Oops. I guess this was the actual patch I sent.

Brian King wrote:
> James Bottomley wrote:
> 
>> On Tue, 2004-08-03 at 10:49, Brian King wrote:
>>
>>> Add locking to scsi_activate_tcq and scsi_deactivate_tcq to fix a race
>>> condition that can occur when disabling tcqing with commands in flight.
>>
>>
>>
>> It's possible to do it like this.  However, we should really quiesce the
>> SCSI device before disabling tcq.  It is not legal in the scsi spec to
>> have both tagged and untagged commands outstanding.  Most drives do the
>> right thing and return BUSY to an untagged request if they have tags in
>> flight.  
> 
> 
> Ok. I agree that we do not want both tagged and untagged requests going 
> to the device. In the case of the ipr driver, the adapter microcode 
> handles this for me. If there are tagged requests outstanding to a 
> device and an untagged request is sent, the tagged requests must first 
> finish, then the untagged request is sent to the device with no other 
> requests outstanding.
> 
>> Also, we have to wait until all tags return before freeing the
>> block layer tag structures...and there's always the devices that do
>> strange things in this situation...
> 
> 
> I sent the following patch to Jens last week as well and he applied it. 
> This fixes the free problem you mention.


-- 
Brian King
eServer Storage I/O
IBM Linux Technology Center