Don't kill the QProcess instance which is running in other thread

The main thread doesn't kill processes directly, but
sets just the cancel flag.

Instead of waiting infinitely long for a process to finish
we poll periodically (every 100ms) for the canceled flag
inside the thread that started the process.

Amends: a30aa4421a

Task-number: QTCREATORBUG-26333
Change-Id: I599d5c6cd69381cadc4a01c65f6a79f9a9bbd3fb
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/qmakeprojectmanager/qmakeproject.cpp

@@ -674,8 +674,9 @@ void QmakeBuildSystem::asyncUpdate()
     connect(watcher, &QFutureWatcher<void>::canceled, this, [this, watcher] {
         if (!m_qmakeGlobals)
             return;
-        watcher->disconnect();
         m_qmakeGlobals->killProcesses();
+        watcher->disconnect();
+        watcher->deleteLater();
     });
     connect(watcher, &QFutureWatcher<void>::finished, this, [watcher] {
         watcher->disconnect();

src/shared/proparser/qmakebuiltins.cpp

@@ -474,12 +474,8 @@ void QMakeEvaluator::runProcess(QProcess *proc, const QString &command) const
     }
 # endif
 # ifdef PROEVALUATOR_THREAD_SAFE
-    m_option->mutex.lock();
+    if (m_option->canceled)
-    if (m_option->canceled) {
-        m_option->mutex.unlock();
         return;
-    }
-    m_option->runningProcs << proc;
 # endif
 # ifdef Q_OS_WIN
     proc->setNativeArguments(QLatin1String("/v:off /s /c \"") + command + QLatin1Char('"'));
@@ -488,12 +484,21 @@ void QMakeEvaluator::runProcess(QProcess *proc, const QString &command) const
     proc->start(QLatin1String("/bin/sh"), QStringList() << QLatin1String("-c") << command);
 # endif
 # ifdef PROEVALUATOR_THREAD_SAFE
-    m_option->mutex.unlock();
+    while (true) {
-# endif
+        if (proc->waitForFinished(100))
-    proc->waitForFinished(-1);
+            break;
-# ifdef PROEVALUATOR_THREAD_SAFE
+        if (m_option->canceled) {
-    QMutexLocker(&m_option->mutex);
+            proc->terminate();
-    m_option->runningProcs.removeOne(proc);
+            if (proc->waitForFinished(1000))
+                break;
+            proc->kill();
+            proc->waitForFinished(1000);
+            break;
+        }
+    }
+# else
+    proc->waitForFinished(-1); // If have have single thread we can't cancel it using
+                               // synchronous API of QProcess
 # endif
 }
 #endif

src/shared/proparser/qmakeglobals.cpp

@@ -92,11 +92,7 @@ QMakeGlobals::~QMakeGlobals()
 void QMakeGlobals::killProcesses()
 {
 #ifdef PROEVALUATOR_THREAD_SAFE
-    QMutexLocker lock(&mutex);
     canceled = true;
-    for (QProcess * const proc : runningProcs)
-        proc->kill();
-    runningProcs.clear();
 #endif
 }
 

src/shared/proparser/qmakeglobals.h

@@ -159,8 +159,7 @@ private:
 
 #ifdef PROEVALUATOR_THREAD_SAFE
     QMutex mutex;
-    bool canceled = false;
+    std::atomic_bool canceled = false;
-    QList<QProcess *> runningProcs;
 #endif
     QHash<QMakeBaseKey, QMakeBaseEnv *> baseEnvs;