I see. MPICH doesn’t trap any signal as I checked
😊. So back to your issue, let’s assume your trap did work, but after the signal handler, which after it called `MPI_Finalize`, the code is still going to run the same code that causes segfault in the first place, right? Wouldn’t that endup in infinite
signal loop or maybe the kernel smart out and by-passed your handler? Just a thought experiment.
Beside, MPICH is thread-safe but not interrupt safe. So you should not really call MPI functions inside signal handlers.
--
Hui Zhou
From: "Mccall, Kurt E. (MSFC-EV41)" <kurt.e.mccall@nasa.gov>
Date: Monday, April 6, 2020 at 4:50 PM
To: "Zhou, Hui" <zhouh@anl.gov>, "discuss@mpich.org" <discuss@mpich.org>
Subject: RE: [mpich-discuss] Abnormal termination on Linux
Hui,
I’d like to trap segfaults so that the process that raised them can be shut down gracefully/finalized without taking down the whole MPI job. Maybe you are right and I shouldn’t trap them.
However, when I install my signal handlers, I check if MPI already has a signal handler installed for each of them. It isn’t reporting that MPI has done so. Perhaps my code is incorrect?
setUpOneHandler(const int signum)
{
struct sigaction sa_new, sa_old;
sa_new.sa_handler = mpiSignalHandler;
sa_new.sa_flags = 0;
sigemptyset(&sa_new.sa_mask);
if (sigaction(signum, NULL, &sa_old) < 0)
{
// ERROR: could not query old handler
} else if (sa_old.sa_handler == SIG_IGN ||
sa_old.sa_handler == SIG_DFL)
{
// MPI hasn't set its own handler for this signal, so we
// will install our own.
if (sigaction(signum, &sa_new, NULL) < 0)
{
// ERROR: could not set new handler
}
} else
{
// MPI already has a handler installed for this signal. Do nothing
}
}
From: Zhou, Hui <zhouh@anl.gov>
Sent: Monday, April 6, 2020 2:08 PM
To: Mccall, Kurt E. (MSFC-EV41) <kurt.e.mccall@nasa.gov>; discuss@mpich.org
Subject: [EXTERNAL] Re: [mpich-discuss] Abnormal termination on Linux
Thanks, Kurt. I think the reason your signal trap didn’t work is because `mpiexec` is trapping it first. Segfault is code error. Why would you want to trap it?
--
Hui Zhou
From: "Mccall, Kurt E. (MSFC-EV41)" <kurt.e.mccall@nasa.gov>
Date: Monday, April 6, 2020 at 1:52 PM
To: "Zhou, Hui" <zhouh@anl.gov>, "discuss@mpich.org" <discuss@mpich.org>
Subject: RE: [mpich-discuss] Abnormal termination on Linux
Hui,
Sorry for not mentioning that. MPICH 3.3.2 compiled with pgc++ 19.5.
Kurt
From: Zhou, Hui <zhouh@anl.gov>
Sent: Monday, April 6, 2020 12:58 PM
To: discuss@mpich.org
Cc: Mccall, Kurt E. (MSFC-EV41) <kurt.e.mccall@nasa.gov>
Subject: [EXTERNAL] Re: [mpich-discuss] Abnormal termination on Linux
Which version of MPICH were you running?
--
Hui Zhou
From: "Mccall, Kurt E. (MSFC-EV41) via discuss" <discuss@mpich.org>
Reply-To: "discuss@mpich.org" <discuss@mpich.org>
Date: Monday, April 6, 2020 at 12:45 PM
To: "discuss@mpich.org" <discuss@mpich.org>
Cc: "Mccall, Kurt E. (MSFC-EV41)" <kurt.e.mccall@nasa.gov>
Subject: Re: [mpich-discuss] Abnormal termination on Linux
I should mention that I am unable to predict in which node or process the abnormal termination occurs, so I can’t practically attach a debugger and try to intercept the error.
Kurt
From: Mccall, Kurt E. (MSFC-EV41) <kurt.e.mccall@nasa.gov>
Sent: Monday, April 6, 2020 11:50 AM
To: discuss@mpich.org
Cc: Mccall, Kurt E. (MSFC-EV41) <kurt.e.mccall@nasa.gov>
Subject: Abnormal termination on Linux
I have a couple of questions about abnormal termination. The EXIT CODE below is 11, which could be signal SIGSEGV, or is it something defined by MPICH? If it is SIGSEGV, it is strange because my signal handler isn’t catching it and cleaning
up properly (the signal handler calls MPI_Finalize()). Is there any way to get more information about the location of the error?
= BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
= PID 14385 RUNNING AT n020.cluster.com
= EXIT CODE: 11
= CLEANING UP REMAINING PROCESSES
= YOU CAN IGNORE THE BELOW CLEANUP MESSAGES
Thanks,
Kurt