newbus integration of MOD_QUIESCE (was Re: cvs commit: src/sbin/kldunload kldunload.8 kldunload.c )

[Poul-Henning Kamp]

In message <Pine.NEB.3.96L.1040713195126.63836A-100000 at fledge.watson.org>, Robe
rt Watson writes:
>
>On Tue, 13 Jul 2004, M. Warner Losh wrote:
>
>> The nasty case I've come up with is what happens when the module is idle
>> (not busy), but becomes busy (not idle) after the MOD_QUIESCE call? 
>> Right now newbus modules that receive a MOD_UNLOAD call attempt to
>> detach all instances of devices contained in that module.  If I have a
>> way to poll the driver to see if it is busy (which is relatively easy to
>> implement), then if it becomes busy after the MOD_QUIESCE call, I get a
>> MOD_UNLOAD which would force instances to detach. 
>
>So, it sounds like a couple of concepts are floating around:

I considered most of what you suggest here myself but concluded that
since we had been able to get by with only -force in mount for so
long, we really only needed two levels:

	MOD_QUIESCE	"stop and prepare for unload if not in use"

	MOD_UNLOAD	"unload unless there are memory references into
			the module which cannot be invalidated"

I did make the kldunloadf() take a flag argument so if people want
higher granularity more can be added, but remember that would come
at a cost of more code in all modules.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.