[uml-devel] Re: [RFC] PATCH 0/4 - Time virtualization

[Jeff Dike <jdike@addtoit.com>]

On Wed, Apr 19, 2006 at 02:25:00AM -0600, Eric W. Biederman wrote:
> That patch should probably be separated, from the rest.
> But it looks like a fairly sane idea. 

Yeah, I'll keep these together for now, but the ptrace one is
conceptually different from the rest.

> I think you missed a couple essential things to a time namespace.
> Timers.  The posix timers, in particular.  The worst
> of those is the monotonic timer.  

Oops, thanks for pointing that out.

> In the case of migration the ugly case to properly handle is the
> monotonic timer.   That needs an offset yet it is absolutely forbidden
> to provide that offset from the inside.  So this is the one namespace
> that I think is inappropriate to use sys_unshare to create.
> We need a system call so that we can specify the minimum or the
> starting monotonic time base.

For migration, it looks like the container will have to specify the
time base at creation so that everything in it will have a consistent
view of time if they get moved around.

So, maybe it belongs in clone as a "backwards" flag similar to
CLONE_NEWNS.

				Jeff


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