HelpIndexFilter: use atomic_bool for the m_needsUpdate field

This will simplify the code, no need for mutex anymore.

Change-Id: I85e0cad7ed3b3288ae1eec03f7504590293c4ea5
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/help/helpindexfilter.cpp

@@ -174,17 +174,11 @@ bool HelpIndexFilter::updateCache(QFutureInterface<LocatorFilterEntry> &future,
 
 QList<LocatorFilterEntry> HelpIndexFilter::matchesFor(QFutureInterface<LocatorFilterEntry> &future, const QString &entry)
 {
-    m_mutex.lock(); // guard m_needsUpdate
-    bool forceUpdate = m_needsUpdate;
-    m_mutex.unlock();
-
-    if (forceUpdate) {
+    if (m_needsUpdate) {
         QStringList indices;
         QMetaObject::invokeMethod(this, [this] { return allIndices(); },
                                   Qt::BlockingQueuedConnection, &indices);
-        m_mutex.lock(); // guard m_needsUpdate
         m_needsUpdate = false;
-        m_mutex.unlock();
         m_allIndicesCache = indices;
         // force updating the cache taking the m_allIndicesCache
         m_lastIndicesCache = QStringList();
@@ -279,7 +273,5 @@ QStringList HelpIndexFilter::allIndices() const
 
 void HelpIndexFilter::invalidateCache()
 {
-    m_mutex.lock();
     m_needsUpdate = true;
-    m_mutex.unlock();
 }

src/plugins/help/helpindexfilter.h

@@ -29,10 +29,11 @@
 
 #include <QIcon>
 #include <QMultiMap>
-#include <QMutex>
 #include <QSet>
 #include <QUrl>
 
+#include <atomic>
+
 namespace Help {
 namespace Internal {
 
@@ -77,8 +78,7 @@ private:
     QStringList m_lastIndicesCache;
     QString m_lastEntry;
 #endif
-    bool m_needsUpdate = true;
-    QMutex m_mutex;
+    std::atomic_bool m_needsUpdate = true;
     QIcon m_icon;
 };