[OT] long-lived spawners (was: RFD: Rework/extending functionality of mdev)

[Laurent Bercot]

On 11/03/2015 14:02, Denys Vlasenko wrote:
> But that nldev process will exist for all time, right? That's not elegant.
> Ideally, this respawning logic should be in the kernel.

  Well there is already a kernel-based solution: hotplug.
  Sure, it's not serialized, but it's there. If you want something
serialized, then you have a stream of information you need to get
to the userspace - and at this point, you might as well send it
as is and let userspace sort it out, and that's exactly what the
netlink does.

  Needing daemons to answer notifications from userspace processes
or the kernel is the Unix way. It's not Hurd's, it's not Plan 9's
(AFAIK), but it's what we have, and it's not even that ugly. The
listening and spawning logic will have to be somewhere anyway, so
why not userspace ? Userspace memory is cheaper (because it can
be swapped), userspace processes are safer, and processes are not
a scarce resource.

-- 
  Laurent