[lxc-users] [CRIU] Live Migration with LXD on Raspberry Pi2

[Cyrill Gorcunov]

On Thu, Jun 16, 2016 at 03:26:09PM -0700, Andrew Vagin wrote:
> > 
> > What kernel versions are you using? To be honest, I'm not too familiar
> > with the VMA code, but I wouldn't be surprised if there was an
> > arch-specific bug, as I'm not sure how well used that path is.
> > 
> > Looking at the kernel code for sys_shmat, I don't understand how you'd
> > get a zero value return from it, as you do in your log:
> 
> Here is something strange. These two lines contain vma_entry->start, but
> in the first line it's equal to 0 and in the second value it's
> 0x76f9b000. How is it possible?
> 
> > 
> > > pie: 644: Attach SYSV shmem 65538 at 0x0
> 
> pr_info("Attach SYSV shmem %d at %"PRIx64"\n", (int)vma_entry->fd, vma_entry->start);
> 
> > > pie: 644: Error (pie/restorer.c:1176): Can't restore 0x76f9b000 mappin>
> > > pie: 644: g with 0x0
> 
> pr_err("Can't restore %"PRIx64" mapping with %lx\n", vma_entry->start, va);
> 
> > > pie: 644: Error (pie/restorer.c:1506): Restorer fail 644
> > 

There are two processes

pie: 644: Attach SYSV shmem 65538 at 0x0
   pie: 644: Error (pie/restorer.c:1176): Can't restore 0x76f9b000 mappin>
   pie: 644: g with 0x0
   pie: 644: Error (pie/restorer.c:1506): Restorer fail 644
...
pie: 645: Attach SYSV shmem 65538 at 0x0
   pie: 645: Error (pie/restorer.c:1176): Can't restore 0x76f9b000 mappin>
   (01.300378) Â  Â  Â 1: Trying to restore recv queue for 42
   pie: 645: g with 0x0

may not we have some kind of race here? Which won't be easy to catch :)