[Devel] Re: [PATCH 08/10] Introduce functions to restart a process

Andrey Mirkin major at openvz.org
Thu Oct 23 21:04:41 PDT 2008


On Thursday 23 October 2008 17:49 Dave Hansen wrote:
> On Thu, 2008-10-23 at 13:54 +0400, Andrey Mirkin wrote:
> > We are putting special structure on stack, which is used at the very end
> > of the whole restart procedure to restore complex states (ptrace is one
> > of such cases). Right now I don't need to use this structure as we have a
> > deal with simple cases, but reservation of 256 bytes on stack is needed
> > for future.
>
> Wow.  So you're saying that, if this patch is accepted, we simply need
> to accept that anything being checkpointed will use an extra 256 bytes
> of stack?  Seems like something to perhaps put in the changelog rather
> than some completely undocumented assembly nugget.

This 256 bytes will be used only during restart procedure and only by our 
module. As you can see in i386_ret_from_resume we are restoring it back. So, 
when process will return to user space it will not have extra 256 bytes 
reserved on stack already. I will add information about it to documentation 
and changelog.

Andrey


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