[CRIU] test/others/rpc test cases

[Andrei Vagin]

On Wed, May 16, 2018 at 05:16:12PM +0100, Dmitry Safonov wrote:
> 2018-05-16 16:52 GMT+01:00 Adrian Reber <adrian at lisas.de>:
> > Hello Andrei,
> >
> > we quickly chatted about the tests in test/others/rpc and I had a look
> > at it.
> >
> > One test (errno.py) dumps itself, keeps on running and tries to restore
> > itself. This should (and does fail) as the PID is already in use by the
> > test case. The test case wants to to test the error handling of 'criu
> > service'. But CRIU just kills all processes which it failed to restore
> > in criu/cr-restore.c (around line 2240 : kill(vpid(pi), SIGKILL);).
> >
> > As the test case is killed by CRIU it counts as a failure. I guess this
> > used to work at some point in time, but with 3.8.1 it does not.
> >
> > I am not sure what the right solution is. Should CRIU kill a process if
> > restore fails, probably to make sure that no half restored process still
> > exists. Maybe the test case does not make sense anymore...
> >
> > Do you have any thoughts on this? Is this a CRIU bug or a wrong test case?
> 
> It looks to me like a valid test. CRIU shouldn't kill existing tasks with
> reused PID. Do we run this errno.py on Travis?
> 
> I haven't even compile tested, but something like this might fix?
> 
> --->8---
> --- a/criu/cr-restore.c
> +++ b/criu/cr-restore.c
> @@ -1510,6 +1510,7 @@ static int do_fork_with_pid(struct pstree_item
> *item, struct ns_id *pid_ns, stru
>         if (pid < 0) {
>                 pr_perror("Can't clone()");
>                 ret = -1;
> +               hlp_pid->ns[i].virt = -1;

If we have three processes A -> B -> C. PID-s of B, C have been reused.
With you patch, virt for B will be set to -1, but a process with the C
pid will be killed.

I think something like this should fix a problem:
@@ -2556,8 +2556,8 @@ out_kill:
                struct pstree_item *pi;
 
                for_each_pstree_item(pi)
-                       if (vpid(pi) > 0)
-                               kill(vpid(pi), SIGKILL);
+                       if (pi->pid->real > 0)
+                               kill(pi->pid->real, SIGKILL);
        }
 
 out:


>                 goto unblock;
>         }
> 
> 
> -- 
>              Dmitry