I'm not sure what you are actually trying to accomplish
I simply want a script that runs the equivalent of:
mpirun command>& out&
tail -f out
such that hitting Ctrl+C stops tail but leaves mpirun running. I can certainly
do this without mpirun, it's not unreasonable to expect to be able to do the
same with mpirun. I need mpirun to either ignore the SIGINT or not receive it
at all -- and as per your comments, ignoring it is not an option.
Let me rephrase my question then. With the following script:
mpirun command>& out&
tail -f out
SIGINT stops tail AND mpirun. That's OK. The following:
(
trap : SIGINT
mpirun command>& out&
)
tail -f out
has the same effect, idicating that mpirun overrides previous traps in the same
subshell. That's OK too. However the following:
(
trap : SIGINT
(
mpirun command>& out&
)
)
tail -f out
also has the same effect. How is mpirun overriding the trap in the *parent*
subshell so that it ends up getting the SIGINT that was supposedly blocked at
that level? Am I missing something trivial? How can I avoid this?
Thanks,
Pablo
On 23/04/11 16:27, Ralph Castain wrote:
On Apr 23, 2011, at 9:11 AM, Pablo Lopez Rios wrote:
Pressing Ctrl+C should stop tail -f, and the MPI job
should continue.
I don't think that is true at all. When you hit ctrl-C,
every process executing in the script receives it. Mpirun
traps the ctrl-c and immediately terminates all running
MPI procs.
By "Ctrl+C should stop tail -f" I mean that this is the
desired behaviour of the script, not that this is what ought
to happen in general. My question is how to achieve this
behaviour, since I'm having trouble working around mpirun
catching sigint.
Like I said in my other response, you can't - mpirun automatically traps sigint
and terminates the job in order to ensure proper cleanup during abnormal
terminations.
I'm not sure what you are actually trying to accomplish, but there are other
signals that don't cause termination. For example, we trap and forward SIGUSR1
and SIGUSR2 to your application procs, if that is of use.
But ctrl-c has a special meaning ("die"), and you can't tell mpirun to ignore
it.
Thanks,
Pablo
On 23/04/11 15:12, Ralph Castain wrote:
On Apr 23, 2011, at 6:20 AM, Reuti wrote:
Hi,
Am 23.04.2011 um 04:31 schrieb Pablo Lopez Rios:
I'm having a bit of a problem with wrapping mpirun in a script. The script
needs to run an MPI job in the background and tail -f the output. Pressing
Ctrl+C should stop tail -f, and the MPI job should continue.
I don't think that is true at all. When you hit ctrl-C, every process executing
in the script receives it. Mpirun traps the ctrl-c and immediately terminates
all running MPI procs.
However mpirun seems to detect the SIGINT that was meant for tail, and kills
the job immediately. I've tried workarounds involving nohup, disown, trap,
subshells (including calling the script from within itself), etc, to no avail.
The problem is that this doesn't happen if I run the command directly instead, without mpirun. Attached is a script that
reproduces the problem. It runs a simple counting script in the background which takes 10 seconds to run, and tails the output. If
called with "nompi" as first argument, it will simply run bash -c "$SCRIPT">& "$out"&,
and with "mpi" it will do the same with 'mpirun -np 1' prepended. The output I get is:
what about:
( trap "" sigint; exec mpiexec ...)&
i.e. replace the subshell with changed interrupt handling with the mpiexec. Well,
maybe mpiexec is adjusting it on its own again. This can be checked in
/proc/<pid>/status
-- Reuti
$ ./ompi_bug.sh mpi
mpi:
1
2
3
4
^C
$ ./ompi_bug.sh nompi
nompi:
1
2
3
4
^C
$ cat output.*
mpi:
1
2
3
4
mpirun: killing job...
--------------------------------------------------------------------------
mpirun noticed that process rank 0 with PID 1222 on node pablomme exited on
signal 0 (Unknown signal 0).
--------------------------------------------------------------------------
mpirun: clean termination accomplished
nompi:
1
2
3
4
5
6
7
8
9
10
Done
This convinces me that there is something strange with OpenMPI, since I expect
no difference in signal handling when running a simple command with or without
mpirun in the middle.
I've tried looking for options to change this behaviour, but I don't seem to
find any. Is there one, preferably in the form of an environment variable? Or
is this a bug?
I'm using OpenMPI v1.4.3 as distributed with Ubuntu 11.04, and also v1.2.8 as
distributed with OpenSUSE 11.3.
Thanks,
Pablo
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