From 27425b62e997cba6589d17f75896dfc7c5f3264d Mon Sep 17 00:00:00 2001
From: Eike Ziller <eike.ziller@theqtcompany.com>
Date: Tue, 12 Jan 2016 14:05:05 +0100
Subject: [PATCH] Locator: Avoid use of QtConcurrent

QtConcurrent limits resource usage to a global number of simultaneous
threads. That means that if some QtConcurrent based algorithm currently
grabs all threads, any other use of QtConcurrent blocks, which is not
what we want.
Use the new threading methods of C++11 instead, but still use
QFuture(Interface) manually for status reporting.

Task-number: QTCREATORBUG-14640
Change-Id: I8fecb43b5235da92c0d239e7dd5f2c108ab32ebf
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>
---
 src/libs/utils/runextensions.h                | 19 +++++++++++++++++++
 .../coreplugin/locator/locatorfiltertest.cpp  |  5 +++--
 .../coreplugin/locator/locatorsearchutils.cpp |  2 +-
 .../coreplugin/locator/locatorsearchutils.h   |  4 ++--
 .../coreplugin/locator/locatorwidget.cpp      |  3 ++-
 5 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/src/libs/utils/runextensions.h b/src/libs/utils/runextensions.h
index 9f5d88a6a12..82854abd731 100644
--- a/src/libs/utils/runextensions.h
+++ b/src/libs/utils/runextensions.h
@@ -520,6 +520,16 @@ void blockingMapReduce(QFutureInterface<ReduceResult> futureInterface, const Con
     futureInterface.reportFinished();
 }
 
+template <typename ResultType, typename Function, typename... Args>
+void runAsyncImpl(QFutureInterface<ResultType> futureInterface, const Function &function, const Args&... args)
+{
+    futureInterface.reportStarted();
+    function(futureInterface, args...);
+    if (futureInterface.isPaused())
+        futureInterface.waitForResume();
+    futureInterface.reportFinished();
+}
+
 } // Internal
 
 template <typename ReduceResult, typename Container, typename InitFunction, typename MapFunction,
@@ -547,6 +557,15 @@ QFuture<ReduceResult> mapReduce(const Container &container, const InitFunction &
     return future;
 }
 
+template <typename ResultType, typename Function, typename... Args>
+QFuture<ResultType> runAsync(Function &&function, Args&&... args)
+{
+    QFutureInterface<ResultType> futureInterface;
+    std::thread(Internal::runAsyncImpl<ResultType,Function,Args...>, futureInterface,
+                std::forward<Function>(function), std::forward<Args>(args)...).detach();
+    return futureInterface.future();
+}
+
 } // Utils
 
 #endif // RUNEXTENSIONS_H
diff --git a/src/plugins/coreplugin/locator/locatorfiltertest.cpp b/src/plugins/coreplugin/locator/locatorfiltertest.cpp
index 18a960b4eea..641acc85a92 100644
--- a/src/plugins/coreplugin/locator/locatorfiltertest.cpp
+++ b/src/plugins/coreplugin/locator/locatorfiltertest.cpp
@@ -51,8 +51,9 @@ QList<LocatorFilterEntry> BasicLocatorFilterTest::matchesFor(const QString &sear
     doBeforeLocatorRun();
     const QList<ILocatorFilter *> filters = QList<ILocatorFilter *>() << m_filter;
     m_filter->prepareSearch(searchText);
-    QFuture<LocatorFilterEntry> locatorSearch = QtConcurrent::run(Internal::runSearch,
-                                                           filters, searchText);
+    QFuture<LocatorFilterEntry> locatorSearch = Utils::runAsync<LocatorFilterEntry>(&Internal::runSearch,
+                                                                                    filters,
+                                                                                    searchText);
     locatorSearch.waitForFinished();
     doAfterLocatorRun();
     return locatorSearch.results();
diff --git a/src/plugins/coreplugin/locator/locatorsearchutils.cpp b/src/plugins/coreplugin/locator/locatorsearchutils.cpp
index b46e784996a..8cda9dee03c 100644
--- a/src/plugins/coreplugin/locator/locatorsearchutils.cpp
+++ b/src/plugins/coreplugin/locator/locatorsearchutils.cpp
@@ -47,7 +47,7 @@ uint qHash(const LocatorFilterEntry &entry)
 } // namespace Core
 
 void Core::Internal::runSearch(QFutureInterface<Core::LocatorFilterEntry> &future,
-                                  QList<ILocatorFilter *> filters, QString searchText)
+                               const QList<ILocatorFilter *> &filters, const QString &searchText)
 {
     QSet<LocatorFilterEntry> alreadyAdded;
     const bool checkDuplicates = (filters.size() > 1);
diff --git a/src/plugins/coreplugin/locator/locatorsearchutils.h b/src/plugins/coreplugin/locator/locatorsearchutils.h
index 88ab089318e..8d545d0dba3 100644
--- a/src/plugins/coreplugin/locator/locatorsearchutils.h
+++ b/src/plugins/coreplugin/locator/locatorsearchutils.h
@@ -37,8 +37,8 @@ namespace Core {
 namespace Internal {
 
 void CORE_EXPORT runSearch(QFutureInterface<LocatorFilterEntry> &future,
-                              QList<ILocatorFilter *> filters,
-                              QString searchText);
+                              const QList<ILocatorFilter *> &filters,
+                              const QString &searchText);
 
 } // namespace Internal
 } // namespace Core
diff --git a/src/plugins/coreplugin/locator/locatorwidget.cpp b/src/plugins/coreplugin/locator/locatorwidget.cpp
index 02ac98f2ef6..7760b0e0838 100644
--- a/src/plugins/coreplugin/locator/locatorwidget.cpp
+++ b/src/plugins/coreplugin/locator/locatorwidget.cpp
@@ -524,7 +524,8 @@ void LocatorWidget::updateCompletionList(const QString &text)
 
     foreach (ILocatorFilter *filter, filters)
         filter->prepareSearch(searchText);
-    QFuture<LocatorFilterEntry> future = QtConcurrent::run(runSearch, filters, searchText);
+    QFuture<LocatorFilterEntry> future = Utils::runAsync<LocatorFilterEntry>(&runSearch, filters,
+                                                                             QString(searchText));
     m_entriesWatcher->setFuture(future);
 }