From 28b8fca7298b7de8caf625837c0d6269fbe6303e Mon Sep 17 00:00:00 2001
From: Igor Kushnir <igorkuo@gmail.com>
Date: Sun, 9 Jun 2019 13:53:47 +0300
Subject: [PATCH] Reader: make PageLoader::working atomic to fix a data race

This data member is modified in PageLoader's own thread and accessed
without locking from an external thread in the public busy() function.

Reorder setting working and img in PageLoader::run() to avoid a data
race in PageLoader::result() called from GoToFlow::updateImageData().
---
 YACReader/goto_flow.cpp | 4 ++--
 YACReader/goto_flow.h   | 4 +++-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/YACReader/goto_flow.cpp b/YACReader/goto_flow.cpp
index 27c0c000..110a4aa1 100644
--- a/YACReader/goto_flow.cpp
+++ b/YACReader/goto_flow.cpp
@@ -244,7 +244,7 @@ PageLoader::~PageLoader()
 
 bool PageLoader::busy() const
 {
-    return isRunning() ? working : false;
+    return isRunning() ? working.load() : false;
 }
 
 void PageLoader::generate(int index, QSize size, const QByteArray &rImage)
@@ -283,8 +283,8 @@ void PageLoader::run()
         mutex->unlock();
 
         mutex->lock();
-        this->working = false;
         this->img = image;
+        this->working = false;
         mutex->unlock();
 
         // put to sleep
diff --git a/YACReader/goto_flow.h b/YACReader/goto_flow.h
index d119e8b5..09fe2ce0 100644
--- a/YACReader/goto_flow.h
+++ b/YACReader/goto_flow.h
@@ -9,6 +9,8 @@
 #include <QWaitCondition>
 #include <QMutex>
 
+#include <atomic>
+
 class QLineEdit;
 class QPushButton;
 class QPixmap;
@@ -89,7 +91,7 @@ private:
     QWaitCondition condition;
 
     bool restart;
-    bool working;
+    std::atomic<bool> working;
     int idx;
 
     QSize size;