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    SubjectRe: [Devel] Re: [PATCH 0/9] OpenVZ kernel based checkpointing/restart

    Andrey Mirkin wrote:
    > On Monday 20 October 2008 19:55 Dave Hansen wrote:
    >> On Mon, 2008-10-20 at 16:14 +0400, Andrey Mirkin wrote:
    >>> Right now my patchset (v2) provides an ability to checkpoint and restart
    >>> a group of processes. The process of checkpointing and restart can be
    >>> initiated from external process (not from the process which should be
    >>> checkpointed).
    >> Absolutely. Oren's code does it this way to make for a smaller patch at
    >> first. The syscall takes a pid argument so it is surely expected to be
    >> expanded upon later.
    >>> Also I think that all the restart job (including process forking) should
    >>> be done in kernel, as in this case we will not depend on user space and
    >>> will be more secure. This is also implemented in my patchset.
    >> Do you think that this is an approach that Oren's patches are married
    >> to, or is this a "feature" we can add on later?
    > Well, AFAICS from Oren's patch set his approach is oriented on process
    > creation in user space. I think we should choose right now what approach will
    > be used for process creation.
    > We have two options here: fork processes in kernel or fork them in user space.
    > If process will be forked in user space, then there will be a gap when process
    > will be in user space and can be killed with received signal before entering

    > kernel. Also we will need a functionolity to create processes with predefined
    > PID. I think it is not very good to provide such ability to user space. That

    Rethinking this -- if the user wishes she can construct a suitable
    checkpoint image that would do exactly that. It takes more effort than
    using a system call, but the result is similar.

    What I had in mind for that special clone-with-pid is to restrict when
    it can be used (e.g. when the container is in a "restarting" state or
    something like that.



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