QtcProcess: Fix terminate() for process launcher

ProcessLauncherImpl::terminate() was behaving the same as
ProcessLauncherImpl::kill() in case of process launcher
implementation - in both cases the launcher
immediately returned confirmation about receiving the
close request and was putting the corresponding
process into its reaper. However, the issue with this approach
is that we can't receive anymore any potential ready
read signal from the process being terminated after
a call to terminate().

The fix is to diverge the behavior of terminate()
and kill() of ProcessLauncherImpl. The behavior of kill()
remains the same, while terminate() just instructs the
process launcher to start termination without putting
the process into the reaper, yet.

Add a test that checks for any possible zombies.

We run the RecursiveBlockingProcess recursively. The most
nested process blocks. After a short wait we terminate
the outermost process. With this test we are trying to see
if terminating the middle process terminates also its
children and doesn't leave zombies.

Before we execute the test (and also by the end of this test)
we call Singleton::deleteAll() in order to ensure that reaping
of previously running processes has finished. We ensure the
number of running processtestapps is zero. Later, we ensure that
the leaf process was already started and the number of running
processtestapps equals the depth of recursion.

Fix apparent bug in getLocalProcessesUsingProc().

Change-Id: I7e2bc46ad5ca22f26620da86fbaf0fa00a7db3c3
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/libs/utils/launcherpackets.cpp

@@ -114,12 +114,14 @@ StopProcessPacket::StopProcessPacket(quintptr token)
 
 void StopProcessPacket::doSerialize(QDataStream &stream) const
 {
-    Q_UNUSED(stream);
+    stream << int(signalType);
 }
 
 void StopProcessPacket::doDeserialize(QDataStream &stream)
 {
-    Q_UNUSED(stream);
+    int sig;
+    stream >> sig;
+    signalType = SignalType(sig);
 }
 
 void WritePacket::doSerialize(QDataStream &stream) const

src/libs/utils/launcherpackets.h

@@ -142,6 +142,13 @@ class StopProcessPacket : public LauncherPacket
 public:
     StopProcessPacket(quintptr token);
 
+    enum class SignalType {
+        Kill,
+        Terminate
+    };
+
+    SignalType signalType = SignalType::Kill;
+
 private:
     void doSerialize(QDataStream &stream) const override;
     void doDeserialize(QDataStream &stream) override;

src/libs/utils/launchersocket.cpp

@@ -308,25 +308,44 @@ QProcess::ProcessState CallerHandle::state() const
     return m_processState;
 }
 
-void CallerHandle::cancel()
+bool CallerHandle::isStartPacketAwaitingAndClear()
 {
-    QTC_ASSERT(isCalledFromCallersThread(), return);
-    switch (m_processState.exchange(QProcess::NotRunning)) {
-    case QProcess::NotRunning:
-        break;
-    case QProcess::Starting:
+    QMutexLocker locker(&m_mutex);
+    const bool startPacketExisted = m_startPacket.get();
+    m_startPacket.reset();
+    return startPacketExisted;
+}
+
+void CallerHandle::sendStopPacket(StopProcessPacket::SignalType signalType)
+{
+    if (m_processState == QProcess::NotRunning)
+        return;
+
+    if (m_processState == QProcess::Running || !isStartPacketAwaitingAndClear()) {
+        StopProcessPacket packet(m_token);
+        packet.signalType = signalType;
+        sendPacket(packet);
+        return;
+    }
+
+    m_processState.store(QProcess::NotRunning);
     m_result.m_errorString = QCoreApplication::translate("Utils::LauncherHandle",
                                                 "Process was canceled before it was started.");
     m_result.m_error = QProcess::FailedToStart;
-        if (LauncherInterface::isReady()) // TODO: race condition with m_processState???
-            sendPacket(StopProcessPacket(m_token));
-        else
     emit errorOccurred(m_result.m_error);
-        break;
-    case QProcess::Running:
-        sendPacket(StopProcessPacket(m_token));
-        break;
 }
+
+
+void CallerHandle::terminate()
+{
+    QTC_ASSERT(isCalledFromCallersThread(), return);
+    sendStopPacket(StopProcessPacket::SignalType::Terminate);
+}
+
+void CallerHandle::kill()
+{
+    QTC_ASSERT(isCalledFromCallersThread(), return);
+    sendStopPacket(StopProcessPacket::SignalType::Kill);
 }
 
 QByteArray CallerHandle::readAllStandardOutput()
@@ -416,7 +435,7 @@ void CallerHandle::doStart()
     if (!m_startPacket)
         return;
     sendPacket(*m_startPacket);
-    m_startPacket.reset(nullptr);
+    m_startPacket.reset();
 }
 
 // Called from caller's or launcher's thread.

src/libs/utils/launchersocket.h

@@ -90,7 +90,10 @@ public:
 
     // Called from caller's or launcher's thread.
     QProcess::ProcessState state() const;
-    void cancel();
+    bool isStartPacketAwaitingAndClear();
+    void sendStopPacket(StopProcessPacket::SignalType signalType);
+    void terminate();
+    void kill();
 
     QByteArray readAllStandardOutput();
     QByteArray readAllStandardError();

src/libs/utils/processinfo.cpp

@@ -98,7 +98,7 @@ static QList<ProcessInfo> getLocalProcessesUsingProc()
 
         if (proc.executable.isEmpty()) {
             QFile statFile(root + QLatin1String("/stat"));
-            if (!statFile.open(QIODevice::ReadOnly)) {
+            if (statFile.open(QIODevice::ReadOnly)) {
                 const QStringList data = QString::fromLocal8Bit(statFile.readAll()).split(QLatin1Char(' '));
                 if (data.size() < 2)
                     continue;

src/libs/utils/qtcprocess.cpp

@@ -422,7 +422,7 @@ public:
     }
     ~ProcessLauncherImpl() final
     {
-        cancel();
+        m_handle->kill();
         LauncherInterface::unregisterHandle(token());
         m_handle = nullptr;
     }
@@ -435,9 +435,9 @@ public:
         if (m_setup->m_useCtrlCStub) // bypass launcher and interrupt directly
             ProcessHelper::interruptPid(processId());
     }
-    void terminate() final { cancel(); } // TODO: what are differences among terminate, kill and close?
-    void kill() final { cancel(); } // TODO: see above
-    void close() final { cancel(); } // TODO: see above
+    void terminate() final { m_handle->terminate(); }
+    void kill() final { m_handle->kill(); }
+    void close() final { m_handle->kill(); } // TODO: is it more like terminate or kill?
     qint64 write(const QByteArray &data) final { return m_handle->write(data); }
 
     ProcessResultData resultData() const final { return m_handle->resultData(); };
@@ -456,8 +456,6 @@ private:
         m_handle->start(program, arguments);
     }
 
-    void cancel();
-
     quintptr token() const { return m_token; }
 
     const uint m_token = 0;
@@ -465,11 +463,6 @@ private:
     CallerHandle *m_handle = nullptr;
 };
 
-void ProcessLauncherImpl::cancel()
-{
-    m_handle->cancel();
-}
-
 static ProcessImpl defaultProcessImpl()
 {
     if (qEnvironmentVariableIsSet("QTC_USE_QPROCESS"))

src/tools/processlauncher/launchersockethandler.cpp

@@ -247,6 +247,15 @@ void LauncherSocketHandler::handleStopPacket()
         logDebug("Got stop request for unknown process");
         return;
     }
+    const auto packet = LauncherPacket::extractPacket<StopProcessPacket>(
+                m_packetParser.token(),
+                m_packetParser.packetData());
+
+    if (packet.signalType == StopProcessPacket::SignalType::Terminate) {
+        process->terminate();
+        return;
+    }
+
     if (process->state() == QProcess::NotRunning) {
         // This shouldn't happen, since as soon as process finishes or error occurrs
         // the process is being removed.

tests/auto/utils/qtcprocess/processtestapp/processtestapp.cpp

@@ -38,6 +38,10 @@
 #ifdef Q_OS_WIN
 #include <fcntl.h>
 #include <io.h>
+#else
+#include <atomic>
+#include <signal.h>
+#include <unistd.h>
 #endif
 
 using namespace Utils;
@@ -210,7 +214,7 @@ int ProcessTestApp::CrashAfterOneSecond::main()
 int ProcessTestApp::RecursiveCrashingProcess::main()
 {
     const int currentDepth = qEnvironmentVariableIntValue(envVar());
-    if (currentDepth == 0) {
+    if (currentDepth == 1) {
         QThread::sleep(1);
         doCrash();
         return 1;
@@ -224,3 +228,56 @@ int ProcessTestApp::RecursiveCrashingProcess::main()
         return process.exitCode();
     return s_crashCode;
 }
+
+#ifndef Q_OS_WIN
+static std::atomic_bool s_terminate = false;
+
+void terminate(int signum)
+{
+    Q_UNUSED(signum)
+    s_terminate.store(true);
+}
+#endif
+
+int ProcessTestApp::RecursiveBlockingProcess::main()
+{
+#ifndef Q_OS_WIN
+    struct sigaction action;
+    memset(&action, 0, sizeof(struct sigaction));
+    action.sa_handler = terminate;
+    sigaction(SIGTERM, &action, NULL);
+#endif
+
+    const int currentDepth = qEnvironmentVariableIntValue(envVar());
+    if (currentDepth == 1) {
+        std::cout << s_leafProcessStarted << std::flush;
+        while (true) {
+            QThread::sleep(1);
+#ifndef Q_OS_WIN
+            if (s_terminate.load()) {
+                std::cout << s_leafProcessTerminated << std::flush;
+                return s_crashCode;
+            }
+#endif
+        }
+    }
+    SubProcessConfig subConfig(envVar(), QString::number(currentDepth - 1));
+    QtcProcess process;
+    subConfig.setupSubProcess(&process);
+    process.setProcessChannelMode(QProcess::ForwardedChannels);
+    process.start();
+    while (true) {
+        if (process.waitForFinished(1000))
+            return 0;
+#ifndef Q_OS_WIN
+        if (s_terminate.load()) {
+            process.terminate();
+            process.waitForFinished(-1);
+            break;
+        }
+#endif
+    }
+    if (process.exitStatus() == QProcess::NormalExit)
+        return process.exitCode();
+    return s_crashCode;
+}

tests/auto/utils/qtcprocess/processtestapp/processtestapp.h

@@ -71,6 +71,7 @@ public:
     SUB_PROCESS(EmitOneErrorOnCrash);
     SUB_PROCESS(CrashAfterOneSecond);
     SUB_PROCESS(RecursiveCrashingProcess);
+    SUB_PROCESS(RecursiveBlockingProcess);
 
     // In order to get a value associated with the certain subprocess use SubProcessClass::envVar().
     // The classes above define different custom executables. Inside invokeSubProcess(), called
@@ -119,5 +120,7 @@ enum class BlockType {
 };
 
 static const int s_crashCode = 123;
+static const char s_leafProcessStarted[] = "Leaf process started";
+static const char s_leafProcessTerminated[] = "Leaf process terminated";
 
 Q_DECLARE_METATYPE(BlockType)

tests/auto/utils/qtcprocess/tst_qtcprocess.cpp

@@ -31,6 +31,7 @@
 #include <utils/hostosinfo.h>
 #include <utils/launcherinterface.h>
 #include <utils/porting.h>
+#include <utils/processinfo.h>
 #include <utils/qtcassert.h>
 #include <utils/qtcprocess.h>
 #include <utils/singleton.h>
@@ -162,6 +163,7 @@ private slots:
     void emitOneErrorOnCrash();
     void crashAfterOneSecond();
     void recursiveCrashingProcess();
+    void recursiveBlockingProcess();
 
     void cleanupTestCase();
 
@@ -1187,7 +1189,7 @@ void tst_QtcProcess::crashAfterOneSecond()
 
 void tst_QtcProcess::recursiveCrashingProcess()
 {
-    const int recursionDepth = 5; // must be at least 1
+    const int recursionDepth = 5; // must be at least 2
     SubProcessConfig subConfig(ProcessTestApp::RecursiveCrashingProcess::envVar(),
                                QString::number(recursionDepth));
     TestProcess process;
@@ -1199,6 +1201,48 @@ void tst_QtcProcess::recursiveCrashingProcess()
     QCOMPARE(process.exitStatus(), QProcess::NormalExit);
     QCOMPARE(process.exitCode(), s_crashCode);
 }
+
+static int runningTestProcessCount()
+{
+    int testProcessCounter = 0;
+    const QList<ProcessInfo> processInfoList = ProcessInfo::processInfoList();
+    for (const ProcessInfo &processInfo : processInfoList) {
+        if (FilePath::fromString(processInfo.executable).baseName() == "processtestapp")
+            ++testProcessCounter;
+    }
+    return testProcessCounter;
+}
+
+void tst_QtcProcess::recursiveBlockingProcess()
+{
+    if (HostOsInfo::isWindowsHost())
+        QSKIP("Windows implementation of this test is lacking handling of WM_CLOSE message.");
+
+    Singleton::deleteAll();
+    QCOMPARE(runningTestProcessCount(), 0);
+    const int recursionDepth = 5; // must be at least 2
+    SubProcessConfig subConfig(ProcessTestApp::RecursiveBlockingProcess::envVar(),
+                               QString::number(recursionDepth));
+    {
+        TestProcess process;
+        subConfig.setupSubProcess(&process);
+        process.start();
+        QVERIFY(process.waitForStarted(1000));
+        QVERIFY(process.waitForReadyRead(1000));
+        QCOMPARE(process.readAllStandardOutput(), s_leafProcessStarted);
+        QCOMPARE(runningTestProcessCount(), recursionDepth);
+        QVERIFY(!process.waitForFinished(1000));
+        process.terminate();
+        QVERIFY(process.waitForReadyRead());
+        QCOMPARE(process.readAllStandardOutput(), s_leafProcessTerminated);
+        QVERIFY(process.waitForFinished());
+        QCOMPARE(process.exitStatus(), QProcess::NormalExit);
+        QCOMPARE(process.exitCode(), s_crashCode);
+    }
+    Singleton::deleteAll();
+    QCOMPARE(runningTestProcessCount(), 0);
+}
+
 QTEST_MAIN(tst_QtcProcess)
 
 #include "tst_qtcprocess.moc"