Re: Changes to Linux/SCSI target mode infrastructure for v2.6.28

[Nicholas A. Bellinger]

On Mon, 2008-12-01 at 22:40 -0800, Mike Anderson wrote:
> Nicholas A. Bellinger <nab@xxxxxxxxxxxxxxx> wrote:
> > On Tue, 2008-12-02 at 13:18 +0900, Tejun Heo wrote:
> > > 
> > > >>> The other one is a BUG_ON in blk/blk-timeout.c:177 in blk_add_timeout()
> > > >>> that happens after a few hundred MB of READ_10 traffic, which also
> > > >>> appears to pass through elv_dequeue_request() at some point:
> > > >>>
> > > >>> http://linux-iscsi.org/builds/user/nab/2.6.28-rc6-oops-2.png
> > > >>> http://linux-iscsi.org/builds/user/nab/2.6.28-rc6-oops-4.png
> > >
> > > Hmmm... this means blk_add_timer() is being called after the request
> > > is already completed.
> 
> or is it possible since elv_dequeue_request BUG_ON check of queuelist did
> not trigger a request is on the queuelist with a timeout_list not empty.
> 
> It would be interesting for a debug run to change the
> "BUG_ON(!list_empty(&req->timeout_list))" in blk_add_timer to print out
> the cmd_flags plus req->atomic_flags and also add a
> "BUG_ON(!list_empty(&rq->timeout_list))" to elv_insert to ensure a request
> is never added to the queuelist with a timeout_list not empty.
> 

Sounds good.   I will retest w/o the previous changes to scsi_lib.c for
elv_dequeue_request() and see what happens.

Thanks for your comments,

--nab

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