how to tell when jobs are finished

Pedro Díaz Jiménez pdiaz88 at terra.es
Sat Aug 4 19:21:52 EDT 2001


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On Saturday 04 August 2001 20:44, Ron Chen wrote:
> Why don't you try to catch the SIGCHLD?

nicer

>
> When child exits, the parent receives SIGCHLD:

and when the child is stopped. I don't know if that could be an issue here

>
> #include <signal.h>
> #include <sys/types.h>
> #include <sys/wait.h>
>
> int sh(int i) /* signal handler */
> {
>  int status;
>  pid_t pid;
>
>  printf("Hello\t");
>  pid = wait(&status);
>  printf("pid = %d  status = %d\n", pid, (status>>8));
> }
>
>
> main()
> {
>  int i;
>
>  signal(SIGCHLD, sh); /* install handler */
>
>  for (i=0;i<3;i++)
>   if (fork()==0)
>    { sleep(i);
>      exit(i);
>    }
>
>  for (i=0; i<10;i++) /* parent work on other stuff */
>    sleep(10);
> }
>
> The parent (main function) may not call sleep(10), I
> used it as a hack. For you, you should call select to
> listen to the new execution request from the cluster
> master (like qmaster in SGE).
>
> The program will print out the pid and exit status:
> Hello	pid = 19443  status = 0
> Hello	pid = 19444  status = 1
> Hello	pid = 19445  status = 2
>
>
> Just wanted to point out one thing here:
> We are working on the process level. We need more work
> to trace the process tree to make sure that we can get
> the information about the job (which consists of 1
> more more processes). Currently, if the child forks
> another child, we won't be able to know.
>
> -Ron
>
> --- Nicholas Henke <henken at seas.upenn.edu> wrote:
> > Thanks guys for the input--
> > 	I think the signal handler with a polling mechanism
> > should work
> > very nice.
> >
> > Nic
> >
> > > Hi,
> > >
> > > I agree with Sean about the use of waitpid().
> >
> > About the daemon, well, I think
> >
> > > is not necesary. If I not  misunderstood you, what
> >
> > you want to do is execute
> >
> > > a certain number of programs and know when anyone
> >
> > of those programs exited.
> >
> > > Here is my proposal, in  the form of a
> >
> > pseudo-shell
> >
> > > 1.read somehow the list of programs to execute
> > > 2. For each program to run, create a child using
> >
> > fork() (the master
> >
> > > creates all the childs)
> > > 3. (optional) you may want to redirect each child
> >
> > output to some file
> >
> > > 4. get from the childs its pid via some IPC
> >
> > mechanism (a pipe will do) and
> >
> > > store the in an array or something (i would use a
> >
> > linked list, or a
> >
> > > search-tree table if you will have lots of pids)
> > > 5. Finally, each child calls exec*() and replaces
> >
> > its memory image with the
> >
> > > program desired - that is - executes the program
> > > 6. Now, you have to know when each of the programs
> >
> > you executed has exited.
> >
> > > For simplicity, lets assume you whant to printf
> >
> > something like "Hey!, PID
> >
> > > XXXX finished!". You can do this in two forms (to
> >
> > mi knowledge):
> > > 	a) loop until all the programs have exited. You
> >
> > can use waitpid with WNOHANG
> >
> > > to poll each pid. Advantage: Simple.
> >
> > Disadvantage: You can't do other
> >
> > > productive things while waiting
> > > 	b) Set a signal handler to the alarm signal, and
> >
> > test say each second for
> >
> > > completion of one of the pids in your list. If
> >
> > completion, print message and
> >
> > > remove that pid from the list. Disable signal
> >
> > callback when list is empty,
> >
> > > and re-enable when list has at leat one element.
> >
> > Advantages: You can do other
> >
> > > productive things, like launching more processes.
> >
> > Disadvantages: A little
> >
> > > more complicated. If you use this option, see
> >
> > sigaction(2) and signal(2)
> >
> >
> >
> > _______________________________________________
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>
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>
>
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- -- 

  __________________________________________________
 /                                                  \
 | Pedro Diaz Jimenez                               |
 |                                                  |
 | pdiaz88 at terra.es      pdiaz at acm.asoc.fi.upm.es   |
 |                                                  |
 |                                                  |
 | http://planetcluster.org                         |
 | Clustering & H.P.C. news and documentation       |
 |                                                  |
 | There are no stupid questions, but there're a    |
 | lot of inquisitive idiots                        |
 |        Anonymous                                 |
 |                                                  |
 | "I find your lack of faith disturbing."          |
 |        Darth Vader, Star Wars Episode IV         |
 \__________________________________________________/

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