[CRIU] [PATCH] criu: Add exec-cmd option (v2)

[Andrew Vagin]

On Thu, Mar 20, 2014 at 10:38:27PM +0400, Pavel Emelyanov wrote:
> On 03/20/2014 08:24 PM, Deyan Doychev wrote:
> > From: Deyan Doychev <deyandoichev at gmail.com>
> > 
> > The --exec-cmd option specifies a command that will be execvp()-ed on successful
> > restore. This way the command specified here will become the parent process of
> > the restored process tree.
> > 
> > When this option is specified criu will fork to become a daemon before it starts
> > restoring the processes. It also implies the -d option so waiting for the
> > restored processes to finish is responsibility of the command specified here.
> > 
> > This option will be used when restoring LinuX Containers and it seems helpful
> > for perf or other use cases when restored processes must be supervised by a
> > parent.
> > 
> > Two directions were researched in order to integrate CRIU and LXC:
> > 
> > 1. We tell to CRIU, that after restoring container is should execve()
> >    lxc properly explaining to it that there's a new container hanging
> >    around.
> > 
> > 2. We make LXC set himself as child subreaper, then fork() criu and ask
> >    it to detach (-d) from restore container afterwards. Being a subreaper,
> >    it should get the container's init into his child list after it.
> > 
> > The main reason for choosing the first option is that the second one can't work
> > with the RPC service. If we call restore via the service then criu service will
> > be the top-most task in the hierarchy and will not be able to reparent the
> > restore trees to any other task in the system. Calling execve from service
> > worker sub-task (and daemonizing it) should solve this.
> > 
> > Signed-off-by: Deyan Doychev <deyandoichev at gmail.com>
> > ---
> >  cr-restore.c         |    5 ++++-
> >  cr-service.c         |   22 ++++++++++++++++++++++
> >  crtools.c            |   33 ++++++++++++++++++++++++++++++++-
> >  include/cr_options.h |    1 +
> >  lib/criu.c           |    5 +++++
> >  protobuf/rpc.proto   |    1 +
> >  6 files changed, 65 insertions(+), 2 deletions(-)
> > 
...
> > @@ -37,6 +37,7 @@ message criu_opts {
> >  
> >  	optional uint32			cpu_cap		= 20 [default = 0xffffffff];
> >  	optional bool			force_irmap	= 21;
> > +	optional string			exec_cmd	= 22;
> 
> Maybe it's better to make this field repeated to allow for spaces in
> arguments and to simplify the parsing (no strtoks would be required)?

+1

> 
> >  }
> >  
> >  message criu_dump_resp {
> > 
> 
>