Re: [PATCH 2/4] scsi: Fix device removal NULL pointer dereference

[Bart Van Assche <bvanassche@acm.org>]

On 06/26/12 07:19, James Bottomley wrote:

> On Mon, 2012-06-25 at 17:05 -0500, Mike Christie wrote:
>> Only the scsi_tgt_lib.c code uses the uses the uspace_req_q. That code
>> does not use it in a traditional way. It passes __scsi_alloc_queue NULL
>> for the request_fn function argument, so this request queue does not
>> have a function that pulls requests off a queue like is done for the
>> initiator path.
>>
>> That target code mostly uses the queue struct so that it can use the
>> block/scsi functions that need a request queue to build scatterlists,
>> cmds, bios, etc. When that code was made originally we were going to use
>> the queue in a more tradition way or break out the queue limits into
>> another struct and pass them around. I think we have the latter now, but
>> the target code has not been converted.
>>
>> But so that is why we cannot hit a race like you are thinking about in
>> the initiator path.
>>
>> It is also a weird use of the queue so it is also why it does not make
>> sense :)
> 
> OK, could we encapsulate all that in the comment so I don't have to ask
> again in a year's time ... ?


Maybe it's easier to implement Tejun's suggestion (swapping the
blk_cleanup_queue() call and freeing the queuedata) ? That should be
readable for everyone and shouldn't need a comment.

Bart.