gecko/ipc/glue/SyncChannel.cpp

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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/. */
#include "mozilla/DebugOnly.h"
#include "mozilla/ipc/SyncChannel.h"
#include "nsDebug.h"
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#include "nsTraceRefcnt.h"
using mozilla::MonitorAutoLock;
template<>
struct RunnableMethodTraits<mozilla::ipc::SyncChannel>
{
static void RetainCallee(mozilla::ipc::SyncChannel* obj) { }
static void ReleaseCallee(mozilla::ipc::SyncChannel* obj) { }
};
namespace mozilla {
namespace ipc {
const int32_t SyncChannel::kNoTimeout = INT32_MIN;
SyncChannel::SyncChannel(SyncListener* aListener)
: AsyncChannel(aListener)
#ifdef OS_WIN
, mTopFrame(NULL)
#endif
, mPendingReply(0)
, mProcessingSyncMessage(false)
, mNextSeqno(0)
, mInTimeoutSecondHalf(false)
, mTimeoutMs(kNoTimeout)
{
MOZ_COUNT_CTOR(SyncChannel);
#ifdef OS_WIN
mEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
NS_ASSERTION(mEvent, "CreateEvent failed! Nothing is going to work!");
#endif
}
SyncChannel::~SyncChannel()
{
MOZ_COUNT_DTOR(SyncChannel);
#ifdef OS_WIN
CloseHandle(mEvent);
#endif
}
// static
bool SyncChannel::sIsPumpingMessages = false;
bool
SyncChannel::EventOccurred()
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
NS_ABORT_IF_FALSE(AwaitingSyncReply(), "not in wait loop");
return (!Connected() || 0 != mRecvd.type() || mRecvd.is_reply_error());
}
bool
SyncChannel::Send(Message* _msg, Message* reply)
{
nsAutoPtr<Message> msg(_msg);
AssertWorkerThread();
mMonitor->AssertNotCurrentThreadOwns();
NS_ABORT_IF_FALSE(!ProcessingSyncMessage(),
"violation of sync handler invariant");
NS_ABORT_IF_FALSE(msg->is_sync(), "can only Send() sync messages here");
#ifdef OS_WIN
SyncStackFrame frame(this, false);
#endif
msg->set_seqno(NextSeqno());
MonitorAutoLock lock(*mMonitor);
if (!Connected()) {
ReportConnectionError("SyncChannel");
return false;
}
mPendingReply = msg->type() + 1;
DebugOnly<int32_t> msgSeqno = msg->seqno();
mLink->SendMessage(msg.forget());
while (1) {
bool maybeTimedOut = !SyncChannel::WaitForNotify();
if (EventOccurred())
break;
if (maybeTimedOut && !ShouldContinueFromTimeout())
return false;
}
if (!Connected()) {
ReportConnectionError("SyncChannel");
return false;
}
// we just received a synchronous message from the other side.
// If it's not the reply we were awaiting, there's a serious
// error: either a mistimed/malformed message or a sync in-message
// that raced with our sync out-message.
// (NB: IPDL prevents the latter from occuring in actor code)
// FIXME/cjones: real error handling
bool replyIsError = mRecvd.is_reply_error();
NS_ABORT_IF_FALSE(mRecvd.is_sync() && mRecvd.is_reply() &&
(replyIsError ||
(mPendingReply == mRecvd.type() &&
msgSeqno == mRecvd.seqno())),
"unexpected sync message");
mPendingReply = 0;
if (!replyIsError) {
*reply = mRecvd;
}
mRecvd = Message();
return !replyIsError;
}
void
SyncChannel::OnDispatchMessage(const Message& msg)
{
AssertWorkerThread();
NS_ABORT_IF_FALSE(msg.is_sync(), "only sync messages here");
NS_ABORT_IF_FALSE(!msg.is_reply(), "wasn't awaiting reply");
Message* reply = 0;
mProcessingSyncMessage = true;
Result rv =
static_cast<SyncListener*>(mListener)->OnMessageReceived(msg, reply);
mProcessingSyncMessage = false;
if (!MaybeHandleError(rv, "SyncChannel")) {
// FIXME/cjones: error handling; OnError()?
delete reply;
reply = new Message();
reply->set_sync();
reply->set_reply();
reply->set_reply_error();
}
reply->set_seqno(msg.seqno());
{
MonitorAutoLock lock(*mMonitor);
if (ChannelConnected == mChannelState)
mLink->SendMessage(reply);
}
}
//
// The methods below run in the context of the link thread, and can proxy
// back to the methods above
//
void
SyncChannel::OnMessageReceivedFromLink(const Message& msg)
{
AssertLinkThread();
mMonitor->AssertCurrentThreadOwns();
if (!msg.is_sync()) {
AsyncChannel::OnMessageReceivedFromLink(msg);
return;
}
if (MaybeInterceptSpecialIOMessage(msg))
return;
if (!AwaitingSyncReply()) {
// wake up the worker, there's work to do
mWorkerLoop->PostTask(
FROM_HERE,
NewRunnableMethod(this, &SyncChannel::OnDispatchMessage, msg));
}
else {
// let the worker know a new sync message has arrived
mRecvd = msg;
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NotifyWorkerThread();
}
}
void
SyncChannel::OnChannelErrorFromLink()
{
AssertLinkThread();
mMonitor->AssertCurrentThreadOwns();
if (AwaitingSyncReply())
NotifyWorkerThread();
AsyncChannel::OnChannelErrorFromLink();
}
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//
// Synchronization between worker and IO threads
//
namespace {
bool
IsTimeoutExpired(PRIntervalTime aStart, PRIntervalTime aTimeout)
{
return (aTimeout != PR_INTERVAL_NO_TIMEOUT) &&
(aTimeout <= (PR_IntervalNow() - aStart));
}
} // namespace <anon>
bool
SyncChannel::ShouldContinueFromTimeout()
{
AssertWorkerThread();
mMonitor->AssertCurrentThreadOwns();
bool cont;
{
MonitorAutoUnlock unlock(*mMonitor);
cont = static_cast<SyncListener*>(mListener)->OnReplyTimeout();
}
if (!cont) {
// NB: there's a sublety here. If parents were allowed to
// send sync messages to children, then it would be possible
// for this synchronous close-on-timeout to race with async
// |OnMessageReceived| tasks arriving from the child, posted
// to the worker thread's event loop. This would complicate
// cleanup of the *Channel. But since IPDL forbids this (and
// since it doesn't support children timing out on parents),
// the parent can only block on RPC messages to the child, and
// in that case arriving async messages are enqueued to the
// RPC channel's special queue. They're then ignored because
// the channel state changes to ChannelTimeout
// (i.e. !Connected).
SynchronouslyClose();
mChannelState = ChannelTimeout;
}
return cont;
}
bool
SyncChannel::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;
}
// Windows versions of the following two functions live in
// WindowsMessageLoop.cpp.
#ifndef OS_WIN
bool
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SyncChannel::WaitForNotify()
{
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));
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}
void
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SyncChannel::NotifyWorkerThread()
{
mMonitor->Notify();
}
#endif // ifndef OS_WIN
} // namespace ipc
} // namespace mozilla