We (Vcolo.com, formerly pdxcolo.net) have been running with a variation on 
the attached patch from day one.  I figure it's probably time to see if it 
should be included in the main distribution finally, especially since the 
API has now changed enough that moving it to 2.6.16 is going to get interesting.

The premise is simple: mconsole should be SOCK_STREAM.  In our case, this is 
used to detect the shutdown of the machine by simply polling for the control 
socket to close.  It's saved us from all kinds of potentially bizarre 
polling modes, so it's been well worth it.

The patch has worked fine so far, but I've never been satisfied with the way 
I kinda had to hack it into place without *fully* understanding the whole 
channel IRQ setup.  Since 2.6.16 changed how that works, I'm now at the 
point where I need more expert advise, hopefully along the way to putting 
this into the mainstream UML kernel.

Also attached is a version of uml_mconsole.c, forked who knows back when 
(~3yrs ago) so I'll have to dig out a file later to diff it against.  The 
only changes that should be in that file are switching to SOCK_STREAM and 
read()/write() instead of recv()/sendto().

Whether this is something that belongs in the main UML kernel or not, I 
would much appreciate it if someone has the time to help me to make sure the 
soft-IRQ handling is sane while moving it to the 2.6.16 codebase.

The patch is against 2.6.15.6 with uml-2.6.15-bs3-tls.patch.  There might be 
some minor line offset fuzz from some other local patches.

TIA,
    Omega
    aka Erik Walthinsen
    omega@vcolo.com