[PATCH] uml: sigio code - reduce spinlock hold time

In a previous patch I shifted an allocation to being atomic.

In this patch, a better but more intrusive solution is implemented, i.e.  hold
the lock only when really needing it, especially not over pipe operations, nor
over the culprit allocation.

Additionally, while at it, add a missing kfree in the failure path, and make
sure that if we fail in forking, write_sigio_pid is -1 and not, say, -ENOMEM.

And fix whitespace, at least for things I was touching anyway.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>