Re: smp dead lock of io_request_lock/queue_lock patch

[Doug Ledford <dledford@redhat.com>]

On Sat, 2004-01-17 at 14:17, Christoph Hellwig wrote:
> On Sat, Jan 17, 2004 at 02:07:33PM -0500, Doug Ledford wrote:
> > #ifdef SCSI_HAS_HOST_LOCK
> > #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
> > 	adapter->lock_ptr = &adapter->lock;
> > 	host->lock = &adapter->lock;
> > #else
> > 	adapter->lock_ptr = &adapter->lock;
> > 	host->host_lock = &adapter->lock;
> > #endif
> > #else
> > 	adapter->lock_ptr = &io_request_lock;
> > #endif
> 
> Still looks wrong for the 2.6 case which should just be;
> 
> 	adapter->lock_ptr = shost->host_lock;
> 
> as I just stated in the review for the megaraid update.

I should pay more attention to what goes on in 2.6.  That was a crap
decision.  There are drivers out there that use global data and need one
lock across all controllers.  Putting a lock in the scsi host struct for
per controller locks is a waste of space.  Let the driver decide if it
needs a global driver lock, a per controller lock (in which case it
should be part of the driver private host struct), or just the global
io_request_lock.  It really is up to the driver and putting it into the
scsi host struct doesn't make sense.

-- 
  Doug Ledford <dledford@redhat.com>     919-754-3700 x44233
         Red Hat, Inc.
         1801 Varsity Dr.
         Raleigh, NC 27606