Re: [OOPS] 2.6.11 - NMI lockup with CFQ scheduler

Christoph Hellwig
2005-04-07T13:22:31Z

On Thu, Apr 07, 2005 at 09:18:38AM -0400, James Bottomley wrote:
> On Thu, 2005-04-07 at 08:49 +0200, Jens Axboe wrote:
> > On Wed, Apr 06 2005, James Bottomley wrote:
> > > My proposal is to correct this by moving the data back to the correct
> > > object, and make any object using it hold a reference, so this would
> > > make the provider of the block request_fn hold a reference to the queue
> > > and initialise the queue lock pointer with the lock currently in the
> > > queue. Drivers that still use a global lock would be unaffected. This
> >
> > But this is the current requirement, as long as you use the queue you
> > must hold a reference to it.
>
> Exactly! that's why I think this solution must work independently of
> subsystem.
>
> > What do you think of the attached, then? Allow NULL lock to be passed
> > in, in which case we use the queue private lock (that no one should ever
> > ever touch). It looks a little confusing that
> > sdev->request_queue->queue_lock now protects some sdev structures, if
> > you want we can retain ->sdev_lock but as a pointer to the queue lock
> > instead.
>
> Looks good. How about the attached modification? It makes sdev_lock a
> pointer that uses the queue lock which we null out when we release it
> (not that I don't trust SCSI or anything ;-)

Do we really need the sdev_lock pointer? There's just a single place
where we're using it and the code would be much more clear if it had just
one name.