зеркало из https://github.com/mozilla/gecko-dev.git
341 строка
11 KiB
C++
341 строка
11 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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* vim: sw=4 ts=4 et :
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* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is Mozilla Plugin App.
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*
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* The Initial Developer of the Original Code is
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* Chris Jones <jones.chris.g@gmail.com>
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* Portions created by the Initial Developer are Copyright (C) 2009
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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#ifndef ipc_glue_RPCChannel_h
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#define ipc_glue_RPCChannel_h 1
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// FIXME/cjones probably shouldn't depend on STL
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#include <queue>
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#include <stack>
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#include "mozilla/ipc/SyncChannel.h"
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namespace mozilla {
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namespace ipc {
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//-----------------------------------------------------------------------------
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class RPCChannel : public SyncChannel
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{
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friend class CxxStackFrame;
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public:
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class /*NS_INTERFACE_CLASS*/ RPCListener :
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public SyncChannel::SyncListener
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{
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public:
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virtual ~RPCListener() { }
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virtual void OnChannelClose() = 0;
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virtual void OnChannelError() = 0;
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virtual Result OnMessageReceived(const Message& aMessage) = 0;
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virtual bool OnReplyTimeout() = 0;
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virtual Result OnMessageReceived(const Message& aMessage,
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Message*& aReply) = 0;
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virtual Result OnCallReceived(const Message& aMessage,
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Message*& aReply) = 0;
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virtual void OnEnteredCxxStack()
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{
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NS_RUNTIMEABORT("default impl shouldn't be invoked");
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}
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virtual void OnExitedCxxStack()
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{
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NS_RUNTIMEABORT("default impl shouldn't be invoked");
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}
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};
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// What happens if RPC calls race?
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enum RacyRPCPolicy {
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RRPError,
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RRPChildWins,
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RRPParentWins
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};
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RPCChannel(RPCListener* aListener, RacyRPCPolicy aPolicy=RRPChildWins);
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virtual ~RPCChannel();
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// Make an RPC to the other side of the channel
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bool Call(Message* msg, Message* reply);
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// RPCChannel overrides these so that the async and sync messages
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// can be counted against mStackFrames
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NS_OVERRIDE
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virtual bool Send(Message* msg);
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NS_OVERRIDE
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virtual bool Send(Message* msg, Message* reply);
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// Asynchronously, send the child a message that puts it in such a
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// state that it can't send messages to the parent unless the
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// parent sends a message to it first. The child stays in this
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// state until the parent calls |UnblockChild()|.
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//
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// It is an error to
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// - call this on the child side of the channel.
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// - nest |BlockChild()| calls
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// - call this when the child is already blocked on a sync or RPC
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// in-/out- message/call
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//
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// Return true iff successful.
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bool BlockChild();
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// Asynchronously undo |BlockChild()|.
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//
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// It is an error to
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// - call this on the child side of the channel
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// - call this without a matching |BlockChild()|
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//
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// Return true iff successful.
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bool UnblockChild();
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NS_OVERRIDE
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virtual bool OnSpecialMessage(uint16 id, const Message& msg);
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// Override the SyncChannel handler so we can dispatch RPC
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// messages. Called on the IO thread only.
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NS_OVERRIDE
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virtual void OnMessageReceived(const Message& msg);
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NS_OVERRIDE
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virtual void OnChannelError();
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#ifdef OS_WIN
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static bool IsSpinLoopActive() {
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return (sInnerEventLoopDepth > 0);
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}
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protected:
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bool WaitForNotify();
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bool IsMessagePending();
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bool SpinInternalEventLoop();
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static void EnterModalLoop() {
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sInnerEventLoopDepth++;
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}
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static void ExitModalLoop() {
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sInnerEventLoopDepth--;
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NS_ASSERTION(sInnerEventLoopDepth >= 0,
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"sInnerEventLoopDepth dropped below zero!");
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}
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static int sInnerEventLoopDepth;
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#endif
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private:
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// Called on worker thread only
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bool EventOccurred();
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void MaybeProcessDeferredIncall();
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void EnqueuePendingMessages();
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void OnMaybeDequeueOne();
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void Incall(const Message& call, size_t stackDepth);
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void DispatchIncall(const Message& call);
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void BlockOnParent();
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void UnblockFromParent();
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// This helper class managed RPCChannel.mCxxStackDepth on behalf
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// of RPCChannel. When the stack depth is incremented from zero
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// to non-zero, it invokes an RPCChannel callback, and similarly
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// for when the depth goes from non-zero to zero;
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void EnteredCxxStack()
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{
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static_cast<RPCListener*>(mListener)->OnEnteredCxxStack();
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}
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void ExitedCxxStack()
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{
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static_cast<RPCListener*>(mListener)->OnExitedCxxStack();
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}
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class NS_STACK_CLASS CxxStackFrame
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{
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public:
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CxxStackFrame(RPCChannel& that) : mThat(that) {
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NS_ABORT_IF_FALSE(0 <= mThat.mCxxStackFrames,
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"mismatched CxxStackFrame ctor/dtor");
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mThat.AssertWorkerThread();
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if (0 == mThat.mCxxStackFrames++)
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mThat.EnteredCxxStack();
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}
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~CxxStackFrame() {
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bool exitingStack = (0 == --mThat.mCxxStackFrames);
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// mListener could have gone away if Close() was called while
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// RPCChannel code was still on the stack
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if (!mThat.mListener)
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return;
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mThat.AssertWorkerThread();
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if (exitingStack)
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mThat.ExitedCxxStack();
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}
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private:
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RPCChannel& mThat;
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// disable harmful methods
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CxxStackFrame();
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CxxStackFrame(const CxxStackFrame&);
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CxxStackFrame& operator=(const CxxStackFrame&);
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};
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// Called from both threads
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size_t StackDepth() {
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mMutex.AssertCurrentThreadOwns();
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return mStack.size();
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}
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void DebugAbort(const char* file, int line, const char* cond,
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const char* why,
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const char* type="rpc", bool reply=false);
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//
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// Queue of all incoming messages, except for replies to sync
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// messages, which are delivered directly to the SyncChannel
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// through its mRecvd member.
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//
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// If both this side and the other side are functioning correctly,
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// the queue can only be in certain configurations. Let
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//
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// |A<| be an async in-message,
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// |S<| be a sync in-message,
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// |C<| be an RPC in-call,
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// |R<| be an RPC reply.
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//
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// The queue can only match this configuration
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//
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// A<* (S< | C< | R< (?{mStack.size() == 1} A<* (S< | C<)))
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//
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// The other side can send as many async messages |A<*| as it
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// wants before sending us a blocking message.
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//
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// The first case is |S<|, a sync in-msg. The other side must be
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// blocked, and thus can't send us any more messages until we
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// process the sync in-msg.
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//
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// The second case is |C<|, an RPC in-call; the other side must be
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// blocked. (There's a subtlety here: this in-call might have
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// raced with an out-call, but we detect that with the mechanism
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// below, |mRemoteStackDepth|, and races don't matter to the
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// queue.)
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//
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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,
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// |?{mStack.size() == 1}|, then other side "finished with us,"
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// and went back to its own business. That business might have
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// included sending any number of async message |A<*| until
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// sending a blocking message |(S< | C<)|. If we had more than
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// one RPC call on our stack, the other side *better* not have
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// sent us another blocking message, because it's blocked on a
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// reply from us.
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//
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std::queue<Message> mPending;
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//
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// Stack of all the RPC out-calls on which this RPCChannel is
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// awaiting a response.
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//
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std::stack<Message> mStack;
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//
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// Map of replies received "out of turn", because of RPC
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// in-calls racing with replies to outstanding in-calls. See
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// https://bugzilla.mozilla.org/show_bug.cgi?id=521929.
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//
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typedef std::map<size_t, Message> MessageMap;
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MessageMap mOutOfTurnReplies;
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//
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// Stack of RPC in-calls that were deferred because of race
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// conditions.
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//
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std::stack<Message> mDeferred;
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//
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// This is what we think the RPC stack depth is on the "other
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// side" of this RPC channel. We maintain this variable so that
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// we can detect racy RPC calls. With each RPC out-call sent, we
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// send along what *we* think the stack depth of the remote side
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// is *before* it will receive the RPC call.
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//
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// After sending the out-call, our stack depth is "incremented"
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// by pushing that pending message onto mPending.
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//
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// Then when processing an in-call |c|, it must be true that
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//
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// mStack.size() == c.remoteDepth
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//
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// i.e., my depth is actually the same as what the other side
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// thought it was when it sent in-call |c|. If this fails to
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// hold, we have detected racy RPC calls.
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//
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// We then increment mRemoteStackDepth *just before* processing
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// the in-call, since we know the other side is waiting on it, and
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// decrement it *just after* finishing processing that in-call,
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// since our response will pop the top of the other side's
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// |mPending|.
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//
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// One nice aspect of this race detection is that it is symmetric;
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// if one side detects a race, then the other side must also
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// detect the same race.
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//
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size_t mRemoteStackDepthGuess;
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RacyRPCPolicy mRacePolicy;
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// True iff the parent has put us in a |BlockChild()| state.
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bool mBlockedOnParent;
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// Approximation of number of Sync/RPCChannel-code frames on the
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// C++ stack. It can only be interpreted as the implication
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//
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// mCxxStackDepth > 0 => RPCChannel code on C++ stack
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//
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// This member is only accessed on the worker thread, and so is
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// not protected by mMutex. It is managed exclusively by the
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// helper |class CxxStackFrame|.
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int mCxxStackFrames;
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};
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} // namespace ipc
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} // namespace mozilla
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#endif // ifndef ipc_glue_RPCChannel_h
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