attempting to fix deadlocks by going mutex crazy (this never ends well)

src/lib/ipc/CIpcClientProxy.cpp

@@ -29,13 +29,11 @@ CEvent::Type			CIpcClientProxy::s_disconnectedEvent = CEvent::kUnknown;
 
 CIpcClientProxy::CIpcClientProxy(synergy::IStream& stream) :
 m_stream(stream),
-m_enableLog(false),
 m_clientType(kIpcClientUnknown),
-m_disconnecting(false),
-m_socketBusy(false)
+m_disconnecting(false)
 {
 	m_mutex = ARCH->newMutex();
-
+	
 	EVENTQUEUE->adoptHandler(
 		m_stream.getInputReadyEvent(), stream.getEventTarget(),
 		new TMethodEventJob<CIpcClientProxy>(
@@ -74,6 +72,7 @@ CIpcClientProxy::~CIpcClientProxy()
 void
 CIpcClientProxy::handleDisconnect(const CEvent&, void*)
 {
+	CArchMutexLock lock(m_mutex);
 	disconnect();
 	LOG((CLOG_DEBUG "ipc client disconnected"));
 }
@@ -81,6 +80,7 @@ CIpcClientProxy::handleDisconnect(const CEvent&, void*)
 void
 CIpcClientProxy::handleWriteError(const CEvent&, void*)
 {
+	CArchMutexLock lock(m_mutex);
 	disconnect();
 	LOG((CLOG_DEBUG "ipc client write error"));
 }
@@ -88,12 +88,7 @@ CIpcClientProxy::handleWriteError(const CEvent&, void*)
 void
 CIpcClientProxy::handleData(const CEvent&, void*)
 {
-	// ugh, not sure if this is needed here. the write function has it to protect
-	// m_socketBusy (for dropping log messages primarily). but i think i saw a
-	// deadlock even after adding this mechanism. my rationale here is that i don't
-	// want the read to deadlock the stream (if that's even possible).
 	CArchMutexLock lock(m_mutex);
-
 	UInt8 code[1];
 	UInt32 n = m_stream.read(code, 1);
 	while (n != 0) {
@@ -103,9 +98,7 @@ CIpcClientProxy::handleData(const CEvent&, void*)
 		m->m_type = type;
 		m->m_source = this;
 
-		if (m_enableLog) {
-			LOG((CLOG_DEBUG "ipc client proxy read: %d", code[0]));
-		}
+		LOG((CLOG_DEBUG "ipc client proxy read: %d", code[0]));
 
 		switch (type) {
 		case kIpcHello:
@@ -132,52 +125,32 @@ CIpcClientProxy::handleData(const CEvent&, void*)
 void
 CIpcClientProxy::send(const CIpcMessage& message)
 {
-	// discard message if we're busy writing already. this is to prevent
-	// deadlock, since this function can sometimes generate log messages
-	// through stream usage.
-	if (m_socketBusy) {
-		return;
-	}
-
 	CArchMutexLock lock(m_mutex);
-	m_socketBusy = true;
-	try {
-		if (m_enableLog) {
-			LOG((CLOG_DEBUG "ipc client proxy write: %d", message.m_type));
-		}
+	LOG((CLOG_DEBUG "ipc client proxy write: %d", message.m_type));
 
-		UInt8 code[1];
-		code[0] = message.m_type;
-		m_stream.write(code, 1);
+	UInt8 code[1];
+	code[0] = message.m_type;
+	m_stream.write(code, 1);
 
-		switch (message.m_type) {
-		case kIpcLogLine: {
-			CString* s = (CString*)message.m_data;
-			const char* data = s->c_str();
+	switch (message.m_type) {
+	case kIpcLogLine: {
+		CString* s = (CString*)message.m_data;
+		const char* data = s->c_str();
 		
-			int len = strlen(data);
-			CProtocolUtil::writef(&m_stream, "%2i", len);
+		int len = strlen(data);
+		CProtocolUtil::writef(&m_stream, "%2i", len);
 
-			m_stream.write(data, len);
-			break;
-		}
-			
-		case kIpcShutdown:
-			// no data.
-			break;
-
-		default:
-			if (m_enableLog) {
-				LOG((CLOG_ERR "message not supported: %d", message.m_type));
-			}
-			break;
-		}
-		
-		m_socketBusy = false;
+		m_stream.write(data, len);
+		break;
 	}
-	catch (...) {
-		m_socketBusy = false;
-		throw;
+			
+	case kIpcShutdown:
+		// no data.
+		break;
+
+	default:
+		LOG((CLOG_ERR "message not supported: %d", message.m_type));
+		break;
 	}
 }
 

src/lib/ipc/CIpcClientProxy.h

@@ -19,7 +19,7 @@
 
 #include "CEvent.h"
 #include "Ipc.h"
-#include "CMutex.h"
+#include "IArchMultithread.h"
 
 namespace synergy { class IStream; }
 class CIpcMessage;
@@ -48,10 +48,8 @@ private:
 
 public:
 	synergy::IStream&	m_stream;
-	bool				m_enableLog;
 	EIpcClientType		m_clientType;
 	bool				m_disconnecting;
-	bool				m_socketBusy;
 	
 private:
 	CArchMutex			m_mutex;

src/lib/ipc/CIpcLogOutputter.cpp

@@ -23,10 +23,13 @@
 #include "CEventQueue.h"
 #include "TMethodEventJob.h"
 #include "CIpcClientProxy.h"
+#include "CArch.h"
 
 CIpcLogOutputter::CIpcLogOutputter(CIpcServer& ipcServer) :
-m_ipcServer(ipcServer)
+m_ipcServer(ipcServer),
+m_sending(false)
 {
+	m_mutex = ARCH->newMutex();
 }
 
 CIpcLogOutputter::~CIpcLogOutputter()
@@ -36,14 +39,32 @@ CIpcLogOutputter::~CIpcLogOutputter()
 void
 CIpcLogOutputter::sendBuffer(CIpcClientProxy& proxy)
 {
-	while (m_buffer.size() != 0) {
-		CString text = m_buffer.front();
-		m_buffer.pop();
+	// drop messages logged while sending over ipc, since ipc can cause
+	// log messages (sending these could cause recursion or deadlocks).
+	// this has the side effect of dropping messages from other threads
+	// which weren't caused by ipc, but that is just the downside of
+	// logging this way.
+	if (m_sending) {
+		return;
+	}
+
+	CArchMutexLock lock(m_mutex);
+	m_sending = true;
+	try {
+		while (m_buffer.size() != 0) {
+			CString text = m_buffer.front();
+			m_buffer.pop();
 		
-		CIpcMessage message;
-		message.m_type = kIpcLogLine;
-		message.m_data = new CString(text);
-		proxy.send(message);
+			CIpcMessage message;
+			message.m_type = kIpcLogLine;
+			message.m_data = new CString(text);
+			proxy.send(message);
+		}
+		m_sending = false;
+	}
+	catch (...) {
+		m_sending = false;
+		throw;
 	}
 }
 
@@ -65,15 +86,33 @@ CIpcLogOutputter::show(bool showIfEmpty)
 bool
 CIpcLogOutputter::write(ELevel level, const char* text)
 {
-	if (m_ipcServer.hasClients(kIpcClientGui)) {
-		CIpcMessage message;
-		message.m_type = kIpcLogLine;
-		message.m_data = new CString(text);
-		m_ipcServer.send(message, kIpcClientGui);
-	}
-	else {
-		m_buffer.push(text);
+	// drop messages logged while sending over ipc, since ipc can cause
+	// log messages (sending these could cause recursion or deadlocks).
+	// this has the side effect of dropping messages from other threads
+	// which weren't caused by ipc, but that is just the downside of
+	// logging this way.
+	if (m_sending) {
+		return false;
 	}
+
+	CArchMutexLock lock(m_mutex);
+	m_sending = true;
 	
-	return true;
+	try {
+		if (m_ipcServer.hasClients(kIpcClientGui)) {
+			CIpcMessage message;
+			message.m_type = kIpcLogLine;
+			message.m_data = new CString(text);
+			m_ipcServer.send(message, kIpcClientGui);
+		}
+		else {
+			m_buffer.push(text);
+		}
+		m_sending = false;
+		return true;
+	}
+	catch (...) {
+		m_sending = false;
+		throw;
+	}
 }

src/lib/ipc/CIpcLogOutputter.h

@@ -47,4 +47,6 @@ private:
 
 	CIpcServer&			m_ipcServer;
 	CIpcLogQueue		m_buffer;
+	CArchMutex			m_mutex;
+	bool				m_sending;
 };