Fixes QProcess on QNX

This patch first re-enables childStartedPipe on QNX and uses, just like other
platforms, to monitor the inferior process life cycle. This also aligns
QNX-specific code logic closer to the common QProcess logic, making it
unecessary to have custom versions of functions such as
QProcess::waitForStarted(). The only difference that remains is the use of
spawn() instead of fork(), because both fork() and vfork() do not support
multi-threaded applications on QNX and will segfault.

Change-Id: I8e1f9823629fcb5e7c3c128fafc2542a403b969e
Reviewed-by: Sean Harmer <sh@theharmers.co.uk>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

3 files changed, 67 insertions, 82 deletions

diff --git a/src/corelib/io/qprocess.cpp b/src/corelib/io/qprocess.cpp
index d6a9f2e2bd..060f503aa5 100644
--- a/src/corelib/io/qprocess.cpp
+++ b/src/corelib/io/qprocess.cpp
@@ -528,6 +528,11 @@ void QProcessPrivate::Channel::clear()
     is not supported. The working directory will always be the private
     directory of the running process.
 
+    \note On QNX, setting the working directory may cause all
+    application threads, with the exception of the QProcess caller
+    thread, to temporarily freeze, owing to a limitation in
+    the operating system.
+
     \section1 Synchronous Process API
 
     QProcess provides a set of functions which allow it to be used
@@ -751,16 +756,12 @@ QProcessPrivate::QProcessPrivate()
     sequenceNumber = 0;
     exitCode = 0;
     exitStatus = QProcess::NormalExit;
-#ifndef Q_OS_QNX
     startupSocketNotifier = 0;
-#endif
     deathNotifier = 0;
     notifier = 0;
     pipeWriter = 0;
-#ifndef Q_OS_QNX
     childStartedPipe[0] = INVALID_Q_PIPE;
     childStartedPipe[1] = INVALID_Q_PIPE;
-#endif
     deathPipe[0] = INVALID_Q_PIPE;
     deathPipe[1] = INVALID_Q_PIPE;
     exitCode = 0;
@@ -829,13 +830,11 @@ void QProcessPrivate::cleanup()
         qDeleteInEventHandler(stdinChannel.notifier);
         stdinChannel.notifier = 0;
     }
-#ifndef Q_OS_QNX
     if (startupSocketNotifier) {
         startupSocketNotifier->setEnabled(false);
         qDeleteInEventHandler(startupSocketNotifier);
         startupSocketNotifier = 0;
     }
-#endif
     if (deathNotifier) {
         deathNotifier->setEnabled(false);
         qDeleteInEventHandler(deathNotifier);
@@ -848,9 +847,7 @@ void QProcessPrivate::cleanup()
     destroyPipe(stdoutChannel.pipe);
     destroyPipe(stderrChannel.pipe);
     destroyPipe(stdinChannel.pipe);
-#ifndef Q_OS_QNX
     destroyPipe(childStartedPipe);
-#endif
     destroyPipe(deathPipe);
 #ifdef Q_OS_UNIX
     serial = 0;
@@ -1085,10 +1082,8 @@ bool QProcessPrivate::_q_startupNotification()
     qDebug("QProcessPrivate::startupNotification()");
 #endif
 
-#ifndef Q_OS_QNX
     if (startupSocketNotifier)
         startupSocketNotifier->setEnabled(false);
-#endif
     if (processStarted()) {
         q->setProcessState(QProcess::Running);
         emit q->started();
@@ -1467,6 +1462,9 @@ QString QProcess::workingDirectory() const
     the private directory of the process is considered its working
     directory.
 
+    \note On QNX, this may cause all application threads to
+    temporarily freeze.
+
     \sa workingDirectory(), start()
 */
 void QProcess::setWorkingDirectory(const QString &dir)
@@ -1789,7 +1787,7 @@ void QProcess::setProcessState(ProcessState state)
     exit().
 
     \warning This function is called by QProcess on Unix and Mac OS X
-    only. On Windows, it is not called.
+    only. On Windows and QNX, it is not called.
 */
 void QProcess::setupChildProcess()
 {
@@ -2197,6 +2195,9 @@ int QProcess::execute(const QString &program)
 
     The process will be started in the directory \a workingDirectory.
 
+    \note On QNX, this may cause all application threads to
+    temporarily freeze.
+
     If the function is successful then *\a pid is set to the process
     identifier of the started process.
 */
diff --git a/src/corelib/io/qprocess_p.h b/src/corelib/io/qprocess_p.h
index 81ba9bc0cb..6eeeeada78 100644
--- a/src/corelib/io/qprocess_p.h
+++ b/src/corelib/io/qprocess_p.h
@@ -288,15 +288,11 @@ public:
     QRingBuffer errorReadBuffer;
     QRingBuffer writeBuffer;
 
-#ifndef Q_OS_QNX
     Q_PIPE childStartedPipe[2];
-#endif
     Q_PIPE deathPipe[2];
     void destroyPipe(Q_PIPE pipe[2]);
 
-#ifndef Q_OS_QNX
     QSocketNotifier *startupSocketNotifier;
-#endif
     QSocketNotifier *deathNotifier;
 
     // the wonderful windows notifier
diff --git a/src/corelib/io/qprocess_unix.cpp b/src/corelib/io/qprocess_unix.cpp
index 44adab01d8..b69961178e 100644
--- a/src/corelib/io/qprocess_unix.cpp
+++ b/src/corelib/io/qprocess_unix.cpp
@@ -106,7 +106,8 @@ QT_END_NAMESPACE
 #include <stdlib.h>
 #include <string.h>
 #ifdef Q_OS_QNX
-#  include <spawn.h>
+#include <spawn.h>
+#include <sys/neutrino.h>
 #endif
 
 
@@ -544,18 +545,14 @@ void QProcessPrivate::startProcess()
         !createChannel(stdoutChannel) ||
         !createChannel(stderrChannel))
         return;
-#if !defined(Q_OS_QNX)
     qt_create_pipe(childStartedPipe);
-#endif
     qt_create_pipe(deathPipe);
 
     if (threadData->eventDispatcher) {
-#if !defined(Q_OS_QNX)
         startupSocketNotifier = new QSocketNotifier(childStartedPipe[0],
                                                     QSocketNotifier::Read, q);
         QObject::connect(startupSocketNotifier, SIGNAL(activated(int)),
                          q, SLOT(_q_startupNotification()));
-#endif
         deathNotifier = new QSocketNotifier(deathPipe[0],
                                             QSocketNotifier::Read, q);
         QObject::connect(deathNotifier, SIGNAL(activated(int)),
@@ -651,8 +648,8 @@ void QProcessPrivate::startProcess()
     pid_t childPid = spawnChild(workingDirPtr, argv, envp);
 #else
     pid_t childPid = fork();
-#endif
     int lastForkErrno = errno;
+#endif
     if (childPid != 0) {
         // Clean up duplicated memory.
         free(dupProgramName);
@@ -666,6 +663,18 @@ void QProcessPrivate::startProcess()
         delete [] envp;
         delete [] path;
     }
+
+    // This is not a valid check under QNX, because the semantics are
+    // different. While under other platforms where fork() may succeed and exec() can still fail,
+    // causing the childPid to hold a valid value (and thus evaluating the
+    // following if to false), and then signaling the error via
+    // childStartedPipe, under QNX on the other hand, spawn() return value will be assigned
+    // to childPid (which will be -1 in case of failure). This will force
+    // QProcess to cleanup, instead of signaling the error via
+    // childStartedPipe. Since it will invalidade the pipes, functions like
+    // QProcess::waitForStarted() will fail, for childStartedPipe will be
+    // '-1' and mess with the select() calls.
+#if !defined(Q_OS_QNX)
     if (childPid < 0) {
         // Cleanup, report error and return
 #if defined (QPROCESS_DEBUG)
@@ -680,7 +689,6 @@ void QProcessPrivate::startProcess()
         return;
     }
 
-#if !defined(Q_OS_QNX)
     // Start the child.
     if (childPid == 0) {
         execChild(workingDirPtr, path, argv, envp);
@@ -697,10 +705,8 @@ void QProcessPrivate::startProcess()
     // parent
     // close the ends we don't use and make all pipes non-blocking
     ::fcntl(deathPipe[0], F_SETFL, ::fcntl(deathPipe[0], F_GETFL) | O_NONBLOCK);
-#if !defined(Q_OS_QNX)
     qt_safe_close(childStartedPipe[1]);
     childStartedPipe[1] = -1;
-#endif
 
     if (stdinChannel.pipe[0] != -1) {
         qt_safe_close(stdinChannel.pipe[0]);
@@ -788,6 +794,8 @@ void QProcessPrivate::execChild(const char *workingDir, char **path, char **argv
     childStartedPipe[1] = -1;
 }
 
+#endif //Q_OS_QNX
+
 bool QProcessPrivate::processStarted()
 {
     ushort buf[errorBufferMax];
@@ -811,9 +819,9 @@ bool QProcessPrivate::processStarted()
     return i <= 0;
 }
 
-#else // Q_OS_QNX
-
-static pid_t doSpawn(int fd_count, int fd_map[], char **argv, char **envp, bool spawn_detached)
+#if defined(Q_OS_QNX)
+static pid_t doSpawn(int fd_count, int fd_map[], char **argv, char **envp,
+        const char *workingDir, bool spawn_detached)
 {
     // A multi threaded QNX Process can't fork so we call spawn() instead.
 
@@ -826,6 +834,19 @@ static pid_t doSpawn(int fd_count, int fd_map[], char **argv, char **envp, bool
     inherit.flags |= SPAWN_SETSIGDEF;
     sigaddset(&inherit.sigdefault, SIGPIPE); // reset the signal that we ignored
 
+    // enter the working directory
+    const char *oldWorkingDir = 0;
+    char buff[PATH_MAX + 1];
+
+    if (workingDir) {
+        //we need to freeze everyone in order to avoid race conditions with //chdir().
+        if (ThreadCtl(_NTO_TCTL_THREADS_HOLD, 0) == -1)
+            qWarning("ThreadCtl(): cannot hold threads: %s", qPrintable(qt_error_string(errno)));
+
+        oldWorkingDir = QT_GETCWD(buff, PATH_MAX + 1);
+        QT_CHDIR(workingDir);
+    }
+
     pid_t childPid;
     EINTR_LOOP(childPid, ::spawn(argv[0], fd_count, fd_map, &inherit, argv, envp));
     if (childPid == -1) {
@@ -833,13 +854,18 @@ static pid_t doSpawn(int fd_count, int fd_map[], char **argv, char **envp, bool
         EINTR_LOOP(childPid, ::spawn(argv[0], fd_count, fd_map, &inherit, argv, envp));
     }
 
+    if (oldWorkingDir) {
+        QT_CHDIR(oldWorkingDir);
+
+        if (ThreadCtl(_NTO_TCTL_THREADS_CONT, 0) == -1)
+            qFatal("ThreadCtl(): cannot resume threads: %s", qPrintable(qt_error_string(errno)));
+    }
+
     return childPid;
 }
 
 pid_t QProcessPrivate::spawnChild(const char *workingDir, char **argv, char **envp)
 {
-    Q_Q(QProcess);
-
     const int fd_count = 3;
     int fd_map[fd_count];
     switch (processChannelMode) {
@@ -860,36 +886,17 @@ pid_t QProcessPrivate::spawnChild(const char *workingDir, char **argv, char **en
         break;
     }
 
-    // enter the working directory
-    char *oldWorkingDir = 0;
-    char buff[PATH_MAX + 1];
-    if (workingDir) {
-        oldWorkingDir = QT_GETCWD(buff, PATH_MAX + 1);
-        QT_CHDIR(workingDir);
-    }
+    pid_t childPid = doSpawn(fd_count, fd_map, argv, envp, workingDir, false);
 
-    pid_t childPid = doSpawn(fd_count, fd_map, argv, envp, false);
-
-    if (oldWorkingDir)
-        QT_CHDIR(oldWorkingDir);
-
-    if (childPid != -1) {
-        q->setProcessState(QProcess::Running);
-        QMetaObject::invokeMethod(q, "_q_startupNotification", Qt::QueuedConnection);
+    if (childPid == -1) {
+        QString error = qt_error_string(errno);
+        qt_safe_write(childStartedPipe[1], error.data(), error.length() * sizeof(QChar));
+        qt_safe_close(childStartedPipe[1]);
+        childStartedPipe[1] = -1;
     }
 
     return childPid;
 }
-
-bool QProcessPrivate::processStarted()
-{
-    return processState == QProcess::Running;
-}
-
-bool QProcessPrivate::waitForStarted(int /*msecs*/)
-{
-    return processStarted();
-}
 #endif // Q_OS_QNX
 
 qint64 QProcessPrivate::bytesAvailableFromStdout() const
@@ -1009,7 +1016,6 @@ static int qt_timeout_value(int msecs, int elapsed)
     return timeout < 0 ? 0 : timeout;
 }
 
-#if !defined(Q_OS_QNX)
 bool QProcessPrivate::waitForStarted(int msecs)
 {
     Q_Q(QProcess);
@@ -1037,7 +1043,6 @@ bool QProcessPrivate::waitForStarted(int msecs)
 #endif
     return startedEmitted;
 }
-#endif // Q_OS_QNX
 
 bool QProcessPrivate::waitForReadyRead(int msecs)
 {
@@ -1059,10 +1064,8 @@ bool QProcessPrivate::waitForReadyRead(int msecs)
         int nfds = deathPipe[0];
         FD_SET(deathPipe[0], &fdread);
 
-#if !defined(Q_OS_QNX)
         if (processState == QProcess::Starting)
             add_fd(nfds, childStartedPipe[0], &fdread);
-#endif
 
         if (stdoutChannel.pipe[0] != -1)
             add_fd(nfds, stdoutChannel.pipe[0], &fdread);
@@ -1083,12 +1086,10 @@ bool QProcessPrivate::waitForReadyRead(int msecs)
 	    return false;
 	}
 
-#if !defined(Q_OS_QNX)
 	if (childStartedPipe[0] != -1 && FD_ISSET(childStartedPipe[0], &fdread)) {
             if (!_q_startupNotification())
                 return false;
 	}
-#endif
 
         bool readyReadEmitted = false;
 	if (stdoutChannel.pipe[0] != -1 && FD_ISSET(stdoutChannel.pipe[0], &fdread)) {
@@ -1135,10 +1136,8 @@ bool QProcessPrivate::waitForBytesWritten(int msecs)
         int nfds = deathPipe[0];
         FD_SET(deathPipe[0], &fdread);
 
-#if !defined(Q_OS_QNX)
         if (processState == QProcess::Starting)
             add_fd(nfds, childStartedPipe[0], &fdread);
-#endif
 
         if (stdoutChannel.pipe[0] != -1)
             add_fd(nfds, stdoutChannel.pipe[0], &fdread);
@@ -1161,12 +1160,10 @@ bool QProcessPrivate::waitForBytesWritten(int msecs)
 	    return false;
 	}
 
-#if !defined(Q_OS_QNX)
 	if (childStartedPipe[0] != -1 && FD_ISSET(childStartedPipe[0], &fdread)) {
 	    if (!_q_startupNotification())
 		return false;
 	}
-#endif
 
 	if (stdinChannel.pipe[1] != -1 && FD_ISSET(stdinChannel.pipe[1], &fdwrite))
 	    return _q_canWrite();
@@ -1204,10 +1201,8 @@ bool QProcessPrivate::waitForFinished(int msecs)
         FD_ZERO(&fdread);
         FD_ZERO(&fdwrite);
 
-#if !defined(Q_OS_QNX)
         if (processState == QProcess::Starting)
             add_fd(nfds, childStartedPipe[0], &fdread);
-#endif
 
         if (stdoutChannel.pipe[0] != -1)
             add_fd(nfds, stdoutChannel.pipe[0], &fdread);
@@ -1231,12 +1226,10 @@ bool QProcessPrivate::waitForFinished(int msecs)
 	    return false;
 	}
 
-#if !defined(Q_OS_QNX)
 	if (childStartedPipe[0] != -1 && FD_ISSET(childStartedPipe[0], &fdread)) {
 	    if (!_q_startupNotification())
 		return false;
 	}
-#endif
 	if (stdinChannel.pipe[1] != -1 && FD_ISSET(stdinChannel.pipe[1], &fdwrite))
 	    _q_canWrite();
 
@@ -1301,16 +1294,6 @@ void QProcessPrivate::_q_notified()
 #if defined(Q_OS_QNX)
 bool QProcessPrivate::startDetached(const QString &program, const QStringList &arguments, const QString &workingDirectory, qint64 *pid)
 {
-    QByteArray encodedWorkingDirectory = QFile::encodeName(workingDirectory);
-
-    // enter the working directory
-    char *oldWorkingDir = 0;
-    char buff[PATH_MAX + 1];
-    if (!encodedWorkingDirectory.isEmpty()) {
-        oldWorkingDir = QT_GETCWD(buff, PATH_MAX + 1);
-        QT_CHDIR(encodedWorkingDirectory.constData());
-    }
-
     const int fd_count = 3;
     int fd_map[fd_count] = { QT_FILENO(stdin), QT_FILENO(stdout), QT_FILENO(stderr) };
 
@@ -1327,13 +1310,18 @@ bool QProcessPrivate::startDetached(const QString &program, const QStringList &a
 
     char **envp = 0; // inherit environment
 
-    pid_t childPid = doSpawn(fd_count, fd_map, raw_argv.data(), envp, true);
+    // Encode the working directory if it's non-empty, otherwise just pass 0.
+    const char *workingDirPtr = 0;
+    QByteArray encodedWorkingDirectory;
+    if (!workingDirectory.isEmpty()) {
+        encodedWorkingDirectory = QFile::encodeName(workingDirectory);
+        workingDirPtr = encodedWorkingDirectory.constData();
+    }
+
+    pid_t childPid = doSpawn(fd_count, fd_map, raw_argv.data(), envp, workingDirPtr, true);
     if (pid && childPid != -1)
         *pid = childPid;
 
-    if (oldWorkingDir)
-        QT_CHDIR(oldWorkingDir);
-
     return childPid != -1;
 }