sema replacement

[Chuck Tuffli]

It looks like the code queues up a request and then uses sema_wait() to 
sleep until the request either completes or fails. In both cases, the 
code calls sema_post(). Maybe this is a better fit for messaging - i.e. 
sema_wait would map to lwkt_waitport() and sema_post would map to 
lwkt_sendmsg()?

Matthew Dillon wrote:
: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
:
:-- 
:Chuck Tuffli
:Agilent Technologies

    I would say we want to use tokens for now.  The ATA driver core should
    be mostly non-blocking, at least presuming that sos hasn't added
    mallocs in the middle of the code (like existed in the original 4.x
    driver).  This makes the token model a better fit.
    I won't even ask why they are using yet another (this is like the 
    8th or 9th now) locking API.  Semaphores don't really fit the model for
    the type of locking they need.

					-Matt
					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>
--
Chuck Tuffli
Agilent Technologies