If UML wants to open an xterm channel and the xterm does not run properly (eg.
 terminates soon after starting) we will get a hang (a comment added in the
patch explains why).

This avoids the most common cause for this and adds a comment (which long term
will go away with a rewrite of that code); the complete fix would be to catch
the xterm process dying, up(&data->sem), and -EIO all requests from that point
onwards.

That applies for some of the other channels too, so part of the code should
probably be abstracted a little and generalized.
Signed-off-by: Chris Wedgwood <cw@f00f.org>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>