");
}
virtual void OnExitedCxxStack()
{
NS_RUNTIMEABORT("default impl shouldn't be invoked");
}
virtual void OnEnteredCall()
{
NS_RUNTIMEABORT("default impl shouldn't be invoked");
}
virtual void OnExitedCall()
{
NS_RUNTIMEABORT("default impl shouldn't be invoked");
}
virtual RacyRPCPolicy MediateRPCRace(const Message& parent,
const Message& child)
{
return RRPChildWins;
}
virtual void ProcessRemoteNativeEventsInRPCCall() {};
};
RPCChannel(RPCListener* aListener);
virtual ~RPCChannel();
void Clear() MOZ_OVERRIDE;
// Make an RPC to the other side of the channel
bool Call(Message* msg, Message* reply);
// RPCChannel overrides these so that the async and sync messages
// can be counted against mStackFrames
virtual bool Send(Message* msg) MOZ_OVERRIDE;
virtual bool Send(Message* msg, Message* reply) MOZ_OVERRIDE;
// Asynchronously, send the child a message that puts it in such a
// state that it can't send messages to the parent unless the
// parent sends a message to it first. The child stays in this
// state until the parent calls |UnblockChild()|.
//
// It is an error to
// - call this on the child side of the channel.
// - nest |BlockChild()| calls
// - call this when the child is already blocked on a sync or RPC
// in-/out- message/call
//
// Return true iff successful.
bool BlockChild();
// Asynchronously undo |BlockChild()|.
//
// It is an error to
// - call this on the child side of the channel
// - call this without a matching |BlockChild()|
//
// Return true iff successful.
bool UnblockChild();
// Return true iff this has code on the C++ stack.
bool IsOnCxxStack() const {
return !mCxxStackFrames.empty();
}
virtual bool OnSpecialMessage(uint16 id, const Message& msg) MOZ_OVERRIDE;
/**
* If there is a pending RPC message, process all pending messages.
*
* @note This method is used on Windows when we detect that an outbound
* OLE RPC call is being made to unblock the parent.
*/
void FlushPendingRPCQueue();
#ifdef OS_WIN
void ProcessNativeEventsInRPCCall();
static void NotifyGeckoEventDispatch();
protected:
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bool WaitForNotify();
void SpinInternalEventLoop();
#endif
protected:
virtual void OnMessageReceivedFromLink(const Message& msg) MOZ_OVERRIDE;
virtual void OnChannelErrorFromLink() MOZ_OVERRIDE;
private:
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// Called on worker thread only
RPCListener* Listener() const {
return static_cast<RPCListener*>(mListener);
}
virtual bool ShouldDeferNotifyMaybeError() const MOZ_OVERRIDE {
return IsOnCxxStack();
}
bool EventOccurred() const;
void MaybeUndeferIncall();
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void EnqueuePendingMessages();
/**
* Process one deferred or pending message.
* @return true if a message was processed
*/
bool OnMaybeDequeueOne();
/**
* 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 RPC 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;
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void Incall(const Message& call, size_t stackDepth);
void DispatchIncall(const Message& call);
void BlockOnParent();
void UnblockFromParent();
// This helper class managed RPCChannel.mCxxStackDepth on behalf
// of RPCChannel. When the stack depth is incremented from zero
// to non-zero, it invokes an RPCChannel callback, and similarly
// for when the depth goes from non-zero to zero;
void EnteredCxxStack()
{
Listener()->OnEnteredCxxStack();
}
void ExitedCxxStack();
void EnteredCall()
{
Listener()->OnEnteredCall();
}
void ExitedCall()
{
Listener()->OnExitedCall();
}
enum Direction { IN_MESSAGE, OUT_MESSAGE };
struct RPCFrame {
RPCFrame(Direction direction, const Message* msg) :
mDirection(direction), mMsg(msg)
{ }
bool IsRPCIncall() const
{
return mMsg->is_rpc() && IN_MESSAGE == mDirection;
}
bool IsRPCOutcall() const
{
return mMsg->is_rpc() && OUT_MESSAGE == mDirection;
}
void Describe(int32* id, const char** dir, const char** sems,
const char** name) const
{
*id = mMsg->routing_id();
*dir = (IN_MESSAGE == mDirection) ? "in" : "out";
*sems = mMsg->is_rpc() ? "rpc" : mMsg->is_sync() ? "sync" : "async";
*name = mMsg->name();
}
Direction mDirection;
const Message* mMsg;
};
class NS_STACK_CLASS CxxStackFrame
{
public:
CxxStackFrame(RPCChannel& that, Direction direction,
const Message* msg) : mThat(that) {
mThat.AssertWorkerThread();
if (mThat.mCxxStackFrames.empty())
mThat.EnteredCxxStack();
mThat.mCxxStackFrames.push_back(RPCFrame(direction, msg));
const RPCFrame& frame = mThat.mCxxStackFrames.back();
if (frame.IsRPCIncall())
mThat.EnteredCall();
mThat.mSawRPCOutMsg |= frame.IsRPCOutcall();
}
~CxxStackFrame() {
bool exitingCall = mThat.mCxxStackFrames.back().IsRPCIncall();
mThat.mCxxStackFrames.pop_back();
bool exitingStack = mThat.mCxxStackFrames.empty();
// mListener could have gone away if Close() was called while
// RPCChannel code was still on the stack
if (!mThat.mListener)
return;
mThat.AssertWorkerThread();
if (exitingCall)
mThat.ExitedCall();
if (exitingStack)
mThat.ExitedCxxStack();
}
private:
RPCChannel& mThat;
// disable harmful methods
CxxStackFrame();
CxxStackFrame(const CxxStackFrame&);
CxxStackFrame& operator=(const CxxStackFrame&);
};
// Called from both threads
size_t StackDepth() const {
mMonitor->AssertCurrentThreadOwns();
return mStack.size();
}
void DebugAbort(const char* file, int line, const char* cond,
const char* why,
const char* type="rpc", bool reply=false) const;
// This method is only safe to call on the worker thread, or in a
// debugger with all threads paused.
void DumpRPCStack(const char* const pfx="") const;
//
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// Queue of all incoming messages, except for replies to sync
// messages, which are delivered directly to the SyncChannel
// through its mRecvd member.
//
// If both this side and the other side are functioning correctly,
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// the queue can only be in certain configurations. Let
//
// |A<| be an async in-message,
// |S<| be a sync in-message,
// |C<| be an RPC in-call,
// |R<| be an RPC reply.
//
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// The queue can only match this configuration
//
// A<* (S< | C< | R< (?{mStack.size() == 1} A<* (S< | C<)))
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//
// 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 RPC 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.)
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//
// Final case, the other side replied to our most recent out-call
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// |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
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// sending a blocking message |(S< | C<)|. If we had more than
// one RPC call on our stack, the other side *better* not have
// sent us another blocking message, because it's blocked on a
// reply from us.
//
typedef std::deque<Message> MessageQueue;
MessageQueue mPending;
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//
// Stack of all the RPC out-calls on which this RPCChannel is
// awaiting a response.
//
std::stack<Message> mStack;
//
// Map of replies received "out of turn", because of RPC
// in-calls racing with replies to outstanding in-calls. See
// https://bugzilla.mozilla.org/show_bug.cgi?id=521929.
//
typedef std::map<size_t, Message> MessageMap;
MessageMap mOutOfTurnReplies;
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//
// Stack of RPC in-calls that were deferred because of race
// conditions.
//
std::stack<Message> mDeferred;
//
// This is what we think the RPC stack depth is on the "other
// side" of this RPC channel. We maintain this variable so that
// we can detect racy RPC calls. With each RPC out-call sent, we
// send along what *we* think the stack depth of the remote side
// is *before* it will receive the RPC 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
//
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// 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 RPC 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;
// True iff the parent has put us in a |BlockChild()| state.
bool mBlockedOnParent;
// Approximation of Sync/RPCChannel-code frames on the C++ stack.
// It can only be interpreted as the implication
//
// !mCxxStackFrames.empty() => RPCChannel 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|.
std::vector<RPCFrame> mCxxStackFrames;
// Did we process an RPC out-call during this stack? Only
// meaningful in ExitedCxxStack(), from which this variable is
// reset.
bool mSawRPCOutMsg;
private:
//
// All dequeuing tasks require a single point of cancellation,
// which is handled via a reference-counted task.
//
class RefCountedTask
{
public:
RefCountedTask(CancelableTask* aTask)
: mTask(aTask)
, mRefCnt(0) {}
~RefCountedTask() { delete mTask; }
void Run() { mTask->Run(); }
void Cancel() { mTask->Cancel(); }
void AddRef() {
NS_AtomicIncrementRefcnt(mRefCnt);
}
void Release() {
if (NS_AtomicDecrementRefcnt(mRefCnt) == 0)
delete this;
}
private:
CancelableTask* mTask;
nsrefcnt mRefCnt;
};
//
// Wrap an existing task which can be cancelled at any time
// without the wrapper's knowledge.
//
class DequeueTask : public Task
{
public:
DequeueTask(RefCountedTask* aTask) : mTask(aTask) {}
void Run() { mTask->Run(); }
private:
nsRefPtr<RefCountedTask> mTask;
};
// A task encapsulating dequeuing one pending task
nsRefPtr<RefCountedTask> mDequeueOneTask;
};
} // namespace ipc
} // namespace mozilla
#endif // ifndef ipc_glue_RPCChannel_h