CFR: fifo_open()/fifo_close() patch

[Don Lewis]

On 16 May, Bruce Evans wrote:
> 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.

That is probably the proper fix for RELENG4 where finer-grained locking
isn't needed because of Giant.  I'd still probably move the resource
deallocation to fifo_inactive().