Re: When must the io_request_lock be held?

Mike Anderson
2002-08-07T18:06:28Z

James Bottomley [James.Bottomley@steeleye.com] wrote:
>
> Well, that's just semantics, I won't get into the argument...
>
> Note also that 2.5 already has per queue locks (that means per individual SCSI
> devices) which are lock pointers. In 2.5 current, all the devices that hang
> off an individual host have their queue_locks initialised to point to the
> single host->host_lock. However, drivers which can do it (the type of
> multi-threaded multi-mailbox ones) will be permitted to use individual and
> separate queue_locks, rather than the single host_lock, to protect their
> mailbox registers. If you are never going to do this, the difference between
> using host_lock and queue_lock is irrelevant to you. If you are, you need to
> begin using the queue_locks.

James,
Maybe I am mis-reading something.

Why would we want to go back to a model of having LL drivers
using locks outside there domain (queue_lock). Should we not be
moving toward having drivers use there own locks.

I would think a future model might be to have queue_locks for
queue operations and possible shared as a scsi device lock, a
host_lock for host data, and LL driver locks used where the
driver needs them.

-Mike
--
Michael Anderson
andmike@us.ibm.com