From 4c75456aeeaf6a0100fe40af9c326a468219fd53 Mon Sep 17 00:00:00 2001
From: Cameron Gutman <aicommander@gmail.com>
Date: Thu, 28 Jun 2018 03:29:22 -0700
Subject: [PATCH] Fix improper handling of polling thread termination

---
 app/backend/computermanager.cpp | 28 +++++++++++++---------------
 app/backend/computermanager.h   |  8 +-------
 2 files changed, 14 insertions(+), 22 deletions(-)

diff --git a/app/backend/computermanager.cpp b/app/backend/computermanager.cpp
index 1e73cd37..4e0a2c3a 100644
--- a/app/backend/computermanager.cpp
+++ b/app/backend/computermanager.cpp
@@ -213,6 +213,10 @@ void ComputerManager::deleteHost(NvComputer* computer)
         // We must wait here because we're going to delete computer
         // and we can't do that out from underneath the poller.
         pollingThread->wait();
+
+        // The thread is safe to delete now
+        Q_ASSERT(pollingThread->isFinished());
+        delete pollingThread;
     }
 
     m_PollThreads.remove(computer->uuid);
@@ -232,8 +236,16 @@ void ComputerManager::stopPollingAsync()
     while (i.hasNext()) {
         i.next();
 
-        // The threads will delete themselves when they terminate
+        QThread* thread = i.value();
+
+        // Let this thread delete itself when it's finished
+        connect(thread, SIGNAL(finished()),
+                thread, SLOT(deleteLater()));
+
+        // The threads will delete themselves when they terminate,
+        // but we remove them from the polling threads map here.
         i.value()->requestInterruption();
+        i.remove();
     }
 }
 
@@ -291,18 +303,6 @@ bool ComputerManager::addNewHost(QString address, bool mdns)
     return true;
 }
 
-void
-ComputerManager::handlePollThreadTermination(NvComputer* computer)
-{
-    QWriteLocker lock(&m_Lock);
-
-    QThread* me = m_PollThreads[computer->uuid];
-    Q_ASSERT(me != nullptr);
-
-    m_PollThreads.remove(computer->uuid);
-    me->deleteLater();
-}
-
 void
 ComputerManager::handleComputerStateChanged(NvComputer* computer)
 {
@@ -326,8 +326,6 @@ ComputerManager::startPollingComputer(NvComputer* computer)
     }
 
     PcMonitorThread* thread = new PcMonitorThread(computer);
-    connect(thread, SIGNAL(terminating(NvComputer*)),
-            this, SLOT(handlePollThreadTermination(NvComputer*)));
     connect(thread, SIGNAL(computerStateChanged(NvComputer*)),
             this, SLOT(handleComputerStateChanged(NvComputer*)));
     m_PollThreads[computer->uuid] = thread;
diff --git a/app/backend/computermanager.h b/app/backend/computermanager.h
index 60f5f001..e7c0253d 100644
--- a/app/backend/computermanager.h
+++ b/app/backend/computermanager.h
@@ -156,7 +156,7 @@ private:
             for (int i = 0; i < TRIES_BEFORE_OFFLINING; i++) {
                 for (auto& address : uniqueAddressList) {
                     if (isInterruptionRequested()) {
-                        goto Terminate;
+                        return;
                     }
 
                     if (tryPollComputer(address, stateChanged)) {
@@ -198,14 +198,10 @@ private:
             // Wait a bit to poll again
             QThread::sleep(3);
         }
-
-    Terminate:
-        emit terminating(m_Computer);
     }
 
 signals:
    void computerStateChanged(NvComputer* computer);
-   void terminating(NvComputer* computer);
 
 private:
     NvComputer* m_Computer;
@@ -235,8 +231,6 @@ signals:
 private slots:
     void handleComputerStateChanged(NvComputer* computer);
 
-    void handlePollThreadTermination(NvComputer* computer);
-
 private:
     void saveHosts();