fcntl(2) lock on /dev/null fails with EINVAL

[Steffen Nurpmeso]

Matthew Dillon <dillon at backplane.com> wrote:
 |I dunno about allowing lockf on /dev/null.  Any process can open /dev/null,
 |it isn't unique to whatever you are testing and there could easily be
 |unintended consequences.  Linux does support it but I dunno how good an
 |idea that is.

I'm surely not going and try to convince you.
(In my case i will finally have an in-code mailbox that can act
similar to /dev/null.)  But it's not that the DragonFly behaviour
revealed a bug.

--steffen