Re: question about drivers/scsi/scsi_transport_fc.c

[Hannes Reinecke <hare@suse.de>]

Christof Schmitt wrote:
> On Sat, Aug 28, 2010 at 07:11:12PM +0200, Julia Lawall wrote:
>> The function fc_bsg_goose_queue in the file drivers/scsi/scsi_transport_fc.c
>> contains the following code:
>>
>>         flagset = test_bit(QUEUE_FLAG_REENTER, &rport->rqst_q->queue_flags) &&
>>                   !test_bit(QUEUE_FLAG_REENTER, &rport->rqst_q->queue_flags);
>>
>> I have the impression that this is always 0.  QUEUE_FLAG_REENTER is 
>> defined with quite a lot of other constants, so I don't really have a 
>> guess as to what was intended.
> 
> I just came across the code in scsi_run_queue in
> drivers/scsi/scsi_lib.c. It looks like the check of QUEUE_FLAG_REENTER
> in fc_bsg_goose_queue is modeled after the check in scsi_run_queue.
> 
> The check in scsi_run_queue has been introduced with this commit,
> maybe this helps understanding the code:
> 
> commit 04846f25920d4b05d6040c531cc601049260db52
> Author: Andreas Herrmann <aherrman@de.ibm.com>
> Date:   Wed Aug 9 17:31:16 2006 +0200
> 
>     [SCSI] limit recursion when flushing shost->starved_list
> 
Then it's still wrong. The above commit has:

+               if (test_bit(QUEUE_FLAG_REENTER, &q->queue_flags) &&
+                   !test_and_set_bit(QUEUE_FLAG_REENTER,
+                                     &sdev->request_queue->queue_flags)) {

Which is slightly different than the above. Looks like a copy and past error.
It probably should read

         flagset = test_bit(QUEUE_FLAG_REENTER, &rport->rqst_q->queue_flags) &&
                   !test_and_set_bit(QUEUE_FLAG_REENTER, &rport->rqst_q->queue_flags);

This was introduced by

commit 9e4f5e29610162fd426366f3b29e3cc6e575b858
Author: James Smart <James.Smart@Emulex.Com>
Date:   Thu Mar 26 13:33:19 2009 -0400

    [SCSI] FC Pass Thru support

so we should be blaming^Wasking him.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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