From d5db236fd5d51bfa237013f4796902ccb4d5b6b3 Mon Sep 17 00:00:00 2001
From: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>
Date: Thu, 28 May 2015 13:35:08 +0200
Subject: ConnectionClient: Fix race conditions regarding the timeout

If the main thread is blocked for a while, it is unclear whether first
the timeout slot is processed or the data from the socket.

Change-Id: Ief1fdf40968f7548a0ad5ca4abc9b40253f79fa8
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>
---
 src/libs/codemodelbackendipc/connectionclient.cpp | 23 ++++++++++++++++++++---
 src/libs/codemodelbackendipc/connectionclient.h   |  2 ++
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/src/libs/codemodelbackendipc/connectionclient.cpp b/src/libs/codemodelbackendipc/connectionclient.cpp
index 61c12e4629..de3b9b7649 100644
--- a/src/libs/codemodelbackendipc/connectionclient.cpp
+++ b/src/libs/codemodelbackendipc/connectionclient.cpp
@@ -53,11 +53,14 @@ QString connectionName()
 }
 
 ConnectionClient::ConnectionClient(IpcClientInterface *client)
-    : serverProxy_(client, &localSocket)
+    : serverProxy_(client, &localSocket),
+      isAliveTimerResetted(false)
 {
     processAliveTimer.setInterval(10000);
 
-    connect(&processAliveTimer, &QTimer::timeout, this, &ConnectionClient::restartProcess);
+    connect(&processAliveTimer, &QTimer::timeout,
+            this, &ConnectionClient::restartProcessIfTimerIsNotResettedAndSocketIsEmpty);
+
     connect(&localSocket,
             static_cast<void (QLocalSocket::*)(QLocalSocket::LocalSocketError)>(&QLocalSocket::error),
             this,
@@ -112,6 +115,7 @@ void ConnectionClient::sendEndCommand()
 
 void ConnectionClient::resetProcessAliveTimer()
 {
+    isAliveTimerResetted = true;
     processAliveTimer.start();
 }
 
@@ -127,7 +131,7 @@ void ConnectionClient::startProcess()
         connectStandardOutputAndError();
         process()->start(processPath(), {connectionName()});
         process()->waitForStarted();
-        processAliveTimer.start();
+        resetProcessAliveTimer();
     }
 }
 
@@ -141,6 +145,19 @@ void ConnectionClient::restartProcess()
     emit processRestarted();
 }
 
+void ConnectionClient::restartProcessIfTimerIsNotResettedAndSocketIsEmpty()
+{
+    if (isAliveTimerResetted) {
+        isAliveTimerResetted = false;
+        return; // Already reset, but we were scheduled after.
+    }
+
+    if (localSocket.bytesAvailable() > 0)
+        return; // We come first, the incoming data was not yet processed.
+
+    restartProcess();
+}
+
 bool ConnectionClient::connectToLocalSocket()
 {
     QThread::msleep(30);
diff --git a/src/libs/codemodelbackendipc/connectionclient.h b/src/libs/codemodelbackendipc/connectionclient.h
index 2e2cb2ef15..fb5d2b4f35 100644
--- a/src/libs/codemodelbackendipc/connectionclient.h
+++ b/src/libs/codemodelbackendipc/connectionclient.h
@@ -70,6 +70,7 @@ public:
 
     void startProcess();
     void restartProcess();
+    void restartProcessIfTimerIsNotResettedAndSocketIsEmpty();
     void finishProcess();
     bool isProcessIsRunning() const;
 
@@ -104,6 +105,7 @@ private:
     IpcServerProxy serverProxy_;
     QTimer processAliveTimer;
     QString processPath_;
+    bool isAliveTimerResetted;
 };
 
 } // namespace CodeModelBackEnd
-- 
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