[CRIU] criu_restore() in Open MPI problems

[Adrian Reber]

On Wed, Apr 09, 2014 at 07:17:15PM +0400, Pavel Emelyanov wrote:
> >> I think the restore scheme should look like this:
> >> We run orterun, which prepare pipes and executes "CRIU restore".
> >> The OpenMPI plugin takes preparate pipes and restores them in a proper
> >> file descriptors.
> > 
> > It took me a while, but now I tried to restore a process from
> > orterun/mpirun with exec()ing 'criu restore' 
> 
> Thanks for doing this! :)
> 
> > I still get this error:
> > 
> > (00.030652)   4277: tty: open type pts id 0x2 index 14 (master 0 sid 0 pgrp 0 inherit 1)
> > (00.030654)   4277: Error (tty.c:541): tty: Can't dup SELF_STDIN_OFF: Bad file descriptor
> > (00.031052) Error (cr-restore.c:1035): 4277 exited, status=255
> > (00.031072) Error (cr-restore.c:1577): Restoring FAILED.
> > 
> > You are talking about a plugin which restores the missing pipes. How
> > would such a plugin have to look like? Do you have any examples on
> > re-creating pipes in a plugin?
> 
> Well, we don't have the pipe-restoring plugins. But we have examples of
> unknown file descriptors plugins at test/zdtm/live/static/criu-rtc.c. This
> one sits on the cr_plugin_dump_file/cr_plugin_restore_file hooks. I think
> it's perfectly possible to add needed for pipes.
> 
> You might also be interested in this mailing thread:
> http://lists.openvz.org/pipermail/criu/2014-March/012929.html
> 
> In it Cyrill tried to provide hooks for intercepting dump of TCP sockets.
> Intercepting of pipes dump should probably look similar.
> 
> BTW, since pipes we're talking about are really external (one end sits
> outside of our dump tree) I think we should detect this fact and call
> plugins for external pipes.
> 
> Hope that helps :) If you need more info -- feel free to ask.

Another thought. I am running mpirun which starts opal-restart which
execvp()'s 'criu restore'. opal-restart's FDs (stdout/stderr) are
already connected to the correct pipes of mpirun. Is there a way for
criu to inherit those FDs. So instead of re-opening stdout/stderr it
just uses the FDs 'criu restore' already uses? So maybe the plugin just
detects that at the same FD there is already a pipe and just re-uses
that pipe?

		Adrian
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