Well, yes and no. When a process abnormally terminates, OMPI will kill the job - this is done by first hitting each process with a SIGTERM, followed shortly thereafter by a SIGKILL. So you do have a short time on each process to attempt to cleanup.

My guess is that your signal handler actually is getting called, but we then kill the process before you can detect that it was called.

You might try adjusting the time between sigterm and sigkill using the odls_base_sigkill_timeout MCA param:

mpirun -mca odls_base_sigkill_timeout N

should cause it to wait for N seconds before issuing the sigkill. Not sure if that will help or not - it used to work for me, but I haven't tried it for awhile. What versions of OMPI are you using?


On Mar 22, 2012, at 4:49 PM, Júlio Hoffimann wrote:

Dear all,

I'm trying to handle signals inside a MPI task farming model. Following is a pseudo-code of what i'm trying to achieve:

volatile sig_atomic_t unexpected_error_occurred = 0;

void my_handler( int sig )
{
    unexpected_error_occurred = 1;
}

//
// somewhere in the code...
//

signal(SIGTERM, my_handler);

if (root process) {

    // do stuff

    if ( unexpected_error_occurred ) {

        // save something

        // reraise the SIGTERM again, but now with the default handler
        signal(SIGTERM, SIG_DFL);
        raise(SIGTERM);
    }
}
else { // slave process

    // do different stuff

    if ( unexpected_error_occurred ) {

        // just propragate the signal to the root
        signal(SIGTERM, SIG_DFL);
        raise(SIGTERM);
    }
}

signal(SIGTERM, SIG_DFL);                       // reassign default handler

// continues the code...

As can be seen, the signal handling is required for implementing a restart feature. All the problem resides in the assumption i made that all processes in the communicator will receive a SIGTERM as a side effect. Is it a valid assumption? How the actual MPI implementation deals with such scenarios?

I also tried to replace all the raise() calls by MPI_Abort(), which according to the documentation (http://www.open-mpi.org/doc/v1.5/man3/MPI_Abort.3.php), sends a SIGTERM to all associated processes. The undesired behaviour persists: when killing a slave process, the save section in the root branch is not executed.

Appreciate any help,
Júlio.
_______________________________________________
users mailing list
users@open-mpi.org
http://www.open-mpi.org/mailman/listinfo.cgi/users