Re: fhpd <program>

[Andrew Cagney <cagney@redhat.com>]

Hi Stan,

I'm not sure what you mean by never regains I/O control.

One key issue though is wiring the child process up to a 
frysk.sys.PseudoTerminal - otherwise the process and fhpd will be 
fighting over control of the terminal.  Don't forget that there are two 
cases to handle:

- fhpd command line where it clearly should create the PTY
- UI where the pty will be part of a Terminal panel and the code should 
bind the created process to that

The alternative approach I've seen implemented in the past is to use 
job-control like mechanisms where fhpd and the child alternate over who 
is the terminal's controlling process; similar to bash and fg/bg et.al.  
Since being able to direct the child's I/O to a graphical terminal is a 
requirement, and this alternative has no such mechanism, the approach is 
considered flawed.

Andrew

Stan Cox wrote:
> This is my rather quick attempt at getting 'fhpd <program>' to work.
> <program> starts as a child of fhpd but fhpd never regains I/O control.
>
> AttachHandler 
> -parse <program>
> -requestCreateAttachedProc for <program>
>
> ProcObserver
> -new
>
>
>   
> ------------------------------------------------------------------------
>
> /home/scox/frysk/src /home/scox/frysk ~
> Index: frysk-core/frysk/cli/hpd/CLI.java
> ===================================================================
> RCS file: /cvs/frysk/frysk-core/frysk/cli/hpd/CLI.java,v
> retrieving revision 1.45
> diff -u -p -r1.45 CLI.java
> --- frysk-core/frysk/cli/hpd/CLI.java	27 Feb 2007 17:16:43 -0000	1.45
> +++ frysk-core/frysk/cli/hpd/CLI.java	1 Mar 2007 15:59:20 -0000
> @@ -62,13 +62,19 @@ import javax.naming.NameNotFoundExceptio
>  
>  import frysk.value.InvalidOperatorException;
>  import frysk.value.Variable;
> +// import frysk.proc.Action;
> +import frysk.proc.Action;
>  import frysk.proc.Host;
>  import frysk.proc.Manager;
>  import frysk.proc.Proc;
>  import frysk.proc.ProcId;
>  import frysk.proc.Task;
> +import frysk.proc.TaskObserver;
>  import frysk.rt.RunState;
>  import frysk.rt.StackFrame;
> +//import frysk.sys.Pid;
> +import frysk.sys.Signal;
> +import frysk.sys.Sig;
>  import frysk.rt.LineBreakpoint;
>  
>  
> @@ -86,6 +92,7 @@ public class CLI 
>    int stackLevel = 0;
>    static Object monitor = new Object();
>    static boolean attached;
> +  static boolean child_created;
>    RunState runState;
>    private RunStateObserver runStateObserver;
>    private ActionpointTable apTable = new ActionpointTable();
> @@ -356,11 +363,13 @@ public class CLI 
>  	}
>      }
>    }
> -
> -  class AttachHandler implements CommandHandler
> +  
> +    class AttachHandler implements CommandHandler
>    {
>      public void handle(Command cmd) throws ParseException
>      {
> +      String[] args = new String[1];
> +
>        refreshSymtab();	// XXX ?
>        ArrayList params = cmd.getParameters();
>        boolean cli = true;
> @@ -391,27 +400,38 @@ public class CLI 
>  	    }
>  	  else if (((String)params.get(idx)).matches("[0-9]+"))
>  	    pid = Integer.parseInt((String)params.get(idx)); 
> +	  else args[0] = (String)params.get(idx);
>  	}
>  
> +      final ProcObserver procObserver = new ProcObserver();
>        if (cli)
> -	{
> -	  Manager.host.requestFindProc(new ProcId(pid), new Host.FindProc() {
> -
> -	      public void procFound (ProcId procId)
> -	      {
> -                  
> -		Manager.eventLoop.requestStop();
> -	      }
> -
> -	      public void procNotFound (ProcId procId, Exception e)
> -	      {
> -	      }});
> -	  Manager.eventLoop.run();
> -	  CLIEventLoop eventLoop = new CLIEventLoop();
> -	  eventLoop.start();
> -	}
> +        {
> +          if (pid > 0)
> +            {
> +              Manager.host.requestFindProc(new ProcId(pid), new Host.FindProc()
> +              {
> +                public void procFound (ProcId procId)
> +                {
> +                  Manager.eventLoop.requestStop();
> +                }
> +
> +                public void procNotFound (ProcId procId, Exception e)
> +                {
> +                }
> +              });
> +            }
> +          else
> +            {
> +              Manager.host.requestCreateAttachedProc(args, procObserver);
> +              child_created = true;
> +            }
> +          Manager.eventLoop.run();
> +          Manager.eventLoop.start();
> +        }
>  
> -      proc = Manager.host.getProc (new ProcId (pid));
> +      proc = Manager.host.getProc(new ProcId(pid));
> +      //Proc me = Manager.host.getProc(new ProcId(Pid.get()));
> +      //me.getMainTask().requestAddSignaledObserver(procObserver);
>        if (proc == null)
>  	{
>  	  addMessage("The event manager is not running.", Message.TYPE_ERROR);
> @@ -962,6 +982,8 @@ public class CLI 
>        DetachHandler detachHandler = new DetachHandler();
>        Command command = new Command ("detach");
>        detachHandler.handle(command);
> +      if (child_created)
> +        Signal.tkill (pid, Sig.TERM);
>        addMessage("Quitting...", Message.TYPE_NORMAL);
>      }
>    }
> @@ -1232,30 +1254,57 @@ public class CLI 
>        }
>      return result;
>    }
> -    
> -  private static class CLIEventLoop extends Thread
> +
> +  private class ProcObserver
> +  implements TaskObserver.Attached,
> +  TaskObserver.Terminated,
> +  TaskObserver.Signaled
>    {
> -    public void run()
> +    
> +    public void addedTo (Object o)
> +    {
> +    }
> +
> +    public Action updateAttached (Task taskp)
> +    {
> +      proc = taskp.getProc();
> +      taskp.requestAddTerminatedObserver(this);
> +      return Action.CONTINUE;
> +    }
> +
> +    public void addFailed  (Object observable, Throwable w)
>      {
> -      try
> -        {
> -          Manager.eventLoop.run();
> -        }
> -      finally
> -        {
> -          synchronized (monitor)
> -	    {
> -	      monitor.notifyAll();
> -	    }
> -        }
>      }
>  
> -    public void requestStop()
> +    public void deletedFrom (Object o)
> +    {
> +    }
> +    
> +    public Action updateTerminated(Task task, boolean signal, int exit)
>      {
>        Manager.eventLoop.requestStop();
> +      return Action.CONTINUE;
>      }
> -  }
>      
> +    public Action updateSignaled (Task task, int signal)
> +    {
> +      System.out.println("From PID: " + task.getProc().getPid() + " TID: " + task.getTid());
> +      switch (signal)
> +      {
> +        case 2:
> +          System.out.println("SIGINT detected");
> +          break;
> +        case 3:
> +          System.out.println("SIGQUIT detected");
> +          break;
> +        case 15:
> +          System.out.println("SIGTERM detected");
> +          break;
> +      }
> +      return Action.CONTINUE;
> +    }
> +  }
> +  
>    private class RunStateObserver implements Observer 
>    {
>      public void update(Observable observable, Object arg)
>