sema replacement

[Chuck Tuffli]

FreeBSD's new ATA code makes use of kernel counting semaphores (sema(9)) 
in the queuing code which don't seem to exist in DragonFly*. I think the 
serializing tokens are the replacement and wanted to see if a) that was 
the right approach and if so, b) do you use lockmgr or is it preferable 
to use the tokens directly. TIA

* though, there does seem to be a private implementation in ffs_softdep.c

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Chuck Tuffli
Agilent Technologies