[CRIU] Questions in CRIU restore mechanism.

[Chanho Park]

> > This error was caused due to /dev/ump and /dev/mali device node which
> are related with mali gpu device.
> 
> Dumping arbitrary device is impossible, since we don't know which state is
> inside the device. So every device should be taken separately and handled
> carefully.

OK. I'll try it separately.

> 
> > So, I passed it temporarily.
> >
> > The next error was produced by /dev/console.
> >
> > Parasite cmd 11/0xb process
> > (00.310244) 3610 fdinfo 0: pos: 0x               0 flags:           400000/0
> > (00.310466) Dumping path for 0 fd via self 759 [/dev/null]
> > (00.310609) fdinfo: type: 0x 1 flags: 0400000/0 pos: 0x       0 fd: 0
> > (00.310684) 3610 fdinfo 1: pos: 0x        ffffffff flags:                2/0
> > (00.310743) tty: Dumping tty 760 with id 0x2
> > (00.310811) Error (tty.c:203): tty: Can't obtain ptmx index
> > : Inappropriate ioctl for device
> > (00.310933) ----------------------------------------
> > (00.310962) Error (cr-dump.c:1419): Dump files (pid: 3610) failed with
> > -1
> >
> > The serial node can't supports GIOCGPTN ioctl.
> > I think only unix-ptmx node will support it.
> > How about you think this problem?
> 
> Consoles are also tricky. So far we've supported only ptys (and there are
> still issues with it). Dumping /dev/console can be done, but yet again --
> carefully with proper status-fetch of the console. What are the
> major:minor pair for the /dev/console you're having in your case?

The console device has 5:1 device number.

-sh-4.1# ls -al /dev/console
crw------- 1 root root 5, 1 Jan  1 09:00 /dev/console

> 
> > There are also some problem to dump character devices.
> > dump_chrdev supports only MEM_MAJOR and TTY types.
> > To dump any other character device types, we need to implement for that
> device. Right?
> 
> Exactly. We need to explore each device carefully and decide whether we
> can just dump one as a regular file, or if there's some state sitting
> inside device, so we should dump it as well.
> 
> 
> Chanho, as I told, we're open for accepting new functionality to CRIU. If
> you're willing to make crtools support the devices you've mentioned -- we
> will be glad to look at the patches, help with it and merge the code into
> the project!

OK. I'll do it if needed some patches.

Best Regards,
Chanho Park