AsyncTask: Centralize setting global future synchronizerHEADmaster

Move the global FutureSynchronizer to Utils and use it
by default for AsyncTask (if that is in the main thread).
This way setting a synchronizer is less prone to be forgotten.
Individual uses can still override this.

Change-Id: I1a12bf4d7f4cb5be99668bf0a4797108c2fe6448
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

5 files changed, 31 insertions, 9 deletions

diff --git a/src/libs/extensionsystem/pluginmanager.cpp b/src/libs/extensionsystem/pluginmanager.cpp
index f0c7e930b4..9aa10709be 100644
--- a/src/libs/extensionsystem/pluginmanager.cpp
+++ b/src/libs/extensionsystem/pluginmanager.cpp
@@ -17,8 +17,8 @@
 #include <utils/futuresynchronizer.h>
 #include <utils/hostosinfo.h>
 #include <utils/mimeutils.h>
-#include <utils/qtcprocess.h>
 #include <utils/qtcassert.h>
+#include <utils/qtcprocess.h>
 #include <utils/qtcsettings.h>
 #include <utils/threadutils.h>
 
@@ -436,7 +436,7 @@ QString PluginManager::systemInformation()
 
 FutureSynchronizer *PluginManager::futureSynchronizer()
 {
-    return d->m_futureSynchronizer.get();
+    return Utils::futureSynchronizer();
 }
 
 /*!
@@ -981,10 +981,7 @@ void PluginManagerPrivate::startDelayedInitialize()
 */
 PluginManagerPrivate::PluginManagerPrivate(PluginManager *pluginManager) :
     q(pluginManager)
-{
-    m_futureSynchronizer.reset(new FutureSynchronizer);
-}
-
+{}
 
 /*!
     \internal
@@ -1047,7 +1044,11 @@ void PluginManagerPrivate::stopAll()
 */
 void PluginManagerPrivate::deleteAll()
 {
-    m_futureSynchronizer.reset(); // Synchronize all futures from all plugins
+    // Guard against someone playing with the setting
+    QTC_ASSERT(
+        Utils::futureSynchronizer()->isCancelOnWait(),
+        Utils::futureSynchronizer()->cancelAllFutures());
+    Utils::futureSynchronizer()->waitForFinished(); // Synchronize all futures from all plugins
     Utils::reverseForeach(loadQueue(), [this](PluginSpec *spec) {
         loadPlugin(spec, PluginSpec::Deleted);
     });
diff --git a/src/libs/extensionsystem/pluginmanager_p.h b/src/libs/extensionsystem/pluginmanager_p.h
index a761614223..ad9d4f81ee 100644
--- a/src/libs/extensionsystem/pluginmanager_p.h
+++ b/src/libs/extensionsystem/pluginmanager_p.h
@@ -136,7 +136,6 @@ public:
     QWaitCondition m_scenarioWaitCondition;
 
     PluginManager::ProcessData m_creatorProcessData;
-    std::unique_ptr<Utils::FutureSynchronizer> m_futureSynchronizer;
 
 private:
     PluginManager *q;
diff --git a/src/libs/utils/async.h b/src/libs/utils/async.h
index af6fb3fd85..8c7155bc13 100644
--- a/src/libs/utils/async.h
+++ b/src/libs/utils/async.h
@@ -7,6 +7,7 @@
 
 #include "futuresynchronizer.h"
 #include "qtcassert.h"
+#include "threadutils.h"
 
 #include <solutions/tasking/tasktree.h>
 
@@ -130,7 +131,9 @@ template <typename ResultType>
 class Async : public AsyncBase
 {
 public:
-    Async() {
+    Async()
+        : m_synchronizer(isMainThread() ? futureSynchronizer() : nullptr)
+    {
         connect(&m_watcher, &QFutureWatcherBase::finished, this, &AsyncBase::done);
         connect(&m_watcher, &QFutureWatcherBase::resultReadyAt, this, &AsyncBase::resultReadyAt);
     }
diff --git a/src/libs/utils/futuresynchronizer.cpp b/src/libs/utils/futuresynchronizer.cpp
index da3347f35e..912de677b9 100644
--- a/src/libs/utils/futuresynchronizer.cpp
+++ b/src/libs/utils/futuresynchronizer.cpp
@@ -3,6 +3,9 @@
 
 #include "futuresynchronizer.h"
 
+#include "qtcassert.h"
+#include "threadutils.h"
+
 /*!
   \class Utils::FutureSynchronizer
   \inmodule QtCreator
@@ -62,4 +65,18 @@ void FutureSynchronizer::flushFinishedFutures()
     m_futures = newFutures;
 }
 
+Q_GLOBAL_STATIC(FutureSynchronizer, s_futureSynchronizer);
+
+/*!
+    Returns a global FutureSynchronizer.
+    The application should cancel and wait for the tasks in this synchronizer before actually
+    unloading any libraries. This is for example done by the plugin manager in Qt Creator.
+    May only be accessed by the main thread.
+*/
+FutureSynchronizer *futureSynchronizer()
+{
+    QTC_ASSERT(isMainThread(), return nullptr);
+    return s_futureSynchronizer;
+}
+
 } // namespace Utils
diff --git a/src/libs/utils/futuresynchronizer.h b/src/libs/utils/futuresynchronizer.h
index 29b1f5e456..83391dbc72 100644
--- a/src/libs/utils/futuresynchronizer.h
+++ b/src/libs/utils/futuresynchronizer.h
@@ -42,4 +42,6 @@ private:
     bool m_cancelOnWait = true;
 };
 
+QTCREATOR_UTILS_EXPORT FutureSynchronizer *futureSynchronizer();
+
 } // namespace Utils