QProcess won’t terminate immediately in a forked process

[lederer]

I have the following problem:

I have a linux application, which can be either run as a standalone application or a service (forked).

My application later starts another application (in this case, mplayer) using a QProcess.
If I terminate my application, I first sent a SIGTERM to my sub process, wait for its termination and then delete my QProcess object and terminate my application. All this works fine, if I am in standalone mode.

If I do the same in service mode, the QProcess will NOT terminate after I sent the SIGTERM, but the started process gots zombie.
The result is that my application waits 30 seconds (even, if I do NOT add a “waitForFinished”) until it kills the QProcess and terminates.

My question now is:
does anyone know, WHY QProcess cannot be terminated/killed, if the application is running in service mode, but can, if it is running normally?

Thx for any help!!

Some details:
Service mode means:

// start player as daemon
        pid_t pid, sid;
        // fork off parent process
        pid = fork();
        if (pid < 0) {
            // fork failed
            fprintf(stderr, "Unable to fork daemon process.");
            exit(EXIT_FAILURE);
        }
        if (pid > 0) {
            // fork succeeded. terminate parent
            qDebug() << "Forking child (" <<  pid << ") succeeded. Terminating parent (" << getpid() << ").\n";
            exit(EXIT_SUCCESS);
        }
 
        // child continues...
        umask(0);
        // start new session
        sid = setsid();
        if (sid < 0) {
            fprintf(stderr, "Unable to start new session.");
            exit(EXIT_FAILURE);
        }

// start player as daemon
        pid_t pid, sid;
        // fork off parent process
        pid = fork();
        if (pid < 0) {
            // fork failed
            fprintf(stderr, "Unable to fork daemon process.");
            exit(EXIT_FAILURE);
        }
        if (pid > 0) {
            // fork succeeded. terminate parent
            qDebug() << "Forking child (" <<  pid << ") succeeded. Terminating parent (" << getpid() << ").\n";
            exit(EXIT_SUCCESS);
        }
     
        // child continues...
        umask(0);
        // start new session
        sid = setsid();
        if (sid < 0) {
            fprintf(stderr, "Unable to start new session.");
            exit(EXIT_FAILURE);
        }

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my QProcess is started:

this->activePlayer = new QProcess(this);
    this->activePlayer->start(QString("mplayer"), this->playerArgs);
    this->activePlayer->waitForStarted();

this->activePlayer = new QProcess(this);
    this->activePlayer->start(QString("mplayer"), this->playerArgs);
    this->activePlayer->waitForStarted();

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and terminated

kill(this->activePlayer->pid(), SIGTERM);
    this->activePlayer->waitForFinished();
    system("killall mplayer 2> /dev/null");  // kill all remaining videoplayer processes!
    delete this->activePlayer;

kill(this->activePlayer->pid(), SIGTERM);
    this->activePlayer->waitForFinished();
    system("killall mplayer 2> /dev/null");  // kill all remaining videoplayer processes!
    delete this->activePlayer;

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Instead of “kill”, I also tried here

this->activePlayer->terminate();

this->activePlayer->terminate();

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and

this->activePlayer->kill();

this->activePlayer->kill();

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same results! :-(

[wysota]

same results! :-(

What results? It seems to me your process should end by itself.