CFR: fifo_open()/fifo_close() patch

[Bruce Evans]

On Fri, 16 May 2003, Don Lewis wrote:

> There are a few problems in the fifo_open() and fifo_close()
> implementations.
> ...
> This patch makes the following changes:
>
> 	Create fifo_inactive() and free the fifo data structures there
> 	instead of in fifo_close() to eliminate the need for fifo_open()
> 	call fifo_close() in some of the failure cases.  This also
> 	eliminates the need for the vrefcnt() call in fifo_close().
>
> 	Protect fip->fi_{readers,writers} with the vnode interlock in both
> 	fifo_open() and fifo_close().
>
> 	Convert from tsleep() to msleep() using the vnode interlock to
> 	eliminate the race condition.

Why not just lock the vnode in fifo_close()?  RELENG[2-4] seems to have
the same bug.  I cannot be fixed there using the vnode interlock.

Bruce