Re: [RFC PATCH] proc, pidns: Add highpid

On 12/01/2014 09:47 AM, Florian Weimer wrote:

* Andy Lutomirski:

quoted

On Nov 30, 2014 1:47 AM, "Florian Weimer" [off-list ref] wrote:

quoted

* Andy Lutomirski:

quoted

The initial implementation is straightforward: highpid is simply a
64-bit counter. If a high-end system can fork every 3 ns (which
would be amazing, given that just allocating a pid requires at
atomic operation), it would take well over 1000 years for highpid to
wrap.

I'm not sure if I'm reading the patch correctly, but is the counter
namespaced?  If yes, why?

It's namespaced so that CRIU can migrate/restore a whole pid namespace.

Oh well, this requirement is at odds with system-wide uniqueness.  Is
CRIU really that important? :-)

Well, in this context it is. Since the main (if not the only) use-case for
highpid is to read one, remember, then compare to new value, restoring it
to wrong/arbitrary value will break the using applications in 100% cases.

Thus we really need the ability to restore this value.

Thanks,
Pavel